| Shell-and-tube heat exchangers especially double pipe heat exchangers are widely used in industrial process, such as the petrochemical industry, metallurgy and pharmacy, etc. In the industrial process, the main heat exchange device which has large energy consumption is a heat exchanger, thus improving the heat exchange efficiency of the double pipe heat exchanger is significative to saving energy and reducing cost.In this paper, the shell-and-pipe heat exchanger were studied through modeling and simulation, and by using the first and second law of thermodynamics, heat transfer and thermal economics basic principle to the object of study with qualitative and quantitative analysis. The main study and result of this paper as follow:First of all, based on the water-water heat exchange, set a3D helical baffle double heat exchanger by using CFD software, and its numerical simulation was carried out. The flow resistance and heat transfer performance of shell side of the heat exchanger was analyzed in the pressure gradient, the coefficient of heat exchanger and friction factor. The results of simulations and analysis indicate that helical baffles reinforced the heat exchange of double pipe heat exchanger. And secondary flow of shell side flow channel section was advantageous to the convective heat exchanger.In the second place, after the experiment proved the correctness and reliability of above helical baffle heat exchanger model,5heat exchanger models whit different helical baffle height and same helical angle have been built. The result indicates that for the same volume flow rate, the heat transfer per unit area, the coefficient of heat transfer and friction factor increases with the increase of baffle spaces; however, the pressure gradient decreases with the increase of baffles space.Thirdly,5heat exchangers were evaluated by2kinds of evaluation method:(1) the ratio of the heat transfer rate of intensified heat exchanger and heat exchanger without intensify;(2) the ratio of the coefficient of heat transfer of intensified heat exchanger and heat exchanger without intensify, considering the effect of friction factor of shell side.Finally, based on the second law of thermodynamics,5helical baffle heat exchangers with different baffle height were analyzed form the point of view that exergy of working fluid and economy. The result indicates that the heat transfer performance of reinforcement increases with the increase of baffle height, however the economy is not the highest. So in heat exchanger design, the actual situation should be considered. |
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