Thermal qualities like temperature, heat, and heat transfer mechanisms are important for building design. Temperature is measured in degrees Celsius and heat is measured in joules. Heat transfers between objects through conduction, convection, and radiation based on temperature differences. A building's heat transfer is analyzed using factors like U-value, solar gain, ventilation rate, and time-lag. Maintaining a building's thermal balance requires considering all heat exchange between the interior and exterior environments.
This document provides an introduction to heat transfer and thermodynamics concepts. It discusses how heat transfer, thermodynamics, and various energy concepts are related. The three main modes of heat transfer - conduction, convection and radiation - are introduced, along with the governing equations for each. Fourier's law of heat conduction, Newton's law of cooling, and the Stefan-Boltzmann law of radiation are outlined. The document also discusses combined heat transfer mechanisms, thermal properties, and applications of heat transfer concepts.
Analysis of Band Gap of Thermoelectric materialsIOSR Journals
This document analyzes how the band gap of thermoelectric materials changes with temperature. It discusses that the band gap, which affects electrical conductivity and thermoelectric performance, decreases as temperature increases. This is because interatomic spacing increases with higher thermal energy. The document then calculates the band gap of germanium, silicon, and gallium arsenide at different temperatures using a specified formula involving material constants and temperature. It finds that the band gap decreases most significantly in germanium as temperature rises, making it useful for enhancing thermoelectric performance through doping or catalysis.
Temperature has a major influence on animal energetics. For animals with variable body temperatures, metabolic rate fluctuates with environmental temperature, while animals that maintain a constant temperature expend energy to do so. Enzymatic reaction rates are highly temperature dependent, so organisms regulate internal temperatures compatible with metabolic reactions. Animals can acclimate to temperature changes through adjustments to enzyme quantities and membrane lipid compositions that stabilize metabolic function over a range of temperatures. Heat transfer between animals and their environments involves conduction, convection, radiation, evaporation and heat storage.
Thermal physics discusses kinetic molecular theory and Brownian motion. Heat is defined as the flow of energy from a warm object to a cooler object. Heat energy is the result of atomic/molecular movement in solids, liquids and gases. Temperature is a measure of heat energy, with higher temperatures indicating faster particle movement. Thermometers measure temperature using various methods like liquid expansion. Thermal conduction transfers heat through particle collisions, while convection transfers heat through fluid movement. Radiation transfers heat as electromagnetic waves. The greenhouse effect occurs naturally but is enhanced by human emissions, contributing to global warming.
The document discusses the physical principles of heat and its properties, including definitions of key terms like heat, temperature, specific heat, types of heat transfer (conduction, convection, radiation), and latent heat. It also covers the differences between moist heat and dry heat as well as superficial heat and deep heat. Physiological effects of heat like increased metabolism and blood flow are also outlined.
This summary provides an overview of key concepts about thermal energy and temperature from the document:
The document discusses different theories of heat and temperature over time, from the caloric theory to the modern kinetic molecular theory. It also explains concepts such as thermal energy, temperature, heat transfer through conduction, convection and radiation, specific heat, and changes of state. The first and second laws of thermodynamics are introduced, with the first law stating that thermal energy can increase through heat or work, and the second law stating that natural processes increase the total entropy of the universe.
Thermal qualities like temperature, heat, and heat transfer mechanisms are important for building design. Temperature is measured in degrees Celsius and heat is measured in joules. Heat transfers between objects through conduction, convection, and radiation based on temperature differences. A building's heat transfer is analyzed using factors like U-value, solar gain, ventilation rate, and time-lag. Maintaining a building's thermal balance requires considering all heat exchange between the interior and exterior environments.
This document provides an introduction to heat transfer and thermodynamics concepts. It discusses how heat transfer, thermodynamics, and various energy concepts are related. The three main modes of heat transfer - conduction, convection and radiation - are introduced, along with the governing equations for each. Fourier's law of heat conduction, Newton's law of cooling, and the Stefan-Boltzmann law of radiation are outlined. The document also discusses combined heat transfer mechanisms, thermal properties, and applications of heat transfer concepts.
Analysis of Band Gap of Thermoelectric materialsIOSR Journals
This document analyzes how the band gap of thermoelectric materials changes with temperature. It discusses that the band gap, which affects electrical conductivity and thermoelectric performance, decreases as temperature increases. This is because interatomic spacing increases with higher thermal energy. The document then calculates the band gap of germanium, silicon, and gallium arsenide at different temperatures using a specified formula involving material constants and temperature. It finds that the band gap decreases most significantly in germanium as temperature rises, making it useful for enhancing thermoelectric performance through doping or catalysis.
Temperature has a major influence on animal energetics. For animals with variable body temperatures, metabolic rate fluctuates with environmental temperature, while animals that maintain a constant temperature expend energy to do so. Enzymatic reaction rates are highly temperature dependent, so organisms regulate internal temperatures compatible with metabolic reactions. Animals can acclimate to temperature changes through adjustments to enzyme quantities and membrane lipid compositions that stabilize metabolic function over a range of temperatures. Heat transfer between animals and their environments involves conduction, convection, radiation, evaporation and heat storage.
Thermal physics discusses kinetic molecular theory and Brownian motion. Heat is defined as the flow of energy from a warm object to a cooler object. Heat energy is the result of atomic/molecular movement in solids, liquids and gases. Temperature is a measure of heat energy, with higher temperatures indicating faster particle movement. Thermometers measure temperature using various methods like liquid expansion. Thermal conduction transfers heat through particle collisions, while convection transfers heat through fluid movement. Radiation transfers heat as electromagnetic waves. The greenhouse effect occurs naturally but is enhanced by human emissions, contributing to global warming.
The document discusses the physical principles of heat and its properties, including definitions of key terms like heat, temperature, specific heat, types of heat transfer (conduction, convection, radiation), and latent heat. It also covers the differences between moist heat and dry heat as well as superficial heat and deep heat. Physiological effects of heat like increased metabolism and blood flow are also outlined.
This summary provides an overview of key concepts about thermal energy and temperature from the document:
The document discusses different theories of heat and temperature over time, from the caloric theory to the modern kinetic molecular theory. It also explains concepts such as thermal energy, temperature, heat transfer through conduction, convection and radiation, specific heat, and changes of state. The first and second laws of thermodynamics are introduced, with the first law stating that thermal energy can increase through heat or work, and the second law stating that natural processes increase the total entropy of the universe.
1. Three main modes of energy transfer in soil are conduction, convection, and radiation. Conduction involves direct particle contact, convection involves bulk fluid movement, and radiation does not require matter.
2. The surface energy balance equation states that energy in equals energy out at the soil surface. This includes net radiation, heat flux into soil, sensible heat flux to air, and latent heat from evaporation.
3. Thermal conductivity describes a material's ability to conduct heat and is measured in watts per meter-kelvin. It is dependent on soil composition, texture, water content, and compaction. Thermal diffusivity incorporates conductivity and describes the speed of heat propagation.
Okay, let's solve this step-by-step:
* Jogger generates 8.0x105 J of heat in 0.5 hours = 3,600 seconds
* Jogger's mass is 65 kg
* Specific heat capacity of the human body is 3500 J/(kg°C)
* Use the heat equation: Q = cmΔT
* Plug in the values: 8.0x105 J = (65 kg) x (3500 J/(kg°C)) x ΔT
* Solve for ΔT: ΔT = 8.0x105 J / (65 kg x 3500 J/(kg°C)) = 1°C
Therefore, if the heat were
The document discusses various concepts related to thermal heat gain and loss in buildings, including:
- Thermal conductivity, resistivity, conductance, and resistance, which describe the ability of materials to allow heat to pass through them.
