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The rate of heat flow is the amount of heat that is transferred per unit of time in some material, usually measured in watts (joules per second). Heat is the flow of thermal energy driven by thermal non-equilibrium, so the term 'heat flow' is a redundancy (i.e. a pleonasm ).
The statement of Newton's law used in the heat transfer literature puts into mathematics the idea that the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings. For a temperature-independent heat transfer coefficient, the statement is:
An additional term may be introduced into the equation to account for radiative loss of heat. According to the Stefan–Boltzmann law , this term is μ ( u 4 − v 4 ) {\displaystyle \mu \left(u^{4}-v^{4}\right)} , where v = v ( x , t ) {\displaystyle v=v(x,t)} is the temperature of the surroundings, and μ {\displaystyle \mu } is a coefficient ...
The overall heat transfer coefficient is a measure of the overall ability of a series of conductive and convective barriers to transfer heat. It is commonly applied to the calculation of heat transfer in heat exchangers, but can be applied equally well to other problems.
The calculation of the heat loss due to linear thermal bridging is relatively simple, given by the formula below: [3] H T B = y ∑ A e x p {\displaystyle H_{TB}=y\sum A_{exp}} In the formula, y = 0.08 {\displaystyle y=0.08} if Accredited Construction details used, and y = 0.15 {\displaystyle y=0.15} otherwise, and ∑ A e x p {\displaystyle ...
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes.
In thermal engineering, the logarithmic mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The LMTD is a logarithmic average of the temperature difference between the hot and cold feeds at each end of the double pipe exchanger.
Thermal conduction is the diffusion of thermal energy (heat) within one material or between materials in contact. The higher temperature object has molecules with more kinetic energy; collisions between molecules distributes this kinetic energy until an object has the same kinetic energy throughout.