Radiation is a mode of heat transfer that does not require a medium. Thermal radiation is emitted from all objects based on their temperature and is characterized by properties like emissivity. Radiation plays a key role in heating the Earth's surface from the Sun. The amount of radiation emitted by an object increases with its temperature, as described by Stefan-Boltzmann law. Radiation interacts with textiles through absorption, emission, transmission, and scattering depending on fiber properties. Research aims to model radiation transfer through textiles and its role in thermal insulation and heat stress protection.
- Radiation heat transfer occurs through electromagnetic waves emitted by surfaces due to their temperature. All real surfaces emit less than ideal blackbodies.
- The key radiative properties are emissivity ε, absorptivity α, reflectivity ρ, and transmissivity τ. For opaque surfaces, α + ρ = 1.
- Blackbodies have ε = 1 and emit thermal radiation described by Planck's law. Real surfaces emit radiation according to their emissivity and temperature.
- The rate of radiative heat transfer between two surfaces depends on their temperatures and emissivities, the shape factor F between their orientations, and the absorptivity of the receiving surface.
Here are the steps to solve this problem:
1. Calculate the radiative heat loss from the absorber:
Qrad = εσA(Ts4 - Tsky4) = 0.1×5.67×10-8×(120+273)4 - (-10+273)4 = 33 W/m2
2. Calculate the convective heat loss:
h = 0.22(Ts - T∞)1/3 = 0.22(120-30)1/3 = 5.1 W/m2K
Qconv = hA(Ts - T∞) = 5.1×(120-30) = 51 W/m2
Thermal radiation is emitted by all objects due to the vibrational and rotational movements of molecules and atoms. It is transported via electromagnetic waves and can propagate through a vacuum. All objects emit radiation at any temperature above absolute zero according to their emissivity.
Blackbody radiation follows Planck's law, with a continuous frequency spectrum that depends only on temperature. It has a peak wavelength defined by Wien's displacement law. The total power output of blackbody radiation is described by Stefan-Boltzmann law.
The view factor is used to account for incomplete radiation exchange between surfaces, describing the fraction of radiation leaving one surface that is received by another. It is essential for calculating radiation heat transfer between surfaces.
- Thermal radiation is electromagnetic radiation emitted by a body as a result of its temperature and is restricted to a limited range of the electromagnetic spectrum.
- Blackbody radiation obeys certain simple laws like Stefan-Boltzmann's law and Planck distribution law that describe how radiation is emitted at different wavelengths and temperatures.
- Real surfaces emit and absorb less radiation than blackbodies and their emissivity is usually less than 1.
Heat transfer due to emission of electromagnetic waves is known as thermal radiation. Heat transfer through radiation takes place in form of electromagnetic waves mainly in the infrared region. Radiation emitted by a body is a consequence of thermal agitation of its composing molecules. The underlying mechanisms and the concepts involved are discussed in the ppt
The document discusses several topics related to emissive power and absorptive power of bodies at different temperatures, including:
- Emissive power is defined as the energy emitted per second per unit surface area within a wavelength range. Absorptive power is defined as the ratio of energy absorbed to energy incident on a surface.
- Kirchhoff's law states that for a body in thermal equilibrium, the emissive power and absorptive power are equal for each wavelength.
- The rate of energy emission from a perfectly black body is directly proportional to the fourth power of its absolute temperature, according to Stefan's law.
- Radiation heat transfer occurs through electromagnetic waves emitted by surfaces due to their temperature. All real surfaces emit less than ideal blackbodies.
- The key radiative properties are emissivity ε, absorptivity α, reflectivity ρ, and transmissivity τ. For opaque surfaces, α + ρ = 1.
- Blackbodies have ε = 1 and emit thermal radiation described by Planck's law. Real surfaces emit radiation according to their emissivity and temperature.
- The rate of radiative heat transfer between two surfaces depends on their temperatures and emissivities, the shape factor F between their orientations, and the absorptivity of the receiving surface.
Here are the steps to solve this problem:
1. Calculate the radiative heat loss from the absorber:
Qrad = εσA(Ts4 - Tsky4) = 0.1×5.67×10-8×(120+273)4 - (-10+273)4 = 33 W/m2
2. Calculate the convective heat loss:
h = 0.22(Ts - T∞)1/3 = 0.22(120-30)1/3 = 5.1 W/m2K
Qconv = hA(Ts - T∞) = 5.1×(120-30) = 51 W/m2
Thermal radiation is emitted by all objects due to the vibrational and rotational movements of molecules and atoms. It is transported via electromagnetic waves and can propagate through a vacuum. All objects emit radiation at any temperature above absolute zero according to their emissivity.
Blackbody radiation follows Planck's law, with a continuous frequency spectrum that depends only on temperature. It has a peak wavelength defined by Wien's displacement law. The total power output of blackbody radiation is described by Stefan-Boltzmann law.
The view factor is used to account for incomplete radiation exchange between surfaces, describing the fraction of radiation leaving one surface that is received by another. It is essential for calculating radiation heat transfer between surfaces.
- Thermal radiation is electromagnetic radiation emitted by a body as a result of its temperature and is restricted to a limited range of the electromagnetic spectrum.
- Blackbody radiation obeys certain simple laws like Stefan-Boltzmann's law and Planck distribution law that describe how radiation is emitted at different wavelengths and temperatures.
- Real surfaces emit and absorb less radiation than blackbodies and their emissivity is usually less than 1.
Heat transfer due to emission of electromagnetic waves is known as thermal radiation. Heat transfer through radiation takes place in form of electromagnetic waves mainly in the infrared region. Radiation emitted by a body is a consequence of thermal agitation of its composing molecules. The underlying mechanisms and the concepts involved are discussed in the ppt
The document discusses several topics related to emissive power and absorptive power of bodies at different temperatures, including:
- Emissive power is defined as the energy emitted per second per unit surface area within a wavelength range. Absorptive power is defined as the ratio of energy absorbed to energy incident on a surface.
- Kirchhoff's law states that for a body in thermal equilibrium, the emissive power and absorptive power are equal for each wavelength.
- The rate of energy emission from a perfectly black body is directly proportional to the fourth power of its absolute temperature, according to Stefan's law.
This document describes an emissivity measurement apparatus that determines the emissivity of gray surfaces. It consists of a black plate and gray test plate that are electrically heated to the same temperature. The power input required to heat the gray plate to the same temperature as the black plate is measured. Since the plates have all other properties identical except emissivity, the difference in power input is due to the difference in emissivity. By measuring this power difference at various temperatures, the emissivity of the gray surface can be determined relative to the black plate.
