Abstract

In this paper, the results of an experimental and computational study on the development of a plate heat exchanger are presented and discussed. We have evaluated the characteristics of a miniature counterflow plate heat exchanger (PHE) using air as the working fluid. Because of the small characteristic channel dimension (Dh ≤ 1.9mm) and specific application of interest, the Reynolds number produced ranged between 20 < ReD < 1500, well within the laminar flow regime. The mass flow rates of the two hot and cold streams were maintained the same. Two different configurations were tested and modeled. The first configuration was the single-layer condition where one cold air stream was adjacent to another hot air stream in a counter-flow arrangement. The second configuration was the interleaved channel arrangement where the different layers alternate between cold and hot streams.

Experiments were performed on a series of heat exchangers made of aluminum and stainless steel. The channel dimensions were 1mm × 20mm × 75mm. Because the flow region consists of hydrodynamically developing and fully developed flow for the range of Reynolds numbers tested, the experimental results show higher pressure drop compared with the results of fully developed parallel-plate channel flow and this difference increases with increasing Reynolds number. The dependency of Nusselt number on Reynolds number in the periodic boundary condition was larger than the single-layer arrangement. Further, the periodic boundary condition generates higher effectiveness than the single-layer arrangement. It was found that when using aluminum plates instead of stainless steel, axial conduction results in nearly 35% reduction in the overall heat transfer coefficient between hot- and cold-side channels. Computational results, corroborated with experimental data, suggested the use of an interleaved channel geometry for obtaining an effectiveness of 90% or higher when operating within the low mass flow rate regime.

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