- Time lag and decrement factor, which characterize periodic heat flow patterns as outdoor temperatures fluctuate daily.
- Methods for calculating conduction, convection, radiation, and ventilation heat exchange in buildings.
- The concept of sol-air temperature, which combines radiant and convective heating effects on buildings.
- Factors like solar gain factor and surface conductance that influence a building's absorption of solar heat gain.
the branch of physical science that deals with the relations between heat and other forms of energy (such as mechanical, electrical, or chemical energy), and, by extension, of the relationships between all forms of energy.
The document discusses heat and thermodynamics, specifically:
1) The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
2) The second law states that it is impossible to convert all heat into work, some heat must be wasted.
3) Heat transfer occurs through conduction, convection, or radiation, moving from warmer to cooler bodies until equilibrium is reached.
Thermal energy naturally transfers from hotter to colder objects through three main methods:
(1) Conduction, where energy transfers through direct contact of particles in substances or between substances;
(2) Convection, where the flow of fluids like gases or liquids transfers energy; and
(3) Radiation, where electromagnetic waves transfer energy without requiring contact between objects. Technologies like furnaces and refrigerators control the rate of heating and cooling through these thermal energy transfer methods.
This document summarizes an experiment to measure the out-of-plane thermal conductivity of flexible substrate materials like polyethylene naphthalate (PEN) and polyethylene teraphthalate (PET). A steady-state method is used where a heat flux is applied through one copper block in contact with the substrate, and the temperature difference across the substrate is measured. Thermal conductivity values are determined from the temperature differences and heat fluxes for substrates of varying thicknesses. The results indicate low thermal conductivity for flexible substrates, which could challenge thermal management in flexible electronics due to limited heat spreading and lack of active cooling options.
This document discusses heat, energy, temperature, and the three methods of heat transfer: conduction, convection, and radiation. It defines key terms like heat, thermal energy, temperature, and explains that heat transfer occurs due to temperature differences between objects. The kinetic molecular theory is also summarized, stating that matter is made up of particles in random motion, possessing kinetic energy.
The document discusses various topics related to heat and thermodynamics including:
1) Heat is a form of energy transferred between objects due to a temperature difference, not a substance that flows.
2) The internal energy of a substance is the total energy of all its molecules. Temperature measures average kinetic energy.
3) Specific heat is a property that determines how much heat is required to change an object's temperature.
This document analyzes energy and exergy of all-glass evacuated solar collector tubes with coaxial fluid conduits. It models T-type and H-type collector tubes using an analytical solution to the energy balance equations. The results show good agreement with previous research. The effects of working fluid properties, tube properties, mass flow rate, solar radiation, temperature, and optical efficiency on outlet temperature, energy efficiency, and exergy efficiency are investigated. The H-type model has higher outlet temperatures and exergy efficiency than the T-type model. Changing the delivery tube properties does not affect outlet temperature but using a selective absorber coating does increase it.
An introductory outline of the Physics of Heat. I created this presentation at Curtin Sarawak Malaysia as a basis for Foundation Physics students and others to edit and expand. Except where otherwise noted, this work is licensed under the Creative Commons Attribution-Share Alike 2.5 Malaysia License.
This document discusses heat transfer and thermal transport in lithium-ion battery cells. The key points are:
1) Thermal conduction within lithium-ion battery cells is dominated by the thermal contact resistance between the cathode and separator, which accounts for around 88% of the total thermal resistance.
2) Measured values of the thermal contact resistance between the cathode and separator agree with theoretical models that account for weak adhesion between the materials.
3) Chemically bridging the cathode-separator interface using an amine reduces the thermal contact resistance by 4 times without negatively impacting electrochemical performance, resulting in an expected 3-fold increase in effective thermal conductivity and 60% reduction in peak temperature rise.
1. Thermodynamics is the study of heat and its relationship to other forms of energy. It describes how heat is converted between thermal energy and other types of energy and how this affects matter.
2. Around 1850, Rudolf Clausius and William Thomson introduced thermodynamics and established the first two laws: the first law states that total energy is conserved, and the second law states that heat does not spontaneously flow from cold to hot bodies.
3. Thermodynamics is concerned with various states and processes involving properties like heat, temperature, thermal energy, and entropy. The laws of thermodynamics establish foundational principles about energy transfer and conservation.
Wk 5 p1 wk 6-p2_12.1-12.2_thermal properties of materialschris lembalemba
Thermal properties of materials can be explained using a kinetic molecular model. Melting and boiling occur at constant temperatures as energy input goes towards overcoming intermolecular forces rather than increasing kinetic energy. Specific heat capacity is the energy required to raise 1kg of a substance by 1°C, while specific latent heats refer to phase changes. The first law of thermodynamics states that the change in internal energy of a system equals heat supplied plus work done on the system.
The document discusses different forms of energy including kinetic energy, potential energy, thermal energy, and nuclear energy. It explains how kinetic energy depends on an object's mass and velocity, and how potential energy depends on an object's mass, height, and gravitational acceleration. The document also covers energy transformations, calculations of kinetic and potential energy, heat transfer through conduction, convection and radiation, and applications of energy including refrigeration and human thermoregulation.
Thermal energy, also called heat energy, is the transfer of energy between objects due to a temperature difference. Temperature is measured in degrees Celsius and indicates how hot an object is, while heat is measured in Joules and refers to the quantity of thermal energy transferred. The specific heat capacity of a substance is the amount of heat energy required to raise its temperature by one degree and one kilogram, and can be used to calculate the energy needed to change an object's temperature. Heat naturally transfers from hotter to cooler objects until they reach thermal equilibrium.
TFESC-12963_Said et al (Piezofan Project)John Bates
This document summarizes a study that investigated the effect of gap distance on heat transfer performance of a piezoelectric fan oriented parallel to a heated surface. Heat transfer coefficient maps were generated for gap distances of 1mm, 3mm, and 5mm. The 3mm gap produced the highest peak heat transfer coefficients and provided optimal cooling for most heater sizes tested. Analysis of centerline heat transfer profiles and optimization contours indicated that while a 1mm gap provided better coverage, the 3mm gap performed best overall and was the optimal configuration for most applications.
Exergy analysis of magnetic refrigerationManoj maurya
The document discusses magnetic refrigeration and exergy analysis of magnetic refrigeration cycles. It explains the magnetocaloric effect and how magnetic fields can be used to achieve cooling via adiabatic demagnetization. Key equations presented include those relating the magnetocaloric effect to changes in magnetic field and temperature. The document also summarizes the reversible Brayton refrigeration cycle used in magnetic refrigeration and equations for the exergy efficiency and exergy destroyed. Major breakthroughs in 1997 that accelerated progress in the field are noted. In closing, the summary states that magnetic refrigeration provides an effective and efficient cooling method and has improved significantly since initial work in the 1920s-1930s.
The document discusses various topics related to the transfer of heat, including:
1. The three main modes of heat transfer are conduction, convection, and radiation. Conduction involves the transfer of heat between particles without particle movement, convection involves heat transfer via actual particle movement, and radiation transfers heat directly via electromagnetic waves.
2. When thermal radiation falls on an object, it can be absorbed, transmitted, or reflected. The absorptance, transmittance, and reflectance of an object describe these properties.
3. Blackbody radiation follows several laws, including Wien's displacement law and Stefan's law. Wien's law states the wavelength of peak emission is inversely proportional to temperature,
Review on Design and Theoretical Model of Thermoelectricijsrd.com
This paper presents the theoretical development of the equations that allow to evaluate the performance of an air conditioning system based on the thermoelectric effect. The cooling system is based on a phenomena discovered by Jean Charles Athanase Peltier, in 1834. According to this when electricity runs through a junction between two semiconductors with different properties, heat is dissipated or absorbed. Thus, thermoelectric modules are made by semiconductors materials sealed between two plates through which a continuous current flows and keeps one plate hot and the other cold. The most important parameters to evaluate the performance of the device thermoelectric refrigeration are the coefficient of performance, the heat pumping rate and the maximum temperature difference between the hot side and the cold side of the thermoelectric module.
