水平烧结管降膜蒸发器管外流动分析

Analysis of flow outside horizontal sintered tube falling film evaporator

烧结管由光滑圆管外表面烧结铝合金或铜合金粉末制备,用于水平管蒸发器传热元件,实现高效传热。模拟分析烧结层材质、喷淋孔流量和烧结层孔隙率对烧结管管外液膜分布的影响。结果表明:比较液柱截面及波峰截面的平均液膜厚度,铝合金烧结层减薄了52.22%,而铜合金烧结层减薄了56.12%,故铝合金烧结层液膜流动较稳定。当烧结层为铝合金时,在喷淋孔流量Qv=140—200 L/h,液膜厚度随着流量增大而增大,增大幅度达到了16.52%。当Qv=160 L/h时,流速随着液膜厚度增大逐渐减小;随着孔隙率增大,液膜厚度在周向角度θ=0°—160°时增大,在θ=160°—170°时减小。当孔隙率n=50%时,平均液膜厚度减薄率较小,表明液膜厚度均匀性较好。2种烧结管表面均可形成连续的流动液膜,烧结层增大了工质接触管壁的传热面积。

The sintered tube was made of sintered aluminum alloy or copper alloy powder on the outer surface of smooth circular tube. It was used as heat transfer element in horizontal evaporator to achieve efficient heat transfer. The effects of sintered material, flow rate and porosity on the distribution of liquid film were simulated. The results show that compared with the average film thickness of the column section and the wave peak section, the aluminum alloy decreases by 52.22%, while the copper alloy decreases by 56.12%. The film of the aluminum alloy is more stable. When the coating is aluminum alloy, the film thickness increases with the increase of flow rate, and increases by 16.52% in Qv=140-200 L/h. When Qv=160 L/h, the flow rate gradually decreases with the increase of film thickness. With the increase of porosity, the film thickness increases within θ=0°-160° and decreases within θ=160°-170°. When n=50%, the reduction rate of the average film thickness is smaller, and the liquid film spreading is well distributed. Continuous flowing liquid film can be formed outside the two sintered tubes, and the sintered layer increases heat transfer area of the working medium contacting the tube wall.