逆流相分离结构微细通道流动沸腾传热与均温性

Flow boiling heat transfer and temperature uniformity in micro-channel with countercurrent phase separation structure

为探究不同相分离结构参数对强化微细通道流动沸腾传热性能和均温性的影响,加工制作了带有不同相分离结构的平行逆流微细通道试验段,分别为相分离结构(PSS)位置不同的PSS-1(上下游均匀分布)、PSS-2(上下游靠近中部)和PSS-3(上下游靠近两端),其中PSS-1分为A、B、C三种,分别对应4孔、6孔、10孔。以乙醇为试验工质,在有效热通量为17.12~87.25 kW/m^(2)、入口温度为70℃、质量流速为86.11 kg(/m^(2)·s)的工况下,对截面为2 mm×2 mm的矩形微细通道开展流动沸腾试验,并利用高速摄影仪对通道进行可视化研究,通过引入传热强化因子和壁面温度标准差研究了不同相分离结构对强化微细通道传热性能和均温性的影响以及相分离结构在高压通道和低压通道内的强化机制。研究表明,传热强化效果随相分离排气孔数增加而提升,相分离结构位置对传热特性的影响在高压通道和低压通道内有所不同。PSS-1-C微细通道的温度均匀性最好,在热通量为83.11 kW/m^(2)时微细通道平均壁面温度较无相分离相同通道降低了1.9℃,温度标准差降低了14.2%。可视化图像表明,相分离结构在压差作用下能实现气相转移,进而强化传热。

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/m^(2)to 87.25 kW/m^(2),the inlet temperature of 70℃,and the mass flow rate of 86.11 kg/(m^(2)·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/m^(2),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.