- Thermal radiation is electromagnetic radiation emitted from objects due to their temperature. It includes infrared, visible light, and some ultraviolet wavelengths. A blackbody is a perfect emitter and absorber of radiation. According to Stefan-Boltzmann law, a blackbody's total emissive power is directly proportional to the fourth power of its absolute temperature. Planck's law describes the spectral distribution of a blackbody's radiative intensity as a function of wavelength and temperature. The emissivity of a surface is the ratio of radiation it emits compared to a blackbody. Kirchhoff's law states that emissivity of a surface is equal to its absorptivity at a given temperature and wavelength. The greenhouse effect
Thermal radiation occurs across a wide spectrum of electromagnetic wavelengths. Most thermal radiation from objects at room temperature falls within the infrared range, which is invisible to the human eye. The wavelength distribution of radiation emitted by an object depends on its temperature according to Planck's law. Nearly all surfaces emit and absorb thermal radiation to some degree, with the ratio between emitted and absorbed radiation determined by the surface's emissivity. Emissivity also affects how much solar energy a surface absorbs. Proper material selection and surface treatments can influence thermal radiation to control heating and cooling in devices and systems.
Kirchhoff's Law states that the emission of a body is equal to the ratio of its emissivity and the blackbody emission at a given wavelength and temperature. Wien's Law establishes that the dominant wavelength of blackbody radiation is inversely proportional to temperature. The Stefan-Boltzmann Law provides that the total energy flux radiated by a blackbody is directly proportional to the fourth power of its absolute temperature.
The document discusses three modes of heat transfer: conduction, convection, and radiation. Radiation is defined as the transfer of heat through space or matter without the need for a medium and occurs via electromagnetic waves or photons. Some key laws governing radiant heat transfer are discussed, including Stefan-Boltzmann's law which states that the emissive power of a black body is proportional to the fourth power of its absolute temperature. Radiative properties like emissivity, absorptivity, and reflectivity are also covered.
The document defines different types of bodies in heat transfer:
1. A black body absorbs all radiation falling on its surface and is a perfect emitter.
2. A white body reflects all incident radiation falling on it.
3. A gray body's absorptivity does not vary with temperature or wavelength of incident radiation.
4. An opaque body does not transmit any radiation through it, while a transparent body transmits all radiation.
This document discusses several laws relating to the radiation of heat, including:
1) Kirchhoff's law, which states that the emission of a body at a given wavelength and temperature is equal to the ratio of the emissivity and blackbody emission. Real objects emit less radiation than black bodies.
2) Wien's law, which says the dominant wavelength at which a blackbody emits radiation is inversely proportional to its temperature.
3) The Stefan-Boltzmann law, stating that a blackbody's total energy flux is directly proportional to the fourth power of its temperature.
This document provides an overview of fundamental radiation concepts. It defines thermal radiation and blackbody radiation, describing the idealized blackbody and Stefan-Boltzmann law. It also covers radiation intensity, radiative properties including emissivity and absorptivity, and Kirchhoff's law relating emissivity and absorptivity. The objectives are to classify electromagnetic radiation, understand blackbody radiation characteristics, and apply concepts of radiation intensity and surface radiative properties.
The document discusses the history and development of theories of blackbody radiation and the concept of the photon. It describes how (1) classical physics could not fully explain experimental observations of blackbody radiation, (2) Planck resolved this issue by proposing that the radiation emitted by cavity walls was quantized into discrete energy packets called quanta (later known as photons), and (3) his theory accurately described blackbody radiation distribution and resolved prior inconsistencies like the ultraviolet catastrophe.
This document discusses blackbody radiation and the laws that describe it. It defines a blackbody as an ideal absorber of all incident radiation. It then explains the four main blackbody radiation laws: 1) The Rayleigh-Jeans law applies to long wavelengths but fails at short wavelengths, 2) The Planck law provides accurate predictions across all wavelengths, 3) The Wien displacement law describes how the peak wavelength shifts to shorter wavelengths at higher temperatures, and 4) The Stefan-Boltzmann law establishes that total radiation emitted increases with the fourth power of temperature. Real objects can be compared to blackbodies, and the document provides an example application calculating the Earth's surface temperature from its energy balance.
Black body is an ideal body that absorbs all incident radiation without reflecting any energy. As temperature increases, the peak wavelength emitted decreases and total energy emitted increases. Early models like Rayleigh-Jeans law failed to accurately predict blackbody radiation at small wavelengths, known as the ultraviolet catastrophe. Planck's law and other laws like Wien's displacement law, Stefan-Boltzmann law accurately describe blackbody radiation. Blackbody radiation spectrum depends only on temperature and not the object.
This document discusses key concepts relating to blackbody radiation. It begins by introducing the concept of a blackbody as an ideal absorber of electromagnetic radiation. It then describes Stefan's Law, which states that the total energy radiated by a blackbody is directly proportional to the fourth power of its thermodynamic temperature. Next, it explains Wein's Displacement Law, which establishes that the peak wavelength of blackbody radiation is inversely proportional to the temperature of the blackbody. The document provides formulas for both laws and gives examples of how they can be applied.
This document discusses the laws of radiation and heat transfer. It defines radiation as electromagnetic energy transfer and outlines four key laws:
1) Kirchhoff's law relates the amount of radiated energy to absorbed energy.
2) Stefan-Boltzmann law describes the amount of radiant energy emitted from a black body, which absorbs all radiation.
3) Planck's law defines the emissive power of a black body as a function of wavelength and temperature.
4) Wien's law describes how the wavelength of maximum radiant intensity decreases proportionally as temperature increases.
Radiation is a form of energy transfer that does not require a medium and travels at the speed of light. Unlike conduction and convection, radiation can transfer heat through a vacuum. All objects emit thermal radiation based on their temperature, with the spectrum and intensity of radiation described by blackbody radiation laws. Radiation transfer is important in applications like solar energy and remote heating/cooling between separated objects.
Radiation heat transfer involves the transfer of heat energy through electromagnetic waves. The three main modes of heat transfer are conduction, convection, and radiation. Radiation is the transfer of heat energy through empty space without a medium and follows the laws of blackbody radiation including Planck's law, Wien's law, Stefan-Boltzmann law, and Kirchhoff's law. Radiation processing uses ionizing radiation like gamma rays and electron beams to destroy pathogens and microbes in foods to increase shelf life and ensure safety while maintaining quality.
