Optimal design of a concentric heat exchanger for high-temperature systems using CFD simulations

Computational fluid dynamics (CFD) has been successfully used to simulate a three-dimensional concentric high temperature heat exchanger. The concentric shell with staggered fin arrays connecting serve not only as a part of the shell structure, but also as a flow-disturbing mechanism in an attempt to enhance heat transfer. This heat exchanger uses helium gas and molten salt as hot and cold streams respectively in a counter-flow mode. Flow fields and heat transfer characteristics of the two concentric channels are examined extensively. A design with an optimal performance of the heat exchanger is achieved by maximizing the effectiveness of the heat exchanger (ε-NTU method) using the following parameters as optimizing variables: the width of the flow channel, the length, pitch, thickness, and angle of the fins. The number of CFD simulation are substantially reduced by Taguchi method, and the optimal configurations of the concentric high temperature heat exchanger are found with a channel width of 1 mm, a fin length of 11 mm, an angle of fin of 2.6°, and a fin thickness of 1.125 mm.