A one-dimensional numerical model for system performance prediction of loop heat pipes and its validation

Abstract

Developing high power density electronics requires effective and highly reliable cooling techniques with low thermal resistance and high heat removal capacity. Loop heat pipes (LHPs) are one kind of two-phase heat transfer device which can meet all these requirements. A physics-based one-dimensional numerical model has been elaborated to further develop this promising electronics cooling solution. In addition, an experimental setup using water as coolant, and which includes an LHP built with transparent materials, is used to validate the numerical model. This validation is obtained by comparing the numerical results with the temperature measurements, the two-phase flow section length in the condenser line, and an energy balance evaluation. The numerical model is then used to predict the system performance of the LHP under investigation. The results indicate that this LHP can only work in fixed conductance mode for the given operating conditions. Further, the influence of the charging mass is assessed. For low charging masses, both the natural convection cooled condenser and the compensation chamber casing can be fully utilized to dissipate the input heat, which can exceed {29.9 W} when the coolant saturation temperature is at {100 \celsius}. The operational limits for LHPs are investigated. For the current LHP under given operating conditions, the heat dissipation limit restricts the maximum input heat power, which in turn induces the activation of the heat leakage limit and the liquid-filling limit. It is shown that the condenser with higher heat dissipation capacity and lower thermal resistance will therefore enlarge the operational envelope.