Evaluation for Optimal Configuration of Twisted Fiber Bundle Wick Heat Pipe with Top Heat Mode

Abstract

The objective of this research was investigating the thermal resistance of the twisted fiber bundle wick (TFBW) heat pipe. TFBW was made by combining between both size copper fiber of 30 μm and 50 μm. These were arranged as the lengthwise and twist together. The variable parameters of the TFBW were focused on the mixing ratio and twisting pitch length. TFBW heat pipe with outer diameter of 3 mm and length of 70 mm was heated in the top heat mode. Heat input was maintained as constant value at the evaporator section. The condenser section was cooled by air. The outer surface of both sections was measured temperature which were using for calculating the thermal resistance. It was observed that the mixing ratio of 50%:50% demonstrated the lowest thermal resistance for twist pitches of 10 mm and 15 mm. Due to the appropriate pore size of the formed wick, it provided high capillary pressure and high permeability. The decreasing of twist pitch (tighter twisting) caused to increasing of thermal resistance. This was because an excessive twist resulted in very small pore sizes led to lower permeability. The mixing ratio of 50%:50% with a pitch length of 20 mm exhibited an opposite trend because that already had the appropriate pore size. Moreover, the twisting with a smaller pitch had smaller pores leading to a higher capillary pressure. Therefore, the optimal configuration of TFBW providing the lowest thermal resistance was the mixing ratio of 50%:50% with a pitch length of 10 mm.