1) Classical theories could not explain the spectrum of blackbody radiation, predicting infinite energy at short wavelengths.
2) Planck hypothesized that the oscillators could only emit or absorb energy in discrete quantized units proportional to frequency, avoiding the infinity.
3) This led to Planck's law of radiation, which correctly described the blackbody spectrum using a quantum of action hν. This founding of quantum theory resolved the ultraviolet catastrophe.
Radiation is the transmission of heat from one place to another without an intervening medium. Thermal radiation emitted by hot bodies is due to their temperature. Thermal radiation exhibits properties of electromagnetic waves like reflection, refraction, interference and diffraction. A perfect black body completely absorbs all wavelengths of radiation incident on it and is an ideal emitter of thermal radiation. Fery's black body is a hollow copper sphere with a fine hole and blackened interior that absorbs radiation through multiple reflections. Stefan's law states that the total radiation emitted from a black body is directly proportional to the fourth power of its absolute temperature.
Absorptivity
Reflectivity
Transmissivity
Emissivity
Grey Body
Black Body
Laws of black body radiation
Stefan-Boltzmann law
Planck’s Law
Wiens Displacement law
Conclusion
Heat transfer is the movement of heat energy from warmer objects to cooler ones. There are three main types of heat transfer: conduction (through direct contact of objects), convection (through the movement of fluids like air or water), and radiation (through electromagnetic waves without direct contact). Heat will continue to transfer until both objects reach the same temperature, with the rate of transfer increasing with a larger difference in temperatures.
Heat is thermal energy transferred from a warmer body to a colder one. Temperature is the measure of the amount of heat in a body. There are three main ways heat transfers between objects: conduction through direct contact, convection through the movement of fluids like liquids and gases, and radiation through electromagnetic waves without contact. Heat causes changes in materials like changes of state between solids, liquids and gases, and changes in volume through expansion and contraction as materials heat up and cool down.
This document describes an emissivity measurement apparatus that determines the emissivity of gray surfaces. It consists of a black plate and gray test plate that are electrically heated to the same temperature. The power input required to heat the gray plate to the same temperature as the black plate is measured. Since the plates have all other properties identical except emissivity, the difference in power input is due to the difference in emissivity. By measuring this power difference at various temperatures, the emissivity of the gray surface can be determined relative to the black plate.
- Thermal radiation is electromagnetic radiation emitted from objects due to their temperature. It includes infrared, visible light, and some ultraviolet wavelengths. A blackbody is a perfect emitter and absorber of radiation. According to Stefan-Boltzmann law, a blackbody's total emissive power is directly proportional to the fourth power of its absolute temperature. Planck's law describes the spectral distribution of a blackbody's radiative intensity as a function of wavelength and temperature. The emissivity of a surface is the ratio of radiation it emits compared to a blackbody. Kirchhoff's law states that emissivity of a surface is equal to its absorptivity at a given temperature and wavelength. The greenhouse effect
Thermal radiation occurs across a wide spectrum of electromagnetic wavelengths. Most thermal radiation from objects at room temperature falls within the infrared range, which is invisible to the human eye. The wavelength distribution of radiation emitted by an object depends on its temperature according to Planck's law. Nearly all surfaces emit and absorb thermal radiation to some degree, with the ratio between emitted and absorbed radiation determined by the surface's emissivity. Emissivity also affects how much solar energy a surface absorbs. Proper material selection and surface treatments can influence thermal radiation to control heating and cooling in devices and systems.
Kirchhoff's Law states that the emission of a body is equal to the ratio of its emissivity and the blackbody emission at a given wavelength and temperature. Wien's Law establishes that the dominant wavelength of blackbody radiation is inversely proportional to temperature. The Stefan-Boltzmann Law provides that the total energy flux radiated by a blackbody is directly proportional to the fourth power of its absolute temperature.
The document discusses three modes of heat transfer: conduction, convection, and radiation. Radiation is defined as the transfer of heat through space or matter without the need for a medium and occurs via electromagnetic waves or photons. Some key laws governing radiant heat transfer are discussed, including Stefan-Boltzmann's law which states that the emissive power of a black body is proportional to the fourth power of its absolute temperature. Radiative properties like emissivity, absorptivity, and reflectivity are also covered.
The document defines different types of bodies in heat transfer:
1. A black body absorbs all radiation falling on its surface and is a perfect emitter.
2. A white body reflects all incident radiation falling on it.
3. A gray body's absorptivity does not vary with temperature or wavelength of incident radiation.
4. An opaque body does not transmit any radiation through it, while a transparent body transmits all radiation.
This document discusses several laws relating to the radiation of heat, including:
1) Kirchhoff's law, which states that the emission of a body at a given wavelength and temperature is equal to the ratio of the emissivity and blackbody emission. Real objects emit less radiation than black bodies.
2) Wien's law, which says the dominant wavelength at which a blackbody emits radiation is inversely proportional to its temperature.
3) The Stefan-Boltzmann law, stating that a blackbody's total energy flux is directly proportional to the fourth power of its temperature.
This document provides an overview of fundamental radiation concepts. It defines thermal radiation and blackbody radiation, describing the idealized blackbody and Stefan-Boltzmann law. It also covers radiation intensity, radiative properties including emissivity and absorptivity, and Kirchhoff's law relating emissivity and absorptivity. The objectives are to classify electromagnetic radiation, understand blackbody radiation characteristics, and apply concepts of radiation intensity and surface radiative properties.
The document discusses the history and development of theories of blackbody radiation and the concept of the photon. It describes how (1) classical physics could not fully explain experimental observations of blackbody radiation, (2) Planck resolved this issue by proposing that the radiation emitted by cavity walls was quantized into discrete energy packets called quanta (later known as photons), and (3) his theory accurately described blackbody radiation distribution and resolved prior inconsistencies like the ultraviolet catastrophe.
This document discusses blackbody radiation and the laws that describe it. It defines a blackbody as an ideal absorber of all incident radiation. It then explains the four main blackbody radiation laws: 1) The Rayleigh-Jeans law applies to long wavelengths but fails at short wavelengths, 2) The Planck law provides accurate predictions across all wavelengths, 3) The Wien displacement law describes how the peak wavelength shifts to shorter wavelengths at higher temperatures, and 4) The Stefan-Boltzmann law establishes that total radiation emitted increases with the fourth power of temperature. Real objects can be compared to blackbodies, and the document provides an example application calculating the Earth's surface temperature from its energy balance.
