Cryogenics is the study of production and behavior of materials at very low temperatures, typically below -150°C. It involves using cryogenic liquids like liquid nitrogen and liquid helium to reach these low temperatures. Some key applications of cryogenics include magnetic resonance imaging (MRI), which uses superconducting magnets cooled by liquid helium; cryogenic rocket engines, which use cryogenically stored liquid oxygen and hydrogen as fuel; and cryogenic processing of metals to improve properties like wear resistance. Cryogenics also enables applications in fields like space technology, electronics, medicine, and more.
Mg university, KTU univeraity
Btech
Module 1 (8 hours)
Introduction: Historical development- application of cryogenics -present areas involving
cryogenic engineering-cryogenics in space technology- cryogenics in biology and medicinesuperconductivity applications.
Module 2 (12 hours)
Basic thermodynamics applied to liquefaction and refrigeration process – isothermal, adiabatic
and Joule Thomson expansion process -efficiency to liquefaction and coefficient of
performances- irreversibility and losses. Low temperature properties of engineering materials:
mechanical properties – thermal properties -electrical and magnetic properties. Properties of
cryogenic fluids- superconductivity and super fluidity - materials of constructions for cryogenic
applications.
Module 3 (15 hours)
Gas liquefaction systems: Production of low temperatures – general liquefaction systemsliquefaction systems for neon, hydrogen and helium.
Module 4 (15hours)
Cryogenic refrigeration systems: ideal refrigeration systems- refrigerators using liquids and gases
as refrigerants- refrigerators using solids as working media - adiabatic demagnetization method.
Module 5 (10 hours)
Cryogenic storage and transfer systems: Cryogenic fluid storage vessels- cryogenic fluid transfer
systems-cryo pumping.
Teaching scheme Credits: 4
3 hours lecture and 1 hour tutorial per week
Text Books
1. Barron R., Cryogenic Systems, Oxford Science Publications
2. Scott R.B., Cryogenic Engineering, Van Nostrand Co.
Reference Books
1. Mamata Mukhopadyay., Fundamentals of Cryogenic Engineering, PHI Learning
2. Haseldon G.G., Cryogenic Fundamentals, Academic Press
3. Flynn T.M., Cryogenic Engineering, Marcel Dekker.
Cryogenics and its applications in space were discussed. Liquid helium and nitrogen are commonly used cryogenic liquids that are stored in Dewars. An Adiabatic Demagnetization Refrigerator (ADR) can attain temperatures below liquid helium by using a magnetocaloric material to absorb and release heat with changing magnetic fields. The X-Ray Spectrometer instrument uses a complex cryogenic system including liquid helium, a mechanical cooler, and an ADR to cool its detectors to ultra-low temperatures needed to minimize noise.
Cryogenics is the study of production and behavior of materials at extremely cold temperatures. It began in the 19th century with scientists liquefying gases. Today, cryogenics has applications like MRI, superconducting cables for power transmission, blood banking, rocket engines using cryogenic fuels, and food freezing. Cryogenics enables sensitive detectors for astronomy and enables cooling electronics to reduce noise. Cryogenic processing improves materials by making them more durable through deep freezing over long periods.
This document outlines the course code, credits, hours, and content for a cryogenics engineering course. The course is divided into 8 units that cover topics such as cryogenic systems applications, gas liquefaction and refrigeration systems, gas separation and purification, ultra-low temperature refrigerators, vacuum technology, cryogenic insulation, fluid storage and transfer systems, and applications of cryogenic systems such as food preservation and superconductors. Key concepts include the thermodynamic properties of materials at low temperatures, common cycles for liquefying and refrigerating gases, critical components, measurement techniques, and the design of cryogenic storage and transfer systems.
Cryogenics is the study of production and behavior of materials at very low temperatures below -150°C. Some important cryogenic fluids include liquid hydrogen, helium, oxygen, nitrogen and air. Key applications of cryogenics include rocket propulsion, magnetic resonance imaging, superconductivity, frozen food storage and more. Cryogenic technology enables efficient rocket engines using liquid hydrogen and oxygen propellants. India has developed its own cryogenic engine GSLV Mk III to launch satellites using this technology. Future prospects include more efficient ion engines and alternative nuclear or solar thermal rocket concepts.
This document discusses the history and types of refrigeration. It begins by defining refrigeration and describing early natural refrigeration methods like ice harvesting and evaporative cooling. It then covers the development of artificial refrigeration, including William Cullen's demonstration of evaporative cooling in 1755. The document goes on to describe various refrigeration cycles and systems in use today, such as vapor compression, gas refrigeration cycles, ejector refrigeration, thermoelectric refrigeration, solar-powered absorption chillers, adsorption chillers, solid desiccant cooling, and liquid desiccant systems. It concludes by discussing direct evaporative cooling units.
This document discusses the history of refrigerant and compressor development. It describes the early use of natural refrigerants like water and how synthetic refrigerants like Freon were developed in the 1920s. It also discusses the key issues with early refrigerants like toxicity and flammability that synthetic refrigerants solved. However, synthetic refrigerants like CFCs were later found to deplete the ozone layer, prompting a search for new non-ozone depleting refrigerants. The document provides a high-level overview of the major developments and issues in both refrigerants and compressor technology over time.
Mg university, KTU univeraity
Btech
Module 1 (8 hours)
Introduction: Historical development- application of cryogenics -present areas involving
cryogenic engineering-cryogenics in space technology- cryogenics in biology and medicinesuperconductivity applications.
Module 2 (12 hours)
Basic thermodynamics applied to liquefaction and refrigeration process – isothermal, adiabatic
and Joule Thomson expansion process -efficiency to liquefaction and coefficient of
performances- irreversibility and losses. Low temperature properties of engineering materials:
mechanical properties – thermal properties -electrical and magnetic properties. Properties of
cryogenic fluids- superconductivity and super fluidity - materials of constructions for cryogenic
applications.
Module 3 (15 hours)
Gas liquefaction systems: Production of low temperatures – general liquefaction systemsliquefaction systems for neon, hydrogen and helium.
Module 4 (15hours)
Cryogenic refrigeration systems: ideal refrigeration systems- refrigerators using liquids and gases
as refrigerants- refrigerators using solids as working media - adiabatic demagnetization method.
Module 5 (10 hours)
Cryogenic storage and transfer systems: Cryogenic fluid storage vessels- cryogenic fluid transfer
systems-cryo pumping.
Teaching scheme Credits: 4
3 hours lecture and 1 hour tutorial per week
Text Books
1. Barron R., Cryogenic Systems, Oxford Science Publications
2. Scott R.B., Cryogenic Engineering, Van Nostrand Co.
Reference Books
1. Mamata Mukhopadyay., Fundamentals of Cryogenic Engineering, PHI Learning
2. Haseldon G.G., Cryogenic Fundamentals, Academic Press
3. Flynn T.M., Cryogenic Engineering, Marcel Dekker.
Cryogenics and its applications in space were discussed. Liquid helium and nitrogen are commonly used cryogenic liquids that are stored in Dewars. An Adiabatic Demagnetization Refrigerator (ADR) can attain temperatures below liquid helium by using a magnetocaloric material to absorb and release heat with changing magnetic fields. The X-Ray Spectrometer instrument uses a complex cryogenic system including liquid helium, a mechanical cooler, and an ADR to cool its detectors to ultra-low temperatures needed to minimize noise.
Cryogenics is the study of production and behavior of materials at extremely cold temperatures. It began in the 19th century with scientists liquefying gases. Today, cryogenics has applications like MRI, superconducting cables for power transmission, blood banking, rocket engines using cryogenic fuels, and food freezing. Cryogenics enables sensitive detectors for astronomy and enables cooling electronics to reduce noise. Cryogenic processing improves materials by making them more durable through deep freezing over long periods.
This document outlines the course code, credits, hours, and content for a cryogenics engineering course. The course is divided into 8 units that cover topics such as cryogenic systems applications, gas liquefaction and refrigeration systems, gas separation and purification, ultra-low temperature refrigerators, vacuum technology, cryogenic insulation, fluid storage and transfer systems, and applications of cryogenic systems such as food preservation and superconductors. Key concepts include the thermodynamic properties of materials at low temperatures, common cycles for liquefying and refrigerating gases, critical components, measurement techniques, and the design of cryogenic storage and transfer systems.
Cryogenics is the study of production and behavior of materials at very low temperatures below -150°C. Some important cryogenic fluids include liquid hydrogen, helium, oxygen, nitrogen and air. Key applications of cryogenics include rocket propulsion, magnetic resonance imaging, superconductivity, frozen food storage and more. Cryogenic technology enables efficient rocket engines using liquid hydrogen and oxygen propellants. India has developed its own cryogenic engine GSLV Mk III to launch satellites using this technology. Future prospects include more efficient ion engines and alternative nuclear or solar thermal rocket concepts.
This document discusses the history and types of refrigeration. It begins by defining refrigeration and describing early natural refrigeration methods like ice harvesting and evaporative cooling. It then covers the development of artificial refrigeration, including William Cullen's demonstration of evaporative cooling in 1755. The document goes on to describe various refrigeration cycles and systems in use today, such as vapor compression, gas refrigeration cycles, ejector refrigeration, thermoelectric refrigeration, solar-powered absorption chillers, adsorption chillers, solid desiccant cooling, and liquid desiccant systems. It concludes by discussing direct evaporative cooling units.
This document discusses the history of refrigerant and compressor development. It describes the early use of natural refrigerants like water and how synthetic refrigerants like Freon were developed in the 1920s. It also discusses the key issues with early refrigerants like toxicity and flammability that synthetic refrigerants solved. However, synthetic refrigerants like CFCs were later found to deplete the ozone layer, prompting a search for new non-ozone depleting refrigerants. The document provides a high-level overview of the major developments and issues in both refrigerants and compressor technology over time.
The document discusses the history and principles of refrigeration and refrigerants. It describes how early refrigeration methods used natural ice and evaporation of liquids before Jacob Perkins developed the first vapor compression refrigeration system using ether as the refrigerant. Modern refrigeration is dominated by vapor compression cycles using halocarbon refrigerants. However, CFC refrigerants were found to deplete the ozone layer, leading to the Montreal Protocol that phased out their production. Selection of new refrigerants must consider thermodynamic properties as well as environmental safety.
