Compensating for the end-plate effect on heat transfer in brazed plate heat exchangers

Abstract

• The end-plate effect in brazed plate heat exchangers is theoretically analyzed. • Numerical and analytical models are developed to quantify the end-plate effect. • The developed models are validated by the experiments. • An algorithm is developed to correct the end-plate effect in heat transfer tests. The two end plates in plate heat exchangers transfer heat through contact with the corrugated surface of the adjacent thermal plate. This phenomenon effectively increases the active heat transfer area and significantly affects the heat transfer when the heat exchanger has a very small number of plates. That is especially important when such a heat exchanger is used for the determination of the heat transfer coefficient in the development of heat transfer correlations. This paper presents a theoretical analysis of the effect of the end plate on heat transfer in brazed plate heat exchangers. The governing equations are derived through the energy balance analysis for a small element of the end plate. Numerical and analytical models are developed to solve the governing equations. The predictions by the two models agree well with each other. The heat transfer data for single-phase water in the BPHEs with different numbers of plates are used to validate the developed models. Both experiments and theoretical analyses show that the influence of the end plate is more significant in a heat exchanger with a small number of plates and a lower convective heat transfer coefficient. An iteration algorithm is developed to compensate for the end-plate effect in the development of heat transfer correlations.