节点文献
中低温热管换热器的理论分析与实验研究
Theoretical Analysis and Experimental Study of the Moderate-low Temperature Heat Pipe Heat Exchanger
【作者】 王丹；
【导师】 夏国栋；
【作者基本信息】 北京工业大学 ， 热能工程， 2013， 硕士
【摘要】 随着热管换热器的使用越来越广泛，普通热管换热器已经不能满足一些特殊场合的应用，中温热管换热器的出现解决了这个问题。但研究发现，采用常规设计方法设计的中温热管换热器，在实际运行中，常常出现前几排中温热管破裂，中低温过渡区的低温热管工作状态不佳等问题。要解决中温热管换热器这些问题，就要合理的预测热管换热器内冷、热流体侧的流场和温度场。本文首先结合现有的热管换热器的数值模拟方法，提出本文数值模拟方法，对热管换热器进行数值模拟研究。为了验证这种方法的正确性，设计和搭建热管换热器实验系统，分析冷、热流体的温度场分布，实验结果与模拟结果相对比。研究表明本文中提出的数值模拟方法是合理的。其次对中温热管换热器进行数值模拟研究。分析中温热管换热器内冷、热流体的流场和温度场以及热管的工作状态。研究表明，改变热流体的入口温度，当入口温度在683~703K时，热流体温度越高换热器中热管内蒸汽温度越高，热管的传热性能越好；但是当热流体入口温度过高时，前几排水热管的管内蒸汽温度高于热管的工作极限温度，会发生爆管现象。改变热流体入口速度，当入口速度在1.5~3.5m/s时，热流体入口速度越大，换热器中热管内蒸汽温度越低；过低的热流体入口速度，会导致前几排水热管的管内蒸汽温度超过热管的工作极限温度，也会发生爆管现象。由于管内蒸汽温度是不连续性的，而管外流体是连续变化的，中温热管换热器内中低温过渡区的热管容易发生爆管现象，文中针对热管爆管现象提出了相应的解决方案，为以后研究提供参考依据。最后为了找到中温热管换热器的最佳运行工况和最佳结构参数，文中对中温热管换热进行优化研究。分析中温热管换热器蒸发段流体不同入口速度和换热器内不同管间距对换热器效率、单位压降换热系数、管内蒸汽温度的影响。研究表明，当管间距为52mm，流体速度在2.5~3.0m/s时中温热管换热器的换热效果最佳。
【Abstract】 With the widespread use of heat pipe heat exchanger, ordinary heat pipe heat exchanger can not meet some special occasions. The moderate temperature heat pipe heat exchanger appears to solve this problem. But the study found that the use of conventional designed methods in the moderate temperature heat pipe heat exchanger, there are often the first few rows of moderate pipes in the heat pipe rupture, a few rows of pipes in the moderate-low transition zone is not working or have poor working condition in actual operation. To resolve this problem in the moderate temperature heat pipe heat exchanger, it is necessary to reasonably predict cold and heat fluid and temperature fields in the heat pipe heat exchanger.Firstly, this paper proposed a new method of the numerical simulation on the heat pipe heat exchanger, combined with the existing numerical simulation In order to verify the correctness of this approach, the paper designded and set up the heat pipe heat exchanger experimental system, analysis the cold and hot temperature field, in the same time compared the experimental results and numerical results. The study showed the new method was reasonable.Secondly, the numerical simulation is used to the moderate temperature heat pipe heat exchanger. Analysis the cold and hot fluid field, temperature field and the heat pipe working condition of the moderate temperature heat pipe heat exchanger. Studies have shown that changing the temperature of the hot fluid inlet, when the inlet temperature changes within the range of683K-703K, the higher the temperature of the hot fluid, the higher the vapor temperature inside heat pipe, and the heat transfer performance of the heat pipe is better. However, when the hot fluid inlet temperature is too high, the vapor temperature inside the first rows of water heat pipes is higher than the limit working temperature of the heat pipe, the phenomenon occurs squib. Changing inlet velocity of the hot fluid, when inlet velocity changes within the range of1.5m/s to3.5m/s, the greater inlet velocity of the hot fluid, the lower the vapor temperature inside heat pipe. Low inlet velocity of the hot fluid will cause the vapor temperature inside the first rows of water heat pipes exceeds the limt working temperature of the heat pipe and heat pipe explosion phenomenon also occurs. Because the vapor temperature in the pipe is not continuous, and the temperature of the fluid is continuously changing, the heat pipes in the moderate-low transition zone of the moderate temperature heat pipe heat exchanger prone to burst pipes. Meanwhile some solutions were proposed to the phenomenon of burst pipes and provided a reference for the future research in the moderate temperature heat pipe heat exchanger.Finally, in order to find the best operating conditions and the best structure parameters, the paper gaves the optimization study to the moderate temperature heat pipe heat exchanger. Analysis fluid inlet velocity in the evaporator section and pipe spacing on the influence of the efficiency of heat exchangers, unit pressure drop in the heat transfer coefficient, and the vapor temperature inside heat pipe in the moderate temperature heat pipe heat exchanger. Studies have shown that when the pipe spacing is52mm and the fluid velocity is within the range of2.5m/s to3.0m/s, the effect of heat transfer in the moderate temperature heat pipe heat exchanger is the best results.