多结构强化管换热特性的实验研究

Experimental study on heat transfer performance of enhanced tubes with various structures

基于单管换热实验系统,研究光管和双侧强化管的换热机理,利用Gnielinski公式和热阻分离法分别计算4种强化结构换热管的管内外换热系数,并对光管外的冷凝过程进行数值模拟。结果表明:冷凝液光管模拟结果与实验结果之间误差<15%,能够较好地呈现冷凝过程;EX3强化管平均总换热系数提升207.02%,提升效果最佳。三角形齿相较于梯形齿对水流的扰动效果更大,管内对流换热效果更好。EX3管外强化冷凝换热效果最佳,同时,带有切槽的整体肋管的冷凝换热效果强于三维强化管,近矩形微肋强化管外侧冷凝性能优于近T形微肋管。存在最优肋间距,使得强化管能够最大化提升冷凝换热效果。基于实验数据拟合EX3与EX4的关联式,误差在±20%的范围内,符合预期可靠性。

Based on a single tube heat transfer experimental system,the heat transfer mechanisms of smooth tubes and double-sided enhanced tubes were studied.The Gnielinski formula and thermal resistance separation method were used to calculate the heat transfer coefficients inside and outside the tubes for four types of enhanced heat transfer structures,and numerical simulations were conducted on the condensation process outside the smooth tubes.The results show that the simulation results of condensed liquid smooth tube are within 15%of the experimental results,which can better present the condensation process.EX3 enhanced tube has an average total heat transfer coefficient increased by 207.02%,with the best improvement effect.Compared with trapezoidal fin,triangular fin has a greater disturbance effect on water flow,and the convection heat transfer coefficient inside the tube is better.EX3 tube exhibits the best external enhancement condensation heat transfer performance.At the same time,the condensation heat transfer performance of the integrated ribbed tube with grooves is stronger than that of the three-dimensional enhanced tube,and the condensation performance of the nearly rectangular micro-ribbed enhanced tube is better than that of the nearly T-shaped micro-ribbed tube.There is an optimal rib spacing that maximizes the condensation heat transfer effect of the enhanced tube.Based on experimental data,the correlation between EX3 and EX4 was fitted,and the error is within±20%,which is consistent with expected reliability.