Transient Modeling of Refrigerant-to-Air Fin-and-Tube Heat Exchangers

A detailed transient model of a refrigerant-to-air fin-and-tube heat exchanger operating either in heating or cooling (including dehumidification) mode is presented. An indexation technique is proposed to account for the complex circuitry of the tubing often found in these types of heat exchangers. In addition, the model addresses the ON/OFF operation of the compressor and of the fan (at compressor shut-down, the fan may be ON or OFF). The partial derivatives equations resulting from the application of the mass, momentum, or energy conservation equations to the single-phase and two-phase flow of the refrigerant in the tubes and to the flow of the air over the tubes walls and fins are solved numerically using the finite volume method. The model is experimentally validated in steady-state and transient conditions. The results of this validation show a good agreement between the experiments and the model.