Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes
1. What is Heat Transfer?
2. APPLICATIONS OF HEAT TRANSFER
3. MODES OF HEAT TRANSFER
4. CONDUCTION
5. Fourier’s law of heat conduction
6. CONVECTION
7. Newton’s law of cooling
8. RADIATION
9. Stefan–Boltzmann law
Fluid Flow, Heat and Mass Transfer at Bodies of Different Shapes: Numerical Solutions presents the current theoretical developments of boundary layer theory, a branch of transport phenomena. Also, the book addresses the theoretical developments in the area and presents a number of physical problems that have been solved by analytical or numerical method. It is focused particularly on fluid flow problems governed by nonlinear differential equations. The book is intended for researchers in applied mathematics, physics, mechanics and engineering.
1. What is Heat Transfer?
2. APPLICATIONS OF HEAT TRANSFER
3. MODES OF HEAT TRANSFER
4. CONDUCTION
5. Fourier’s law of heat conduction
6. CONVECTION
7. Newton’s law of cooling
8. RADIATION
9. Stefan–Boltzmann law
Fluid Flow, Heat and Mass Transfer at Bodies of Different Shapes: Numerical Solutions presents the current theoretical developments of boundary layer theory, a branch of transport phenomena. Also, the book addresses the theoretical developments in the area and presents a number of physical problems that have been solved by analytical or numerical method. It is focused particularly on fluid flow problems governed by nonlinear differential equations. The book is intended for researchers in applied mathematics, physics, mechanics and engineering.
Introduction
Mechanism of Heat Flow
Conduction
Heat Flow through a Cylinder-Conduction
Conduction through fluids
Convection
Film type condensation
Cold liquid-boiling of liquids
Modes of Feed-Heat Transfer
Thermal Radiation
Black Body
Grey body
Equipments
References
2.1 Heat
Heat is a form of energy. According to the principle of thermodynamics whenever a physical or chemical transformation occurs heat flow into or leaves the system.
A number of sources of heat are used for industrial scale operations steam and electric power is the chief sources to transfer heat. It is essential to cover steam without any loses to the apparatus in which it is used. The study of heat transfer processes helps in be signing the plant efficiently and economically
2.2 Heat Transfer:-
Work is one of the basic modes of energy transfer in machines the action of force on a moving body is identified as work. The work is done by a force as it acts upon a body moving in the direction of the force.
Work transfer is considered as occurring between the system and the surroundings work is said to be done by a system is the sole effect on things external to the system can be reduced to the raising of a weight.
If a system has a non-adiabatic boundary its temperature is not independent of the temperature of the surroundings and for the system between the states 1 and 2 the work w depends on path and the differential d-w is inexact. The work depends on the terminal state 1 and 2 as well as non-adiabatic path connecting them. For consistency with the principle of conservation of energy. Some type of energy transfer must have occurred because of the temperature difference between the system and its surroundings and it is identified as heat thus when an effect in a system occurs solely as result of temperature difference between the system and some other system the process in which the effect occur shall be called a transfer of heat from the system at the higher temperature to the system at the lower temperature.
1.1 Evaporation
1.2 Distillation
1.3 Drying
1.4 Crystallization
1.5 Sterilization
Application of Heat Transfer in Pharmaceuticals Industries
Heat is a form of energy. According to the principle of thermodynamics whenever a physical or chemical transformation occurs heat flow into or leaves the system.
A number of sources of heat are used for industrial scale operations steam and electric power is the chief sources to transfer heat. It is essential to cover steam without any loses to the apparatus in which it is used. The study of heat transfer processes helps in be signing the plant efficiently and economically
Fluid Mechanics introduction for UG students
Fluid properties
Reynolds experiment
Manometer
Orificemeter
Venturimeter
Pitot tube
Rotameter
Current flow meter
Introduction
Mechanism of Heat Flow
Conduction
Heat Flow through a Cylinder-Conduction
Conduction through fluids
Convection
Film type condensation
Cold liquid-boiling of liquids
Modes of Feed-Heat Transfer
Thermal Radiation
Black Body
Grey body
Equipments
References
2.1 Heat
Heat is a form of energy. According to the principle of thermodynamics whenever a physical or chemical transformation occurs heat flow into or leaves the system.
