In the automotive industry, it is frequently not practical to test a full size heat exchanger for reasons such as limits of wind tunnel capability, tooling availability, or economy; consequently cooling system engineers are required to predict heat transfer performance of a heat exchanger such as radiator, charge air cooler, or oil cooler, based on test results from a sample smaller than the actual exchanger.
A popular short cut is to plot the performance curve using average coolant temperature and extrapolate linearly. This may result in errors ranging from a few percent to physically impossible, that is, the calculated outlet coolant temperature being lower than the ambient temperature.
The method for the prediction as described in this paper is simple and straight forward, and above all, mathematically correct. It takes known heat transfer equations and numerical methods, and puts them together like building blocks to fabricate the complete procedure. It is valid for any heat exchanger without phase change, as long as the specific mass flow rates for both the hot and cold side are kept constant.