In
ThermodynamicsIn physics, thermodynamics is the study of the conversion of energy into work and heat and its relation to macroscopic variables such as temperature, volume and pressure...
, the
thermal effusivity of a material is defined as the square root of the product of the material's
thermal conductivityIn physics, thermal conductivity, , is the property of a material that indicates its ability to conduct heat. It appears primarily in Fourier's Law for heat conduction.-Measurement:...
and its
volumetric heat capacityVolumetric heat capacity describes the ability of a given volume of a substance to store internal energy while undergoing a given temperature change, but without undergoing a phase change. It is different from specific heat capacity in that the VHC depends on the volume of the material, while the...
.
Here,
k is the thermal conductivity,
' is the densityThe density of a material is defined as its mass per unit volume. The symbol of density is ρ .- Formula :Mathematically:where: is the density, is the mass, is the volume....
and ' is the
specific heat capacitySpecific heat capacity, often shortened to specific heat, is the measure of the heat energy required to increase the temperature of a of a substance by unit degree. The term originated primarily through the work of 18th-century physicist Joseph Black who conducted various heat measurements and...
. The product of
' and ' is known as the
volumetric heat capacity.
A material's thermal effusivity is a measure of its ability to exchange thermal energy with its surroundings.
If two semi-infinite bodies initially at temperatures
T1 and
T2 are brought in perfect thermal contact, the temperature at the contact surface
Tm will be given by their relative effusivities.
Discussion
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In
ThermodynamicsIn physics, thermodynamics is the study of the conversion of energy into work and heat and its relation to macroscopic variables such as temperature, volume and pressure...
, the
thermal effusivity of a material is defined as the square root of the product of the material's
thermal conductivityIn physics, thermal conductivity, , is the property of a material that indicates its ability to conduct heat. It appears primarily in Fourier's Law for heat conduction.-Measurement:...
and its
volumetric heat capacityVolumetric heat capacity describes the ability of a given volume of a substance to store internal energy while undergoing a given temperature change, but without undergoing a phase change. It is different from specific heat capacity in that the VHC depends on the volume of the material, while the...
.
Here,
k is the thermal conductivity,
' is the densityThe density of a material is defined as its mass per unit volume. The symbol of density is ρ .- Formula :Mathematically:where: is the density, is the mass, is the volume....
and ' is the
specific heat capacitySpecific heat capacity, often shortened to specific heat, is the measure of the heat energy required to increase the temperature of a of a substance by unit degree. The term originated primarily through the work of 18th-century physicist Joseph Black who conducted various heat measurements and...
. The product of
' and ' is known as the
volumetric heat capacity.
A material's thermal effusivity is a measure of its ability to exchange thermal energy with its surroundings.
If two semi-infinite bodies initially at temperatures
T1 and
T2 are brought in perfect thermal contact, the temperature at the contact surface
Tm will be given by their relative effusivities.
This expression is valid for all times for semi-infinite bodies in perfect thermal contact. It is also a good first guess for the initial contact temperature for finite bodies.
See also
- thermal inertia
- thermal diffusivity
In heat transfer analysis, thermal diffusivity is the ratio of thermal conductivity to volumetric heat capacity...
- heat capacity
- specific heat capacity
Specific heat capacity, often shortened to specific heat, is the measure of the heat energy required to increase the temperature of a of a substance by unit degree. The term originated primarily through the work of 18th-century physicist Joseph Black who conducted various heat measurements and...
- heat equation
The heat equation is an important partial differential equation which describes the distribution of heat in a given region over time...
- thermal conductivity
In physics, thermal conductivity, , is the property of a material that indicates its ability to conduct heat. It appears primarily in Fourier's Law for heat conduction.-Measurement:...
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