Numerical Investigation of Counter Flow Plate Heat Exchanger

Abstract

Flow and heat transfer in a recuperative counter flow plate air-to-air heat exchanger were investigated numerically using Fluent software. It was employed previously developed methods to generate a computational mesh and assumed a zero thickness of the plates to calculate the flow in an air-to-air heat exchanger. Pressure loss and effectiveness were evaluated as functions of inner velocity. Obtained numerical data were substituted by suggested functions dependent on the Reynolds number. A function for the loss coefficient was based on the presumption that losses consist of local losses and friction losses. The function for the Nusselt number used the ordinary power function of the Reynolds number for forced convection. The effect of material thickness on pressure loss and effectiveness was illustrated. Even a very thin material for the plate significantly affects pressure loss, while the effect on the effectiveness depended on the thermal conductivity of plate material used. From this results, it is obvious that a thin as possible material is crucial for creating the most effective recuperative air-to-air heat exchanger with high effectiveness and low pressure loss, while the properties of the material itself are unimportant. We compared numerical data with data obtained by measuring a real heat exchanger. The results for effectiveness corresponded well and corrections made were negligible. The results for pressure loss differed significantly, but this difference was lowered by correcting for plate thickness.