Black body is an ideal body that absorbs all incident radiation without reflecting any energy. As temperature increases, the peak wavelength emitted decreases and total energy emitted increases. Early models like Rayleigh-Jeans law failed to accurately predict blackbody radiation at small wavelengths, known as the ultraviolet catastrophe. Planck's law and other laws like Wien's displacement law, Stefan-Boltzmann law accurately describe blackbody radiation. Blackbody radiation spectrum depends only on temperature and not the object.
This document discusses key concepts relating to blackbody radiation. It begins by introducing the concept of a blackbody as an ideal absorber of electromagnetic radiation. It then describes Stefan's Law, which states that the total energy radiated by a blackbody is directly proportional to the fourth power of its thermodynamic temperature. Next, it explains Wein's Displacement Law, which establishes that the peak wavelength of blackbody radiation is inversely proportional to the temperature of the blackbody. The document provides formulas for both laws and gives examples of how they can be applied.
This document discusses the laws of radiation and heat transfer. It defines radiation as electromagnetic energy transfer and outlines four key laws:
1) Kirchhoff's law relates the amount of radiated energy to absorbed energy.
2) Stefan-Boltzmann law describes the amount of radiant energy emitted from a black body, which absorbs all radiation.
3) Planck's law defines the emissive power of a black body as a function of wavelength and temperature.
4) Wien's law describes how the wavelength of maximum radiant intensity decreases proportionally as temperature increases.
Radiation is a form of energy transfer that does not require a medium and travels at the speed of light. Unlike conduction and convection, radiation can transfer heat through a vacuum. All objects emit thermal radiation based on their temperature, with the spectrum and intensity of radiation described by blackbody radiation laws. Radiation transfer is important in applications like solar energy and remote heating/cooling between separated objects.
Radiation heat transfer involves the transfer of heat energy through electromagnetic waves. The three main modes of heat transfer are conduction, convection, and radiation. Radiation is the transfer of heat energy through empty space without a medium and follows the laws of blackbody radiation including Planck's law, Wien's law, Stefan-Boltzmann law, and Kirchhoff's law. Radiation processing uses ionizing radiation like gamma rays and electron beams to destroy pathogens and microbes in foods to increase shelf life and ensure safety while maintaining quality.
1) Classical theories could not explain the spectrum of blackbody radiation, predicting infinite energy at short wavelengths.
2) Planck hypothesized that the oscillators could only emit or absorb energy in discrete quantized units proportional to frequency, avoiding the infinity.
3) This led to Planck's law of radiation, which correctly described the blackbody spectrum using a quantum of action hν. This founding of quantum theory resolved the ultraviolet catastrophe.
Radiation is the transmission of heat from one place to another without an intervening medium. Thermal radiation emitted by hot bodies is due to their temperature. Thermal radiation exhibits properties of electromagnetic waves like reflection, refraction, interference and diffraction. A perfect black body completely absorbs all wavelengths of radiation incident on it and is an ideal emitter of thermal radiation. Fery's black body is a hollow copper sphere with a fine hole and blackened interior that absorbs radiation through multiple reflections. Stefan's law states that the total radiation emitted from a black body is directly proportional to the fourth power of its absolute temperature.
Absorptivity
Reflectivity
Transmissivity
Emissivity
Grey Body
Black Body
Laws of black body radiation
Stefan-Boltzmann law
Planck’s Law
Wiens Displacement law
Conclusion
Heat transfer is the movement of heat energy from warmer objects to cooler ones. There are three main types of heat transfer: conduction (through direct contact of objects), convection (through the movement of fluids like air or water), and radiation (through electromagnetic waves without direct contact). Heat will continue to transfer until both objects reach the same temperature, with the rate of transfer increasing with a larger difference in temperatures.
Heat is thermal energy transferred from a warmer body to a colder one. Temperature is the measure of the amount of heat in a body. There are three main ways heat transfers between objects: conduction through direct contact, convection through the movement of fluids like liquids and gases, and radiation through electromagnetic waves without contact. Heat causes changes in materials like changes of state between solids, liquids and gases, and changes in volume through expansion and contraction as materials heat up and cool down.
The document discusses plate tectonics and the structure of the Earth. It explains that Earth's outer layer is divided into plates that move over Earth's mantle in a constant state of motion. This motion of plates causes continental drift and is responsible for geological features and events like earthquakes, volcanic eruptions, and mountain building. The theory of plate tectonics developed in the 1960s to explain phenomena like sea floor spreading and the movement of continents over geologic time.
Methods of heat transfer and thermal properties of soil dathan cs
1. Heat transfer in soils occurs through three modes: conduction, convection, and radiation. Conduction involves the transfer of heat between contacting surfaces of the same or different substances. Convection involves the transfer of heat by the actual movement of heated molecules within gases and liquids. Radiation involves the transfer of heat through empty space by electromagnetic waves.
2. Key thermal properties of soils include specific heat, thermal conductivity, and thermal diffusivity. Specific heat refers to the amount of heat required to change a substance's temperature. Thermal conductivity measures a material's ability to conduct heat. Thermal diffusivity indicates a material's ability to conduct thermal energy relative to its ability to store energy.
3.
The structure of the earth and plate tectonicsccbthirdgrade
The Earth is composed of four main layers - the inner core, outer core, mantle, and crust. The crust is divided into tectonic plates that slowly move due to convection currents in the mantle. There are three types of plate boundaries - divergent where plates move apart, convergent where they move together, and transform where they slide past each other. Plate interactions at boundaries cause volcanic and seismic activity, with volcanoes and earthquakes concentrated near plate margins.
The document describes different types of landforms and features found on Earth's surface, as well as processes that shape them. It explains that landforms include mountains, hills, valleys, and plateaus. Bodies of water and glaciers also shape landforms by eroding and depositing material. Volcanoes and earthquakes cause rapid changes through erupting lava and shifting crustal plates, which further alter the landscape over time.
The document discusses various landforms and features of the Earth's surface and interior. It defines a landform as a physical feature on the Earth's surface and describes features of the ocean floor such as ocean basins, continental shelves, slopes, canyons, and rises. It also discusses how elevation and topographical maps are used to map Earth's landforms. Finally, it outlines Earth's major layers including the atmosphere, hydrosphere, crust, mantle, outer core, and inner core.
