엇갈림 배열을 가지는 마이크로 핀 휜 채널 내 극저온 유동에 대한 실험적 연구

Abstract

Due to the high integration and miniaturization of semiconductors, the power density and heat density of electronic and photonic device have increased. To address these issues, extensive research on single-phase and two-phase convective heat transfer using various working fluids on micro-scale surfaces had been actively pursued in the past few decades. In various studies for electronic and photonic device cooling, deionized water and synthetic refrigerants were commonly used as working fluids. But deionized water was difficult to use as a coolant in the harsh environment, and synthetic refrigerants have limited to use for high global warming potential(GWP). Therefore, the use of natural refrigerants was considered, and related research was actively conducted. Bar-Cohen et al. [14, 15] experimentally investigated the thermal performance of cryogenic micro-gap and micro pin fin cooler made of copper with two-phase liquid nitrogen flows. The micro pin fin cooler was made up of a central manifold, an upper insert, a lower insert and a square, inline pin fin array with 150 μm fin width, 300 μm fin height, and 300 μm pin spacing. The micro-gap cooler referred to a cooler without a micro pin fin array in a micro pin fin cooler. In contrast, in this study, experimental investigation was performed in a circular silicon micro-pin fin heat sink channel and liquid nitrogen as the working fluid. The micro-pin fin heat sink was fabricated using micro- electromechanical systems(MEMS) for mass production of various types. It was designed on an 8-inch silicon wafer with 1 cm × 1 cm base area, 100 μm fin diameter, 200 μm fin height and 200 to 400 μm fin spacing in inline and staggered arrangement for considering fin spacing and array arrangement effect. Platinum thin film heater deposited on the back side of wafer to simulate heater, minimize contact resistance, and apply uniform and constant heat flux. Also, the micro cooler with an internal flow path was designed to facilitate specimen replacement. A micro pin fin heat sink with 200 μm fin spacing in staggered arrangement was selected for experiment and was attached to the internal flow path of the micro cooler. The experiments were conducted at the range of 2.2 to 2.5 g/s mass flow rate and 6.7 to 55.2 W/cm2 effective heat flux. The experiment results show that a base heat transfer coefficient was determined as 78 kW/m2∙K to 133 kW/m2∙K and expected quality of 0.05 to 0.14 was calculated. The comparison of thermal performance among the current study, previous study, and flow boiling heat transfer coefficient correlations derived results has been conducted.