Permeability and capillary performance are the most important parameters relating to the thermal performance of heat pipes. These parameters are deeply linked to pore structure, which has been influenced by the starting powder utilized. In this paper, the effect of particle size and geometry of copper powder on the porosity and capillary performance of porous wicks were systematically studied. Sintered porous wicks were made from different-sized spherical (58 μm, 89 μm, 125 μm) and dendritic (59 μm, 86 μm, 130 μm) Cu powders. The results demonstrated that the porosity and capillary performance of both types of copper powder increase with particle size due to an increase in the connectivity between internal pores. In comparison to the spherical powder, the dendritic powder demonstrated superior capillary efficiency as well as greater porosity. Additionally, a model was proposed for the capillary performance and permeability of sintered porous copper. The predicted results were quite comparable to the experimental data, demonstrating the effect of the starting powder. These findings suggest that porosity and capillary performance of porous wicks are strongly related to powder geometry as well as particle size.

In this paper, a ground heat source cooling system based on a novel underground heat exchanger is proposed for cooling of a Base Transceiver Station (BTS) in the scope of KC05.21/16-20 project entitled “Research, design and manufacture geothermal cooling systems for Base Transceiver Station”. Compared to traditional underground heat exchanger, the perforated borehole tube is used to improve the heat transfer efficiency by favorizing the interaction between ground water flow and hot water flow in U-type tube. Since the heat transfer from the cooling water and the infinity soil, which is impacted by the soil structure and the groundwater accumulated in the void space, is complicated, the analytical computation is not suitable. The Computational Fluid Dynamics (CFD) model of underground U-type heat exchanger was developed to benchmarking the heat transfer efficiency. The influence of flow configurations and of U-type tube length on the heat load and overall thermal resistance were investigated.