Abstract:

In order to improve the heat transfer efficiency of the steam heat exchanger, a new steam heat exchanger tube structure that with a mandrel inserted into a horizontal heat exchanger tube is proposed, and a two-phase flow model is built with commercial software FLUENT to analyze the heat transfer characteristics of the proposed heat transfer tube. Simulation results show that as the insertion of the mandrel, the heat transfer efficiency of the proposed heat transfer tube is improved by the increase of the average velocity and the velocity gradient near the tube wall of the two-phase flow. Quantitatively, the heat transfer ratio has the maximum value while the ratio of mandrel diameter to the horizontal heat transfer tube diameter, ?, is between the range [0.52, 0.57] for there are higher condensation ratio and higher velocity gradient, which make sure the temperature at the outlet of the heat transfer tube is lower and the heat transfer efficiency is more stable. Meanwhile, by according to the field synergy theory, the synergy characteristic increases as the increase of the ratio ?, and while ?>0.52, the mandrel has obvious effect on the enhancing of heat transfer ratio.

Key words: printing and dyeing, heat setting machine, steam heat exchanger, mandrel, in-pipe condensation, two-phase flow, enhanced heat transfer