Development of microclimate personal cooling system based on thermoelectric e...Ijrdt Journal
This document describes the development of a personal cooling system using thermoelectric cooling. It aims to maintain a stable core body temperature for workers in high heat environments. The system involves a cooling vest with water circulating tubes to remove a calculated heat load of 206W and keep skin temperature at 35°C. Heat transfer calculations are shown to determine the load from environmental, metabolic, and evaporative sources. Copper tubing is considered for its high thermal conductivity, with alternatives like PPS and LCP also evaluated. The low-cost, lightweight thermoelectric cooling vest could maintain core temperatures in situations where air conditioning is not possible.
1. Three main modes of energy transfer in soil are conduction, convection, and radiation. Conduction involves direct particle contact, convection involves bulk fluid movement, and radiation does not require matter.
2. The surface energy balance equation states that energy in equals energy out at the soil surface. This includes net radiation, heat flux into soil, sensible heat flux to air, and latent heat from evaporation.
3. Thermal conductivity describes a material's ability to conduct heat and is measured in watts per meter-kelvin. It is dependent on soil composition, texture, water content, and compaction. Thermal diffusivity incorporates conductivity and describes the speed of heat propagation.
Okay, let's solve this step-by-step:
* Jogger generates 8.0x105 J of heat in 0.5 hours = 3,600 seconds
* Jogger's mass is 65 kg
* Specific heat capacity of the human body is 3500 J/(kg°C)
* Use the heat equation: Q = cmΔT
* Plug in the values: 8.0x105 J = (65 kg) x (3500 J/(kg°C)) x ΔT
* Solve for ΔT: ΔT = 8.0x105 J / (65 kg x 3500 J/(kg°C)) = 1°C
Therefore, if the heat were
The document discusses various concepts related to thermal heat gain and loss in buildings, including:
- Thermal conductivity, resistivity, conductance, and resistance, which describe the ability of materials to allow heat to pass through them.
- Time lag and decrement factor, which characterize periodic heat flow patterns as outdoor temperatures fluctuate daily.
- Methods for calculating conduction, convection, radiation, and ventilation heat exchange in buildings.
- The concept of sol-air temperature, which combines radiant and convective heating effects on buildings.
- Factors like solar gain factor and surface conductance that influence a building's absorption of solar heat gain.
the branch of physical science that deals with the relations between heat and other forms of energy (such as mechanical, electrical, or chemical energy), and, by extension, of the relationships between all forms of energy.
The document discusses heat and thermodynamics, specifically:
1) The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
2) The second law states that it is impossible to convert all heat into work, some heat must be wasted.
3) Heat transfer occurs through conduction, convection, or radiation, moving from warmer to cooler bodies until equilibrium is reached.
Thermal energy naturally transfers from hotter to colder objects through three main methods:
(1) Conduction, where energy transfers through direct contact of particles in substances or between substances;
(2) Convection, where the flow of fluids like gases or liquids transfers energy; and
(3) Radiation, where electromagnetic waves transfer energy without requiring contact between objects. Technologies like furnaces and refrigerators control the rate of heating and cooling through these thermal energy transfer methods.
This document summarizes an experiment to measure the out-of-plane thermal conductivity of flexible substrate materials like polyethylene naphthalate (PEN) and polyethylene teraphthalate (PET). A steady-state method is used where a heat flux is applied through one copper block in contact with the substrate, and the temperature difference across the substrate is measured. Thermal conductivity values are determined from the temperature differences and heat fluxes for substrates of varying thicknesses. The results indicate low thermal conductivity for flexible substrates, which could challenge thermal management in flexible electronics due to limited heat spreading and lack of active cooling options.
This document discusses heat, energy, temperature, and the three methods of heat transfer: conduction, convection, and radiation. It defines key terms like heat, thermal energy, temperature, and explains that heat transfer occurs due to temperature differences between objects. The kinetic molecular theory is also summarized, stating that matter is made up of particles in random motion, possessing kinetic energy.
The document discusses various topics related to heat and thermodynamics including:
1) Heat is a form of energy transferred between objects due to a temperature difference, not a substance that flows.
2) The internal energy of a substance is the total energy of all its molecules. Temperature measures average kinetic energy.
3) Specific heat is a property that determines how much heat is required to change an object's temperature.
This document analyzes energy and exergy of all-glass evacuated solar collector tubes with coaxial fluid conduits. It models T-type and H-type collector tubes using an analytical solution to the energy balance equations. The results show good agreement with previous research. The effects of working fluid properties, tube properties, mass flow rate, solar radiation, temperature, and optical efficiency on outlet temperature, energy efficiency, and exergy efficiency are investigated. The H-type model has higher outlet temperatures and exergy efficiency than the T-type model. Changing the delivery tube properties does not affect outlet temperature but using a selective absorber coating does increase it.
An introductory outline of the Physics of Heat. I created this presentation at Curtin Sarawak Malaysia as a basis for Foundation Physics students and others to edit and expand. Except where otherwise noted, this work is licensed under the Creative Commons Attribution-Share Alike 2.5 Malaysia License.
This document discusses heat transfer and thermal transport in lithium-ion battery cells. The key points are:
1) Thermal conduction within lithium-ion battery cells is dominated by the thermal contact resistance between the cathode and separator, which accounts for around 88% of the total thermal resistance.
2) Measured values of the thermal contact resistance between the cathode and separator agree with theoretical models that account for weak adhesion between the materials.
3) Chemically bridging the cathode-separator interface using an amine reduces the thermal contact resistance by 4 times without negatively impacting electrochemical performance, resulting in an expected 3-fold increase in effective thermal conductivity and 60% reduction in peak temperature rise.
1. Thermodynamics is the study of heat and its relationship to other forms of energy. It describes how heat is converted between thermal energy and other types of energy and how this affects matter.
2. Around 1850, Rudolf Clausius and William Thomson introduced thermodynamics and established the first two laws: the first law states that total energy is conserved, and the second law states that heat does not spontaneously flow from cold to hot bodies.
3. Thermodynamics is concerned with various states and processes involving properties like heat, temperature, thermal energy, and entropy. The laws of thermodynamics establish foundational principles about energy transfer and conservation.
Wk 5 p1 wk 6-p2_12.1-12.2_thermal properties of materialschris lembalemba
Thermal properties of materials can be explained using a kinetic molecular model. Melting and boiling occur at constant temperatures as energy input goes towards overcoming intermolecular forces rather than increasing kinetic energy. Specific heat capacity is the energy required to raise 1kg of a substance by 1°C, while specific latent heats refer to phase changes. The first law of thermodynamics states that the change in internal energy of a system equals heat supplied plus work done on the system.
The document discusses different forms of energy including kinetic energy, potential energy, thermal energy, and nuclear energy. It explains how kinetic energy depends on an object's mass and velocity, and how potential energy depends on an object's mass, height, and gravitational acceleration. The document also covers energy transformations, calculations of kinetic and potential energy, heat transfer through conduction, convection and radiation, and applications of energy including refrigeration and human thermoregulation.
Thermal energy, also called heat energy, is the transfer of energy between objects due to a temperature difference. Temperature is measured in degrees Celsius and indicates how hot an object is, while heat is measured in Joules and refers to the quantity of thermal energy transferred. The specific heat capacity of a substance is the amount of heat energy required to raise its temperature by one degree and one kilogram, and can be used to calculate the energy needed to change an object's temperature. Heat naturally transfers from hotter to cooler objects until they reach thermal equilibrium.
