Improved heat storage rate for an automobile coolant waste heat recovery system using phase-change material in a fin–tube heat exchanger

• Published in: Applied energy 2014-01, Vol.113, p.680-689
• Main Authors: Shon, Jungwook, Kim, Hyungik, Lee, Kihyung
• Format: Article
• Language: English
• Subjects: Applied sciences; Coolant waste heat storage device; Devices using thermal energy; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Heat exchangers (included heat transformers, condensers, cooling towers); Heat storage rate; Latent heat; Phase-change material (PCM); Transport and storage of energy
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2013.07.049

•The actual heat transfer coefficient of a PCM was measured by experiments.•The heat transfer rate and melting time of the heat exchanger filled with PCM was theoretically analyzed.•Improving convective heat transfer inside the tube is the most effective way to increase heat absorption efficiency.•The space between the heat transfer surfaces where PCM is charged should be as thin as possible.•Warm-up experiment was carried out under idle conditions in an actual engine and then, warm-up time was shortened 33.7%. In this study, the actual heat transfer coefficient of a phase-change material (PCM) was measured experimentally with the purpose of improving the heat storage rate of an automotive coolant waste heat storage system using the latent heat of the PCM. The heat transfer rate and time required to store heat was theoretically analyzed in the system where engine coolant was heated by a fin–tube heat exchanger filled with solid PCM. The amount of heat storage necessary for sufficient heating of vehicle coolant was calculated, and the appropriate amount of PCM was determined accordingly. Based on this data, a heat exchanger capable of storing heat under the lowest possible influence of natural convection and conduction thermal resistance of the PCM was designed, and its estimated heat storage rate was calculated. We identified the most effective methods to improve the heat storage rate and efficiency of the PCM-filled heat exchanger.