Wen-xiao Chu

CFD simulation and optimization of fluid flow distribution inside printed circuit heat exchanger headers

ABSTRACT Fluid flow distribution is related to the performance of heat exchangers. Gross flow distribution is often linked to conventional headers and thus jeopardizes the thermo-hydraulic performance. The objective of this paper is to design several configurations of printed circuit heat exchanger headers to enhance its flow uniformity while leveraging its etched nature. Four kinds of inlet headers, i.e., trapezoid header, double header with detail of bypass holes, core integrated header with one layer, and core integrated header with multilayers, are compared. It is found that the traditional headers induce poor flow distributions. Based on the flow characteristics in traditional headers, a novel core integrated header with seven merged channels is proposed. The flow nonuniformity of the heat exchanger with this novel inlet and outlet headers is reduced by 91%, but the pressure drop is increased by 114% compared with the baseline configuration, whereas it shows the best heat transfer performance as well due to the improvement of flow uniformity.

CFD Study on Counterflow Ceramic Microchannel Heat Exchanger With Different Fins

The conventional heat exchangers cannot satisfy the high efficiency and power requirements due to the low heat transfer performance and large volume. With the development of micro-scale manufacture technology, the ceramic micro-channel heat exchangers are recommended to be used to the highly-efficiency power and propulsion systems, especially the very high temperature conditions. The present paper analyzes the thermal hydraulic performance of the alumina-based ceramic microchannel heat exchangers with four different fins (straight, Z-shaped, airfoil and S-shaped). The numerical results show that the maximal heat transfer rate and heat transfer effectiveness of the heat exchanger with Z-shaped fins reach 90.7 W and 61%, respectively. The temperature distribution of both fluid sides and solid body is predicted. Moreover, the pressure drop and the ratio of E/k are used to evaluate the general heat exchanger performance. The ratio of E/k is smaller than unit of ten at the low Reynolds number and increases greatly at high Reynolds number.Copyright