# Heat capacity rate

Heat capacity rate

The heat capacity rate is heat transfer terminology used in thermodynamics and different forms of engineering denoting the ability of a fluid to resist change in temperature as heat transfer occurs. It is typically denoted as C, listed from empirical data experimentally determined in various reference works, and is typically stated as a comparison between a hot and a cold fluid, Ch and Cc either graphically, or as a linearized equation. It is an important quantity in heat exchanger technology common to either heating or cooling systems and needs, and the solution of many real world problems such as the design of disparate items as different as a microprocessor and an internal combustion engine.

Basis

A hot fluid's heat capacity rate can be much greater than, equal to, or much less than the heat capacity rate of the same fluid when cold. In practice, it is most important in specifying heat-exchanger systems, wherein one fluid usually of dissimilar nature is used to cool another fluid such as the hot gases or steam cooled in a power plant by a heat sink from a water source&mdash;a case of dissimilar fluids, or for specifying the minimal cooling needs of heat transfer across boundaries, such as in air cooling.

As the ability of a fluid to resist change in temperature itself changes as heat transfer occurs changing it's net average instantaneous temperature, it is a quantity of interest in designs which have to compensate for the fact that it varies continuously in a dynamic system. While itself varying, such change must be taken into account when designing a system for overall behavior to stimuli or likely environmental conditions, and in particular the worst case conditions encountered under the high stressess imposed near the limits of operability&mdash; for example, an air cooled engine in a desert clime on a very hot day.

If the hot fluid had a much larger heat capacity rate, then when hot and cold fluids went through a heat exchanger, the hot fluid would have a very small change in temperature while the cold fluid would heat up a significant amount. If the cool fluid has a much lower heat capacity rate, that is desirable. If they were equal, they would both change more or less temperature equally, assuming equal mass-flow per unit time through a heat exchanger. In practice, a cooling fluid which has both a higher specific heat capacity and a lower heat capacity rate is desirable, accounting for the pervasiveness of water cooling solutions in technology&mdash;the polar nature of the water molecule creates some distinct sub-atomic behaviors favorable in practice.

$C=frac\left\{dm\right\}\left\{dt\right\}*c_p$

where "C" = heat capacity rate of the fluid of interest,
"dm/dt" = mass flow rate of the fluid of interest and
"cp" = specific heat of the fluid of interest.

* Heat
* Heat capacity
* Heat capacity ratio
* Heat equation
* Heat transfer coefficient
* Latent heat
* Specific heat capacity
* Specific melting heat
* Specific heat of vaporization
* Temperature
* Thermodynamics
* Thermodynamic (absolute) temperature
* Thermodynamic equations
* Volumetric heat capacity

References

"Fundamentals of Heat and Mass Transfer" (6th edition) Incorpera, DeWitt, Bergmann, and Lavine

Wikimedia Foundation. 2010.

### Look at other dictionaries:

• Specific heat capacity — Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval. The term originated primarily through the work …   Wikipedia

• Heat exchanger — An interchangeable plate heat exchanger Tubular heat exchan …   Wikipedia

• Heat equation — The heat equation is an important partial differential equation which describes the distribution of heat (or variation in temperature) in a given region over time. For a function of three spatial variables ( x , y , z ) and one time variable t ,… …   Wikipedia

• Heat — In physics, heat, symbolized by Q , is energy transferred from one body or system to another due to a difference in temperature. [cite book|author= Daintith, John |title=Oxford Dictionary of Physics|publisher=Oxford University… …   Wikipedia

• Heat flux sensor — A heat flux sensor is a commonly used name for a transducer generating a signal that is proportional to the local heat flux. This heat flux can have different origins; in principle convective , radiative as well as conductive heat can be measured …   Wikipedia

• Heat transfer coefficient — The heat transfer coefficient, in thermodynamics and in mechanical and chemical engineering, is used in calculating the heat transfer, typically by convection or phase change between a fluid and a solid::Delta Q=h cdot A cdot Delta T cdot Delta… …   Wikipedia

• Heat sink — A heat sink (or heatsink) is an environment or object that absorbs and dissipates heat from another object using thermal contact (either direct or radiant). Heat sinks are used in a wide range of applications wherever efficient heat dissipation… …   Wikipedia

• Heat pipe — A heat pipe is a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperature between the hotter and colder interfaces. Inside a heat pipe, at the hot interface a fluid turns to vapour and the… …   Wikipedia

• Enhanced heat transfer — Heat exchangers were initially developed to use plain (or smooth) heat transfer surfaces. An Enhanced heat transfer surface has a special surface geometry that provides a higher thermal performance, per unit base surface area than a plain surface …   Wikipedia

• Convective heat transfer — See also: Heat transfer and convection This figure shows a calculation for thermal convection. Colors closer to red are hot areas and colors closer to blue are cold areas. In this figure, a hot, less dense lower boundary layer sends plumes… …   Wikipedia