This document summarizes a study that investigated using a propane-butane mixture as an alternative refrigerant in household refrigerators instead of R-134a. The study found that using a mixed refrigerant of 80% propane and 20% butane by mass achieved higher cooling capacity and lower freezer temperatures compared to R-134a, with energy consumption reduced by nearly 10.8%. Mixed refrigerants are a potential environmentally-friendly alternative to hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs) that are banned for depleting the ozone layer. The experimental results indicate that mixed refrigerants show promise as refrigerants in household refrigerators.
Document describes, the Cryogenic definition, applications, various Melting Points and Boiling Points of cryogenic liquids and other liquids. selection of materials for cryogenic service, Timeline for Cryogenic Technology.
The document is a chapter outline for a textbook on refrigeration fundamentals. It lists 10 main topics that will be covered in the book, including thermodynamics, heat and work, thermodynamic properties of substances, liquid-vapor properties of pure substances, P-V-T behavior of gases, thermodynamic processes, heat transfer, refrigeration cycles, multi-pressure refrigeration systems, and direct expansion and chilled water systems. Each topic is further broken down into sections and subsections that provide more detail on the information that will be presented.
The document defines refrigerants as heat carrying mediums that absorb heat from low temperature systems and discard it to higher temperature systems. It lists desirable properties of ideal refrigerants such as low boiling point, high critical temperature, and being non-toxic. Refrigerants are classified as primary or secondary, with primary refrigerants further divided into halo-carbon, azeotrope, inorganic, and hydrocarbon types. Thermodynamic and physical properties that impact refrigerant selection are also outlined.
Refrigeration and air conditioning (repaired)Prashanth J
1. Refrigeration involves extracting heat from a body to maintain it at a lower temperature than its surroundings. Air conditioning provides thermal comfort by controlling temperature and humidity.
2. A refrigeration system uses a refrigerant to absorb heat from a cold space and reject it to a hot space. Common components are an evaporator, compressor, condenser, and expansion valve. The refrigerant undergoes phase changes between gas and liquid.
3. Vapour compression and vapour absorption are two main refrigeration cycles. Vapour compression uses a compressor to raise the refrigerant's pressure and temperature before condensing. Vapour absorption relies on chemical reactions between a refrigerant and absorbent like ammonia and water.
This document discusses refrigerants, including their classification, properties, environmental impacts, and alternatives. Refrigerants are heat carrying fluids that absorb heat from a low temperature system and release it to a high temperature system. Natural substances like ice were early refrigerants, followed by ether, ammonia, and sulfur dioxide in the 19th century. Chlorofluorocarbons (CFCs) became popular but were later banned due to ozone depletion and global warming. Current alternatives include hydrocarbons, ammonia, carbon dioxide, and hydrofluorocarbons. An ideal refrigerant has desirable properties like high critical temperature, low boiling point, non-toxicity, stability, and being environmentally friendly.
T.H. Chemicals wants to produce nitrogen, oxygen, and argon from air using cryogenic distillation. Cryogenic air separation is the dominant technology for producing large quantities of high-purity liquified gases. The process involves compressing and cooling air, removing impurities via membrane separation, further cooling the air using heat exchangers, and fractionating the components in distillation columns. Oxygen is recovered from the bottom of the low pressure column at 99.49% purity, nitrogen from the top at 99.275% purity, and argon from the middle. Heat integration occurs between the condenser and reboiler to improve efficiency.
Refrigerants are substances used in refrigeration cycles to absorb and remove heat from the space being refrigerated. The main types are primary and secondary refrigerants. Primary refrigerants directly cool spaces through phase change processes. Common primary refrigerants include ammonia, hydrocarbons, halocarbons like Freon, and inorganic substances. Secondary refrigerants indirectly cool spaces by transferring heat between the evaporator and load. Brines are commonly used secondary refrigerants. Refrigerants are designated by "R" numbers to identify their chemical composition and properties. Desirable properties include thermodynamic efficiency, safety, and minimal environmental impact as measured by ODP and GWP.
This document provides information on refrigerants including their definition, history, classification, properties, and environmental impact. It discusses early natural refrigerants and the development of artificial refrigerants over time. Refrigerants are classified based on their working principle and chemical properties. Key criteria for refrigerant selection include thermodynamic properties, environmental and safety factors, and cost. Common synthetic refrigerants discussed are CFCs, HCFCs, HFCs, hydrocarbons, and inorganic refrigerants like ammonia and carbon dioxide.
The document discusses the classification and properties of refrigerants. It defines refrigerants as the working fluid in a refrigeration system that absorbs or releases heat during the cooling process. Refrigerants are classified based on their working principle, safety, chemical composition, and physical state. Common refrigerants discussed include ammonia, carbon dioxide, sulfur dioxide, and halocarbon compounds like R12 and R22. Key thermodynamic properties of refrigerants that are desirable include high critical temperature and moderate pressure, low specific heats, high heat of vaporization, and high coefficient of performance. Primary refrigerants can be used directly for cooling, while secondary refrigerants require a heat exchanger.
The document discusses refrigeration and air conditioning applications and refrigerants. It covers four major applications of refrigeration: food processing and preservation, chemical and process industries, special applications, and comfort air conditioning. It then discusses different types of refrigerants including halocarbons, hydrocarbons, inorganic compounds, azeotropic mixtures, and non-azeotropic mixtures. Finally, it covers topics like ozone layer depletion, global warming potential, and total equivalent warming impact as a metric for comparing refrigerants.
“Refrigerant is the media (fluid) used for heat transfer in a refrigerating system that absorbs heat during evaporation from the region of low temperature and pressure, and releases heat during condensation at a region of higher temperature and pressure.”
This document discusses various types of refrigerants including halocarbon, azeotropic, zeotropic, inorganic, and hydrocarbon refrigerants. It provides examples of commonly used refrigerants for each type and notes their properties such as ozone depletion potential and global warming potential. Natural refrigerants like ammonia, hydrocarbons, and carbon dioxide are highlighted as having better environmental profiles than synthetic halocarbons or HFCs. The document advocates for increased use of natural refrigerants in refrigeration and air conditioning equipment to lower total environmental impact.
This document provides an overview of refrigeration and refrigeration systems. It discusses the objectives of refrigeration including preserving foods and reducing losses. It then describes the basic vapor compression refrigeration cycle including the components of compressor, condenser, expansion valve, and evaporator. Finally, it discusses factors that influence the coefficient of performance such as pressure losses, heat transfer, compression efficiency, subcooling, and superheating.
1) The document presents an experimental study on reducing frost accumulation in a refrigerator evaporator coil by applying a 662 S-silicone grease coating.
2) Experiments were conducted with varying water loads kept in the refrigerator over time periods of 25, 50, and 75 hours, with and without the silicone grease coating on the evaporator. Less frost accumulated on the coated evaporator across all experiments.
3) The silicone grease coating is proposed to reduce frost accumulation due to its smooth, low-temperature resistant, and non-wetting properties which allow water droplets to easily roll off the surface. Reducing frost accumulation could improve refrigerator performance and efficiency.
A phase change material (PCM) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, PCMs are classified as latent heat storage (LHS) units.
This document discusses air conditioning and mechanical engineering. It is from Sana'a University and focuses on the work of Dr. Abduljalil Al-Abidi in the HVAC department. It covers several topics:
- The four conditions controlled by air conditioning: temperature, humidity, purity, and air velocity/circulation.
- Classification of air conditioning systems by function (comfort, industrial), season (winter, summer, year-round), and equipment arrangement (central, unitary, dual duct, variable air volume, variable refrigerant flow).
- Key processes in air conditioning like heating, cooling, humidifying, dehumidifying, cleaning, and air motion.
- Psychrometrics, the properties of
Presentation on Alternative Refrigerants related to mechanical engineering for application in mechanical systems (air conditoning and refrigerators etc) and chemical engineering
The document discusses refrigerants and their properties. It defines refrigerants as the primary working fluids used in refrigeration systems that absorb heat at low temperatures and release it at higher temperatures. Key properties of refrigerants include low boiling point, high latent heat, non-toxicity, and non-corrosiveness. The document also covers classifications of refrigerants such as halocarbon, azeotrope, inorganic, and hydrocarbons. Environmental impacts and economics are additional factors in refrigerant selection.
Intervento di due ore alla BTS 2013 di Montecatini Terme
"Un miliardo di utenti pronti a collaborare alla costruzione del nostro prodotto ed a promuovere la nostra struttura commentando e condividendo la loro esperienza nel nostro hotel .
Quali sono le leve da sfruttare e come stimolare in modo strategico l'interazione con attuali o potenziali clienti , monitorare a migliorare la brand reputation fino a disintermediare grazie ad un vero e proprio social revenue .
Strumenti , strategie e case histories
D.E.A.L. Disintermediazione , engagement , app e leading. Intervento alla BT...VARNER FERRATO
Il termine DEAL diventa una nuova formula per incrementare il ROI dell'hotel .
Il ROI si evince da una nuova ridefinizione dello stesso.
Idee per disintermediare aumentando l'engagement , con azioni di leading attraverso l'utilizzo delle app .
The document discusses the history and principles of refrigeration and refrigerants. It describes how early refrigeration methods used natural ice and evaporation of liquids before Jacob Perkins developed the first vapor compression refrigeration system using ether as the refrigerant. Modern refrigeration is dominated by vapor compression cycles using halocarbon refrigerants. However, CFC refrigerants were found to deplete the ozone layer, leading to the Montreal Protocol that phased out their production. Selection of new refrigerants must consider thermodynamic properties as well as environmental safety.
This document summarizes a study that investigated using a propane-butane mixture as an alternative refrigerant in household refrigerators instead of R-134a. The study found that using a mixed refrigerant of 80% propane and 20% butane by mass achieved higher cooling capacity and lower freezer temperatures compared to R-134a, with energy consumption reduced by nearly 10.8%. Mixed refrigerants are a potential environmentally-friendly alternative to hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs) that are banned for depleting the ozone layer. The experimental results indicate that mixed refrigerants show promise as refrigerants in household refrigerators.
