Volume 12: Low Carbon Cities and Urban Energy Systems: Part I

An Experimental Study on Effects of Steady and Unsteady Heat Flux on Flow Boiling in Straight Microchannel Jiaojiao Zhuang, Hao Yu, Ning Mao

Abstract

The high heat flux on the PV cells can lead to the decrease of electricity efficiency. To tackle with the high temperature problems in PV cells microchannel is attracting increasing attentions recently due to its much higher heat flux. In this paper, the characteristics of flow boiling pressure drop and heat transfer of deionized water flow boiling in a microchannel with hydraulic diameter of 400 μm had been experimentally investigated. To further understand the effect of variation of solar radiation on cooling performance of the PV cells, unsteady and steady heat flux were respectively used and the corresponding pressure drop and heat dissipation of the microchannel under different mass fluxes (G=410.69, 513.36 and 718.71 kg/m2s) were studied. It was found that with the increase of heat flux, the pressure drop first shows a slight downward trend, then increases sharply. The average heat transfer coefficient and local heat transfer coefficient increase with the increase of heat flux and decrease with the increase of mass flux. With the sudden increase of heat flux, a much longer variation of the pressure drop and wall temperature was observed.

Keywords microchannel, flow boiling, pressure drop, heat transfer coefficient, unsteady heat flux