TFESC-12963_Said et al (Piezofan Project)John Bates
This document summarizes a study that investigated the effect of gap distance on heat transfer performance of a piezoelectric fan oriented parallel to a heated surface. Heat transfer coefficient maps were generated for gap distances of 1mm, 3mm, and 5mm. The 3mm gap produced the highest peak heat transfer coefficients and provided optimal cooling for most heater sizes tested. Analysis of centerline heat transfer profiles and optimization contours indicated that while a 1mm gap provided better coverage, the 3mm gap performed best overall and was the optimal configuration for most applications.
Exergy analysis of magnetic refrigerationManoj maurya
The document discusses magnetic refrigeration and exergy analysis of magnetic refrigeration cycles. It explains the magnetocaloric effect and how magnetic fields can be used to achieve cooling via adiabatic demagnetization. Key equations presented include those relating the magnetocaloric effect to changes in magnetic field and temperature. The document also summarizes the reversible Brayton refrigeration cycle used in magnetic refrigeration and equations for the exergy efficiency and exergy destroyed. Major breakthroughs in 1997 that accelerated progress in the field are noted. In closing, the summary states that magnetic refrigeration provides an effective and efficient cooling method and has improved significantly since initial work in the 1920s-1930s.
The document discusses various topics related to the transfer of heat, including:
1. The three main modes of heat transfer are conduction, convection, and radiation. Conduction involves the transfer of heat between particles without particle movement, convection involves heat transfer via actual particle movement, and radiation transfers heat directly via electromagnetic waves.
2. When thermal radiation falls on an object, it can be absorbed, transmitted, or reflected. The absorptance, transmittance, and reflectance of an object describe these properties.
3. Blackbody radiation follows several laws, including Wien's displacement law and Stefan's law. Wien's law states the wavelength of peak emission is inversely proportional to temperature,
Review on Design and Theoretical Model of Thermoelectricijsrd.com
This paper presents the theoretical development of the equations that allow to evaluate the performance of an air conditioning system based on the thermoelectric effect. The cooling system is based on a phenomena discovered by Jean Charles Athanase Peltier, in 1834. According to this when electricity runs through a junction between two semiconductors with different properties, heat is dissipated or absorbed. Thus, thermoelectric modules are made by semiconductors materials sealed between two plates through which a continuous current flows and keeps one plate hot and the other cold. The most important parameters to evaluate the performance of the device thermoelectric refrigeration are the coefficient of performance, the heat pumping rate and the maximum temperature difference between the hot side and the cold side of the thermoelectric module.
Development of microclimate personal cooling system based on thermoelectric e...Ijrdt Journal
This document describes the development of a personal cooling system using thermoelectric cooling. It aims to maintain a stable core body temperature for workers in high heat environments. The system involves a cooling vest with water circulating tubes to remove a calculated heat load of 206W and keep skin temperature at 35°C. Heat transfer calculations are shown to determine the load from environmental, metabolic, and evaporative sources. Copper tubing is considered for its high thermal conductivity, with alternatives like PPS and LCP also evaluated. The low-cost, lightweight thermoelectric cooling vest could maintain core temperatures in situations where air conditioning is not possible.
This document describes the development of a personal cooling system based on thermoelectric cooling. The system aims to maintain a stable core body temperature for workers in extreme heat environments. It involves calculating the heat load that must be removed to keep core temperature at safe levels, designing a cooling vest with copper tubing, and using thermoelectric modules to cool water circulating through the tubes. Software and experimental analysis was conducted to test the design. The proposed low-cost, lightweight cooling vest could provide an alternative to air conditioning in harsh working conditions.
Review on Thermoelectric materials and applicationsijsrd.com
In this paper thermoelectric materials are theoretically analyzed. The thermoelectric cooler device proposed here uses semiconductor material and uses current to transport energy (i.e., heat) from a cold source to a hot source via n- and p-type carriers. This device is fabricated by combining the standard n- and p-channel solid-state thermoelectric cooler with a two-element device inserted into each of the two channels to eliminate the solid-state thermal conductivity. The heat removed from the cold source is the energy difference, because of field emitted electrons from the n-type and p-type semiconductors. The cooling efficiency is operationally defined as where V is the anode bias voltage The cooling device here is shown to have an energy transport (i.e., heat) per electron of about500 me V depending on concentration and field while, in good thermoelectric coolers, it is about 50-60 me V at room temperature.
This study measured the thermal conductivity and viscosity of TiO2 nanoparticles dispersed in deionized water at concentrations up to 3% volume fraction and temperatures from 13°C to 55°C. Thermal conductivity was measured using the 3ω method, which was validated on pure fluids. Results showed thermal conductivity increased with particle concentration but not anomalously, and was not strongly temperature dependent. Viscosity significantly increased with particle concentration beyond classical models, and decreased exponentially with temperature like the base fluid. Increasing temperature and particle concentration both increased heat transfer properties, with viscosity enhanced more than thermal conductivity.
Thermoelectric Refrigeration System Running On Solar Energypaperpublications3
Abstract: The global increasing demand for refrigeration in field of refrigeration, food preservation, storages, medical services, and cooling of electronic devices, led to production of more electricity and consequently more release of CO2 all over the world which it is contributing factor of global warming on climate change. With the increase awareness towards environmental degradation due to the production, use and disposal of Chloro Fluoro Carbons (CFCs) and Hydro Chlorofluorocarbons (HCFCs) as heat carrier fluids in conventional refrigeration and air conditioning systems. Thermoelectric refrigeration is new alternative because it can convert waste electricity into useful cooling, is expected to play an important role in today's energy challenges. It does not require working fluids or any moving parts, which is friendly to the environment and it simply uses electrons rather than refrigerants as a heat carrier. Continuous efforts are given by researchers for development of thermo electric materials with increase figure of merit may provide a potential commercial use of thermoelectric refrigeration system.
In this work it has been identified that there is enormous scope to develop TER system running on solar energy and its performance evaluation along with mathematical modeling. Mathematical results can be correlate by performing experimental test set up. Present paper especially focuses on evaluation of numbers of thermoelectric cooling module; heat sink fan assembly for each module which is used to increase heat dissipation rate and time required for attaining the cooling of heat sink fan assembly after a solar power is applied.
The document discusses thermoelectric generators and their working principles. Thermoelectric generators can directly convert temperature differences into electricity through the Seebeck effect and vice versa through the Peltier effect. They have applications in waste heat recovery from vehicles, industry, and solar power generation due to their solid-state operation without moving parts. However, their efficiency is still relatively low. The document also discusses thermoelectric materials and provides examples of applications of thermoelectric generators in Egypt.
1. The document is a project report on thermoelectric refrigeration written by Debasis Ray for his degree examination in physics.
2. It provides background on the historical discoveries of the Seebeck, Peltier, and Thomson effects that form the basis of thermoelectric cooling.
3. Thermoelectric coolers have no moving parts, provide precise temperature control, and can operate in any orientation, making them suitable for applications in electronics, medical, aerospace, and other industries.
Electricity Generation using Thermoelectric System from Waste Heat of Flue Gasesijsrd.com
Energy related cost have become a significant fraction of cost in any industry. The three top operating expenses are often to be found in any industry like energy (both electrical and thermal), labour and materials. If we were found the manageability of the above equipment's the energy emerges a top ranker. So energy is best field in any industry for the reduction of cost and increasing the saving opportunity. Thermoelectric methods imposed on the application of the thermoelectric generators and the possibility application of Thermoelectrity can contribute as a "Green Technology" in particular in the industry for the recovery of waste heat. Finally the main attention is too focused on selecting the thermoelectric system and representing the analytical and theoretical calculation to represent the Thermoelectric System.