Document describes, the Cryogenic definition, applications, various Melting Points and Boiling Points of cryogenic liquids and other liquids. selection of materials for cryogenic service, Timeline for Cryogenic Technology.
The document is a chapter outline for a textbook on refrigeration fundamentals. It lists 10 main topics that will be covered in the book, including thermodynamics, heat and work, thermodynamic properties of substances, liquid-vapor properties of pure substances, P-V-T behavior of gases, thermodynamic processes, heat transfer, refrigeration cycles, multi-pressure refrigeration systems, and direct expansion and chilled water systems. Each topic is further broken down into sections and subsections that provide more detail on the information that will be presented.
The document defines refrigerants as heat carrying mediums that absorb heat from low temperature systems and discard it to higher temperature systems. It lists desirable properties of ideal refrigerants such as low boiling point, high critical temperature, and being non-toxic. Refrigerants are classified as primary or secondary, with primary refrigerants further divided into halo-carbon, azeotrope, inorganic, and hydrocarbon types. Thermodynamic and physical properties that impact refrigerant selection are also outlined.
Refrigeration and air conditioning (repaired)Prashanth J
1. Refrigeration involves extracting heat from a body to maintain it at a lower temperature than its surroundings. Air conditioning provides thermal comfort by controlling temperature and humidity.
2. A refrigeration system uses a refrigerant to absorb heat from a cold space and reject it to a hot space. Common components are an evaporator, compressor, condenser, and expansion valve. The refrigerant undergoes phase changes between gas and liquid.
3. Vapour compression and vapour absorption are two main refrigeration cycles. Vapour compression uses a compressor to raise the refrigerant's pressure and temperature before condensing. Vapour absorption relies on chemical reactions between a refrigerant and absorbent like ammonia and water.
This document discusses refrigerants, including their classification, properties, environmental impacts, and alternatives. Refrigerants are heat carrying fluids that absorb heat from a low temperature system and release it to a high temperature system. Natural substances like ice were early refrigerants, followed by ether, ammonia, and sulfur dioxide in the 19th century. Chlorofluorocarbons (CFCs) became popular but were later banned due to ozone depletion and global warming. Current alternatives include hydrocarbons, ammonia, carbon dioxide, and hydrofluorocarbons. An ideal refrigerant has desirable properties like high critical temperature, low boiling point, non-toxicity, stability, and being environmentally friendly.
T.H. Chemicals wants to produce nitrogen, oxygen, and argon from air using cryogenic distillation. Cryogenic air separation is the dominant technology for producing large quantities of high-purity liquified gases. The process involves compressing and cooling air, removing impurities via membrane separation, further cooling the air using heat exchangers, and fractionating the components in distillation columns. Oxygen is recovered from the bottom of the low pressure column at 99.49% purity, nitrogen from the top at 99.275% purity, and argon from the middle. Heat integration occurs between the condenser and reboiler to improve efficiency.
Refrigerants are substances used in refrigeration cycles to absorb and remove heat from the space being refrigerated. The main types are primary and secondary refrigerants. Primary refrigerants directly cool spaces through phase change processes. Common primary refrigerants include ammonia, hydrocarbons, halocarbons like Freon, and inorganic substances. Secondary refrigerants indirectly cool spaces by transferring heat between the evaporator and load. Brines are commonly used secondary refrigerants. Refrigerants are designated by "R" numbers to identify their chemical composition and properties. Desirable properties include thermodynamic efficiency, safety, and minimal environmental impact as measured by ODP and GWP.
This document provides information on refrigerants including their definition, history, classification, properties, and environmental impact. It discusses early natural refrigerants and the development of artificial refrigerants over time. Refrigerants are classified based on their working principle and chemical properties. Key criteria for refrigerant selection include thermodynamic properties, environmental and safety factors, and cost. Common synthetic refrigerants discussed are CFCs, HCFCs, HFCs, hydrocarbons, and inorganic refrigerants like ammonia and carbon dioxide.
The document discusses the classification and properties of refrigerants. It defines refrigerants as the working fluid in a refrigeration system that absorbs or releases heat during the cooling process. Refrigerants are classified based on their working principle, safety, chemical composition, and physical state. Common refrigerants discussed include ammonia, carbon dioxide, sulfur dioxide, and halocarbon compounds like R12 and R22. Key thermodynamic properties of refrigerants that are desirable include high critical temperature and moderate pressure, low specific heats, high heat of vaporization, and high coefficient of performance. Primary refrigerants can be used directly for cooling, while secondary refrigerants require a heat exchanger.
The document discusses refrigeration and air conditioning applications and refrigerants. It covers four major applications of refrigeration: food processing and preservation, chemical and process industries, special applications, and comfort air conditioning. It then discusses different types of refrigerants including halocarbons, hydrocarbons, inorganic compounds, azeotropic mixtures, and non-azeotropic mixtures. Finally, it covers topics like ozone layer depletion, global warming potential, and total equivalent warming impact as a metric for comparing refrigerants.
“Refrigerant is the media (fluid) used for heat transfer in a refrigerating system that absorbs heat during evaporation from the region of low temperature and pressure, and releases heat during condensation at a region of higher temperature and pressure.”
This document discusses various types of refrigerants including halocarbon, azeotropic, zeotropic, inorganic, and hydrocarbon refrigerants. It provides examples of commonly used refrigerants for each type and notes their properties such as ozone depletion potential and global warming potential. Natural refrigerants like ammonia, hydrocarbons, and carbon dioxide are highlighted as having better environmental profiles than synthetic halocarbons or HFCs. The document advocates for increased use of natural refrigerants in refrigeration and air conditioning equipment to lower total environmental impact.
This document provides an overview of refrigeration and refrigeration systems. It discusses the objectives of refrigeration including preserving foods and reducing losses. It then describes the basic vapor compression refrigeration cycle including the components of compressor, condenser, expansion valve, and evaporator. Finally, it discusses factors that influence the coefficient of performance such as pressure losses, heat transfer, compression efficiency, subcooling, and superheating.
1) The document presents an experimental study on reducing frost accumulation in a refrigerator evaporator coil by applying a 662 S-silicone grease coating.
2) Experiments were conducted with varying water loads kept in the refrigerator over time periods of 25, 50, and 75 hours, with and without the silicone grease coating on the evaporator. Less frost accumulated on the coated evaporator across all experiments.
3) The silicone grease coating is proposed to reduce frost accumulation due to its smooth, low-temperature resistant, and non-wetting properties which allow water droplets to easily roll off the surface. Reducing frost accumulation could improve refrigerator performance and efficiency.
A phase change material (PCM) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, PCMs are classified as latent heat storage (LHS) units.
This document discusses air conditioning and mechanical engineering. It is from Sana'a University and focuses on the work of Dr. Abduljalil Al-Abidi in the HVAC department. It covers several topics:
- The four conditions controlled by air conditioning: temperature, humidity, purity, and air velocity/circulation.
- Classification of air conditioning systems by function (comfort, industrial), season (winter, summer, year-round), and equipment arrangement (central, unitary, dual duct, variable air volume, variable refrigerant flow).
- Key processes in air conditioning like heating, cooling, humidifying, dehumidifying, cleaning, and air motion.
- Psychrometrics, the properties of
Presentation on Alternative Refrigerants related to mechanical engineering for application in mechanical systems (air conditoning and refrigerators etc) and chemical engineering
The document discusses refrigerants and their properties. It defines refrigerants as the primary working fluids used in refrigeration systems that absorb heat at low temperatures and release it at higher temperatures. Key properties of refrigerants include low boiling point, high latent heat, non-toxicity, and non-corrosiveness. The document also covers classifications of refrigerants such as halocarbon, azeotrope, inorganic, and hydrocarbons. Environmental impacts and economics are additional factors in refrigerant selection.
Intervento di due ore alla BTS 2013 di Montecatini Terme
"Un miliardo di utenti pronti a collaborare alla costruzione del nostro prodotto ed a promuovere la nostra struttura commentando e condividendo la loro esperienza nel nostro hotel .
Quali sono le leve da sfruttare e come stimolare in modo strategico l'interazione con attuali o potenziali clienti , monitorare a migliorare la brand reputation fino a disintermediare grazie ad un vero e proprio social revenue .
Strumenti , strategie e case histories
D.E.A.L. Disintermediazione , engagement , app e leading. Intervento alla BT...VARNER FERRATO
Il termine DEAL diventa una nuova formula per incrementare il ROI dell'hotel .
Il ROI si evince da una nuova ridefinizione dello stesso.
Idee per disintermediare aumentando l'engagement , con azioni di leading attraverso l'utilizzo delle app .
Slides I use in my workshop on Goal setting. It is a motivational 1.5 hour talk.. I am prepared to travel worldwide to deliver this seminar. Feel free to contact me at patlynch@stockmarkettraining.ie or call me at +353872416668
Adam Consulting is a global management consulting and corporate services firm providing expertise in various industries. It aims to exceed client expectations through transparency, honesty, integrity, respect, and speed with accuracy. The company offers services such as company formation, intellectual property services, outsourcing, hospitality consulting, language services, and has clients globally.
This document discusses the importance of knowing one's values in order to be the person you want to be. It provides exercises to help identify an individual's top values by imagining one's funeral and what would be said about their character. Key words from these imagined speeches can reveal core values like love, freedom and security. The document advises ranking values by importance and reflecting on what each value means in order to guide decision making and ensure one's actions align with who they aim to be.
Presentazione con il collega Nicola Zoppi in occasione di #noipiemonte organizzato da Bto Educational a Barolo il 17 Settembre 2013
Dalla recensione ai commenti sui social network , dalla reputazione alla qualità quali sono le leve su cui agire per arrivare a migliorare le performance dell'hotel ed arrivare al "social revenue"
Cryogenic refrigeration involves cooling materials to extremely low temperatures below -153°C using compressed gases like nitrogen and oxygen. It is achieved through a refrigeration cycle where a gas is compressed, cooled, expanded to condense and cool a material. Applications include producing rocket fuels, MRI machines, food storage and preservation, and cooling superconductors. Refrigerators receive star ratings from 1-5 stars based on their energy efficiency, with 5-star models using the most efficient compressors like inverters.
