Performance of serrated finned plate exhaust heat exchangers coupled with soot deposition characteristics

Abstract

In exhaust waste heat recovery (WHR) heat exchangers, the deposition of soot particles on the heat transfer surface significantly affects the performance of the heat exchanger. In this paper, the two-fluid model (TFM) for particle deposition was improved, and the performance of serrated finned plate exhaust heat exchanger considering soot deposition was studied. In the model, the real wall temperature distribution was also considered, instead of the simplified constant wall temperature assumption. The particle wall adhesion energy criterion and particle adhesion probability were also considered. Using the model, the effects of fin spacing, fin height and fin interrupted length on particle deposition characteristics and thermal-hydraulic performance of the serrated finned plate heat exchanger were studied. The results show that when the initial kinetic energy of soot particles exceeds the critical value, the adhesion probability decreases with the increase of initial kinetic energy. Moreover, larger particles exhibit a lower critical value, indicating that smaller particles are more likely to stick on the heat transfer surface. After 4 h deposition of soot particles, the comprehensive performance j/f^1/3 of the heat exchanger decreased by 24.78 %–31.94 %. The deposition of soot particles is more significant in serrated fin heat transfer structures with large fin spacing, large fin height, and small fin interrupted length. In addition, the particle deposition distribution inside the heat exchanger has also been studied. More deposition occurs in the front and back regions of the fins, and the amount of deposition inside the heat exchanger gradually decreases along the direction of exhaust flow.