Ivanolegov thermodynamics serbian 4th edition test bank 1Ivan Olegov
Thermal energy is the energy a compound or system has due to its temperature, i.e., the power of moving or shaking molecules, according to the Power Education web site of the Texas Education Company. Thermodynamics involves determining this energy, which can be "exceptionally complicated," according to David McKee, a teacher of physics at Missouri Southern State University. Commonly this is idealized as the mass of the system, the stress of the system, and the quantity of the system, or some various other comparable set of numbers.
The document discusses entropy and the second law of thermodynamics. It provides three key points:
1) Entropy is a measure of unavailable or unusable energy in a system. It quantifies the disorder or randomness in a closed system, which always increases over time as the system tends towards equilibrium.
2) The second law of thermodynamics states that heat cannot spontaneously flow from a cold body to a hot body. This is equivalent to requiring that the net entropy change in such a process be positive.
3) The second law limits the maximum possible efficiency of heat engines and converters. No engine can be 100% efficient because this would require violating the second law by decreasing total entropy.
Solar Energy based Refrigeration System using Peltier Device 18 ABHISHEK.pdfkeshavkumar403723
This document summarizes a research paper on a solar energy-based refrigeration system using Peltier devices. The system utilizes solar energy to power thermoelectric modules that provide refrigeration without the need for refrigerants or mechanical devices like compressors. The system is intended to provide refrigeration to remote areas without reliable power sources. It describes the construction of the refrigeration system, including the thermoelectric module, refrigeration chamber, battery, solar cells, and frame. It also provides background on thermoelectric effects like the Peltier effect that allow the system to operate.
The document compares the experimental performance of a thermoelectric refrigerator to a vapor compression refrigerator. It finds that for 325 ml of water cooled from 32°C to below 6°C:
- In the commercial refrigerator's freezer compartment, the water temperature decreased linearly with time, taking 61 minutes to reach 6°C.
- In the thermoelectric refrigerator, the water temperature decreased exponentially with time, taking 69 minutes to reach 6°C.
- For most of the cooling time, the thermoelectric refrigerator cooled at a faster rate than the commercial refrigerator.
Thermodynamic Principal #chemical engineering microproject Mr.pradip Waghmare
The document discusses the second law of thermodynamics in several parts:
1) It states that the second law asserts that processes occur in a certain direction and that energy has quality as well as quantity.
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effective, pollution free forms of energy conversion, aiming at efficiencies as high as possible. Low-dimensional structures have proved to be promising candidates for enhancing the thermoelectric properties of semiconductors. Here, we discuss the idea of implementation of dense arrays of armchair graphene nanoribbons in microfabricated structures to develop planar unileg thermoelectric microgenerators to convert heat fl ow into electrical energy. This paper is a discussion on energy scavenging to provide power autonomy to devices on a human body i.e., thermoelectric conversion of human heat and thereby summarizes the advantages of this material for commercial use because of its extra ordinary thermo electric performance.
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This document discusses the design and analysis of an air-conditioned tricycle that uses thermoelectric cooling. The system uses multiple thermoelectric Peltier modules to absorb heat from the air and provide cooling. Rectangular fins and fiber sheets are used to improve heat transfer from the modules. The design is intended to provide cooling without using ozone-depleting refrigerants. Experimental results showed the thermoelectric system was able to achieve a cooling power of 50W per module with a coefficient of performance between 1.5-2. The document reviews several other studies on thermoelectric cooling systems and their advantages over traditional vapor-compression air conditioners.
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2. LEONOV: THERMOELECTRIC ENERGY HARVESTING OF HUMAN BODY HEAT 2285
Fig. 1. Wearable TEHs used in this paper for measurements of thermal
properties of humans and power generation on people at different ambient
conditions. (1) TEH with a 3×3×1.5 cm radiator. (2) 6.5-mm-thin TEH
with a thermopile between two plates; it is similar to the TEH modules used
in an electrocardiography shirt [1], [2]. (3) and (4) TEHs recently used in two
self-powered electroencephalography systems [1], [6].
In case of very small or very large thermal resistance Rtp,
either T or W approaches zero, respectively. Therefore, in
both cases, the generated power P approaches zero, too. The
power reaches maximum when the product of heat flow by
temperature drop maximizes. From the thermal impedance
matching theory [5], a wearable thermopile must have high
thermal impedance of the order of those observed in the ambi-
ent air and human being. For a TEH optimization, knowledge
of those thermal impedances is required. As the former is well-
known, the experimental study in this paper was concentrated
at measurement of heat flows, skin temperature and thermal
resistance of humans at different ambient conditions and in
different locations on a person.
III. RELEVANT THERMAL PROPERTIES OF HUMANS FOR
DESIGNING WEARABLE TEHS
Several TEHs have been fabricated and used in this paper
for experimental study of power production on humans, Fig. 1.
The thermopiles (from Thermix, Kiev, Ukraine) typically had
a footprint of less than 1cm2 per thermopile, however, they
were usually provided with a much larger “hot” plate (the
one touching the skin) for decreasing the thermal resistance
of human body (devices 2 to 4, Fig. 1). For decreasing the
thermal resistance of ambient air, a “cold” plate or a radiator
was always attached to the cold side of thermopiles.
A thermopile with known thermal resistance is a good tool
for heat flow measurements. It is obtained using open-circuit
voltage, Vopen, as W = Vopen/(2SnR0), where n is the number
of thermocouples, and R0 is Rtp at open circuit. Therefore,
the TEHs were also used in the study for this purpose. The
skin temperature was measured with a thermocouple located
between the TEH and skin. The tympanic temperature was
measured with infrared ear thermometer. Fig. 2 illustrates
dependence of skin temperature of a person on ambient
(a)
(b)
Fig. 2. (a) Dependence of skin temperature under a TEH #1 shown in
Fig. 1 on ambient temperature in different locations. (1) In the middle of
chest. (2) On the wrist, over the radial artery. (3) On the anterior leg, about
25cm above the knee, i.e., far from arteries. The TEH increases heat flow
above natural one because of large radiator and therefore locally decreases
skin temperature under the hot plate. Lines: polinomial fits. Clothing: weather
conditions, e.g., (b) gloves are worn at low ambient temperature for keeping
hands warm.
temperature in three different locations. At ambient temper-
ature of 25 °C, the skin temperature closely approaches body
core temperature of 36.8 °C (in this experiment). Typically,
the chest, head and warmest zone of the wrist (close to the
radial artery) approach it first on the person in the office.
Therefore, these body parts are good for energy harvesting.
The chest is however more sensitive to local cooling in cold
weather, and for comfort of the person, heat flow must be
substantially limited. Therefore, in the experiment at low
ambient temperatures, maximum power was obtained in a TEH
worn on the wrist despite lower skin temperature [7].
The human skin has nonuniform temperature over the body.
This nonuniformity increases at low ambient temperatures.
Therefore, the temperature difference between the body core
and skin depends on chosen location on the body and ambient
temperature. This means the thermal resistance of heat path in
the body from its core to the skin may depend on location of
TEH, clothes (they increase the skin temperature) and wind
speed. It also must depend on air temperature. To prove this
guess, the skin temperature was measured with a thermistor
in the middle of forehead of clothed person at ambient
temperatures of 16 °C to 33.5 °C in still air. Such variation of
temperature was expected to significantly change the thermal
3. 2286 IEEE SENSORS JOURNAL, VOL. 13, NO. 6, JUNE 2013
Fig. 3. Dependence of heat flow through the TEH #1 on temperature in
three locations measured on the standing or sitting person. Triangles: over the
radial artery in the wrist. Circles: on the anterior leg about 25 cm above the
knee. Diamonds: in the middle of the chest.
resistance of extremities due to vasomotor response, but not
to affect the thermal resistance in trunk, neck (near arteries)
and head. The experiment was conducted on a person resting
in a chair. It has shown that a human being demonstrates
variable core-to-skin thermal insulation depending on ambient
temperature even in locations proximal to body core organs
like brain, see [8] for details.
