Flow and heat transfer characteristics and comprehensive evaluation of asymmetric plate heat exchangers for centralized heat supply

The structure of flow channel on both sides of the conventional plate heat exchanger(CPHE) is symmetrical. CPHEs are struggle to perform efficiently when subjected to asymmetric working conditions in district heating system. In order to improve the performance of plate heat exchangers under asymmetric conditions, asymmetric plate heat exchangers(APHEs) was designed. In this paper, APHEs were parameterized by asymmetric factor a. An evaluation index eta for APHE is introduced to quantitatively analyze APHE's suitability in district heating system. Numerical simulations were performed to investigate the heat transfer characteristics and resistance characteristics of the APHEs with 11 asymmetric factors a. Through using eta, APHEs with the best comprehensive performance were found, when the flow ratio is 1.50, 1.75, 2.00, 2.25, 2.50 and 2.75. In flow ratio, APHEs provide the comprehensive performances with an improvements of 28 %, 39 %, 54 %, 65 %, 72 % and 83 % compared with CPHEs. Correlations equation for the average Nu and f on both hot and cold sides of the APHEs were established. There exists a correlation between Nu and f for the APHEs with respect to asymmetry factor a and flow ratio.