Performance analysis of groove-cut tube based double-pipe heat exchanger using microencapsulated phase change material slurry

Abstract

It is commonly accepted practice to improve a thermal-fluid device by adopting surface enhancement techniques for better heat transfer. On the other hand, Microencapsulated phase change material (MPCM) slurry has been used as a heat transfer fluid (HTF) due to its improved heat capacity and heat transfer performance. The current paper attempted to study the combined effect of the two enhancement methods in a double-pipe heat exchanger. The results were first validated with experimental work taking into account the hydraulic and heat transfer characteristics of the MPCM slurry flow. Groove-cut geometrical models of MGGC, RGC, CGC, and TGC were proposed to modify heat transfer tube geometry. The effect of the number of helical turns (3, 4, 5, and 6-turns) and various Reynolds numbers were also considered for the investigation. The result showed that the proposed groove-cut models demonstrate enhanced flow mixing for MPCM slurry but with a higher friction factor, which increases with increasing helical turns. The impact was also manifested by improving the heat transfer by facilitating a uniform melting of MPCM particles, and the RGC model shows higher performance. The overall thermohydraulic performance assessment showed that the groove-cut tube models outperformed the corresponding plain tube. The highest performance factor value of 1.24 was observed for the RGC model, while the TGC model shows only 1.14 for the 6-turns. Similarly, the Q/Wp ratio indicates that the groove cut models transport more heat than the pumping power requirement for MPCM slurry.