1) Temperature is defined as the average kinetic energy of air molecules, with higher temperatures indicating faster moving molecules. Different temperature scales are discussed, including Fahrenheit, Celsius, and Kelvin.
2) Heat is the transfer of energy that changes an object's temperature, with specific heat referring to the amount of heat needed to change an object's temperature. Water has a specific heat of 1.0.
3) Latent heat is the energy required for phase changes between solid, liquid, and gas, such as melting or evaporation. Latent heat drives thunderstorms and hurricanes.
The document summarizes key concepts about the atmosphere and weather, including that the atmosphere interacts with solar radiation to cause weather changes via heat, air pressure, wind, and moisture. It describes the three main types of solar radiation - visible light, ultraviolet radiation, and infrared radiation, which is a form of heat energy. It also explains the three methods of heat transfer - radiation, conduction, and convection - and the greenhouse effect by which atmospheric gases like carbon dioxide absorb and transfer heat.
The document defines and categorizes different types of landforms. It discusses the two main processes that change landforms: endogenous processes that occur underground like faulting and folding, and exogenous processes that occur above ground like weathering, erosion, and deposition. Landforms are categorized into three orders of relief based on their size - first order includes continents and oceans, second order includes mountains and plains, and third order includes smaller landforms formed by erosion and deposition. Four major landforms are described in detail: plains, mountains, plateaus, and hills. Four minor landforms are also defined: valleys, basins, buttes, and canyons. Examples of each landform type are provided.
The physical environment chapter discusses the components that make up Earth's physical environment: land, air, water, and the living environment. It describes key landforms like mountains and rivers, as well as geological processes that create and modify landforms such as plate tectonics, folding, volcanism, and erosion. Weathering and erosion by forces such as water, wind, and plant growth gradually break rocks into sediment and transport material from one place to another over long periods of time, shaping the surface of the planet. Human activities and settlement patterns are also influenced by landforms and geological characteristics of different regions.
The Earth is composed of several concentric layers. The inner core is solid and suspended in the molten outer core, which generates the Earth's magnetic field through convection. Below this is the lower mantle, composed primarily of silicon, magnesium and oxygen. The upper mantle extends from 10-400km deep and includes olivine and pyroxene minerals, and may partially be molten. Above this is the transition region that includes basaltic magmas and minerals like garnet. The outermost layers are the oceanic and continental crusts, the former made of basalt from sea floor spreading and the latter composed mainly of low-density minerals like quartz and feldspar.
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.
The document summarizes key aspects of Earth's structure and composition. It describes Earth's distinct atmospheric layers and how pressure decreases with altitude. It also outlines Earth's internal layering, including the crust, mantle, and core. The crust is divided into continental and oceanic types based on differences in density and thickness. The mantle conveys heat via convection currents. The liquid outer core generates Earth's magnetic field through the geodynamo process.
The document discusses key concepts of Earth and space science. It describes how the Earth rotates on its axis creating night and day, and revolves around the sun in its yearly orbit. It classifies the objects in our solar system as inner planets, outer planets, and dwarf planets. It also discusses the rare occurrence of a blue moon, which is when there are two full moons in a single calendar month. A link is provided about blue moons.
This document discusses how landforms are changed through weathering and erosion. It describes how weathering is the breaking down and changing of rocks through processes like water freezing in cracks which causes the rocks to break apart over time. Erosion is then defined as the movement of weathered rocks and soils by agents like wind, water, and glaciers which can further shape the land over long periods.
The document discusses the layered internal structure of the Earth based on differences in composition, density, seismic wave velocities, and mechanical properties. It is divided into five main layers from outermost to innermost: the crust, mantle, outer core, and inner core. The crust and upper mantle are solid and composed of silicate rocks, while the lower mantle, outer core, and inner core are increasingly dense with the inner core being solid iron-nickel alloy. Seismic discontinuities exist that help delineate the boundaries between layers.
The Earth is made up of layers including an inner solid iron core, outer liquid core, mantle composed of silicates and magnesium oxide that is mostly solid but allows for convection currents, and a thin crust on top made of oceanic or continental plates that are the youngest and most brittle part of the planet.
The document discusses heat transfer and ways to reduce heat loss from homes. It explains that heat always moves from warmer to cooler areas and names some common household devices that waste energy as heat or sound. It then discusses different insulation methods that can be used to reduce heat loss from homes, including double glazing, loft insulation, and cavity wall insulation.
1) The document discusses concepts related to heat transfer through thermal radiation including Planck's law, Wien's displacement law, and the Stefan-Boltzmann equation. 2) It introduces the concepts of blackbody and graybody radiation and how real surfaces have radiation properties that depend on wavelength and direction. 3) Key radiation properties discussed include emissivity, absorptivity, reflectivity, and transmissivity as well as Kirchhoff's law relating these properties.
This document provides an overview of radiation heat transfer and outlines the course content for an undergraduate course on the topic. It discusses key concepts such as blackbody radiation, Planck's law, Stefan-Boltzmann law, and Wien's displacement law. Example problems are provided to illustrate calculating the spectral and total emissive power of blackbody radiation sources. The summary highlights that radiation transfer does not require a medium, occurs at the speed of light, and that surfaces behave as blackbodies when enclosed in an isothermal cavity.
This chapter discusses the fundamentals of thermal radiation. It defines key concepts like blackbody radiation, radiation intensity, and radiative properties. Blackbody radiation describes the maximum emission from an idealized radiating surface. Real surfaces have emissivity, absorptivity, reflectivity, and transmissivity that determine their radiative behavior. Kirchhoff's law relates these properties. Atmospheric effects like the greenhouse effect and solar radiation inputs are also covered.
This document provides an introduction to remote sensing, including the electromagnetic spectrum, interaction of electromagnetic radiation with the atmosphere and Earth's surface, and spectral signatures. It discusses that remote sensing uses electromagnetic energy from the sun as the energy source. It interacts with the atmosphere through scattering and absorption before reaching Earth's surface where it can be reflected, absorbed, or transmitted by different features. The varying reflectance across the electromagnetic spectrum creates unique spectral signatures that can be used for feature identification in remote sensing images.
- Radiation is the transfer of heat through electromagnetic waves between objects, even in a vacuum. Unlike conduction and convection, radiation can occur over distances without a medium.
- The rate of radiation heat transfer depends on the temperature of the objects - hotter objects radiate more energy than colder objects. All objects with temperatures above absolute zero radiate energy.
