What is mean by thermal diffusivity?
Thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure. It measures the ability of a material to conduct thermal energy relative to its ability to store thermal energy. High diffusivity means heat transfers rapidly.
What is the difference between thermal conductivity and thermal diffusivity?
What is the physical difference between thermal conductivity and thermal diffusivity? Thermal conductivity (l) is a property that determines HOW MUCH heat will flow in a material, while thermal diffusivity (a) determines HOW RAPIDLY heat will flow within it.
What is thermal conductivity?
Thermal conductivity can be defined as the rate at which heat is transferred by conduction through a unit cross-section area of a material, when a temperature gradient exits perpendicular to the area.
What is meant by thermal capacity?
“The thermal capacity of a body is the heat necessary to raise the temperature of the body by one degree.” Thermal capacity = mass of body × specific heat. EXAMPLE.
What is the unit of thermal value?
A U-value is a measure of thermal transmittance, or the amount of heat energy that moves through a floor, wall or roof, from the warm (heated) side to the cold side. It is the number of Watts per square metre of the construction, per degree of temperature difference between one side and the other (W/m2K).
How do you calculate CP from CV?
cp = cv + R The specific heat constants for constant pressure and constant volume processes are related to the gas constant for a given gas.
What is the ratio of CP CV for gas if the pressure?
The heat capacity at constant volume, Cv, is the derivative of the internal energy with respect to the temperature, so for our monoatomic gas, Cv = 3/2 R. The heat capacity at constant pressure can be estimated because the difference between the molar Cp and Cv is R; Cp – Cv = R.
Does specific heat of air change with pressure?
The specific heat of dry air – CP and CV – will vary with pressure and temperature. This may influence on the accuracy of industrial air handling process calculations.
How does heat capacity change with pressure?
Conventional thermodynamic expression predicts that the isobaric heat capacity decreases with increasing pressure. In model calculations, heat capacity increases with pressure, decreases, or remains insensitive to pressure, depending on the model applied.
Does specific heat capacity change with temperature?
The specific heat capacity often varies with temperature, and is different for each state of matter. Liquid water has one of the highest specific heats among common substances, about 4182 J/(K kg) at 20 °C; but that of ice just below 0 °C is only 2093 J/(K kg).
Why is specific heat capacity different for different materials?
1 Answer. Because 1g of one substance does not contain the same number of atoms in another substance.
What is difference between specific heat capacity and heat capacity?
Heat capacity is the ratio of the amount of heat energy transferred to an object to the resulting increase in its temperature. Specific heat capacity is a measure of the amount of heat necessary to raise the temperature of one gram of a pure substance by one degree K.
What is heat capacity used for?
Heat capacity or specific heat is the amount of heat per unit mass that is required to raise the temperature by 1°C. Specific heat is helpful in determining the processing temperatures and amount of heat necessary for processing and can be helpful in differentiating between two polymeric composites.
Is heat capacity an extensive property?
Heat energy is the internal energy of a substance. This includes kinetic and potential energy. As a reminder, an extensive property of a substance is one where QUANTITY does matter. Specific heat capacity is an intensive property.
What is hidden heat called?
latent heat
Why is Latent Heat called hidden heat?
The reason it is called latent or “hidden” is because the temperature of the system does not change even as you are putting in all this heat into the system – all it does is change its phase, from solid → liquid, or liquid → gas. Latent is NOT chemical energy.
What is latent heat in simple words?
Latent heat, energy absorbed or released by a substance during a change in its physical state (phase) that occurs without changing its temperature. The latent heat is normally expressed as the amount of heat (in units of joules or calories) per mole or unit mass of the substance undergoing a change of state.
Why does latent heat not increase water temperature?
Previously, we have discussed temperature change due to heat transfer. Energy is required to melt a solid because the cohesive bonds between the molecules in the solid must be broken apart so that the molecules can move around at comparable kinetic energies; thus, there is no rise in temperature.
What is an example of sensible heat?
Sensible heat is literally the heat that can be felt. It is the energy moving from one system to another that changes the temperature rather than changing its phase. For example, it warms water rather than melting ice. Adding heat to water can either raise the temperature or change the phase.