Heat exchanger theory

Summary

A heat exchanger moves heat from a hot fluid stream to a cold one through a separating wall, without mixing the fluids. Heat exchanger theory models it by an energy balance for each stream and a local rate law that uses an overall heat transfer coefficient. From this model come the two standard design methods, the log mean temperature difference method and the NTU method. The flow arrangement, such as parallel flow, counterflow or crossflow, changes how much heat a given exchanger can transfer.