Effect of metal oxide particles on the flow and forced convective heat transfer behaviour of microencapsulated PCM slurry

Abstract

ZnO, nano ZnO and nano Al2O3 were mixed with microencapsulated phase change material slurry (MPCS) for improving the heat transfer performance of slurries in this paper. The thermal and rheological properties of MPCS were measured using DSC, thermal conductivity meter and rheometer. The results show that the thermal conductivity of 5 wt% MPCS with 1 wt% ZnO, nano ZnO and nano Al2O3 was 17.9 %, 19.4 % and 23.5 % higher than that of 5 wt% MPCS, respectively. The forced convection heat transfer experiment of slurries was carried out in a loop system with various heat flux and flow conditions. The influences of heat flux, flow rate and metal oxide particles on the flow and heat transfer behaviour of slurries were investigated. The results show that the heat transfer was significantly enhanced for all slurries with metal oxide particles under three flow conditions. Compared with water, the local heat transfer coefficient (hx) of MPCSs with 1 wt% ZnO, nano ZnO and nano Al2O3 increased by 6.5 %, 9.1 % and 12.4 % under laminar flow, 6.6 %, 15.5 % and 14.9 % under transition flow, and 15.7 %, 19.0 % and 21.6 % in turbulent condition, respectively.