- Plank's law describes the spectral distribution of radiation emitted by a blackbody, which is the perfect emitter and absorber. It shows that radiation intensity peaks at shorter wavelengths as temperature increases.
1. Radiation can be described using both wave and particle theories, with photons traveling at the speed of light and having energy levels related to their frequency.
2. Thermal radiation emitted from surfaces is within the wavelength range of 10-7 to 10-4 m. The human eye can detect wavelengths from 3.8x10-7 to 7.6x10-7 m, known as visible radiation.
3. A blackbody is an idealized radiating surface that absorbs all radiation falling on it and reaches the maximum possible emissive power at each wavelength for a given temperature.
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Thermal radiation is electromagnetic radiation emitted by bodies due to their temperature. Radiative heat transfer depends on the temperature, nature, and state of the emitting surface. The wavelength of thermal radiation ranges from 0.1 to 100 μm. Black bodies are ideal absorbers that absorb all radiation, while real bodies absorb partially. The total radiation emitted by a black body is directly proportional to its absolute temperature raised to the fourth power, as described by Stefan-Boltzman's law. The wavelength of maximum emission shifts to shorter wavelengths as temperature increases, according to Wien's displacement law.
This document discusses fundamentals of thermal radiation. It begins by defining radiation and distinguishing it from conduction and convection. Radiation transfer occurs via electromagnetic waves and is characterized by frequency and wavelength. Thermal radiation emitted by all objects above absolute zero is within the spectrum of 0.1 to 100 micrometers. The document then covers blackbody radiation, spectral emissive power, radiation intensity, radiative properties of materials including emissivity and absorptivity, and Kirchhoff's law relating emissivity and absorptivity.
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Black body radiation,planck's radiation, wien's law, stephen boltzmann law in...P.K. Mani
This document discusses remote sensing and its applications in soil resource mapping. It begins with an introduction to how remote sensing is affected by how well radiation penetrates the atmosphere, especially over long distances from satellites. It then provides background on the nature of light and electromagnetic radiation, including Maxwell's equations and Kirchhoff's laws of thermal radiation. The document discusses key concepts in remote sensing like blackbody radiation, Planck's radiation law, the Rayleigh-Jeans law, Wein's displacement law, and the Stefan-Boltzmann law. It also covers atmospheric interactions with electromagnetic radiation like absorption, scattering, and transmission windows.
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2. Solar radiation transfers energy via electromagnetic waves from the sun to Earth within 8 minutes.
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HT-Lecture-16-Modes of heat transfer Radiation .pptxWaheedMiran1
This document discusses heat transfer by radiation. It defines key concepts such as black bodies, which absorb all radiation, and Planck's distribution law, which describes the spectral radiative power of a black body as a function of temperature and wavelength. It also covers Wein's displacement law relating the wavelength of maximum emission to temperature, and the Stefan-Boltzmann law for total radiation emitted from a black body. Radiative properties of materials like emissivity and view factors are also discussed.
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2) Radiation behaves both as particles (photons) and waves, and is characterized by wavelength and frequency. Thermal radiation is confined to the infrared, visible, and ultraviolet regions of the electromagnetic spectrum.
3) A blackbody is an idealized perfect emitter and absorber of radiation. It has a characteristic spectral distribution of radiation that depends only on its temperature, as described by Planck's law and the Stefan-Boltzmann law.
This document discusses key concepts relating to blackbody radiation. It begins by introducing the concept of a blackbody as an ideal absorber of electromagnetic radiation. It then describes Stefan's Law, which states that the total energy radiated by a blackbody is directly proportional to the fourth power of its thermodynamic temperature. Next, it explains Wein's Displacement Law, which establishes that the peak wavelength of blackbody radiation is inversely proportional to the temperature of the blackbody. The document provides formulas for both laws and gives examples of how they can be applied.
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This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
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বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
Pollock and Snow "DEIA in the Scholarly Landscape, Session One: Setting Expec...
Radiation heat transfer and clothing comfort
1. Radiation as a Mode of Heat Transfer in Textiles and Clothing
Dr. Kausik Bal
KHT, TUL
2. Radiation is the energy emitted by matter in the form of electro-magnetic waves.
Thermal radiation is energy emitted by matter that is at a finite temperature above the
absolute zero. Unlike conduction or convection, it does not require any medium of transfer.
What is thermal radiation?
3. Radiation in Nature: The Sun
Coronal Mass Ejection as viewed by the Solar Dynamics Observatory on June 7,
2011. Credit: NASA/SDO
Distance to Earth: 149,600,000 km (light travels from the Sun to Earth in about 8 minutes and 19 seconds.)
Surface temperature: 5,778 K
Mass: 1.98930 kg
Radius: 695,500 km
7. Heating of Earth Surface: Global Warming
http://earthobservatory.nasa.gov/Features/GlobalWarming/page2.php
8. Solar Energy Spectrum
Solar Constant = 1.36 kW/m2 (amount of incoming solar radiation per unit area on a plane perpendicular
to the rays at a distance of 1 astronomical unit [AU]).
9. The speed of radiation
Electromagnetic waves are characterized by their frequency (ν) [Hz] and wavelength
(λ) [m] where
λν =
𝑐0
𝑛
n = index of refraction of the medium
(n = 1 for air)
𝑐0 = 3 × 108 [ 𝑚 𝑠] is the speed of light (or the EM wave) in vacuum
10. Radiation at interface of two media
𝐴𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑣𝑖𝑡𝑦 = α
𝑅𝑒𝑓𝑙𝑒𝑐𝑡𝑖𝑣𝑖𝑡𝑦 = ρ
𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑣𝑖𝑡𝑦 = τ
α + ρ + τ = 1
For opaque surface, τ = 0 and hence, α + ρ = 1
Irradiation = Radiation flux
incident on a surface
(denoted by G)
SUN
Incident solar
radiation 100%
Reflected
radiation 8%
Transmitted
radiation 80%
Absorbed
radiation 12%
Outward transfer of
absorbed radiation 8%
Inward transfer of
absorbed radiation 4%
11. Blackbody
Blackbody is a hypothetical (or theoretical) surface which is a perfect absorber of
electromagnetic radiation, i.e., for the surface of blackbody, absorptivity α = 1.
A blackbody absorbs all the radiation that falls on it, converts it into internal energy
(heat), and then re-radiates this energy into the surroundings. The re-radiated thermal
energy, known as blackbody radiation, has a continuous spectrum governed solely by
the body's temperature.
