Model prediction of the critical heat flux and thermal resistance of a rectangular thin-strip evaporator with distributed liquid supply capillary wicks for high heat flux cooling

Abstract

• A rectangular thin-strip evaporator with distributed liquid supply capillary wicks (RTEDCW) is designed and the performance predicted using a thermal-hydraulic model. • CHF is attained when the liquid pressure drop in the wick equals the wick's capillary pumping capability. • The overall thermal resistance is the ratio of the wick superheat and the corresponding input heat flux. • CHF increases from 275 W/cm2 to 655 W/cm2 as the particle size increases from 30 mm to 100 mm. • The overall thermal resistance increases from 0.045 K/(W/cm2) to 0.175 K/(W/cm2) as the particle size increases from 30 mm to 100 mm. The heat transfer performance characteristics, mainly the upper limit of heat flux and the overall thermal resistance, of two-phase liquid-vapor-based heat spreaders primarily developed for concentrated-heat dissipation in microelectronics are dependent, predominantly, on the thickness and particle size of the evaporation wick as well as on the distribution of the high-permeable liquid supply channels, also known as arteries. In this study we develop a heat and mass transfer (thermal-hydraulic) model to predict the critical heat flux and the overall thermal resistance of a novel wick with rectangular thin-strip evaporator (with a large length-to-thickness ratio, L / t ≥ 3.5), with distributed liquid supply capillary wicks in a downward-facing orientation, each made of sintered copper particles, for microgravity applications. The liquid supply capillary wicks are made of 350-μm-diameter particle sizes. With the thermal-hydraulic model, we predict the CHF and overall thermal resistance for three evaporation wick particle sizes, i.e., 30, 60, and 100 μm, monolayer each, and show that both performance characteristics are primarily controlled by the hydraulic properties of the evaporation wick. The predicted CHF and minimum thermal resistance are 275 (12.3 °C superheat) and 0.045 K/(W/cm 2 ), 599 (56.7 °C superheat) and 0.095 K/(W/cm 2 ), and 655 W/cm 2 (114.4 °C superheat) and 0.175 K/(W/cm 2 ), for the 30, 60, and 100 μm particles, respectively. Finally, we compare the results of the present work with some of the existing numerical and experimental data for different thin wick designs found in the literature.