A number of sources of heat are used for industrial scale operations steam and electric power is the chief sources to transfer heat. It is essential to cover steam without any loses to the apparatus in which it is used. The study of heat transfer processes helps in be signing the plant efficiently and economically
2.2 Heat Transfer:-
Work is one of the basic modes of energy transfer in machines the action of force on a moving body is identified as work. The work is done by a force as it acts upon a body moving in the direction of the force.
Work transfer is considered as occurring between the system and the surroundings work is said to be done by a system is the sole effect on things external to the system can be reduced to the raising of a weight.
If a system has a non-adiabatic boundary its temperature is not independent of the temperature of the surroundings and for the system between the states 1 and 2 the work w depends on path and the differential d-w is inexact. The work depends on the terminal state 1 and 2 as well as non-adiabatic path connecting them. For consistency with the principle of conservation of energy. Some type of energy transfer must have occurred because of the temperature difference between the system and its surroundings and it is identified as heat thus when an effect in a system occurs solely as result of temperature difference between the system and some other system the process in which the effect occur shall be called a transfer of heat from the system at the higher temperature to the system at the lower temperature.
1.1 Evaporation
1.2 Distillation
1.3 Drying
1.4 Crystallization
1.5 Sterilization
Application of Heat Transfer in Pharmaceuticals Industries
Heat is a form of energy. According to the principle of thermodynamics whenever a physical or chemical transformation occurs heat flow into or leaves the system.
A number of sources of heat are used for industrial scale operations steam and electric power is the chief sources to transfer heat. It is essential to cover steam without any loses to the apparatus in which it is used. The study of heat transfer processes helps in be signing the plant efficiently and economically
Fluid Mechanics introduction for UG students
Fluid properties
Reynolds experiment
Manometer
Orificemeter
Venturimeter
Pitot tube
Rotameter
Current flow meter
Virus, infectious agent of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria. The name is from a Latin word meaning “slimy liquid” or “poison.”
Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans as a source for tinder, traditional medicine, food, and entheogens, as well as their dangers, such as toxicity or infection.
In the late 16th century several Dutch lens makers designed devices that magnified objects, but in 1609 Galileo Galilei perfected the first device known as a microscope. Dutch spectacle makers Zaccharias Janssen and Hans Lipperhey are noted as the first men to develop the concept of the compound microscope.
In the late 16th century several Dutch lens makers designed devices that magnified objects, but in 1609 Galileo Galilei perfected the first device known as a microscope. Dutch spectacle makers Zaccharias Janssen and Hans Lipperhey are noted as the first men to develop the concept of the compound microscope.
Microbial Spoilage include the contamination of Pharmaceutical products with the microbes which lead to spoilage of the product affecting Drug safety and quality, and is not intended for use. Shortly Microbial Spoilage is defined as deterioration of pharmaceutical products by the contaminant microbe.
In the late 16th century several Dutch lens makers designed devices that magnified objects, but in 1609 Galileo Galilei perfected the first device known as a microscope. Dutch spectacle makers Zaccharias Janssen and Hans Lipperhey are noted as the first men to develop the concept of the compound microscope.
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats
Microbiology is the study of organisms that are usually too small to be seen by the unaided eye; it employs techniques—such as sterilization and the use of culture media—that are required to isolate and grow these microorganisms.
Bacteria have existed from very early in the history of life on Earth. Bacteria fossils discovered in rocks date from at least the Devonian Period (419.2 million to 358.9 million years ago), and there are convincing arguments that bacteria have been present since early Precambrian time, about 3.5 billion years ago.
Bacteria are microscopic, single-celled organisms that thrive in diverse environments. These organisms can live in soil, the ocean and inside the human gut. Humans' relationship with bacteria is complex. Sometimes bacteria lend us a helping hand, such as by curdling milk into yogurt or helping with our digestion
Bacteria are microscopic, single-celled organisms that thrive in diverse environments. These organisms can live in soil, the ocean and inside the human gut. Humans' relationship with bacteria is complex. Sometimes bacteria lend us a helping hand, such as by curdling milk into yogurt or helping with our digestion
Diuretics, also called water pills, are medications designed to increase the amount of water and salt expelled from the body as urine. There are three types of prescription diuretics. They're often prescribed to help treat high blood pressure, but they're used for other conditions as well.
