Experimental Investigation on Heat Transfer and Pressure Drop in a Microtubine Recuperator With Cross-Wavy Primary Surface Channels

Compact heat exchangers are used in a wide variety of applications. Typical utilization is a low-cost recuperator for power generation microturbines. In this scenario, a recuperator takes heat from the exhaust gas and preheats the compressor discharge air before it reaches the combustion chamber. To achieve thermal efficiency over 30%, recuperators with high thermal performance surfaces geometries are needed. It has been shown that Cross-Wavy Primary Surface (CWPS) has superior performance and high commercial potential in compact recuperators based on previous studies. In the present study, we successfully implemented a prototype recuperator with CWPS channels for a 100kW microturbine. The material we used in the recuperator core is a 0.12mm-thick stainless steel strip, which has good high-temperature mechanical and corrosion properties. The working mediums are compressed air and hot gas for the two sides of the recuperator. We tested comprehensively the thermal performance of the recuperator in terms of the overall heat transfer coefficients and friction factors vs. Reynolds numbers in the CWPS channels, with Reynolds number ranging from 250 to 400. The exhaust hot gas temperature was much non-uniform, indicating the importance of flow arrangement when designing the recuperator. We also investigated the heat transfer coefficients and friction factors vs. Reynolds numbers, and obtained corresponding correlations.