The experiment also confirms dependence of body thermal
resistance on chosen location on the body. As shown in
Fig. 2, the skin temperature varies at fixed ambient temperature
depending on location of the TEH. The dependence of heat
flow on ambient temperature measured in the same locations
as in Fig. 2 using the same TEH #1 is shown in Fig. 3.
Within the 10 °C to 15 °C range, the heat flow enhanced by
the radiator was very similar in all three locations. However,
the radial artery seems to be the best choice because beyond
this temperature range the heat flow is highest among the
studied locations. Solid lines in Fig. 3 are polynomial fits.
Almost all experimental points correspond to sensation of
comfort. There was however two experimental points (on the
chest, diamonds, at a temperature of 3 °C), where the person
reported sensation of cold. Therefore, the maximum heat flow
on the chest should not reach the measured value. The dashed
part of the fitting curve shows approximate expectation for
the maximum heat flow. As one can see, the chest that is
always warm due to clothes shows the minimum acceptable
heat flow. Using the temperature difference between the body
core (typically 37 °C) and skin temperature, Fig. 2, one may
obtain the dependence of thermal resistance for a human being
on ambient temperature in the chosen location. The typical
thermal resistances observed in several locations were reported
in [7], [9], [10]. It is worth mentioning that the maximum
heat flow observed through a TEH on the wrist, Fig. 3,
coincides with the lowest thermal resistance of human body.
A thermal resistance of about 110cm2K/W has been measured
in this location with TEH #1 at room temperature. At zero
degrees Celsius, on the same person wearing appropriate cloth
ensemble (Fig. 2b) it increased a little to 140 cm2K/W.
Fig. 4. Dependence of core-to-skin temperature difference on heat flow
measured using TEH #2 in two locations of sitting person. Circles: over the
radial artery in the wrist. Triangles: on the anterior leg. Lines: linear fits.
There is also a dependence of body thermal resistance on
heat flow at fixed both ambient temperature and location of
the TEH. In the experiment performed on a sitting person at
temperatures within the 21 °C to 23.7 °C range, the TEH #2
was attached to the anterior leg, about 25cm above the knee,
using an elastic band. The radiator was cooled to different
extent and the open-circuit voltage generated by TEH was
recorded after temperature stabilization. Simultaneously, the
skin temperature was measured using a thermocouple glued to
the hot plate and located between the skin and the TEH. Then,
the TEH was relocated to the inner side of the wrist and posi-
tioned over the radial artery, Fig. 2b, and the experiment was
repeated. Periodically, the ambient temperature was measured.
The tympanic and oral temperatures were measured with
infrared thermometer and found very stable (36.9 ± 0.1 °C)
during the experiment that took a few days. The results are
shown in Fig. 4. The experiment shows linear dependence of
temperature difference between the body core and hot plate
on heat flow through a TEH.
The slope of dependences, i.e., dT/dW, is the thermal
resistance of the studied material, namely, the human tissue
in vivo. The fitting lines in Fig. 4 give a thermal resistance of
147 cm2K/W on the leg and 42 cm2K/W on the radial artery.
In principle, these values enable TEH modeling and design
optimization. However, there is a general problem. At zero
heat flow, a difference of a few degrees Celsius is observed
between the core and skin temperatures. As seen in Fig. 4, this
offset varies depending on TEH location. It must also vary with
wind speed (or a speed of person movement in respect to still
air), metabolic rate and the shape of radiator. It is believed
that the offset is related to the facts that: 1) the radiator
of TEH is immersed in a heated body-induced convection
layer, but TEH has high thermal resistance, therefore, the cold
plate/radiator temperature may approach the temperature of
convection layer, 2) even at zero heat flow on open skin, there
4. LEONOV: THERMOELECTRIC ENERGY HARVESTING OF HUMAN BODY HEAT 2287
Fig. 5. Dependence of thermal resistance of human body defined by
(3) on heat flow. Lines: experimental results obtained using the data of
Fig. 4 at different factor B (1.5 K for the radial artery and 4.8 K for the
leg). Experimental points have been measured using four different TEHs in
following locations. Triangles: over the radial artery in the wrist. Squares: on
the anterior leg. Diamonds: in trunk and arm. Open diamonds: with the lowest
thermal resistance registered in the middle of the chest. Circles: on the outer
side of the wrist where a watch is typically worn.
is heat transfer through sweat vaporization, and 3) only a
part of heat dissipated through the TEH is produced in the
body core, so there is no strong thermal link to the core in
extremities, especially during exercise.
The offset complicates the design optimization of a TEH.
Indeed, changing the shape of a TEH or a radiator during
optimization affects the offset. Therefore, it was proposed in
[11] to use a parameter called thermal resistance of human
body, Rh. It accounts for a nice reference point, namely, the
near-constant core temperature in a healthy subject, as
Rh = (Tcore − Tskin)/W. (3)
This approach simplifies the thermal circuit of a wearable TEH
[12] by giving a ‘ground’ point fixed at 37 °C. The experi-
mental data on Rh have been reported in [7], [9]–[11], [13].
Examples of TEH modeling using Rh can be found in, e.g.,
[5], [13], [14].
Under chosen ambient conditions, the maximum power of
wearable TEH can be reached in locations with low body
thermal resistance, such as a forehead or an artery passing
close to the skin, e.g., in the neck or wrist. The data presented
in Fig. 4 are recalculated to the thermal resistance and plotted
as two curves in Fig. 5. These curves mark the area for
thermal resistance of human being to be used in typical indoor
conditions. They can be described by the equation
Rh = B(1/W + 28)[cm2
K/W] (4)
where the factor B is 4.8K for the top curve (on the leg)
and 1.5K for the bottom curve (the radial artery), and W is
heat flow in W/cm2. These two curves reflect very different
conditions on the human body: on the radial artery, the lowest
thermal resistance is observed, so the maximum power can
be obtained in a TEH, while the measurement point on the
leg is located in the zone of thickest muscles and far away
from the artery, so the thermal resistance is very high and the
power is near its minimum. In the distal area of extremities the
situation can be worse, but the designer of TEH will certainly
not place it there. Therefore, it is believed at this stage of the
research that in case of wearable TEH, B should be always
within the 1.5 to 4.8K range. (This statement refers to average
values with possible deviation of Rh by a factor of two for
any particular experimental point). As example of realistic
ranges for the thermal resistance of the body and heat flow, the
experimental data are plotted in Fig. 5 as experimental points.
These data have been obtained using TEHs #1 and #2, Fig. 1,
at ambient temperatures within the 23 °C to 24.8 °C range in
different locations on the body. Some other TEHs, with larger
radiators, namely, 16×36×38mm and 33×45 ×50mm were
also used within the 19.7 °C to 22.5 °C range (circles in
Fig. 5). (These large-size TEHs frequently caused complaints
of users stating that the device induced sensation of cold.
Nowadays, they are no longer used in our research).
Despite certain scattering of experimental points obtained in
every location, Fig. 5 confirms that (4) is valid for using it for
the design optimization of a TEH. For a general optimization
of a TEH irrespective of its possible location on the human
body, it is recommended using (4) with B ≈ 3K. However,
such an optimized TEH could show up to a few-fold deviation
of power from the calculated value depending on its location.