Cryogenic fluids like liquid nitrogen, helium, and hydrogen must be appropriately stored and transported after purification and liquefaction. Dewar vessels provide excellent thermal insulation to store these extremely cold liquids. Flexible vacuum-insulated hoses are commonly used to transfer cryogens between storage dewars and end uses, like laboratories. During transfer, highly effective insulation and consideration of two-phase fluid dynamics are needed to prevent heat leakage and maintain safe operations.
Cryogenics is the study of very low temperatures below -150°C and how materials behave at those temperatures. During World War II, scientists found that metals frozen to low temperatures showed more resistance to wear. A Dewar flask provides very good thermal insulation and is commonly used to store liquid nitrogen in laboratories. Liquid nitrogen boils at -196°C and is useful for many applications. Liquid helium exists only at 4K and is used to produce superconducting magnets. A superfluid has no viscosity and infinite thermal conductivity, allowing it to flow uncontrollably. MRI machines and electric power transmission use cryogenics.
The document discusses refrigeration and refrigeration cycles. It provides details on:
1) The basic components and process of a refrigerator, which uses ammonia as a refrigerant to draw heat from the freezer and fridge compartments via a compression and evaporation cycle.
2) Refrigeration cycles in general work by using a refrigerant to move heat from one place to another through evaporation and condensation.
3) The vapor compression refrigeration cycle involves compressing, condensing, expanding, and evaporating stages to transfer heat from the evaporator to the condenser.
This document discusses cryogenics, which is the science of producing very cold temperatures below 123 K. Some key applications of cryogenics mentioned include space applications like rocket propulsion using liquid hydrogen and oxygen, medicine like cryosurgery and cell preservation, food processing like freezing foods, industrial gas production through cryogenic distillation of air, superconductivity in technologies like MRI machines, and high energy physics experiments like those at CERN.
Refrigeration is defined as reducing and maintaining the temperature of materials below the surrounding temperature. There are several types of refrigeration including non-cyclic, cyclic, thermoelectric, and magnetic. Cyclic refrigeration includes vapor compression and vapor absorption refrigeration cycles which use a refrigerant and involve compression, condensation, expansion, and evaporation/cooling. Refrigeration has many commercial and industrial uses such as food transportation and storage.
This document discusses refrigeration and its various applications and methods. It begins by defining refrigeration as the process of achieving and maintaining a temperature below surroundings through the removal of heat. The main types of refrigeration are then listed as domestic, commercial, industrial, marine, air conditioning, and food preservation. Various natural and early mechanical refrigeration techniques are described, such as the use of icehouses and evaporative cooling. The ideal vapor compression refrigeration cycle is explained through its four processes. Absorption refrigeration using ammonia-water and lithium bromide-water systems is also summarized. Compressor types including reciprocating, rotary, and centrifugal are defined. Key refrigeration system components and their functions are outlined.
Cryogenic engines use cryogenic fuels that must be stored at extremely low temperatures in liquid form, such as liquid hydrogen at -253°C and liquid oxygen at -183°C. The basic principle is that the chemical energy from burning the cryogenic fuel in the thrust chamber is converted to kinetic energy through expansion in the rocket nozzle to produce thrust. Some key components of a cryogenic engine include the combustion chamber, fuel and oxidizer pumps, valves and regulators, fuel tanks, and rocket nozzle. Cryogenic engines provide high energy density but the low temperatures make storage and leakage challenges. They find applications in rocketry due to their performance and in other areas such as cooling and medical uses.
Cryogenics is the production and behavior of materials at very low temperatures, below 120K. There are four main methods for producing cryogenic temperatures: heat conduction, evaporative cooling, the Joule-Thomson effect, and adiabatic demagnetization. Cryogenics has many applications, including in rocket fuel as cryogenic liquids like liquid hydrogen provide high energy per unit mass. Other applications include cryosurgery, frozen food storage, and specialty effects using liquid nitrogen fog. Issues include the dangerous nature of handling cryogenic gases and liquids as well as storage challenges posed by low temperatures and high pressures.
This presentation is about cryogenic technology which includes working history and applications. tastefully added morph transition to add some aesthetic approach. Freely available to take reference from it don't copy directly make changes according to need
Submitted by sudarshan patil from D.N.Patel collage of engineering shahada
Refrigeration is a process that removes heat from an enclosed space to lower its temperature below the surrounding temperature. Zeolites are microporous minerals commonly used as commercial adsorbents. They have a crystalline structure made up of silicon, aluminum and oxygen tetrahedra that form pores and cavities. Zeolites can adsorb large amounts of water due to their porous structure and electrostatic fields. Their ability to adsorb water makes them promising candidates for solar refrigeration applications by utilizing the zeolite-water adsorption process.
Cryogenics is the study of extremely low temperatures produced by cryogens like liquid nitrogen and liquid helium. Liquid nitrogen is an inert, colorless, and odorless liquid used in many applications due to its ability to become extremely cold when evaporating. Cryogenic techniques are used in medical imaging, power transmission, food storage, infrared cameras, blood banking, rocket engines, metal processing, medical treatments, and research. Cryogenics enables important technologies and helps advance science.
This slide is about some new green cooling system (refrigeration system) and green refrigerant. For the Ozone layer depletion and green house effect, it is high time to find new refrigerant and refrigeration system.
Cryogenic treatment is a process that involves cooling materials like steel to very low cryogenic temperatures, typically between -150 to -300°C, to improve properties. There are two main types: shallow cryogenic treatment cools just the surface, while deep cryogenic treatment cools the entire cross-section. The cryogenic process modifies the material's microstructure and properties. Some benefits of cryogenic treatment for steels include improved wear resistance, hardness, and fatigue strength of cutting tools, dies, and other industrial parts. It can extend the lifetime of tooling and reduce manufacturing costs. Cryogenic treatment uses liquid nitrogen or helium stored in vacuum-insulated containers called Dewars to achieve very low temperatures needed.
This document provides an introduction and overview of refrigeration. It begins by defining refrigeration as the process of extracting heat from a low temperature source and transferring it to a higher temperature sink. A refrigeration system combines components in a sequential order to produce this refrigerating effect. Applications discussed include food preservation using refrigerators and freezers, as well as air conditioning. A brief history of developments in refrigeration technology is also presented.
The document discusses the design and fabrication of pulse tube refrigeration systems. It begins with an abstract describing how pulse tube refrigerators were first observed in the 1960s by Gifford and Longsworth. It then provides three sentences summarizing cryogenics and cryocoolers before discussing the specific types of cryocoolers in more detail over several chapters.
Cryogenics is the study of very low temperatures, including temperatures below -150°C that can be attained using cryogenic liquids like liquid nitrogen and liquid helium stored in Dewar flasks. Some key applications of cryogenics discussed include cryogenic rocket engines, which provide high energy per unit mass and were pioneered by the US and India. Cryogenic grinding is also discussed as an application, which avoids problems with heat generation, tool wear, and oxidation seen in conventional grinding. Both advantages like lower grinding costs and finer particle sizes, and disadvantages like high operating costs are reviewed. Health hazards associated with cryogenic liquids like frostbite and cold embrittlement are also summarized.
Cryogenic Applications and Importance of Cryogenic Vesselsinoxindia123
For the transportation of gases it is very important for storage and for that cryogenic storage vessel is required. Considering its importance also there are certain industrial application required in various sectors.
This document discusses cryogenics and its applications. Cryogenics involves producing and studying very low temperatures, from around -100°C to absolute zero. Common cryogenic liquids used are liquid nitrogen and helium. Liquid nitrogen condenses around -196°C and freezes at -210°C, while liquid helium boils at -269°C and does not freeze at atmospheric pressure. Cryogenic technology is used in rocket propulsion systems, medical cryosurgery, manufacturing, electronics, and fuel research. Some key applications include aerospace cryogenic engines, medical cryosurgery, frozen food transportation, and blood banking.
This document provides an introduction to refrigeration and vapor compression refrigeration systems. It begins with definitions of refrigeration and air conditioning. It then discusses the laws of thermodynamics and concepts like sensible heat, latent heat, and specific heat. It introduces the unit of refrigeration as ton of refrigeration. The document describes natural and artificial refrigeration methods. It provides diagrams and explanations of the reversed Carnot cycle, basic vapor compression refrigeration system and components like the evaporator, compressor, condenser and expansion device. The document concludes with analysis of the standard vapor compression refrigeration cycle on P-h charts.
“An Outlook of the Ongoing and Future Relationship between Blockchain Technologies and Process-aware Information Systems.” Invited talk at the joint workshop on Blockchain for Information Systems (BC4IS) and Blockchain for Trusted Data Sharing (B4TDS), co-located with with the 36th International Conference on Advanced Information Systems Engineering (CAiSE), 3 June 2024, Limassol, Cyprus.
Maruthi Prithivirajan, Head of ASEAN & IN Solution Architecture, Neo4j
Get an inside look at the latest Neo4j innovations that enable relationship-driven intelligence at scale. Learn more about the newest cloud integrations and product enhancements that make Neo4j an essential choice for developers building apps with interconnected data and generative AI.
Threats to mobile devices are more prevalent and increasing in scope and complexity. Users of mobile devices desire to take full advantage of the features
available on those devices, but many of the features provide convenience and capability but sacrifice security. This best practices guide outlines steps the users can take to better protect personal devices and information.
For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2024/06/building-and-scaling-ai-applications-with-the-nx-ai-manager-a-presentation-from-network-optix/
Robin van Emden, Senior Director of Data Science at Network Optix, presents the “Building and Scaling AI Applications with the Nx AI Manager,” tutorial at the May 2024 Embedded Vision Summit.
In this presentation, van Emden covers the basics of scaling edge AI solutions using the Nx tool kit. He emphasizes the process of developing AI models and deploying them globally. He also showcases the conversion of AI models and the creation of effective edge AI pipelines, with a focus on pre-processing, model conversion, selecting the appropriate inference engine for the target hardware and post-processing.
van Emden shows how Nx can simplify the developer’s life and facilitate a rapid transition from concept to production-ready applications.He provides valuable insights into developing scalable and efficient edge AI solutions, with a strong focus on practical implementation.
