In order to comply with the recent demand for downsizing of the electric equipment, the minia- turization and the improvement in heat transfer performance of a heat sink under natural air-cooling are increasingly requ...In order to comply with the recent demand for downsizing of the electric equipment, the minia- turization and the improvement in heat transfer performance of a heat sink under natural air-cooling are increasingly required. This paper describes the experimental and numerical investigations of heat sinks with miniature/micro pins and the effect of the pin size, pin height and the number of pins on heat transfer characteristics of heat sinks. Five types of basic heat sink models are investigated in this study. The whole heat transfer area of heat sinks having the different pin size, pin height and the number of pins respectively is kept constant. From a series of experiments and numerical analyses, it has been clarified that the heat sink temperature rises with increase in the number of pins. That is, the heat sink with miniaturized fine pins showed almost no effect on the heat transfer enhancement. This is because of the choking phenomenon occurred in the air space among the pin fins. Reflecting these results, it is confirmed that the heat transfer coefficient reduces with miniaturization of pins. Concerning the effects of the heat transfer area on the heat sink performance, almost the same tendency has been observed in other three series of large surface area, that is, higher pin height. Furthermore as a result of studying non-dimensional convection heat transfer performance, it was found that the relation between the Nusselt number (Nu) and the Rayleight number (Ra) is given by Nu = 0.16 Ra0.52.展开更多
A laser-micromilling process was developed for fabricating micro pin fins on inclined V-shaped microchannel walls for enhanced microchannel heat sinks.A pulsed nanosecond fiber laser was utilized.The feasibility and m...A laser-micromilling process was developed for fabricating micro pin fins on inclined V-shaped microchannel walls for enhanced microchannel heat sinks.A pulsed nanosecond fiber laser was utilized.The feasibility and mechanism of the formation of micro pin fins on inclined microchannel walls were investigated for a wide range of processing parameters.The effects of the laser output power,scanning speed,and line spacing on the surface morphologies and geometric sizes of the micro-pin fins were comprehensively examined,together with the material removal mechanisms.Micro pin fins with acute cone tips were readily formed on the V-shaped microchannel walls via the piling of recast layers and the downflow of re-solidified materials in the laser-ablation process.The pin-fin height exhibited an increasing trend when the scanning speed increased from 100mm/s to 300 mm/s,and it decreased continuously when the line spacing increased from 5μm to 20μm.The optimal processing parameters for preparing micro pin fins on V-shaped microchannels were found to be a laser output power of 21 W,scanning speed of 100-300 mm/s,and line spacing of 2-5μm.Moreover,the V-shaped microchannels with micro pin fins induced a 7%-538%boiling heat-transfer enhancement over their counterpart without micro pin fins.展开更多
Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes （CNTs） have been proven as a potential material for micro-coolers due to the superior ...Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes （CNTs） have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper, an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid dynamics （CFD） simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the. micro-pin-fin heat sink were obtained, and the heat removal efficiency was evaluated.展开更多
文摘In order to comply with the recent demand for downsizing of the electric equipment, the minia- turization and the improvement in heat transfer performance of a heat sink under natural air-cooling are increasingly required. This paper describes the experimental and numerical investigations of heat sinks with miniature/micro pins and the effect of the pin size, pin height and the number of pins on heat transfer characteristics of heat sinks. Five types of basic heat sink models are investigated in this study. The whole heat transfer area of heat sinks having the different pin size, pin height and the number of pins respectively is kept constant. From a series of experiments and numerical analyses, it has been clarified that the heat sink temperature rises with increase in the number of pins. That is, the heat sink with miniaturized fine pins showed almost no effect on the heat transfer enhancement. This is because of the choking phenomenon occurred in the air space among the pin fins. Reflecting these results, it is confirmed that the heat transfer coefficient reduces with miniaturization of pins. Concerning the effects of the heat transfer area on the heat sink performance, almost the same tendency has been observed in other three series of large surface area, that is, higher pin height. Furthermore as a result of studying non-dimensional convection heat transfer performance, it was found that the relation between the Nusselt number (Nu) and the Rayleight number (Ra) is given by Nu = 0.16 Ra0.52.
基金This study is financially supported under the Grants of the National Natural Science Foundation of China(Grant No.51775464)and was partially supported by Basic research projects of Shenzhen Research&Development Fund(Grant No.JCYJ20200109112808109).
文摘A laser-micromilling process was developed for fabricating micro pin fins on inclined V-shaped microchannel walls for enhanced microchannel heat sinks.A pulsed nanosecond fiber laser was utilized.The feasibility and mechanism of the formation of micro pin fins on inclined microchannel walls were investigated for a wide range of processing parameters.The effects of the laser output power,scanning speed,and line spacing on the surface morphologies and geometric sizes of the micro-pin fins were comprehensively examined,together with the material removal mechanisms.Micro pin fins with acute cone tips were readily formed on the V-shaped microchannel walls via the piling of recast layers and the downflow of re-solidified materials in the laser-ablation process.The pin-fin height exhibited an increasing trend when the scanning speed increased from 100mm/s to 300 mm/s,and it decreased continuously when the line spacing increased from 5μm to 20μm.The optimal processing parameters for preparing micro pin fins on V-shaped microchannels were found to be a laser output power of 21 W,scanning speed of 100-300 mm/s,and line spacing of 2-5μm.Moreover,the V-shaped microchannels with micro pin fins induced a 7%-538%boiling heat-transfer enhancement over their counterpart without micro pin fins.
基金supported by the National Natural Science Foundation of China(Grant No.10702037)the National High-Technology Research and Development Program(Grant No.2008AA04Z301)
文摘Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes （CNTs） have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper, an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid dynamics （CFD） simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the. micro-pin-fin heat sink were obtained, and the heat removal efficiency was evaluated.
