Flow Boiling of Ammonia in a Diamond-Made Microchannel Heat Sink for High Heat Flux Hotspots
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https://doi.org/10.1007/s11630-019-1208-3
Article ID: 1003-2169(2019)00-0000-00
Flow Boiling of Ammonia in a Diamond-Made Microchannel Heat Sink for High Heat Flux Hotspots YANG Qi1,2, MIAO Jianyin2, ZHAO Jingquan1, HUANG Yanpei1,2, FU Weichun2, SHEN Xiaobin1* 1. School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China 2. Beijing Key Laboratory of Space Thermal Control Technology, Beijing Institute of Spacecraft System Engineering, China Academy of Space Technology, Beijing 100094, China © Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract: To solve the heat dissipation problem of electronic devices with high heat flux hotspots, a diamond microchannel heat sink consisting of 37 parallel triangular microchannels with channel lengths of 45 mm and hydraulic diameters of 280 µm was designed. The flow boiling heat transfer characteristics of ammonia in the microchannels were investigated under high heat fluxes of 473.9–1000.4 W/cm2. Saturated flow boiling experiments with saturation temperatures of 25, 30, and 35°C and mass fluxes of 98–1200 kg/m2s were conducted, as well as subcooled flow boiling with inlet subcooling of 5°C as a comparison. The temperature and pressure drop measurements were analyzed, and the main conclusions below can be drawn. (1) At a given heat flux, the heat source temperature first decreased and then increased with the mass flux, and there existed an optimum mass flux to optimize the cooling performance of the heat sink. (2) The heat transfer performance under the saturated inlet condition was obviously better than that under the subcooled inlet condition. (3) A larger saturation temperature leaded to weakening of both the heat transfer capacity and the stability of the microchannel heat sink. Notably, with the high heat diffusion ability of the diamond substrate and the great heat transfer capacity of ammonia flow boiling in microchannels, the heat sink can achieve a heat removal capacity of up to 1000.4 W/cm2.
Keywords: high heat flux, flow boiling, microchannel, ammonia, multipoint heat sources
1. Introduction In the 1960s, Feynman proposed that the miniaturezation of electronic devices would become an important direction of scientific and technological development [1]. Currently, with the decreasing size of electronic devices and the increasing degree of integration, the heat flux of electronic chips is approaching the scale of kW/cm2 [2]. It is well known that the reliability of electronic devices
Received: May 05, 2019
AE: MING Tingzhen
depends heavily on the operating temperature. When the operating temperature exceeds the safe operating temperature range, the failure rate rises exponentially with the temperature [3]. To manage the heat dissipation problem of electronic devices with high heat fluxes, single/twophase flow in microchannels, jet impingement and spray cooling [4] are the most effective techniques at present. The ICECool Applications program initiated by DARPA (
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