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Discover how Changi Airport Group (CAG) leverages graph technologies and generative AI to revolutionize their search capabilities. This session delves into the unique search needs of CAG’s diverse passengers and customers, showcasing how graph data structures enhance the accuracy and relevance of AI-generated search results, mitigating the risk of “hallucinations” and improving the overall customer journey.
AI 101: An Introduction to the Basics and Impact of Artificial IntelligenceIndexBug
Imagine a world where machines not only perform tasks but also learn, adapt, and make decisions. This is the promise of Artificial Intelligence (AI), a technology that's not just enhancing our lives but revolutionizing entire industries.
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Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
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Partecipate alla presentazione per immergervi in una storia di interoperabilità, standard e formati aperti, per poi discutere del ruolo importante che i contributori hanno in una comunità open source sostenibile.
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UiPath Test Automation using UiPath Test Suite series, part 6DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 6. In this session, we will cover Test Automation with generative AI and Open AI.
UiPath Test Automation with generative AI and Open AI webinar offers an in-depth exploration of leveraging cutting-edge technologies for test automation within the UiPath platform. Attendees will delve into the integration of generative AI, a test automation solution, with Open AI advanced natural language processing capabilities.
Throughout the session, participants will discover how this synergy empowers testers to automate repetitive tasks, enhance testing accuracy, and expedite the software testing life cycle. Topics covered include the seamless integration process, practical use cases, and the benefits of harnessing AI-driven automation for UiPath testing initiatives. By attending this webinar, testers, and automation professionals can gain valuable insights into harnessing the power of AI to optimize their test automation workflows within the UiPath ecosystem, ultimately driving efficiency and quality in software development processes.
What will you get from this session?
1. Insights into integrating generative AI.
2. Understanding how this integration enhances test automation within the UiPath platform
3. Practical demonstrations
4. Exploration of real-world use cases illustrating the benefits of AI-driven test automation for UiPath
Topics covered:
What is generative AI
Test Automation with generative AI and Open AI.
UiPath integration with generative AI
Speaker:
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• Demo on Platform overview
• Q/A
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In this work, we equipped AFL, a popular fuzzer, with DIAR and examined two critical Linux libraries -- Libxml's xmllint, a tool for parsing xml documents, and Binutil's readelf, an essential debugging and security analysis command-line tool used to display detailed information about ELF (Executable and Linkable Format). Our preliminary results show that AFL+DIAR does not only discover new paths more quickly but also achieves higher coverage overall. This work thus showcases how starting with lean and optimized seeds can lead to faster, more comprehensive fuzzing campaigns -- and DIAR helps you find such seeds.
- These are slides of the talk given at IEEE International Conference on Software Testing Verification and Validation Workshop, ICSTW 2022.
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My slides at Nordic Testing Days 6.6.2024
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Climate Impact of Software Testing at Nordic Testing Days
Cryoref
1. in physics, cryogenics is the study of the production of very low temperature (below −150°C, −238°F or
123K) and the behavior of materials at those temperatures. A person who studies elements under
extremely cold temperature is called a cryogenicist. Rather than the relative temperature scales of
Celsius and Fahrenheit, cryogenicists use the absolute temperature scales. These are Kelvin (SI units) or
Rankine scale (Imperial & US units).
Definitions and distinctions
Cryogenics
The branches of physics and engineering that involve the study of very low temperatures, how
to produce them, and how materials behave at those temperatures.
Cryobiology
The branch of biology involving the study of the effects of low temperatures on organisms (most
often for the purpose of achieving cryopreservation).
Cryosurgery
The branch of surgery applying very low temperatures (down to -196 °C) to destroy malignant
tissue, e.g. cancer cells.
Cryonics
The emerging medical technology of cryopreserving humans and animals with the intention of
future revival. Researchers in the field seek to apply the results of many sciences, including
cryobiology, cryogenics, rheology, emergency medicine, etc.
Cryoelectronics
The field of research regarding superconductivity at low temperatures.
Cryotronics
The practical application of cryoelectronics.
[edit] Etymology
The word cryogenics stems from Greek and means "the production of freezing cold"; however
the term is used today as a synonym for the low-temperature state. It is not well-defined at what
point on the temperature scale refrigeration ends and cryogenics begins, but most scientists[1]
assume it starts at or below -150°C or 123°K K (about -240°F). The National Institute of
Standards and Technology at Boulder, Colorado has chosen to consider the field of cryogenics as
that involving temperatures below −180°C (-292°F or 93.15°K). This is a logical dividing line,
since the normal boiling points of the so-called permanent gases (such as helium, hydrogen,
2. neon, nitrogen, oxygen, and normal air) lie below −180 °C while the Freon refrigerants,
hydrogen sulfide, and other common refrigerants have boiling points above −180°C.
[edit] Industrial application
Cryogenic valve
Further information: Timeline of low-temperature technology
Liquefied gases, such as liquid nitrogen and liquid helium, are used in many cryogenic
applications. Liquid nitrogen is the most commonly used element in cryogenics and is legally
purchasable around the world. Liquid helium is also commonly used and allows for the lowest
attainable temperatures to be reached.
These liquids are held in either special containers known as Dewar flasks, which are generally
about six feet tall (1.8 m) and three feet (91.5 cm) in diameter, or giant tanks in larger
commercial operations. Dewar flasks are named after their inventor, James Dewar, the man who
first liquefied hydrogen. Museums typically display smaller vacuum flasks fitted in a protective
casing.
Cryogenic transfer pumps are the pumps used on LNG piers to transfer liquefied natural gas
from LNG carriers to LNG storage tanks, as are cryogenic valves.
[edit] Cryogenic processing
The field of cryogenics advanced during World War II when scientists found that metals frozen
to low temperatures showed more resistance to wear. Based on this theory of cryogenic
hardening, the commercial cryogenic processing industry was founded in 1966 by Ed Busch.
With a background in the heat treating industry, Busch founded a company in Detroit called
CryoTech in 1966. Though CryoTech later merged with 300 Below to create the largest and
oldest commercial cryogenics company in the world, they originally experimented with the
possibility of increasing the life of metal tools to anywhere between 200%-400% of the original
life expectancy using cryogenic tempering instead of heat treating. This evolved in the late 1990s
into the treatment of other parts (that did more than just increase the life of a product) such as
amplifier valves (improved sound quality), baseball bats (greater sweet spot), golf clubs (greater
sweet spot), racing engines (greater performance under stress), firearms (less warping after
3. continuous shooting), knives, razor blades, brake rotors and even pantyhose. The theory was
based on how heat-treating metal works (the temperatures are lowered to room temperature from
a high degree causing certain strength increases in the molecular structure to occur) and
supposed that continuing the descent would allow for further strength increases. Using liquid
nitrogen, CryoTech formulated the first early version of the cryogenic processor. Unfortunately
for the newly born industry, the results were unstable, as components sometimes experienced
thermal shock when they were cooled too quickly. Some components in early tests even
shattered because of the ultra-low temperatures. In the late twentieth century, the field improved
significantly with the rise of applied research, which coupled microprocessor based industrial
controls to the cryogenic processor in order to create more stable results.
Cryogens, like liquid nitrogen, are further used for specialty chilling and freezing applications.
Some chemical reactions, like those used to produce the active ingredients for the popular statin
drugs, must occur at low temperatures of approximately −100°C (about -148°F). Special
cryogenic chemical reactors are used to remove reaction heat and provide a low temperature
environment. The freezing of foods and biotechnology products, like vaccines, requires nitrogen
in blast freezing or immersion freezing systems. Certain soft or elastic materials become hard
and brittle at very low temperatures, which makes cryogenic milling (cryomilling) an option for
some materials that cannot easily be milled at higher temperatures.
Cryogenic processing is not a substitute for heat treatment, but rather an extension of the heating
- quenching - tempering cycle. Normally, when an item is quenched, the final temperature is
ambient. The only reason for this is that most heat treaters do not have cooling equipment. There
is nothing metallurgically significant about ambient temperature. The cryogenic process
continues this action from ambient temperature down to −320 °F (140 °R; 78 K; −196 °C). In
most instances the cryogenic cycle is followed by a heat tempering procedure. As all alloys do
not have the same chemical constituents, the tempering procedure varies according to the
material's chemical composition, thermal history and/or a tool's particular service application.
The entire process takes 3–4 days.
[edit] Fuels
Another use of cryogenics is cryogenic fuels. Cryogenic fuels, mainly liquid hydrogen, have
been used as rocket fuels. Liquid oxygen is used as an oxidizer of hydrogen, but oxygen is not,
strictly speaking, a fuel. For example, NASA's workhorse space shuttle uses cryogenic hydrogen
fuel as its primary means of getting into orbit, as did all of the rockets built for the Soviet space
program by Sergei Korolev.
Russian aircraft manufacturer Tupolev developed a version of its popular design Tu-154 with a
cryogenic fuel system, known as the Tu-155. The plane uses a fuel referred to as liquefied
natural gas or LNG, and made its first flight in 1989.
[edit] Applications
Some applications of cryogenics:
4. Magnetic resonance imaging (MRI)
MRI is a method of imaging objects that uses a strong magnetic field to detect the relaxation of
protons that have been perturbed by a radio-frequency pulse. This magnetic field is generated
by electromagnets, and high field strengths can be achieved by using superconducting magnets.
Traditionally, liquid helium is used to cool the coils because it has a boiling point of around 4 K at
ambient pressure, and cheap metallic superconductors can be used for the coil wiring. So-called
high-temperature superconducting compounds can be made to superconduct with the use of
liquid nitrogen which boils at around 77 K.
Electric power transmission in big cities
It is difficult to transmit power by overhead cables in big cities, so underground cables are used.
But underground cables get heated and the resistance of the wire increases leading to waste of
power. Superconductors are frequently used to increase power throughput, requiring cryogenic
liquids such as nitrogen or helium to cool special alloy-containing cables to increase power
transmission.[citation needed].