Therefore, the TEH designing must preferably be performed
for the specified location on the human being.
IV. DEMONSTRATION OF MAXIMUM POWER OF
WEARABLE TEH
The key factor for reaching power maximum in a TEH is
its thermal impedance matching to the thermal impedance of
the environment [5], which is the electro-thermal equivalent
of electrical matching of the load and generator impedances.
In the simplest form, the thermal circuit of a TEH and
equations for its design optimization were presented, e.g.,
in [15]. At the thermal impedance matching point, the
maximum power generated by wearable TEH on electrically
matched load is
Pmax = Z(Tcore − Tair)2
/[16(1 − N−1
)(Rh + Rair)] (5)
where Tair and Rair are the temperature and thermal resistance
of ambient air, and N is a dimensionless thermal insulation
factor, defined in [16] as
N = Rempty/(Rh + Rair) (6)
where Rempty is the thermal resistance of the TEH embodi-
ment, which would be observed upon removal of thermoelec-
tric material from TEH, so-called “empty” TEH. This is a
design-related parameter: the higher N, the lower is adverse
effect of parasitic heat flow in the TEH on power. Thus, both a
thick TEH (high Rempty) and a TEH occupying large area (low
both Rh and Rair) are preferable for reaching maximum power.
Although such a TEH may reach unacceptable form factor,
it reaches peak power. For the experiment in this paper, the
TEH #1 with a size of 3 × 3 × 3cm was fabricated for
5. 2288 IEEE SENSORS JOURNAL, VOL. 13, NO. 6, JUNE 2013
Fig. 6. Dependence of power generated by TEH #1 on ambient temperature.
Power is shown per unit footprint area of the radiator on electrically matched
load. Device was located over the radial artery in the wrist as shown
in Fig. 2(b). Results are obtained on a sitting or standing person. Line:
polynomial fit.
practical demonstration of maximum power in a wearable
TEH. It was placed on the radial artery as shown in Fig. 2b.
The results are shown in Fig. 6.
It is believed that the data shown in Fig. 6 reflect the near-
maximum power per unit footprint area of TEH, which can
be obtained on a standing or sitting person in thermal comfort
with no wind, no direct sunlight. The maximum power is about
60μW/cm2 indoors and about 600μW/cm2 at a temperature
of 0 °C. These values were calculated per unit area of the
radiator (9cm2). The hot plate area was however smaller
(5cm2) than the footprint of radiator. Therefore, the measured
maximum power corresponds to about 100μW per cm2 of skin
indoors and over 1mW/cm2 at ambient temperature of 0 °C.
These are estimates for the maximum power of a TEH, which
can be obtained unobtrusively (with no sensation of cold) on
average on a sitting or standing person with a thermoelectric
material showing a Z of 0.0025K−1. In practical applications,
the produced power may essentially fluctuate around these
average values and at any particular moment deviate from the
average by a factor of 2 to 3, in typical situations.
From the experiments reported above, the head, trunk and
zones proximal to arteries are the best locations for demon-
stration of maximum power in a wearable TEH. It has to be
mentioned that the heat flow on skin changes its direction
at ambient temperature of 36–37 °C. This temperature corre-
sponds to minimum power generation [17]. In real life, the
average power of a TEH does not decrease to zero; it just
shows its minimum [18]. At higher ambient temperatures,
power increases again.
From (5), (6), the power depends on a form factor of a TEH.
Therefore, for comparison of power generated by different
devices, one may use power produced per unit volume of TEH.
Comparison of devices on power per unit area occupied on
the skin is not correct because the factor N varies within
the large range. In Fig. 7, the power produced by different
Fig. 7. Dependence of power of four different TEHs shown in Fig. 1 per unit
volume on ambient temperature measured on sitting, standing, and walking
people. TEHs were worn in different locations on the body. Lines: guides for
eyes. Solid line: average power. Dashed lines: deviation from the average by
a factor of two. The air between radiator and skin is also accounted for the
volume.
devices in practical applications is shown versus ambient
temperature. The data have been obtained using four devices
shown in Fig. 1 in different locations on the body (forehead, on
hear, wrist, trunk, legs), at different typical activities (sitting,
standing, working in the office, walking indoors/outdoors)
and at different ambient conditions (in wind or still air, at
different temperatures). Some data points refer to average
power production in 14 TEHs #2 integrated into a shirt [2].
The volume of a TEH used for calculations was equal to its
thickness multiplied by the area of cold plate or the radiator.
Fig. 7 shows that despite very different size and shape of
TEHs, they can successfully be compared to each other using
power per unit volume of the device.
Further increase of power in a wearable TEH can only be
obtained through improvement of material quality, i.e., through
increasing the factor Z, see (5). However, the author does not
expect to witness rapid progress in this area.
V. INTEGRATION OF A TEH IN CLOTHING
Four ways of integration of TEH #2 into clothes have been
investigated, Fig. 8. The TEH had a round hot plate of 3cm
in diameter, a 5mm-thick two-stage thermopile with 256 BiTe
thermocouples from Thermix (Kiev, Ukraine), and a cold plate
with dimensions of 40×30×1mm. The thickness of TEH
was 6.5mm. The thermopile with a footprint of 8 × 9mm
showed a thermal resistance of 76K/W. This is much less than
required for reaching optimal thermal impedance matching
with the environment [5]. Therefore, the latter, i.e., Rh + Rair,
was decreased by using large interfaces, namely, hot and cold
plates. The thermopile was encapsulated using 0.2mm-thick
polyethylene. For shock protection of the thermopile, four
thermally insulating pillars of 1mm in diameter were placed
between the plates of TEH, Fig. 8a.
In the first way of integration of such a TEH, the hot plate
was placed in direct contact with skin under a textile, while the
cold plate was at about 4mm from the cotton layer, Fig. 8a.
Although the cold plate works in the most efficient way in
this scheme (both sides of it participate in heat exchange with
ambient air), appearance of metal plates in a piece of clothing
seems not the most attractive solution on the market.
6. LEONOV: THERMOELECTRIC ENERGY HARVESTING OF HUMAN BODY HEAT 2289
Fig. 8. (a)–(d) Four ways to integrate TEH #2 in garments (not in
scale). Numbers denote: (1) thermopile, (2) polyethylene encapsulation, (3)
thermally insulating spacers, (4) textile, (5) a carbon fabric heat-spreading
layer, (6) neoprene foam spacers, (7) an additional textile layer, and (8) cotton-
based spacers. (a) TEH passes through the hole made in textile. (b) TEH is
placed under the textile layer. (c) Heat-spreading layer is glued to the cold
plate and to the cotton, while foam spacers enable keeping some distance
between the heat-spreading layer and skin. (d) Additional layer of cotton is
glued to the TEH and sewed inside of clothing.
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70 80
Power(µW)
Measurementnumber
94.9%
55.4%
Fig. 9. Power generated by TEH #2 in the office depending on the way of
its integration in a shirt. Compared with TEH open to ambient air [(closed
circles; correspond to Fig. 8(a)], the power only slightly decreases if the TEH
is placed under cotton [(open circles; correspond to Fig. 8(b)], but decreases to
a half of it if air gap is observed between the cotton and cold plate (triangles).
Lines: corresponding average levels.
Therefore, in the second way of integration, the TEH was
just placed between the cotton of an office-style shirt and skin.
A weak elastic band held the device on the chest at about
10–12cm below the chin. Then, comparative measurements
were conducted in the office at three positions of cotton:
1) tight to the cold plate, Fig. 8b, 2) cotton pulled from TEH
to make about 5–10mm air gap between the cold plate and
cotton, and 3) the cotton was pulled to left and right a little
leaving the TEH completely open, similar to the case shown in
Fig. 8a. The results on power generation are shown in Fig. 9.
