Thermal study of the natural air cooling using roll bond flat heat pipe as plate fin under multi-heat source condition

Conventional radiators with the solid metal fins are difficult to meet the 5G base stations with greatly increased cooling requirements. Therefore, a novel phase-change device, named roll-bond flat heat pipe (RBFHP), has emerged as an alternative fin with the merits of easy to fabricate into large surface but thin, low-cost, and high heat transfer coefficient. In this study, the RBFHPs were tested with multi-heat source under natural air-cooling condition, to reflect the practical application scenario. And the thermal performances were investigated and optimized in terms of the heat source distribution, filling ratio, inclination angle, and power distribution mode. The results show the thermal performance is highly relevant to the relative position between the liquid-vapor interface and the higher load heat source. It is improper for the RBFHP to function when the latter is above the former, on the contrary, when the latter is beneath the former, the phase change cycling in the RBFHP can be prompted and sustainable. The final optimized RBFHP was working in 30 inclination angle with 20% filling ratio, and the largest heat source was the bottom one among the 3 lower distributed heat sources. And its total thermal resistance and temperature rise can be reduced by 15.3% and 10 C respectively, compared to an evenly heated aluminium plate at 48 W total heat load.