Cryogenic gases delivery truck at a supermarket, Ypsilanti, Michigan
Frozen food
Cryogenic gases are used in transportation of large masses of frozen food. When very large
quantities of food must be transported to regions like war fields, earthquake hit regions, etc.,
they must be stored for a long time, so cryogenic food freezing is used. Cryogenic food freezing
is also helpful for large scale food processing industries.
Forward looking infrared (FLIR)
Many infra-red cameras require their detectors to be cryogenically cooled.
Blood banking
Certain rare blood groups are stored at low temperatures, such as -165 degrees C.
[edit] Production
Cryogenic cooling of devices and material is usually achieved via the use of liquid nitrogen,
liquid helium, or a cryocompressor (which uses high pressure helium lines). Newer devices such
as pulse cryocoolers and Stirling cryocoolers have been devised. The most recent development in
cryogenics is the use of magnets as regenerators as well as refrigerators. These devices work on
the principle known as the magnetocaloric effect.
[edit] Detectors
5. Cryogenic temperatures, usually well below 77 K (−196 °C) are required to operate cryogenic
detectors.
INTRODUCTION :
INTRODUCTION Cryogenics may be defined as the branch of physics which deals with the production of
very low temperature and their effect on matter. It may also be defined as the science and technology
of temperatures below 120K. The word “cryo” is derived from a Greek word “kruos” which means cold.
Methods to Produce Low Temperatures :
Methods to Produce Low Temperatures Magnetism produces low temperatures. When a material is
magnetized it becomes warm and cold when demagnetized in controlled atmosphere thus producing
low temperatures. By compressing the gas, the gas is cooled releasing heat and later allowed to expand
producing ultra low temperatures.
Cryogenics in fuels :
Cryogenics in fuels Fluids are stored at 93.5k(-180degree) or below Due to air friction ,it gets ignited
Cools engine on expansion. On expansion pressure increases providing high thrust Satellite payload
increases
Cryogenic Rocket Engines :
Cryogenic Rocket Engines Cryogenic rocket engines are one of the important applications in the field of
cryogenics. The higher thrust levels required for a rocket engines are achieved when liquid oxygen and
liquid hydrocarbons are used as fuel. But at atmospheric conditions, LOX and low molecular
hydrocarbons are in gaseous state. Therefore these are stored in liquid form by cooling them down
using cryogenics. Hence the name Cryogenic Rocket Engines.
VULCAIN 2 ROCKET ENGINE :
VULCAIN 2 ROCKET ENGINE THRUST -1359KN INLET CONDITIONS: LH2; Pressure=182.1bar
Temperature=36k LO2: Pressure=153.9 Temperature=96.7k Combustion chamber pressure=117.3bar
Thrust chamber mass=909kg
Cryogenic Heat Treatment :
Cryogenic Heat Treatment This is a process of treating metals, plastics, ceramics at temperatures below
120K to their crystal structures and properties. This increases their wear resistance, and life of metals
and plastics. They are used in the field of super conductors, cryo microbiology, and space programs.
6. Unlike other processes here permanent coating is completely impart through the metal surface. The
symbol used to represent cryogenic heat treatment
In alloy steels:- :
In alloy steels:- In this process the alloy steels are treated to convert the entire austenite into a
martensite matrix such it changes the molecular structure of the steel and forms an entirely new, more
refined grain structure which partly relieves the thermal stresses. The number of countable carbides
increase from 30,000 to 80,000 per square millimeter which forms a “super hard” surface on the metal.
After deep cryogenic heat treatment
Slide 9:
Before CI Processing After CI Processing Comparative microphotographs (1000x) of steel samples show
the change in microstructure produced by the controlled deep cryogenic process. Uniform, more
completely transformed microstructure and less retained austenite at right, is related to improvements
in strength, stability and resistance to wear. *Cryogenics International's Cryogenics International (CI)
was granted a U.S. patent for its revolutionary new computerized deep cryogenic treatment systems.
Cryogenics International now makes dramatic cost savings and increased productivity available to many
people and industries around the world.
Advantages of Cryogenic Processing :
Advantages of Cryogenic Processing The following properties are attained to the materials treated:-
Increases wear resistance Increases corrosion resistance Good dimensionality High strength Good
quality Cost reduction in the material manufactured Lower stress corrosion Cryogenic heat treatment
helps to reduce the stored stress in the metal by creating a unified bond between the crystals.
Slide 11:
This process is eco friendly in nature There is no waste deposition The nitrogen which used in the
process is liquefied from the atmosphere and later released back into it thereby creating no imbalance
to the ecosystem.
Cryogenic fuels :
Cryogenic fuels Cryogenics has made possible the commercial transportation of liquefied natural gas.
Without cryogenics, nuclear research would lack liquid hydrogen and helium for use in particle detectors
and for the powerful electromagnets needed in large particle accelerators. Such magnets are also being
used in nuclear fusion research.
7. Slide 13:
Cryogenic cooling is often used in space telescopes that observe objects in infrared and microwave
wavelengths. More efficient and compact cryocoolers allow cryogenic temperatures to be used in an
increasing variety of military, medical, scientific, civilian, and commercial applications, including infrared
sensors, superconducting electronics, and magnetic levitation trains.
Slide 14:
Cryogenics is used in artificial insemination to store semens and embryos. One such use in bio field is
Cryosurgery. Cryosurgery sometimes is referred to as cryotherapy or cryoablation. It is a surgical
technique in which freezing is used to destroy undesirable tissues. Liquid nitrogen, which boils at -196°C,
is the most effective cryogen for clinical use. Temperatures of -25°C to -50°C can be achieved within 30
seconds if a sufficient amount of liquid nitrogen is applied by spray or probe. Cryogenics in biology
Other uses of cryogenics :
Other uses of cryogenics IN SPORTS:- Cryogenics are also used to treat many types of sports equipment,
the most common being golf clubs. Because cryogenics increases the molecular density of treated
materials, it improves the distribution of energy (in this case kinetic energy) through the object. The
treatment also increases the rigidity of the metal, which in this case might affect the shaft of the golf
club. Combined, the increases in kinetic energy distribution and rigidity of the shaft make for a longer
and straighter drive.
Future of Cryogenics :
Future of Cryogenics Cryogenic rocket engine which will be used by NASA for its next manned moon
mission. ICICLES
CONCLUSION :
CONCLUSION From this presentation it can be concluded as cryogenics can be applied to almost
everywhere in every field. It finds its application in military, tooling industry, agricultural industry,
aerospace, medical, recycling, household, automobile industry, cryogenics is found to improve the grain
structure of everything treated be it metal or plastic or coils or engines or musical instruments or fiber.
This field could be put to many other applications in various fields. Its reaches in the mentioned
industries hold a good chance of extension. Hence Cryogenics proves to be very promising for the future
in this world of materials.
8. Improve
Cryogenic refrigeration is refrigeration which uses freezing mixtures such as dry ice, soilid co2,
liquid co2, or liquid nitrogen. In the liquid co2 or liquid nitrogen method, a compartment is fitted
with a temperature sensing element that can be preset. This is in turn connected to a control panel
which activates liquid co2 or liquid nitrogen cylinder fitted with regulators to release the
refrigerant. This is delivered through a spray header into the compartment until the desired
temperature is achieved.
What is cryogenics
Cryogenics is the study of the production of very low temperatures (below –150 °C, –238 °F or
123 K) and the behavior of materials at those temperatures. (Rather than the familiar
temperature...
What is the refrigeration
Many people have a misconception that Refrigeration is adding cold. The absence of heat is cold
and hence Refrigeration can be defined as the process of heat removal from any enclosed space
or...
What is refrigeration
Refrigeration is a heat removal process in which we reduce the surrounding temperature for the
preservative of food, or in medical treatment it is the lowering of a body's temperature for
therapeutic...
What is the net refrigeration effect in the refrigeration cycle
The quantity of heat that each pound of refrigerant absorbs from the refrigerated space to
produce useful cooling.
What is cryogenic refrigerant
Refrigerant is the medium contained in the system. Originally salt water, it progressed through
Freon to R18.
9. Cryogenic Refrigeration Equipment
Freezers for the Food Processing Industry
The Cryogenic Institute of New England, Inc. offers cryogenic refrigeration equipment for the
food processing industry. We are capable of manufacturing customized cryogenic refrigeration
systems built to our customers' specifications. Typical cryogenic refrigeration systems include
batch freezers, spiral freezers, single belt tunnel freezers, linear tunnel freezers and multipass
linear tunnel freezers. Most of these cryogenic refrigeration systems have the option of using
liquified nitrogen or liquified carbon dioxide as refrigerant. In addition, all our machines are
made of stainless steel for long in-service life.
At the present time, we have new batch freezers available including single batch freezers, double
batch freezers, dual batch freezers, cryo-test batch freezers and batch freezers with a rotating
product trolley.
Our batch freezers are available in an E-Class and S-Class trim level. The E-Class has insulated
panels with stainless steel cladding on the outside and fully welded stainless steel cladding
inside. The S-Class has fully welded stainless steel construction with injected high pressure
insulation. These machines have a small footprint, low capital cost, and are easy to maintain.
The spiral freezers that we offer come in standard models, but can also be made-to-order. Up and
down cage spiral freezer systems are available. These spiral freezers are highly efficient and
made for products that need long residence time. Temperature is automatically controlled. Belt
layouts can be set at 90-180-270 degrees, however standard spiral freezers come with straight
through belt layouts.
The single belt tunnel freezers that we provide are made for continuous food procesors in the
bakery, red meat, fish, poultry and vegetable industries. The standard product offerings are
capabler of cooling or freezing small items the size of a beef patty to large items such as loafs of
bread. These single belt freezers are built solely with stainless steel to ensure long service life
and trouble-free operation. Three different standard series machines are available. The P.O.D.B.
has a pneumatically operated dropping bottom. The H.O.T.L. which has a hydraulically operated
top lifting mechanism. Lastly, the H.O.D.B. which has a hydraulically operated dropping bottom.
Four standard belt widths are available including 26", 36", 48" and 60". Like all our machines,
this can be modified to suit your needs.
