DESIGN AND PERFORMANCE OF A MICROCHANNEL SUPERCRITICAL CARBON DIOXIDE RECUPERATOR WITH INTEGRATED HEADER ARCHITECTURE

Supercritical carbon dioxide (sCO(2)) power cycles have gained attention due to the relatively high efficiency and potential for simple controls. Because the temperature drop across the turbine is fairly low in sCO(2) cycles, heat recuperation is key to high cycle efficiency. In this paper, an integrated header microchannel (IHM) recuperator design is proposed for the sCO(2) power cycle. The recuperator consists of multiple short unit cells connected together by a series of flow headers to inlet and exit plena. Within each unit cell, sCO(2) flows through a microscale pin-fin array on the hot and cold sides. The thermal-fluidic performance of a representative three-layered unit cell stack is experimentally characterized. Three-dimensional computational fluid dynamics and structural analysis simulations are performed to develop the unit cell design. Experimental results indicate that effectiveness in the range of 84-95% can be achieved for a unit cell length of 18 cm and a heat capacity rate ratio ranging from 0.35 to 1. The experimentally determined overall heat transfer coefficient and pressure drop are compared against correlations in literature. The Prasher et al. [J. Heat Transfer, vol. 129, no. 2, pp. 141-153, 2007] correlation predicts the experimental pressure drop to within 9%. No heat transfer correlation was found to predict the experimental data well, with the Rasouli et al. [Int. J. Heat Mass Transfer, vol. 118, pp. 416-428, 2018] correlation showing the lowest mean average error of 29%. A heat exchanger model is developed based on the Prasher et al. and Rasouli et al. correlations. The model is integrated within a single recuperator sCO(2) cycle model to assess the impact of the IHM recuperator on the cycle efficiency.