Research On Enhancement Of Heat Transfer In Shell Side Of Shell And Tube Heat Exchanger

Shell and tube heat exchanger is abroad used as a kind of energy exchange facility in industry, it's concerned that how to improve its performance of heat transfer effectively, while the enhancement of heat transfer is an important means for improving its performance of heat transfer. The enhancement technology of heat transfer of shell and tube heat exchanger includes two main aspects which are enhancement of heat transfer in tube side and shell side, while the enhancement in shell side is always the emphases. The support structure of shell side is not only used in supporting the tube bundles but also disturbing the liquid and enhancing the heat transfer in the shell side, so a reasonable kind of shell side support structure is important for the mechanical performance as well as the performance of heat transfer and flow resistance. A reasonable kind of shell side support structure should satisfy some requests as follows: effective support on the tube bundles; effective disturbance on the shell side liquid to satisfy the performance of heat transfer and flow resistance of the heat exchanger; convenient manufacture and installation.In this article, the research status on the enhancement of heat transfer in shell side of shell and tube heat exchanger in recent several years has been reviewed, and a new kind of shell side support structure--flower baffle has been proposed. Experiment based on similarity principle has been taken in order to investigate the performance of heat transfer and flow resistance of the flower baffle heat exchanger, and according to that the criteria relationship expressions of heat transfer and flow resistance have been obtained.Basing on the deep research on the performance evaluation methods of heat exchanger, several different methods based on the first law of thermodynamics and second law of thermodynamics (the single performance evaluation method of heat transfer or flow resistance, the integrated performance evaluation method of heat transfer and flow resistance, the rate of total entropy increase method) have been used on the evaluation and comparison of the performance of flower baffle heat exchanger and single segmental baffle heat exchanger. The results are as follows:When both the flow rate of tube side and shell side in the two heat exchangers are equal, the total heat transfer coefficient k of the flower baffle heat exchanger is 80%~90% of that of the single segmental baffle heat exchanger, the shell side pressure dropΔp is about 70% of that of the single segmental baffle heat exchanger, while the integrated performance k/Δp increases 10%~30% compared with that of the single segmental baffle heat exchanger.When the Re of shell side in the two heat exchangers are equal, the Nu of shell side of the flower baffle heat exchanger is about 50% of that of the single segmental baffle heat exchanger, the shell side pressure dropΔp is about 30% of that of the single segmental baffle heat exchanger, while the shell side integrated performance Nu/Δp increases about 60% compared with that of the single segmental baffle heat exchanger.When the liquid velocity both in tube and shell in the two heat exchangers are equal and that when the liquid velocity in shell side uo>0.25m/s, the rate of total entropy increase Ys of the flower baffle heat exchanger is much smaller than that of the single segmental baffle heat exchanger, in other words, the exergy consumed on transferring unit heat of the flower baffle heat exchanger is less than that of the single segmental baffle heat exchanger.The results of comparison show that the performance evaluation on heat exchanger should be comprehensive.The summarization is made and some propositions about the deep research are proposed at the last of this article.