Volumetric heat capacity (
VHC) describes the ability of a given
volumeThe volume of any solid, liquid, gas, plasma, theoretical object, or vacuum is how much three-dimensional space it occupies, often quantified numerically. One-dimensional figures and two-dimensional shapes are assigned zero volume in the three-dimensional space...
of a substance to store
internal energyIn thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules and the potential energy associated with the vibrational and electric energy of atoms...
while undergoing a given
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
change, but without undergoing a phase change. It is different from
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...
in that the VHC depends on the volume of the material, while the specific heat is based on the
massIn physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass...
of the material. If given a specific heat value of a substance, one can convert it to the VHC by
multiplyMultiplication is the mathematical operation of scaling one number by another. It is one of the four basic operations in elementary arithmetic ....
ing the specific heat by 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....
of the substance.
DulongPierre Louis Dulong was a French physicist and chemist, remembered today largely for the law of Dulong and Petit.- Life and work :Dulong was born in Rouen, France...
and
PetitAlexis Thérèse Petit was a French physicist. Petit is known for is work on the efficiencies of air- and steam-engines, published in 1818...
predicted in 1818 that ρc
p would be constant for all solids (the Dulong-Petit law).
Volumetric heat capacity (
VHC) describes the ability of a given
volumeThe volume of any solid, liquid, gas, plasma, theoretical object, or vacuum is how much three-dimensional space it occupies, often quantified numerically. One-dimensional figures and two-dimensional shapes are assigned zero volume in the three-dimensional space...
of a substance to store
internal energyIn thermodynamics, the internal energy of a thermodynamic system, or a body with well-defined boundaries, denoted by U, or sometimes E, is the total of the kinetic energy due to the motion of molecules and the potential energy associated with the vibrational and electric energy of atoms...
while undergoing a given
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
change, but without undergoing a phase change. It is different from
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...
in that the VHC depends on the volume of the material, while the specific heat is based on the
massIn physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass...
of the material. If given a specific heat value of a substance, one can convert it to the VHC by
multiplyMultiplication is the mathematical operation of scaling one number by another. It is one of the four basic operations in elementary arithmetic ....
ing the specific heat by 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....
of the substance.
DulongPierre Louis Dulong was a French physicist and chemist, remembered today largely for the law of Dulong and Petit.- Life and work :Dulong was born in Rouen, France...
and
PetitAlexis Thérèse Petit was a French physicist. Petit is known for is work on the efficiencies of air- and steam-engines, published in 1818...
predicted in 1818 that ρc
p would be constant for all solids (the Dulong-Petit law). In fact, the quantity varies from about 1.2 to 4.5 MJ/m³K. For liquids it is in the range 1.3 to 1.9, and for gases it is a constant 1.0 kJ/m³K.
The volumetric heat capacity is defined as having
SISi, si, or SI may refer to :- Places :* Mount Si, a mountain in state of Washington* Si County, county in Anhui, China* Si River, a river in China* Slovenia, a European nation Si, si, or SI may refer to (all SI unless otherwise stated):- Places :* Mount Si, a mountain in state of Washington* Si...
units of
JThe joule , named for James Prescott Joule, is the derived unit of energy in the International System of Units. It is the energy exerted by a force of one newton acting to move an object through a distance of one metre...
/(
m³The cubic metre is the SI derived unit of volume. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère...
·
KThe kelvin is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero kelvin...
). It can also be described in Imperial units of
BTUThe British thermal unit is a traditional unit of energy. It is approximately the amount of energy needed to heat one pound of water one degree Fahrenheit. One Btu is equal to about 1.06 kilojoules. It is used in the power, steam generation, heating and air conditioning industries...
/(
ft³The cubic foot is an imperial and US customary unit of volume, used in the United States, Canada and the United Kingdom. It is defined as the volume of a cube with sides of one foot in length.- Symbols :...
·
F°Fahrenheit is the temperature scale proposed in 1724 by, and named after, the physicist Daniel Gabriel Fahrenheit . Today, the scale has been replaced by the Celsius scale in most countries; it is still in use for non-scientific purposes in the United States and a few other nations, such as...
).
Thermal inertia
Thermal inertia is a term commonly used by
scientistA scientist, in the broadest sense, is any person who engages in a systematic activity to acquire knowledge or an individual that engages in such practices and traditions that are linked to schools of thought or philosophy. In a more restricted sense, a scientist is an individual who uses the...
s and engineers modelling
heat transferHeat transfer is the transition of thermal energy from a hotter object to a cooler object...
s and is a bulk material property related to
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 volumetric heat capacity. For example,
this material has a high thermal inertia, or
thermal inertia plays an important role in this system, which means that dynamic effects are prevalent in a model, so that a steady-state calculation will yield inaccurate results.
The term is a scientific analogy, and is not directly related to the mass-and-velocity term used in
mechanicsMechanics is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment....
, where
inertiaInertia is the resistance of any physical object, to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by...
is that which limits the
accelerationIn physics, and more specifically kinematics, acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up or slows...
of an object. In a similar way, thermal inertia is a measure of the thermal mass and the velocity of the thermal wave which controls the surface temperature of a material. In
heat transferHeat transfer is the transition of thermal energy from a hotter object to a cooler object...
, a higher value of the volumetric heat capacity means a longer time for the system to reach
equilibriumIn thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, radiative equilibrium, and chemical equilibrium. Classical thermodynamics deals with dynamic equilibrium states...
.
The thermal inertia of a material is defined as the square root of the product of the material's bulk
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
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...
, where the latter is the product of
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
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...
:
See also
Thermal effusivityIn Thermodynamics, the thermal effusivity of a material is defined as the square root of the product of the material's thermal conductivity and its volumetric heat capacity....
SISi, si, or SI may refer to :- Places :* Mount Si, a mountain in state of Washington* Si County, county in Anhui, China* Si River, a river in China* Slovenia, a European nation Si, si, or SI may refer to (all SI unless otherwise stated):- Places :* Mount Si, a mountain in state of Washington* Si...
units of thermal inertia are J m K s also occasionally referred to as Kieffers, or more rarely, tiu.
For planetary surface materials, thermal inertia is the key property controlling the diurnal and seasonal surface temperature variations and is typically dependent on the physical properties of near-surface geologic materials. In
remote sensingRemote sensing is the small or large-scale acquisition of information of an object or phenomenon, by the use of either recording or real-time sensing device that are wireless, or not in physical or intimate contact with the object...
applications, thermal inertia represents a complex combination of particle size, rock abundance, bedrock outcropping and the degree of induration. A rough approximation to thermal inertia is sometimes obtained from the amplitude of the diurnal temperature curve (i.e., maximum minus minimum surface temperature). The temperature of a material with low thermal inertia changes significantly during the day, while the temperature of a material with high thermal inertia does not change as drastically.
Deriving and understanding the thermal inertia of the surface can help to recognize small-scale features of that surface. In conjunction with other data, thermal inertia can help to characterize surface materials and the geologic processes responsible for forming these materials.
Constant volume and constant pressure.
For gases it is useful to distinguish between volumetric heat capacity at constant volume and at constant
pressurePressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
. This distinction has the same meaning as for
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...
.
See also
- Thermal effusivity
In Thermodynamics, the thermal effusivity of a material is defined as the square root of the product of the material's thermal conductivity and its volumetric heat capacity....
- Temperature
In physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
- 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...
- Thermodynamic equations
In thermodynamics, there are a large number of equations relating the variousthermodynamic quantities. In chemical thermodynamics, which is a sub-branch of thermodynamics, for example, there are millions of useful equations. In particular, the structure of chemical thermodynamics is based on the...