Flow boiling heat transfer and temperature uniformity in micro-channel with countercurrent phase separation structure
To explorethe effects of different phase separation structure parameters on the heat transfer performance and temperature uniformity of enhanced micro-channel flow boiling,a parallel counterflow minichannel test section with different phase separation structures was fabricated:PSS-1(uniformly distributed in the upstream and downstream),PSS-2(near the central part in the upstream and downstream),PSS-3(close to both ends in the upstream and downstream)with different phase separation structure positions.Among them,PSS-1 is divided into three types:A,B and C,corresponding to 4 holes,6 holes and 10 holes respectively.Ethanol was used as the test working medium,and the flow boiling test was performed on the rectangular minichannel with a cross-section of 2 mm×2 mm under the effective heat flux density ranges from 17.12 kW/m2 to 87.25 kW/m2,the inlet temperature of 70℃,and the mass flow rate of 86.11 kg/(m2·s).The visualization of the channel is studied by using high-speed camera.By introducing the heat transfer enhancement factor and the wall temperature standard deviation,the effects of different phase separation structures on the heat transfer performance and temperature uniformity of the enhanced micro-channel and the strengthening mechanism of phase separation structures in high pressure and low pressure channels were studied.The results show that under the experimental conditions,the heat transfer enhancement effect increases with the increase of the number of phase separation exhaust holes.The influence of exhaust position on heat transfer characteristics is different in high pressure channel and low pressure channel.In addition,the PSS-1-C micro-channel has the best temperature uniformity.When the heat flux is 83.11 kW/m2,the average wall temperature of the micro-channel is 1.9℃ lower than the same channel without phase separation,and the temperature standard deviation is reduced by 14.2％.The visual image shows that the phase separation structure can realize gas phase transfer under the action of pressure difference,thereby enhancing heat transfer.
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