12. Emissivity of a surface
(Total hemispherical) Emissivity ε 𝑇 =
𝐸 𝑇
𝐸 𝑏 𝑇
is the ratio of the total radiation energy
emitted by the surface at a given temperature over all wavelengths in all directions to the
same emitted by a blackbody at the same temperature.
By definition, the emissivity of a blackbody is maximum and equals to unity.
All real surfaces have emissivity less than unity and are known as grey body. In the
extreme case, a white body is a hypothetical surface which does not absorb any
wavelength of radiation incident upon it at any direction.
Materials Temperature (°C) Typical emissivity
Commercial aluminium sheet 100 0.09
Pure highly polished gold 100 0.02
Brick (Building) 1000 0.45
Concrete 0 - 100 0.94
Smooth glass 0 - 200 0.95
Graphite 0 - 3600 0.7 – 0.8
Human skin 36 0.985
Wood (Oak, sanded) 93 0.82
Opaque plastics (any colour) 25 0.95
www.transmetra.ch
13. Stefan – Boltzmann Law
𝐸 𝑏 𝑇 = σ𝑇4
[ 𝑊 𝑚2
]
σ = 5.670 × 10−8
[ 𝑊 𝑚2
𝐾4
] is Stefan-Boltzmann constant
Example:
1. What is the radiation flux emitted by human skin? (Take ε = 0.95)
Solution: Skin temperature = 305 [K], hence, the radiative heat flux is:
𝐸 𝑇 = 305 = 0.95 × 5.670 × 10−8 × 3054 = 466 𝑊 𝑚2
2. Calculate the radiation flux from a wall with ε = 0.64 which is at 20°C.
Solution: Wall temperature = 293 [K], hence the radiative heat flux is:
𝐸 𝑇 = 293 = 0.5 × 5.670 × 10−8
× 2934
= 267 𝑊 𝑚2
The total radiation flux emitted by a blackbody at temperature T is a function of its
temperature only
Therefore, for a real surface (grey body with surface emissivity ε, the total radiation flux
emitted is E 𝑇 = εσ𝑇4.
14. Kirchhoff’s Law
The total hemispherical emissivity of a surface at temperature T is equal to its total
hemispherical absorptivity for radiation coming from a blackbody at the same
temperature.
ε 𝑇 = α 𝑇
T
T
(ε, α)
E(T)
17. Radiation Geometry I: Solid angle
2D 3D
𝑑ω =
𝑑𝑆
𝑟2
= sin 𝜃 𝑑𝜃𝑑φ
dS
φ
θ
r
Unit of solid angle: sr (steradian)
18. Intensity of radiation
The Radiation Intensity 𝐼𝑒 θ, φ is defined as the rate at which radiation energy 𝑑𝑄 𝑒
is emitted in the θ, φ direction per unit area normal to this direction and per unit
solid angle about this direction.
𝐼𝑒 𝜃, φ =
𝑑𝑄 𝑒
𝑑𝐴 cos 𝜃 sin 𝜃𝑑𝜃𝑑φ
𝑊 𝑚2
. 𝑠𝑟
19. Emissive power
The radiation flux for emitted radiation is the emissive power E, i.e., the rate at which
radiation energy is emitted per unit area of the emitting surface.
𝐸 =
ℎ𝑒𝑚𝑖𝑠𝑝ℎ𝑒𝑟𝑒
𝑑𝐸 =
φ=0
2𝜋
𝜃=0
𝜋
2
𝐼𝑒 𝜃, 𝜑 cos 𝜃 sin 𝜃 𝑑𝜃𝑑𝜑 𝑊 𝑚2
In case of diffusely emitting surface, 𝐸 = 𝜋𝐼𝑒 𝑊 𝑚2
Therefore, in case of a blackbody, the following is valid:
𝐼 𝑏 𝑇 =
𝐸 𝑏 𝑇
𝜋
=
𝜎𝑇4
𝜋
𝑊 𝑚2 . 𝑠𝑟
20. Irradiation
The intensity of incident radiation 𝐼𝑖 𝜃, 𝜑 is defined as the rate at which radiation energy 𝑑𝐺 is
incident from the 𝜃, 𝜑 direction per unit area of the receiving surface normal to this direction and
per unit solid angle about this direction. When incident radiation is diffused, 𝐼𝑖 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡.
𝐺 =
ℎ𝑒𝑚𝑖𝑠𝑝ℎ𝑒𝑟𝑒
𝑑𝐺 =
φ=0
2𝜋
𝜃=0
𝜋
2
𝐼𝑖 𝜃, 𝜑 cos 𝜃 sin 𝜃 𝑑𝜃𝑑𝜑 𝑊 𝑚2
The radiation flux incident on a surface from all directions is called irradiation (G).
For diffusely incident radiation, 𝐺 = 𝜋𝐼𝑒 𝑊 𝑚2
21. Radiosity
The rate at which radiation energy leaves a unit area of a surface in all directions is termed as
Radiosity (J).
𝐽 =
φ=0
2𝜋
𝜃=0
𝜋
2
𝐼𝑒+𝑟 𝜃, 𝜑 cos 𝜃 sin 𝜃 𝑑𝜃𝑑𝜑 𝑊 𝑚2
G
J
E
𝐺 𝑟𝑒𝑓
25. Radiation heat transfer
𝑇1 𝑇2
𝑄1
𝑄2
𝐴1 𝐴2 Net radiation transfer from surface 1 to 2 (both black) is:
𝑄12 = 𝐴1 𝐹12 𝜎 𝑇1
4
− 𝑇2
4
𝑊
Net radiation transfer from non-black surface i is:
𝑄𝑖 =
𝐴𝑖 𝜀𝑖
1 − 𝜀𝑖
𝐸 𝑏𝑖 − 𝐽𝑖
Electrical analogy: 𝑄𝑖 =
𝐸 𝑏𝑖−𝐽 𝑖
𝑅 𝑖
where, 𝑅𝑖 =
1−𝜀𝑖
𝐴 𝑖 𝜀𝑖
is Surface Resistance
When the two surfaces are diffuse, opaque and grey, net
radiation heat transfer from surface i to surface j:
𝑄𝑖𝑗 =
𝐽 𝑖−𝐽 𝑗
𝑅 𝑖𝑗
where 𝑅𝑖𝑗 =
1
𝐴 𝑖 𝐹 𝑖𝑗
is Space Resistance
𝐸 𝑏𝑖
𝑅𝑖
𝐽𝑖
𝑅𝑗
𝐽𝑗
𝐸 𝑏𝑗
𝑅𝑖𝑗
𝑄𝑖𝑗
27. Reflecting surfaces and coating
Surface Absorptivity
Aluminum, dull/rough polished 0.4 - 0.65
Aluminum. polished 0.1 - 0-40
Asbestos Cement, old 0.83
Black matt 0.95
Chromium plate 0.20
Iron, galvanised old 0.89 - 0.92
Grey paint 0.95
Light gren paint 0.95
Limestone 0.33 - 0.53
Red clay brick 0.94
White paint 0.89
For opaque materials, practically there is no transmission 𝜏 = 0 of radiation incident
on its surface. Hence, in such cases, ρ = 1 − 𝛼
28. Scattering
It is the process in which electromagnetic radiation or particles are deflected or
diffused. Such deflection can be due to the presence of other particle (s) or due to
localized non-uniformities of the medium.
