Numerical modeling of unsteady state operation of tube and plate fin heat exchangers

Cross-flow tubular heat exchangers are applied as condensers and evaporators in air conditioners and heat pumps or as air heaters in heating systems. They are also applied as water coolers in so called 'dry' water cooling systems of power plants, as well as car radiators. There are analytical and numerical mathematical models of heat exchangers of that type to determine the steady state temperature distribution of fluids and the rate of heat transferred between fluids. In view of the wide range of applications in practice, these heat exchangers were experimentally examined in steady-state conditions, mostly to determine the overall heat transfer coefficient or the correlation for the heat transfer coefficients on the air side and on the internal surface of the tubes. There exist many references on the transient response of heat exchangers. Most of them, however, focus on the non-steady-state heat transfer processes in parallel and counter flow heat exchangers. In this paper, the new equation set describing transient heat transfer process in tube and fin cross-flow tube exchanger will be given and subsequently solved using the finite volume method.