Another type of cryogenic refrigeration system that we offer is the multipass linear tunnel
freezers. In a multipass tunnel, the products move along multiple tiers of conveyer belts. The
speed of each belt can be independently controlled. Even cold temperature distribution can be
obtained through the optimum combination of recirculation and side wall fans. This allows the
10. belt loading density to be higher. Our standard machine has three belts. One standard series is
currently available named the H.O.T.L.; which stands for hydraulically operated top lifting. We
offer four standard belt widths including 26", 36", 48" and 60".
Here at the Cryogenic Institute of New England, Inc., we offer an independent review of your
application and can specify the most appropriate cryogenic equipment solution for your
requirements. We broker used cryogenic equipment, represent manufacturers of new cryogenic
equipment, modify off-the-shelf solutions for cryogenic applications or adapt existing cryogenic
equipment to specific industrial use. Our goal is to provide cost-effective cryogenic solutions that
will fit seamlessly within your existing operations.
THE CRYOGENIC REFRIGERATION PROCESS
MCR REFRIGERANT COMPOSITION
The Multi Component Refrigerant (MCR) has the following approximate composition:
Nitrogen (N2) 5%
Methane (CH4) (C1) 35%
Ethane (C2H6) (C2) 45%
Propane (C3H8) (C3) 10%
Butane (C4H10) (C4) 5%
The above MCR inventory is maintained by the controlled injection of required components
obtained from the fractionation unit. (Except for the Nitrogen which is provided by the Nitrogen
generation unit). Excess inventory can be vented to flare as needed.
The volume of MCR (as vapour) required to liquefy the feed gas is FOUR times the volume of
feed gas processed.
MCR COMPRESSION AND COOLING SYSTEM
(See Figure: 16)
Beginning at the MCR vapour return line from the Cryogenic towers - EC.1 (Main) and EC.2
(Sub). The cold MCR vapour flow through the sub-cryogenic tower is achieved by passing the
MCR from the tower bottom into a Venturi-tube placed in the main tower MCR outlet line. The
pressure drop across the Venturi gives sufficient DP across EC. 2. to provide the required MCR
flow. The 'A' bundle feed gas outlet temperature is controlled by a TCV placed in the outlet line.
The combined refrigerant flow at about 20 psig now passes to the MCR compression units. It
first enters a suction knock-out drum to prevent any liquid from entering the 1st stage
11. compressor. Any liquid which may separate out here is re-vaporised by a hot sparge gas injection
into the vessel bottom via a perforated pipe. This is done to preserve the total inventory of the
MCR vapour.
On leaving the KO drum, the make-up components are added to the MCR flow via control
systems. The MCR now passes into the 1st stage MCR compressor. This is a multi-stage,
centrifugal compressor drive by a condensing steam turbine. (A combustion Gas Turbine may be
used in some locations).
The first stage of compression increases the MCR to 125 psi and about 225 °F. It is then cooled
to about 110 °F in the inter-coolers and passed into the inter-stage drum where again, any liquid
dropout is re-vaporised by hot sparge gas.
A computerised flow controller (FRC) is placed in the compressor discharge line. Should the
Mass Flow drop below a pre-set point, the controller will begin to open the recycle valve and
take discharge gas back to the compressor suction to maintain a pre-set Minimum Flow through
the compressor. This is necessary to prevent 'Surging' in the compressor.
(Surging in this type of machine must be avoided in order to prevent damage to the compressor,
its internals and associated equipment and piping caused by high vibrations set up by the surging
action).
The 2nd stage MCR compressor takes suction from the inter-stage drum and raises the gas
pressure to 450 psi and about 250 °F. The MCR is discharged through the salt water cooled after-
coolers and piped to the first MCR separator D.1 on the main cryogenic tower EC. 1.
Again, as in the first stage, a computerised flow element meters the mass flow and controls a
recycle system for minimum flow protection against surging.
Both MCR compressors may be driven by condensing steam turbines or by combustion gas
turbines as required by the Company. Each machine also has over-pressure protection by safety
valves to flare, installed in the discharge line. Suction and discharge lines are fitted with electric
motor 'Remote Operated Valves' (ROV's) for quick operation if emergency operation is required.
The following simplified diagram (Figure: 16) shows the layout of the MCR compression
system.
12. Refrigeration - CRYOGENIC EXCHANGER - BASIC OPERATION
CRYOGENIC EXCHANGER - BASIC OPERATION
(See Figure: 17)
The MCR from the 2nd stage compression and cooling process enters the first separator D.1.
Here, the butane (C4) and some propane (C3) separate out as liquid.
REFRIGERANT VAPOUR FLOW
The MCR Vapour from D.1. is piped through the 'B' vapour coils of the main cryogenic tower
EC.1. (cooled by the sprays from D.5.), and into separator D.2. where C3 and some C4 separate
as liquid.
13. Vapour from D.2. is piped through the 'C' vapour coils (cooled by the sprays from D.6.), and into
separator D.3. where C2 and some C1 separate as liquid.
From D.3, the vapour is cooled in the 'D' bundles by sprays from D.7. then passes through 'E'
bundle cooled to -262 °F.
From the 'E' bundle the MCR, now mainly liquid Methane (C1) and Nitrogen (N2) passes into
D.4. via an expansion valve where the pressure gives a final refrigerant temperature of about -
275°F which feeds the 'E' bundle sprays. The vapour from D.4. is piped directly into the main
tower top.
The expansion valve at D.4. maintains the upstream MCR at high pressure - some pressure loss
from the original pressure occurs through the system, due to the liquids formed in the preceding
separators and friction due to the restriction to flow through the tube bundles and other fittings in
the system.
2. REFRIGERANT LIQUID FLOW
The C4/C3 liquid from D.1. is passed through the 'B' liquid coils and piped to Refrigerant drum
D.5. via an expansion valve (Temperature Control Valve) which controls the temperature of the
MCR vapour leaving the 'B' bundle. The expansion valve causes a sudden pressure drop in D.5.
and, due to the 'Joules-Thomson' effect the expansion of the high pressure liquid causes its
partial vaporisation and therefore a large decrease in its temperature. The cold vapour from D.5.
is passed directly into the main cryogenic tower. The sub-cooled liquid is sprayed over the 'B'
bundles i.e. the refrigerant liquid and vapour coils, and the Feed Gas coils, cooling the bundles to
the operation requirement. This begins the cryogenic process.
The MCR liquid (C3/C2), that separates out in D.2. passes through the 'C' MCR liquid bundles
before passing into D. 6. via the expansion valve. The pressure drop further reduces this liquid
temperature. This liquid is sprayed over the 'C' bundles thus further decreasing the temperature
of the three streams. (Upstream of the D.6. expansion valve, some refrigerant is piped to the
fractionation unit for the cooling process in the recovery of Methane & Ethane. This MCR is
returned to the system downstream of the D.5. expansion valve).
The MCR vapour from the 'C' bundles passes into D. 3. where C2/C1 liquids drop out to be piped
through the 'D' MCR liquid bundle, through the expansion valve into 'D. 7.' where the pressure
drop produces a much lower liquid MCR temperature.
This is sprayed over the 'D' bundles to give their required outlet temperatures.
The liquid refrigerant formed in D. 4. consists mainly of methane and some nitrogen after the
expansion valve produces a final MCR temperature of about - 275 °F.
This liquid is sprayed over the 'E' MCR vapour bundle and feed gas bundle to give an 'E' bundle
outlet temperature of - 262 °F.
14. The LNG leaving the 'E' bundle at - 262 °F and reduced pressure, passes through a TCV which,
due to its throttling action, will decrease the pressure further before the LNG finally enters the
rundown line to the LNG storage tanks.
The tanks' pressure is maintained at 0.5 psi (just above atmospheric pressure).
From storage the LNG is pumped into special cryogenic tankers for shipment abroad. Provision
is made to send off-spec LNG to burn-pit during start-up and shut-down operations.
15.
16. Cryogenic Compressors for Ever! The Development of the "Oxford" Cryocooler
Paul Bailey
The Need for Cooling
In the late 1970s there was a desire to learn more about the Earth's atmosphere, and a satellite
instrument called ISAMS (Improved Stratospheric And Mesospheric Sounder) was designed to
measure the vertical profiles of temperature in the atmosphere and also a number of the
atmospheric constituents.
The signal-to-noise ratio of this instrument would be enhanced if the sensor was kept at a
temperature of about 80 K. On the face of it this seems easy - space is a very cold place - but in
fact, satellites are NOT cold. Because of the size and mass of radiators, satellites are typically at
about 300 K, so a sensor at 80 K would need to be cooled in some way. The thermodynamic
cycle most suitable for this was the Stirling cycle, a gas cycle which, in theory, approaches the
ideal 'Carnot' efficiency.
Originally developed for producing power, the Stirling cycle can also be used for refrigeration.
The main components are a compressor, which produces pressure pulsations, and a cold head,
which contains a 'displacer piston' and heat exchangers. The displacer is synchronised with the
compressor piston and is usually operated at a phase angle of about 90° to the compressor piston.
Hence when the gas is expanding, much of the gas is at the cold end, and takes in heat from its
surroundings, and when it is compressed, the gas has been moved to the warm end, where heat is
rejected. By this means heat is pumped from a low temperature to a high temperature.
The specification for this cryocooler was:
1 Watt of cooling at 80 K, rejecting heat at 300 K
10 year life
230 K to 340 K survival temperature
Survival of launch vibration (non-operating)
Low exported vibration
High efficiency
NO MAINTENANCE POSSIBLE
The last requirement was the problem. A simple single cylinder reciprocating machine has at
least five bearings, and all of these need to be lubricated. With the 'cold end' of the cryocooler at
80 K, any oil would solidify and block the heat exchangers. Therefore the unit must be oil free.
There are a variety of oil free compressors - oil separators, ceramic pistons and metal or rubber
diaphragms have all been used, but all of them would need periodic maintenance to survive ten
years.
17. Early Development
The solution to this was provided by Dr Gordon Davey, who adapted a 'Pressure Modulator'
developed by Oxford's Atmospheric Physics Department. The key features of the new cryocooler
were:
Clearance Seals are not seals - they are leaks! If the radial clearance between piston and
cylinder is made small enough, the resulting leakage can be tolerated. The clearance needed is
10-20 µm, and this requires both piston and cylinder to be very cylindrical, with good
concentricity maintained between them.
