High-performance energy-saving miniature loop heat pipe for cooling compact power semiconductors

Abstract A miniature loop heat pipe (mLHP) is developed to cool compact wide bandgap power semiconductors with a high heat flux (≥30 W/cm2) and high allowable operating temperature (≤250 °C) for the first time. Since the mLHP consists of an evaporator (15 × 16 × 3 mm), a condenser (12 × 12.5 × 2 mm), and transport tubes (100 mm), it can be mounted on a small product equivalent to the size of a gaming smartphone. To achieve high heat flux performance, the mLHP uses Shirasu porous glass for the wick and ethanol for the working fluid. Moreover, for the condenser, heat dissipation is enhanced using a thin copper plate (60 × 60 × 0.5 mm), a thin aluminum cold plate (35 × 20 × 3 mm), or a small cooling fan (17 × 17 × 3 mm). When the condenser dissipates heat using the thin aluminum cold plate, the mLHP achieves a maximum heat-transport performance of 15 W (60 W/cm2) in the horizontal attitude. At the maximum heat load, the heat-source temperature, evaporator temperature, and system thermal resistance at 15 W are 249.8 °C, 142.2 °C, and 0.72 °C/W, respectively. Additionally, the heat transfer coefficient of evaporation at the evaporator is approximately 24,000 W/m2/K. The proposed steady-state numerical model is consistent with the experimental results, excluding the condenser part, with a relative error of 7%.