Flow and heat transfer in a Double-pipe heat exchanger using Microencapsulated phase change material (MPCM) slurry

As the energy demands for many industrial processes increase day by day, it is essential to consider enhancing the performance of an industrial device for efficient energy utilization and conservation. An improved heat transfer fluid (HTF) is one of the mechanisms to be implemented to enhance the heat transfer performance of thermal-fluid devices such as heat exchangers. And the other prevalent heat transfer enhancement technique is employing heat transfer augmentation in the heat transfer tubes. Microencapsulated phase change material (MPCM) slurry has been adopted as an HTF and energy storage medium due to its high heat capacity and heat transfer performance. The present work investigates an MPCM slurry as an HTF in comparison to plain water in a double-pipe heat exchanger. In addition, a groove-cut tube has been proposed as a passive heat transfer enhancement mechanism to improve heat transfer performance. A numerical model based on the Eulerian-Eulerian multiphase flow model has been adopted for the investigation, and the accuracy of the model has been validated with experimental work. It has been found that the model well predicts the flow behaviour and heat transfer characteristics of the slurry. The heat transfer and energy transport performance of the HTFs has been analysed with respect to various flow parameters. The result showed that the performance of the heat exchanger improved for MPCM slurry as it transports more heat than the corresponding plain water. However, the heat transfer performance of the HTFs was highly dependent on the Reynolds number of the flow. The performance index analysis indicated that the thermos-fluidic performance of the double pipe heat exchanger enhanced with a groove cut tube compared to a plain tube. The MPCM slurry exhibits a higher pressure drop than the improved heat transfer at high Reynolds numbers.