Laminar heat transfer and friction characteristics of microencapsulated phase change material slurry in a circular tube with twisted tape inserts

It is novel and better method that microencapsulated phase change material (MPCM) slurry and the tube with twisted tape inserts are adopted together to enhance convective heat transfer. In this paper, numerical analyses were carried out to study laminar heat transfer and friction characteristics of MPCM slurry in a circular tube with twisted tape inserts. It is found that the MPCM slurry in the tube with twisted tape insert leads to the best performance of convective heat transfer for the bigger apparent specific heat and the intensive swirl flow. Furthermore, the modified average Nusselt number increases with decreasing bulk Stefan number, twisted ratio and increasing Re, while the friction factor increases with increasing Re and decreasing twisted ratio. It is also found that the heat transfer enhanced efficiency increases with increasing Re and decreasing Steb, and the heat transfer enhancement effects of twisted tape for low Steb slurry are better than that for high Steb slurry. Moreover, the thermal-hydraulic performance ratios increase to a peak, then decrease gradually with increasing Re for different twist ratio. The performance ratio increases with decreasing the twist ratio only in a definite Re range, and the Re range decreases with decreasing twist ratio.