Heat Transport Characteristics and its Mechanism of Heat Transport Device Using Parallel Tubes

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The increasing power consumption of the CPUs has made the thermal management one of the critical factors in their design. The present investigators proposed a new type of heat transport device, called parallel tube heat transport device (PTH) consisting of multiple capillary tubes and headers on both ends. PTH has a heat transport potential higher than any other heat transport devices previously proposed. The objective of this study is to examine the fundamental heat transport characteristics of PTH and to clarify its heat transport mechanism.In the heat transport experiments, two types of test sections were used. First test section had six copper tubes. The working fluid was R-134a, and the tube inner diameter and tube length were 2mm and 100mm, respectively. In this case, the heat was supplied by circulating the hot water around an evaporator. Second test section had two (inner diameter of 6.5mm and 3.5mm) or six (inner diameter of 2.8mm) copper tubes and used water as a working flui … More d. In this second case, the electric heater was used to heat the evaporator, and the effects of inclination angle, heating rate, and tube length were examined.In the flow visualization experiments, in order for the test section to be endurable against the high pressure caused by a working fluid of R-134a, the test section was made out of a brass plate by machining channels (2mm x 2mm x100mm) and covering it with a transparent plastic plate. The number of channels was three or six. In the case of six-channel test section, the effect of the combination of different channel sizes was also examined by replacing two channels out of six with those having larger side length of 4mm. Three-channel test section showed the unidirectional circulating flow or the oscillating flow depending on the temperature difference between two headers. In the results of the six-channel test section, the transported heat increased by combining two channel sizes. The image processing system developed in this study can capture the upward and downward flow velocities, its temporal change, and the flow pattern in the multiple channels. Less