Experimental study on heat transfer performance of enhanced tubes with various structures
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.
horizontal single-pipeenhanced heat transferenhanced structureheat transfer mechanismheat transfer coefficient
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