Enter the specific heat capacity, the density, flow rate, and change in temperature into the calculator to determine the heat rejection.

Heat Rejection Formula

The following equation is used to calculate the Heat Rejection.

Q = c*p*F*Δ T

  • Where Q is the heat rejection (kW)
  • c is the specific heat capacity (kJ/kg*c)
  • p is the density (kg/m^3)
  • F is the flow rate (m^3/hr)
  • Δ T is the change in temperature (K or C)

What is Heat Rejection?

Heat rejection describes a process where energy is rejected from the heat exchanger back into the fluid stream. This can be achieved through the use of various methods, like the addition of phase change materials (PCM), which absorb and store the heat that would otherwise be transferred to the fluid, or by using fins and plates to provide an interface between fluids to which heat can be rejected.

Although the term technically applies to any process that rejects heat, in practice it is used almost exclusively in reference to cooling.

Turbine engines are usually cooled by air drawn into the engine and then expelled through a series of tubes called a “cold section” (also known as an “intercooler”). The colder the temperature of the incoming air, the more efficient the engine will be.

his is where heat rejection comes into play. In order to reach optimal efficiency, turbine engines require cold air at high pressure to flow over their hot components. This process creates a lot of heat that has to be rejected before it reaches the engine. Heat is rejected by forcing cold air over the hot components at high pressure; this produces lower temperatures.