Study of Direct Contact Heat Transfer Characteristics from a Liquid Ice

对空气与液态冰之间的直接接触换热特性进行了实验研究。研究了溶液浓度、进风温度、液冰床高度和进风流速对脱热性能的影响。结果表明，进气流量对直接接触换热特性有较大影响，总放热可能存在最佳进气流量条件。平均热去除率与进风流量、进风与溶液初始浓度平衡冻结温度之间的温度差呈正相关。实验装置主要由试验段、冷却-盐水循环回路和风冷系统组成。采用三相流化床的流化空气作为直接接触传热介质。空气是凉的，提前在空气室里进行了除湿。在流量和空气温度、湿度控制良好后，将其引入试验段。试验段由试验筒、分布器和静压段组成。试验容器由透明的透明玻璃管制成，内径150毫米，长330毫米。为了在试验段入口获得均匀的气流，在管道入口处采用了不锈钢网（20目）和尼龙布（200目）以及分配器。将细冰粒与设定温度和浓度的乙二醇溶液混合制成测试液冰。冰填料系数设为62%。实验中，测试液冰h_b的初始高度为170 mm。对固体-空气-液体三相流态化液体冰床的直接接触换热特性进行了实验研究。以下结论可以在本研究所涵盖的参数范围内得出。(1)除热速率主要受进风流量、进风温度和溶液初始浓度的影响，而受液冰床高度的影响较小。(2)随着空气流速的增加，总散热量减少，主要是由于壁面与液冰之间的摩擦产生热量。(3)在<正负> 15delta_ <ave>=1.131 Q_a^<1.127>DELTAT^<1.248> Less的偏差范围内，平均放热速率由下式相关

An experimental study has been performed to investigate the direct contact heat transfer characteristics between air and liquid ice. The effects of concentration of solution, inlet-air temperature, height of liquid-ice bed, and the flow rate of inle-air on the heat-removal performances were extensively examined. The results revealed that the flow rate of inlet-air exertes considerable effects on the direct contact heat transfer characteristics, and that there might be an optimum condition of the flow rate of air for total removed heat. The average heat removal rate was favorably correlated by the flow rate of inlt-air and the temperature difference between inlet-air and equilibrium freezing temperature of initial concentration of solution.The experimental apparatus fundamentally consists of test section, cooling-brine circulating loop, and air cooling system. The fluidization air for the three-phase fluidized bed was utilized as the medium of direct contact heat transfer. Air was coole … More d and dehuminided in the air chamber in advance. After both the flow rate and the temperature of air and humidity were favorably controlled, it was introduced to the test section. The test section consists of a test bessel, a distributor, and the calming section. The test vessel is made of transparent lucite tube which has dimensions of 150 mm in inner diameter and 330 mm in length. In order to obtain the uniform air flow at the inlet of test section, stainless mesh (20 mesh) and the Nylon cloth (200 mesh) along with the distributor were utilized at the inlet of the tube.The testing liquid ice was made up by mixing the fine ice particles and ethylene-glycol solution whose temperature and concentration were set in prescribed value. Ice packing factor was set constant at 62%. The initial height of the testing liquid ice h_b was set at 170 mm throu the experiments.Experiments were carried out to study the direct contact heat transfer characteristics of the solid-air-liquid three-phase fluidized liquid ice-bed. The following conclusions may be drawn within the parameters covered in the present study.(1) The heat removal rate is affected by the flow rate of inlet-air mostly and the temperature of inlet-air and initial concentration of solution, while it is little affected by the height of the liquid ice bed.(2) The total removed heat decreases as the flow rate of air increases owing to mainly the heat generation by the friction between the wall and liquid ice.(3) The average heat removal rate is correlated by the following equation within the deviation of <plus-minus>15DELTAh_<ave>=1.131 Q_a^<1.127>DELTAT^<1.248> Less