The main site of diuretic action is well established for the different groups of diuretics: carbonic anhydrase inhibitors act on the proximal tubulus, loop diuretics on the diluting segment, thiazides on the cortical diluting segment/distal tubulus, and potassium-sparing agents on distal tubulus/collecting ducts.
Diuretics, also called water pills, are medications designed to increase the amount of water and salt expelled from the body as urine. There are three types of prescription diuretics. They’re often prescribed to help treat high blood pressure, but they’re used for other conditions as well.
Proton-pump inhibitors are a group of medications whose main action is a pronounced and long-lasting reduction of stomach acid production. Within the class of medications, there is no clear evidence that one agent works better than another. They are the most potent inhibitors of acid secretion available.
The main site of diuretic action is well established for the different groups of diuretics: carbonic anhydrase inhibitors act on the proximal tubulus, loop diuretics on the diluting segment, thiazides on the cortical diluting segment/distal tubulus, and potassium-sparing agents on distal tubulus/collecting ducts.
In conclusion, the present study found that esomeprazole 40 mg daily may be more effective than either omeprazole 20 mg daily, pantoprazole 40 mg daily or lansoprazole 30 mg daily for the rapid relief of heartburn symptoms in patients with endoscopically proven reflux esophagitis.
Mechanisms of diuretic drugs. Diuretic drugs increase urine output by the kidney (i.e., promote diuresis). This is accomplished by altering how the kidney handles sodium. If the kidney excretes more sodium, then water excretion will also increase.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
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These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
2. Heat is a form of energy associated with
disordered and chaotic movement of
molecules and ions. The higher the
temperature of a material, the faster the
molecules and ions are moving, and
hence the greater the amount of energy
present as heat.
A substance will have no heat content only
if it is at a temperature of absolute zero (0
K).
Heat is a form of energy and hence can be
measured and expressed in Joules,
practically in Kilo joules (KJ; a 1000 times)
or Mega joules (MJ; 1000 000 times).
e.g. It takes about 65kJ of heat to raise
200mL of water from room temperature to
its boiling point.
3. Heat transfer is the exchange
or movement of heat energy
and will occur spontaneously
wherever there is a
temperature gradient. The
rate of heat transfer indicates
how quickly heat is
exchanged and is expressed
in J s-1 or watts (W).
Many Pharmaceutical processes
involve the transfer of heat:
• Melting materials.
• Creating an elevated
temperature during cream,
suppository or ointment
production.
• Controlled cooling of the
same products.
• Heating of solvents to hasten
dissolution processes.
• Sterilization of products e.g.
using steam in autoclaves.
• Heating or cooling of air in air-
conditioning plant.
• Drying granules for tablet
production.
4. Methods of heat transfer
Heat transfer can take place by three
methods:
1. Conduction
2. Convection
3. Radiation
1. Conduction – Heat transfer by
conduction in solids result from the
movement of heat energy to adjacent
molecules by vibrational energy transfer
and the motion of free electrons. No
mixing action is involved so that the
conduction is limited to solids and fluids
that are ‘bound’ in some way that
prevents free movement.
2.
The molecule/electron donating the heat
energy will subsequently vibrate to a lesser
extent and therefore cool down whereas
the molecule receiving the heat energy will
vibrate to a greater extent and therefore
increase in temperature.
In case of a solid no appreciable
movement of the molecules occurs.
Heat transfer due to electron movement
is generally a greater effect than that
due to vibration of atoms. Therefore,
metallic solids (more free electrons) are
better conductors of heat than non-
metallic solids.
In static fluid (and therefore through
boundary layers) the mechanisms are
virtually the same. Heat is transferred
between molecules as a result of
molecular collisions.
Gases become better conductors at
higher temperatures owing to the faster
movement of the molecules, whereas
most liquids (with the notable exception
of water) become poorer conductors at
higher temperatures.
