水平圆管大空间自然对流实验的改进

Improvement of Reforming Experiment on Heat Exchange with Natural Convection over Horizontal Circular Pipe in Large Space

在原有水平管外自然对流实验台的基础上,设计并校核了4套新增实验管段,同时对实验系统中热电偶的冷端补偿方式进行改造。实验结果表明,改造后实验系统具有更好的稳定性,实验准则式与水平圆管大空间自然对流的经典经验公式更接近,实验测量结果分布更均匀。在此基础上,针对预热时间对实验结果的影响进行了讨论,结果发现,7 h预热时间的实验结果已经能够满足实验要求,且预热时间越长,测量结果越接近于理论值。通过误差分析,改造后的实验测得的对流换热系数最大误差约为5. 2%,表明实验台性能可靠。

Based on the original horizontal external convection test system,four sets of experimental pipe sections were designed and checked,and the thermocouple compensation of free-junction in the experimental system was also modified.The experimental results show that the stability of the experimental system is improved,the fitting curve is closer to the theoretical curve than before,and the measurement results are evenly distributed.We also discussed the effect of preheating time on the experimental results.It is found that the experimental results of 7-hour preheating time are able to meet the experimental requirements.What’s more,the longer the preheating time is,the closer the measurement results are to the theoretical value.It shows that the maximum error is 5.2%after modification through error analysis,which indicates good performance of the modified system.