Numerical Study On The Heat Transfer Enhancement Of The Complicated Structure Of Heat Sink

With the rapid development of modern science and technology, powerful variable-frequency drive (VFD) is increasingly applied in various industries, of which the unit power requirement has been upgraded to30,000HP, both heat generation and heat density from power electronics components increase significantly. So heat transfer enhancement technology is badly needed in the heat exchanger. This article began to research the heat transfer enhancement in the heat exchanger from the following two aspects:heat sink structure and the coolant.1.For the snake-fin flat tube which is installed in the air-cooling island, the finned tube gap between two tube was numerical studied on the performances of hydraulic and heat transfer, and corresponding correlations of Nu with Re were also obtained. According to the comprehensive evaluation index which is widely used in the evaluation of fin tube, no finned tube has the absolute good or bad, different aperture of finned tube has its best application in wind speed range. This paper gives the instruction in the fin-tube installation in the power station optimization.2. The VFD cooling must be enhanced from air-cooling to liquid-cooling. To ensure the operation in cold environment, water/glycol mixture can be selected as working fluid. In the present study, the characteristics of liquid-cooling for powerful variable-frequency cells with discrete heat sinks were studied by numerical simulation. The thermal and hydraulic performances of different geometric construction of the channels, as well as different working fluids were revealed. Comparing the heat transfer performance of straight rectangular channel with that of alternating rectangular channel, it is found that only the later one can meet the demands of the heat sink under the given circumstance,. Considering the ununiform and discrete heat sources and the tremendous heat load, different arrangements of the channels are compared with different coolants, including that of water and water/glycol mixture. The results show that until the channels comes up to40, can the heat sink dissipate all the waste heat with the external temperature of the heat sink under358K for long-term, high-performance operation of the device. At last, the influences of different coolants on the performances of heat transfer and hydraulic were studied by numerical simulations, which were100%de-ionized water, mixture of50%ethylene glycol and50%de-ionized water by weight, and mixture of60%propylene glycol and40%de-ionized water by weight. The variations of fluid physical properties with temperature were taken into account. It is concluded that the coolants PGW or EGW with40alternating channels in arrangement could satisfy the rigor requirements of the heat sink.