5. Methods of heat transfer
2. Convection – Heat transfer by convection is due to the movement of
molecules and their associated heat energy on a macroscopic scale. It
involves the mixing of molecules and occurs within fluids, where the
molecules are free to move around. This process can occur naturally (e.g.
warm less dense air rises in the atmosphere to be replaced by colder more
dense air) and forcefully by moving the fluid mechanically using e.g. mixing
blade.
If forced convection also induces turbulent flow then the heat transfer process
is aided as there will be a reduction in the fluid boundary layer thickness. It is
a faster process compared to conduction.
3. Radiation – Heat transmission by radiation occurs by energy transfer
through space (even vacuum) by electromagnetic radiation. E.g. the energy
emitted by the sun. These waves can be reflected, transmitted or absorbed.
When they are absorbed by a material on which they fall, energy reappears
as heat and the material increases in temperature. Heat transfer by radiation
is only of pharmaceutical practical importance during microwave drying. Black
colored objects are the perfect emitter and absorber of radiation, although all
bodies radiate to some extent.
6. Heat energy from the gas burner is transferred by conduction through the
container wall to the water in the bath, which therefore increases in
temperature until its boiling point is reached. This heat gained is referred to
as sensible heat, as it produces an appreciable rise in temperature and
the change can be detected by the senses.
When the boiling point is reached, further heat generates steam without
further increase in temperature. This heat gain by the steam is termed
latent heat of evaporation or latent heat of vaporization.
Conduction
7. • The steam produced rises and contacts
the cool outer surface of the dish wall
and condenses giving up its latent heat
and forming a condensate layer on the
wall that runs down and drops back
into the water bath. Fresh condensate
is continually formed to take its place.
• The latent heat that is liberated by the
condensation passes by conduction
through the wall of the dish and into
the contents to be heated. Heat is then
transferred through the fluid by
natural convection and conduction.
• The advantage of using
steam as a heat transfer
agent in this setup:
– Causes indirect heating where
the temperature can never
exceed 100˚C (at atmospheric
pressure) and therefore there
is less chance of localized
overheating damaging the
product being heated.
– Since the steam circulates
over the whole dish surface,
heating is much more uniform
than It would have been if the
dish was heated directly over
the gas flame.
8. TS = steam temperature
TL = temperature of the
boiling liquid
TI and TO = temperature of the
inner and outer
surface of the dish
Above, heat transfer/flow undergoes three barriers which are the condensate layer, the dish
wall & the liquid side boundary.
The rate of heat transfer i.e. the quantity of heat transferred (Q, Joules) in
unit time (t, seconds) depends on the temperature difference between inner
and outer surface, the dish thickness LD and the area available for heat
transfer A.
Introducing a proportionality constant KD, the factors can be combined as:-
Q/t = KD A (TO – TI)/LD
9. • KD is also known as the co-efficient of thermal
conductivity and expressed in W/m K. It gives an
indication of the ability of the material to conducti heat;
higher the value, the more easily heat is conducted.
Question: Calculate the quantity of heat passing in
a period of 4 minutes through a pure Aluminium
dish (204 W/m K) whose effective heating surface
area is 30cm2 and whose thickness is 1.5mm, if the
temperature at the surfaces of the dish are 90˚C
and 75˚C respectively.
10. Steam as a heating medium
• The most commonly used heating medium. The reasons for
continued widespread use of steam include:
1. The raw material (water) is cheap and plentiful
2. It is easy to generate, distribute and control
3. It is generally cheaper than viable alternative forms of
heating e.g. electricity.
4. It is clean, almost colorless and tasteless, and so
accidental contamination of the product is less likely to
be serious like diesel and patrol. It is therefore also
environment friendly.
5. It has a high heat content (in the form of latent heat)
and can heat materials very quickly.
6. The heat is given up at a constant temperature, which
is useful in controlling heating processes and in
sterilization.
11. From kinetic theory of heat, a vapor contains heat in two
forms:-
i) Sensible Heat:- can be detected by the sense, i.e. a
temperature change when sensible heat is taken up or
given out.
ii) Latent Heat:- invisible heat, not detected as a
temperature change. So it is taken up or given out at
constant temp. as a change of phase between solid or
liquid or vapor.