Fig. 10. Four of eight thermopiles assembled on additional piece of textile.
Two such pieces of textile were sewed from the inner side of the shirt.
The results shown in Fig. 9 give almost the same average
power (about 95%) in case 1) compared to case 3). The air
gap between the TEH and cotton, case 2), results in the worst
power generation, only about a half of power compared to
cases 1) and 3). Therefore, hiding a TEH under textile is
feasible at negligible loss of power if cotton is in contact with
cold plate. Cotton acts as the radiator of TEH.
To make a large-area cotton radiator, a piece of carbon fabric
was glued inside a T-shirt to cotton, and the cold plate of TEH
was glued to carbon fabric, Fig. 8c. Simultaneous comparative
measurements of two TEH units, Figs. 8b and 8c, has shown
a 30% increase of power due to heat-spreading layer made of
carbon fabric. For fabrication of a shirt with such TEH units,
an additional textile layer was added to the design, Fig. 8d.
It slightly decreases power due to its thermal resistance, but
makes the TEH completely hidden between two cotton layers
and comfortable to the user.
Targeting at comparing the power of the shirt with hidden
TEH to a similar thermoelectric shirt with metal plates, Fig. 8a,
reported in [2], sixteen thermopiles have been integrated on
the front side of a shirt. Their hot plates have been glued to a
piece of cotton, and after wiring, Fig. 10, they were assembled
as shown in Fig. 8d. Two pieces of carbon fabric of 375cm2
each have been used on the left and right sides of the shirt.
The shirt is shown in Fig. 11. Unlike in earlier developed
thermoelectric shirt [2], there are no elastic bands in the shirt.
The thickness of thermopiles used in the newly developed shirt
was decreased to 3.5mm (equal to the thickness of buttons)
at the same other characteristics as of two-stage thermopiles
discussed above. The decreased thickness increases parasitic
heat flow in the TEH, but improves its acceptance by the user.
VI. PERFORMANCE CHARACTERISTICS OF THE
THERMOELECTRIC SHIRT
The characterization of the TEH was conducted on people
working in the office or walking indoors, and also during
outdoor activities. At ambient temperatures below 18 °C, the
person was standing or walking outdoors for short time, about
10min maximum. Therefore, low ambient temperatures did
not affect the overall body heat content and thermal comfort.
The measurements show the hidden TEH with 16 thermopiles
7. 2290 IEEE SENSORS JOURNAL, VOL. 13, NO. 6, JUNE 2013
Fig. 11. Shirt with hidden integrated TEH.
Fig. 12. Power generated by the TEH hidden in a shirt at different
ambient temperatures and activities (points). For comparison, two dashed lines
illustrate power in a TEH of electroencephalography shirt with metal plates
located beyond the external surface of a shirt [2]: on a walking person (top)
and standing/sitting person (bottom).
and no elastic bands produces approximately the same power
(see experimental points in Fig. 12) as 14 units of TEH #2
with elastic bands and external cold plates reported earlier
[2] (lines in Fig. 12). An average power of 1mW (at 1.2V
on the matched electrical load) observed in the office at
22 °C doubles if the person walks in a corridor. The effect is
caused by forced air convection, but not related to increased
metabolic rate in a walking person. The power also doubles
at ambient temperature of 17 °C, i.e., it increases to 2mW
on a standing or sitting person, and to 4mW on a walking
person, Fig. 12. This thermoelectric shirt seems to be the most
comfortable device among the wearable TEHs developed to
the moment. Of course, the power might have been slightly
higher if the thermopiles were always pushed to the skin. The
additional cotton layer located between the skin and hot plate
also adversely affects the power, but it affords better comfort,
especially in case of sweating.
The shirt is not slim and the thermopiles are not always
well attached to the skin all the time. Nevertheless, despite
Fig. 13. Power generation during cycling at a metabolic rate of four
METs. Shown is the power generated by the thermoelectric shirt with hidden
integrated TEH. The energy expenditure is shown in units of a basal metabolic
rate (MET).
periodic disconnection of some of units from the skin and the
related power loss, the power is very close to the case where
elastic bands push them to the skin [2].
For demonstration of power at increased metabolic rate,
a one-hour outdoor experiment was performed during exercise.
Cycling was chosen for this experiment as a typical example of
an exercise. The maximum power was reached on a standing
person before the exercise. During the cycling, the power
gradually decreased and finally reached the level observed
in the office, Fig. 13. One may also draw attention to the
fact that during last minutes of cycling at 4MET, the power
was the same as afterwards, on a standing person, and also
the same as the one observed in the office before cycling
(1.5MET).
Another experiment performed in this paper on a cyclist
wearing a TEH on the wrist was reported in [8]. These
experimental results confirm our earlier observations that,
in typical situations, the power generated by wearable ther-
mopiles does not depend on metabolic rate, but on overall
body heat content and air speed in respect to the person,
especially, on the latter. It also depends on sweating rate. In the
beginning of exercise, the power increases for a while because
of forced air convection. The same increase was observed
on the standing cyclist (35 to 45 min in Fig. 13), where the
power rose because of wind. Then, it dramatically decreased
because of exercise-induced sweating. This power drop is
explained by decrease of skin temperature due to extensive
sweat vaporization. Therefore, the statements made in some
papers on energy harvesting concerning dramatic power rise
proportionally to metabolic rate were incorrect. Indeed, at
fixed skin and ambient temperatures, any metabolic rate results
in the same heat flow (but the rate of sweating is variable).
Sometimes, a certain rise of heat flow during exercise is only
observed in extremities due to vasodilatation if hands were
relatively cold before the exercise.
VII. CONCLUSION
The experimental maxima of power in a wearable TEH
with a Z of 0.0025K−1 have been demonstrated, Figs. 6
and 7. At any studied ambient conditions, no sensation of
8. LEONOV: THERMOELECTRIC ENERGY HARVESTING OF HUMAN BODY HEAT 2291
thermal discomfort was reported. The TEH in the shirt does
not require any modifications to existing garments: it is just
glued and sewed to the shirt purchased in a shop. The device is
comfortable because of cotton layer on the skin and a radiator
made of carbon fabric and cotton. It is a reliable power supply
for low-power wearable electronics such as health-monitoring
devices. For example, wireless electrocardiography requires
about 0.4 mW today [1], [2] and in the near future it is
supposed to drop below 0.1mW. The hidden TEH seems to be
a good power supply for low-power wearable electronics like
health-monitoring devices. It is quite competitive with batteries
of the same thickness and weight. The cost of TEHs is still
by a factor of 10 higher than of batteries. However, modern
fabrication technologies for thermopiles can change this ratio
in favor of TEH in the near future. The demonstrator shirt with
a TEH is being handled in the same way as other clothing,
i.e., with periodic machine washing and ironing.
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Vladimir Leonov was born in St. Petersburg, Rus-
sia. He received the Ph.D. degree in optical devices
from the State Optical Institute, St. Petersburg.
He has been working on cryogenic and uncooled
thermal detectors and arrays as a Senior Scientist
with the State Optical Institute since 1981. From
1998 to 2000, he was with Southern Methodist
University, Dallas, TX, USA, where he worked on
pyroelectric infrared arrays. From 2000 to 2003,
he was a Principal Scientist with Xenics, Leuven,
Belgium, and in 2003, he was a Senior Scientist at
IMEC, Leuven. He has developed a spectrum of wearable energy harvesters
and authored over 160 publications and 15 patents. His current research
interests include wearable sensors and inorganic electret technologies.