Numerical Analysis for the Characterization of Non-ordinary Heat Exchangers

Heat exchangers are an essential component of any energy production system. Obtaining a detailed characterization of them is a must for the design and operation of an energy plant. This article presents a characterization process of a finned tube heat exchanger with an unusual configuration. Throughout the article, the proceedings to study the influence of two unusual features that make unsuitable the use of reference models for heat exchangers are explained. One is the inclination of the tubes in the direction transverse to the flow velocity, which causes variable spacing between finned tubes. The other feature that prevents the application of the reference models is the importance of bypass flow, not negligible due to the small distance between walls compared with the width of the flow path near to the walls. A computational fluid dynamics (CFD) steady-state analysis has been completed in order to study this problem. The results show that although the inclination of the tubes does not affect considerably the overall performance of the exchanger, the influence of bypass flow close to the wall causes a significant reduction in pressure drop and a substantially lower heat transfer capacity than calculated with analytical models. This study was conducted within the Seventh Framework Programmes FP7, for the HYSOL project. HYSOL plant has been proposed as an alternative to deliver dispatchable and firm energy regardless the climate conditions throughout the whole year while it uses 100% renewable energy sources for electricity production through is innovative hybrid system