09. Heat and Mass Transfer

In this study, visualization of two-phase working fluid behaviour inside a loop heat pipe (LHP) with dual evaporator was carried out using neutron radiography. The operation of LHP entails complicated hydrodynamic phenomena, particularly in scenarios where many vapor-liquid interfaces are involved, and neutron radiography has advantages over other visualization method, mainly providing good contrast between metal enclosure and hydrogen-based working fluid, allowing these phenomena to be observed in real time. The LHP is mainly made of copper with stainless steel screen mesh as wicks, and deionized water as the working fluid, with 50% filling ratio. To understand the flow behavior phenomena under steady state condition, neutron images were taken while heat load was varied up to 120 W in total, where three cartridge heaters were utilized to simulate multiple heat sources with 40 W heat load at each heat source. The results demonstrated that the proposed loop heat pipe design works well in maintaining stable performance under the given heat load. In addition, neutron radiography demonstrated some interesting findings such as working fluid carry over in the vapor chamber and the vapor line, and different liquid distributions during no heat, startup and steady state operation.

Sholahuddin

Dr.