Calculating the Thermal Resistance of a Liquid Cold Plate
To select the best cold plate for your application, you need to know the cooling fluid flow rate, fluid inlet temperature, heat load of the devices attached to the cold plate, and the maximum desired cold plate surface temperature, Tmax. From these you can determine the maximum allowable thermal resistance of the cold plate.
First, calculate the maximum temperature of the fluid when it leaves the cold plate, Tout. This is important because if Tout is greater than Tmax, there is no solution to the problem.
Alternatively, you can use the heat capacity graphs found in our Thermal Reference Guide in the technical library. These graphs describe the change in temperature, ΔT, that occurs along the fluid path. To find Tout
, add ΔT to the inlet temperature, Tin
is less than Tmax
, the next step is to determine the required normalized thermal resistance (θ) for the cold plate using this equation:
Any cold plate technology that provides a normalized thermal resistance less than or equal to the calculated value will be a suitable solution.