Generally speaking, in case of waves (e.g. EM waves), the interaction with a matter
may cause two types of reflections from the surface where the wave is incident, one is
specular reflection and another is diffused reflection. The second type is a common
example of scattering.
In case of light (EM wave) scattering from a small particles, scattering is categorized in
three domains based on a dimensionless parameter.
Rayleigh Scattering: 𝛼 ≪ 1
Mie Scattering: 𝛼 ≈ 1
Geometric Scattering: 𝛼 ≫ 1
D Here, 𝛼 =
𝜋𝐷
λ
29. Thermal radiation and textiles
Radiation, emitted by a hot surface may pass through the straight
pores (holes) across the textile.
Radiation, while passing through a textile, may be scattered by
the solid fibres or yarn.
Radiation incident on fibres, yarns or fabric surface may partly
be absorbed.
The fibres, yarns or fabric itself may emit radiation as a grey
body which depends on its temperature and emissivity.
Some fibres may allow the radiation to be transmitted through
them by refraction
In case of special fibres (e.g., metallic) or in case of textiles with
reflective coating (e.g. metallic coating), a significant amount of
incident radiation may be reflected back by specular reflection.
30. Research on the thermal radiation in textiles
Theoretical prediction of radiation through woven (and/or knitted fabric) in the
light of the fabric structure.
Theoretical prediction of radiation through nonwovens and random fibrous
assemblies.
Development of measurement techniques with fabrics in single and multiple
layers.
Development of measurement techniques with clothing.
Empirical and semi-empirical modelling of insulation from thermal radiation in
respect of protection from heat stress.
Empirical and semi-empirical modelling of radiation transfer and shielding in case
of UV protection.
Empirical analysis of structure – property relations to find total effective thermal
resistance.
31. Interaction of thermal radiation with fibres and yarns
Considering the typical diameter of textile fibres which has a range 10−6 [𝑚] - 10−4 [𝑚],
and the wavelength of thermal radiation being between 10−7
[𝑚] and 10−3
[𝑚].
Therefore, fibres can cause scattering of thermal radiation and such scattering is
often considered to be in the Mie Scattering regime.
Yarns have typical diameters in the range 10−5
[𝑚] - 10−3
[𝑚], and therefore
such yarns as a solid material can also cause scattering of thermal radiation and
such scattering is also often considered to be in the Mie Scattering regime.
Some researchers have developed models of radiation
heat transfer in fibrous materials such as nonwovens
assuming that there is no scattering.
1. B. Farnworth, Mechanism of heat flow through clothing insulation, Textile Research Journal, Vol. 53 (12), 1983.
2. X. Wan; J. Fan, Heat transfer through fibrous assemblies incorporating reflective interlayers, International Journal of heat & Mass Transfer, Vol.
55, 2012.
3. D. Bhattacharjee & V. K. Kothari, A theoretical model to predict the thermal resistance of plain woven fabrics, Indian Journal of Fibre & Textile
research, Vol. 30 (3), 2005.
32. Modelling thermal radiation transfer through fabrics
In situation where the total heat transfer by conduction through fabric is much higher
than the heat transfer by radiation, the total thermal conductivity (or resistance) can be
considered as a linear sum of the individual components due to conduction and radiation.
λ 𝑒𝑓𝑓 = λ 𝑐𝑜𝑛𝑑 + λ 𝑟𝑎𝑑
In such cases, it is assumed that it is possible to express the radiative heat flux in terms
of the temperature gradient at steady state which resembles Fourier’s law of thermal
conductivity.
𝑞 𝑟𝑎𝑑 = λ 𝑟𝑎𝑑 𝑇1 − 𝑇2
Where λ 𝑟𝑎𝑑 = 4𝜎𝑇 𝑚
3
𝜀1
−1 + 𝜀2
−1 − 1 and 𝑇 𝑚 = 𝑇1 + 𝑇2 2
In case of nonwovens or similar low density fabrics, the radiation is given as
λ 𝑟𝑎𝑑 =
4ℎ𝜎𝑇 𝑚
3
2
𝜀
− 1
𝑒
0.188ℎ ν−1 𝜇
𝑟√𝜋
ℎ = thickness
ν = (idealized) portion of fibres
oriented vertically
𝜇 = filling coefficient of the fabric
1. M. Boguslawska-Baczek; L. Hes, Determination of heat transfer by radiation in textile fabrics by means of method with known emissivity of
plates, Journal of Industrial Textiles, 2013.
33. Radiation heat transfer through clothing
• Clothing acts as a barrier to radiation heat transfer
between skin and environment.
• The insulation or protection provided by the clothing can
reduce heat stress and discomfort and can even be a life
saver when the clothed human is exposed to very intense
thermal radiation.
Intense solar radiation (dry deserts and snow-capped
mountain peaks)
Fire-fighting
Furnace-work
Space-travel
Very limited models exist for the radiation heat transfer through clothing, some empirical
and some semi-analytical and almost all approximate.
1. E. A. D. Hartog; G. Havenith, Analytical study of the heat loss attenuation by clothing on thermal manikins under radiative heat loads,
International Journal of occupational Safety and Ergonomics, Vol. 16 92), 2010.
34. Protection Vs. Comfort: Clothing for radiative environments
The requirements of protection and comfort are
often contradictory. It may be obvious to give
more weightage to protection in case of short
duration use, but comfort becomes more
important for longer duration of continuous use
and performance.
35. Thank you for your attention.
For further discussion, please contact by email: kb.iitd@gmail.com