ME-GI 엔진 고압 압축기용 인터쿨러의 열전달 특성에 관한 연구

Abstract

Due to the strengthening of the regulations of International Maritime Organization (IMO), the importance of safety, security and environmental performance of the shipping industry has emerged. Hence research on eco-friendly engines is increasing. Marine Engine – Gas Injection (ME-GI) engine has been in the spotlight recently as the next-generation engine that has high energy efficiency using both bunker C oil and Liquefied Natural Gas (LNG) as fuels. Shell and tube heat exchanger is used as an intercooler in the fuel supply system for ME-GI engines. There has been many studies on heat exchangers, but understanding their characteristics has been difficult, due to variety of design factors and complexity of flow and heat transfer in shells. In recent years, design improvement cases were increased by analyzing complex flows using Computational Fluid Dynamics (CFD). In this study, the design and analysis results of the intercooler were compared and verified to improve the heat transfer performance in it. From this, suitable operating conditions of cooling water and heat transfer characteristics for cooling water inlet temperature and flow rate change were found out. Various geometrical factors, such as baffle height, baffle number, baffle placement and baffle types are considered in this study. An ideal optimal shape was proposed by considering the heat transfer characteristics such as heat transfer rate, outlet temperature of tube and pressure drop.

The results shows the following: (1). When the baffle height was changed - out of the five height factors, namely 198mm, 216mm, 235mm, 252mm and 270mm - the baffle height with 216mm was found to have the best cooling performance. (2). When the baffle number was changed – out of the six cases, namely 8, 10, 12, 14, 16 and 20 – the highest number of baffles (20) was found to have higher heat transfer performance. (3). For the baffle placements case, mixed baffle placements were found to be appropriate for cooling. In comparison to the cases of down to up and up to down placements, the up or down placements does not effect the cooling performance. (4). Out of the three types of baffles used in this study, namely, single-segment, double-segment and ring-donut types, the ring-donut type was found to have the best cooling performance of the heat exchanger.