| dc.description.abstract | With the development of the semiconductor industry, the heating density of electronic equipment has increased. Therefore, it has become an important issue to solve the problem of thermal crash caused by high heat generation of electronic equipment. Traditional air cooling or single-phase water cooling is difficult to solve such high heat flux due to its low heat transfer coefficient, so the two-phase evaporative cooling system has become a possible solution to the heat dissipation problem of high heat flux components. If the same heat transfer watts is to be solved, since the latent heat of the liquid is higher than the sensible heat, the flow requirement for two-phase cooling is much lower than that for single-phase cooling, which can reduce the pumping power. For the study of two -phase evaporative cooling system, many researchers tried to reduce the flow channel size which can increase the heat transfer area in the two-phase evaporative heat exchanger, but it caused the problems of dry out and bubble back flow. In order to solve these problems, this study will apply the previous research of enhanced boiling heat transfer performance with microporous surfaces and preliminary results of microporous surface heat exchangers in this laboratory, and actually apply microporous coating on straight channels and expansion type channel heat exchangers which are used for high heat flux heat dissipation, a large number of nucleated sites and capillary force of the microporous coating are used to enhance the heat transfer performance and delay the heat exchanger dries out. In this study, straight channel heat exchangers with different channel depths and expansion type channel heat exchanger are designed, and sprayed aluminum powder with an average particle size of about 20 µm on the heat exchangers. Compared the heat transfer performance with different type flow channel and coated and non-coated heat exchangers.
The experimental results show that channel depth 5 mm straight channels heat exchanger with microporous surface has better heat transfer performance. Due to the deeper flow channel depth, a stratified flow is formed in the channel, so liquid still flows at the bottom of channel. In addition, the connected passage between particles can help liquid move into channel and wet the boiling surface and then delay the dry out. In the expansion type channel heat exchanger, because the cross-sectional area of the flow channel increases with the flow direction, so the pressure drop of bubbles move toward the outlet of the flow channel is reduced. Bubbles move to the outlet and reduce the bubble backflow and blockage phenomenon which increase heat transfer performance. | en_US |