Spiral Disc Springs are used to maintain the alignment of the piston within the cylinder (see
Figure 1). They are photoetched from thin sheet - an inexpensive process which can easily
generate the curved shapes required. The spring arms defined by the slots act as cantilevers
'built-in' at both ends. Axially the springs are compliant, allowing the piston to move up and
down in the cylinder, but radially they are stiff, so that the piston remains aligned concentrically
in the cylinder. A 10 year design life at 50 Hz is equivalent to 1.6 x 1010 cycles, so the material
used for the springs - usually austenitic stainless steel or beryllium copper - must have a "fatigue
limit", and the spring is designed so that the peak stress is safely below this limit.
Figure 1: Spiral disc spring
Linear Motion. A 'loudspeaker' type moving coil, permanent magnet motor is used to drive the
compressors. With the motor, piston and springs all aligned on a common axis, there are
negligible sideways forces during operation. A typical assembly suspended on spiral springs
would have a radial movement of ± 3 µm for a stroke of ± 5 mm.
A diagram of this machine is shown in Figure 2. The compressor has a moving shaft mounted on
two stacks of springs, with a moving piston in the cylinder at the top. The motor is positioned
between the two spring stacks. The cold head is of similar design, with the displacer housed in a
18. 'cold finger', the tip of which is connected to the sensor being cooled. The regenerator, which
stores heat as gas passes between the hot and cold ends of the displacer, is housed within the
displacer.
Machines to this basic design were made by the Rutherford-Appleton Laboratory and by
Oxford's Atmospheric Physics Department and flown on the ISAMS and ATSR experiments,
and the design was also developed by British Aerospace (and then Matra Marconi and Astrium),
Lucas, Ball and Hughes/Raytheon and several other companies.
Figure 2: Schematic of an early split Stirling cryocooler
Second Generation Cryocoolers
The first generation machines were expensive to make and difficult to assemble, and there was a
requirement for smaller, lower cost machines that would be suitable for non-space use. To meet
these requirements, an 'Integral' cryocooler was developed, which had the following
characteristics:
A single unit, with the displacer integral with the compressor
Moving cylinder and fixed piston
The long thin shaft of the early machines was replaced by a short fat tube acting as the moving
cylinder
Only one motor - the displacer is driven pneumatically by the pressure pulsation
More robust and easier to assemble
These units were developed in partnership with the Hymatic Engineering Company (now
Honeywell Hymatic) for 'tactical' and commercial markets, and there was also a transfer of
19. technology to TRW (now part of Northrop Grumman Space Technology (NGST)). These
licensing agreements are made through Isis Innovation, the University of Oxford's technology
transfer company.
The Third Generation
TRW had a requirement for a compressor to drive a cold head, but with tight restrictions on the
diameter and length of the compressor. To achieve this, a new moving coil motor was designed,
and improvements were made to the spiral disc springs. The original design developed into a
back-to-back configuration with two identical compressors acting on a common cylinder space,
and this was used as the basis for the High Efficiency Cryocooler (HEC), shown in Figure 3.
Figure 3: Northrop Grumman's HEC cryocooler
To develop this new machine, a three-way collaboration was established between:
Oxford University - original design & consultancy
Hymatic - detailed design and production
TRW - cold head and system design and integration
These machines were made using a carefully controlled production process, with extensive in-
process and acceptance testing. Over 20 of these 'flight' compressors have now been produced -
this may not seem a large number, but by the standards of space hardware it is huge.
20. From the original machine, which was a 6 cm3 balanced compressor, a range of units have been
developed from 26 cm3 (the High Capacity Cryocooler - HCC) to a 0.6 cm3 "Mini" unit. These
compressors are typically mated to a 'pulse tube' cold head, which uses simple plumbing
(typically an orifice and an 'inertance' tank), rather than a mechanical displacer, to give the
correct pressure-volume phase relationship at the cold head.
Heat Engines - the TASHE
In a collaboration with NGST, Hymatic and NASA's Los Alamos laboratory, one of the
compressors was used in a Thermo Acoustic Stirling Heat Engine. The TASHE was a prototype
for a prime mover to supply power for deep space or planetary missions, which would use
plutonium as a heat source.
In a thermo-acoustic engine, a high temperature gradient can excite acoustic oscillations in a gas.
If this source of sound is connected to a piston which resonates at the same frequency, it is
possible to get power out of the system.
In this prototype TASHE, an HEC compressor was modified by increasing the size of the
pistons, and these were mated to a thermo-acoustic engine: instead of converting electricity into
pressure pulsations, the compressors acted in reverse - absorbing acoustic power and generating
AC electricity. The complete system achieved a thermal efficiency of 18% with an electrical
power output of 40 W.
Valved Compressors
All of the machines mentioned so far have an oscillating flow - the compressors are "AC"
devices used to produce a pressure oscillation. By adding valves, these compressors can be used
to create a "DC" flow through a system. One application for this is in conventional vapour
compression refrigeration, or to produce a flow for a Joule-Thomson (J-T) cooler.
An example of the latter is a system being developed by NGST to cool the Mid-Infra-Red
Instrument (MIRI) on the James Webb Space Telescope - the successor to the Hubble. The MIRI
instrument requires 65 mW of cooling at 6 K, and the system being developed consists of a three
stage pulse tube cooler powered by an HCC compressor, which is used to pre-cool the bottom
stage, which is a J-T system with a valved HEC compressor.
The prototype valved compressor was built by Oxford and Hymatic, and is being tested on the
complete J-T system by NGST.
Computer Cooling
Oxford has just started a new project which will further develop the valved linear compressor.
Computers have reached the stage where performance is being limited by the heat generated in
CPU chips. Because they are very small, the heat flux required to cool them is higher than can be
obtained with a forced convection heat sink clamped to the top surface.
21. Suitable heat fluxes can be obtained by evaporative cooling, especially if a very fine extended
heat transfer surface can be formed into the surface of the chip, which would become the
'evaporator' of a conventional vapour compression refrigerator. The problem with an 'off-the-
shelf' system is the presence of oil, which circulates with the refrigerant, and would quickly find
its way to the fine extended surface, which it would block.
The Oxford compressors provide a solution to this problem - the clearance seal/spring system
requires no lubrication and produces no debris that would foul the extended surface. Oxford has
just started a three-year project, in collaboration with Newcastle University and London South
Bank University, to develop this technology.
The moving coil compressors used to date are too expensive to be used in applications such as
these, so a new low-cost moving magnet linear motor has been designed. Instead of magnetic
yokes machined from pure iron, and delicate moving coils, the new motor uses silicon-iron
laminations and conventional windings similar to those in a standard rotary motor.
Oil Free Compressors
There are several other benefits of oil free compressors.
The absence of oil makes these compressors suitable for use with high purity and medical gases,
where oil cannot be tolerated.
Oil acts as a catalyst for the breakdown of refrigerants at high temperatures in vapour
compression systems. Oil free compression could widen the choice of refrigerants and increase
the possible temperature range.
It is inefficient to control conventional refrigerators by on/off cycling. The output of a linear
compressor can be easily modulated by reducing the stroke, which can be done by dropping the
supply voltage.
Do They Live Forever?
No.
But they should last a long time; there are very few failure mechanisms in these simple machines
- the springs are unlikely to fail, there is no wear and no oil or debris to cause blockages.
There is the potential for electrical failure within the machine, particularly soldered joints, but
failure of external controls and drive electronics is much more likely.
The one definite failure mode is gas leakage. Space cryocoolers are typically tested to ensure that
the leak rate is less than 5 x 10-7 mbar l/s, which is equivalent to a pressure drop of about 1% in
25 years; pressure drops of 5% or so would be tolerable before the efficiency would fall
significantly.
22. Life test data compiled for "Oxford" type machines in 1998 showed a total of 49 machine-years
with no failures. More recent data from cryocoolers flown on satellites shows one failure in 38
machine-years (this was a displacer failure - the compressor was OK).
The future prospects of the "Oxford" compressor are very promising. The third generation
compressors are very compact and robust, and have a high performance. They have been used
for valved compressors and as a part of a heat engine. The new moving magnet concept will lead
to a lower cost machine, and this will encourage its much wider use.
Mechanical & Cryogenic Refrigeration
Recent reports within the food processing industry indicate that the average cost of food freezing
is up to 12 cents more per pound with the use of Cryogenic systems than with a similar
Mechanical system. This dramatic discrepancy is the result of costly, non-renewable Liquid
Nitrogen (LN) consumption.
According to conservative estimates, LN costs approximately 3 cents per pound. Depending
upon the product, cryogenic freezing can consume between 0.5 and 1.5 pounds of gas for every
pound of product. Therefore, a production system that runs 40 hours per week at 5,000 pounds
per hour will incur an operating cost of $27,000 per
month. A similar mechanical, air-blast system
will use 35 kilowatt-hours of electricity, resulting in a monthly energy bill around $630
(assuming 10 cent per kilowatt-hour rates).
Still, many food processors continue to turn to cryogenic solutions for the relatively low initial
capital investment. In spite of the rapid pay-back period for mechanical systems, some sources
maintain that cryogenic systems are feasible for start-up operations, but should be replaced with
mechanical solutions as soon as the investment can be made.
According to Process Engineering & Fabrication president, Bob Amacker, “When testing the
market for your product, it may be savvy to keep capital expenditures low. However, once you
have gained a clearer picture of the demand for your product and increased confidence in your
ability to fill that demand, it is best to switch to the lowest long-term cost option.” With a pay-
back period under 2 years, mechanical freezing is that option. Given that a cryogenic system
could incur variable costs in excess of $2 million over a 10-year period, the initial price of a
similar spiral system is negligible.
23. Food processors still face important considerations in the mechanical/cryogenic
debate. Cryogenic tunnels do not have a clear advantage in factory footprint over conventional
spiral freezers, but cryogenic spiral freezers are clearly the most compact option. Issues of
factory footprint, crust freezing, and freeze-rate favor cryogenic spirals, whereas spirals with
mechanical freezing reduce operation costs significantly, and are the best choice for the long-
term.