Experimental study on flow boiling characteristics of R-1233zd(E) of counter-flow interconnected minichannel heat sink

Abstract

Two-phase mini/micro-channel heat sink is one of the most effective solutions to the heat dissipation of high-power electronic devices in a narrow space. Flow boiling instability and wall temperature nonuniformity are however the two notorious problems of two-phase mini/micro-channel heat sink that have hindered their practical applications to a large degree. This study proposed a counter-flow interconnected minichannel (CFIM) to improve the flow boiling stability and the temperature uniformity of a mechanically machined copper minichannel heat sink. Firstly, a comprehensive comparative study of CFIM and co-current minichannel (CCM) was carried out concerning two-phase flow patterns, boiling heat transfer characteristics, and wall temperature uniformity. Secondly, the effects of mass flux, subcooling and saturation temperature on the boiling heat transfer performance of the two kinds of heat sinks were further investigated. Experiments were carried out at a saturated temperature of 40 ∼ 50°C, mass flux of 291∼ 618 kg/(m2·s), and subcooling of 15 ∼ 30°C, using a new generation of environment-friendly coolant with a low boiling point, R1233zd(E). In particular, no backflow or partial dry-out is observed in the channel throughout all the tested conditions. Due to the mixing of fluid between adjacent channels with counter flow caused by interconnected slots in CFIM, low upstream vapor quality and high downstream vapor quality were avoided. Therefore, this counter-flow interconnected mechanism in the current design can be significantly enhanced in flow boiling stability and temperature uniformity, up to an effective heat flux of 230.4 W/cm2 with 51.2% increment of heat transfer coefficient, 56% increment of coefficient of performance (COP) and 48.5% reduction of pressure drop when compared with those of traditional CCM design. Overall, the research results have good guidance and reference for the application and research of two-phase minichannel heat sinks.