Both of these heat contents are very important properties
of steam.
12. Converting ice to steam
Initially the heat supplied will be used to convert ice to liquid
without any rise in temperature (latent heat of fusion).
Latent heat of fusion - The heat absorbed as a substance
changes phase from solid to liquid. Specific latent heat of water
(LF) is equal to 334 kJ kg-1.
So, for 1kg water, latent heat of fusion = 334 kJ
F
F
13. The specific heat capacity equation can be used to calculate
the amount of energy required to raise the temperature of liquid
water to its boiling point.
14. All the heat supplied will be sensible heat to rise the temperature of the
water (0˚C) to the boiling point 100˚C.
The heat required is given by –
mass of water x specific heat capacity x temp. rise
1kg 4.2 KJ 100˚C
So, 420 KJ requires to raise 1kg water to its boiling point. Once the water
has reached boiling point, further heat energy input will not raise the
temperature of the water but will convert the boiling water at 100˚C to
steam at 100˚C. Steam at a temperature corresponding to the water boiling
point at that pressure (as in this case) is referred to as saturated steam.
15. The steam at this instance contains 2260 kJ of latent heat energy.
Steam in this state is referred to as dry saturated steam, as all the
liquid water has been converted to steam. This form of steam should
ideally be used for heating and sterilization processes as it contains
maximum latent heat energy and no associated air or water.
So only if further heated, will some of water convert into steam by supplying
latent heat of vaporization at constant temp (100˚C).
Latent heat of vaporization - The heat absorbed as a substance changes
phase from liquid to vapor. Specific latent heat of water (LV) is equal to 2260
kJ kg-1. So, for 1kg liquid water at 100˚C to convert to steam at 100˚C it would
require 2260 kJ of energy.
V
V
16.
17. Dryness fraction: It is the fraction of water converted to steam
at particular time. Latent heat of vaporization is 2260 kJ/kg, so
it requires 0.5x2260 = 1130 kJ heat to produce dryness
fraction of 0.5.
Once all the water has been converted to steam, any further
heat energy input increases the steam temperature i.e. the
steam gains sensible heat. Steam at a temperature above the
saturation temperature is called superheated steam.
18. Design of Heating Equipment
Considering the factors affecting heat transfer, a number of precautions
must be taken in designing equipment for heating operation, especially
when steam is the source of heat.
1. AREA - Heating should take place over as surface as possible.
Q/t=Kd A(To – Ti)/Ld
2. TEMPERATURE GRADIENT - a suitable temperature gradient should
be employed, theoretically, as great as possible. But this is not in
practice-
a) Many pharmaceutical substances are thermo-labile & would be
damaged with a contact of high temperature surface.
b) Liquids boiling on hot surface form irregular streams of vapor
bubbles. Each stream originates from a point on the surface, called
nucleate boiling (Boiling in which bubble formation is at the liquid-
solid interface rather than from external or mechanical devices).
Above a critical surface temperature however, evolution of vapor is so
rapid that it cannot escape and the surface acquires a blanket of vapor
which forms an additional resistance to heat transfer, known as film
boiling.
19. 3. MATERIALS OF CONSTRUCTION – The plant should be made from
materials of suitable thermal conductivity.
4. GENERAL DESIGN - The design of plant construction should be such
that resistance due to surface layers are minimized.
a. Air Removal – Elimination, as far as possible, of air in steam is of
extreme importance. Film of air if present reduces the overall co-
efficient of heat transfer (4% air reduces 3/4th of co-efficient value!).
Moreover, the total pressure will be a mixture of a partial pressure
of air and steam, i.e. the temperature of the mixture will be lower
than that of saturated steam at same pressure.
b. Cleanliness - The surfaces of the vessel should be kept clean and
free from deposits of solids or scale.
c. Condensate Removal – The system should be arranged to permit
correct drainage and removal of the condensate formed as the
steam gives up its heat. The system could include a steam trap, a
device to distinguish between water & steam, allowing the former to be
discharged & the latter retained.
d. Liquid Circulation – Turbulent flow should be maintained by
avoiding awkward shapes where stagnation might occur and using
forced circulation if natural circulation is inadequate due to density
or viscosity changes.