Numerical Study And Structural Optimization On Heat Transfer And Flow Performance In Shell-side Of Helical Baffle Heat Exchangers

Helical baffle heat exchanger has many advantages, such as good heat transfer performance, small shell-side pressure drop, less bundle deposit and preventing bundle fluid from induced vibration. With more and more energy saving demands, a comprehensive comparison between influence factors of shell-side performance needs to be drawn. At the same time, the novel heat exchanger of heat transfer augmentation with low penalty of pressure drop is urgent to be studied and promoted.Based on the numerical simulation method, the helical baffle heat exchanger was calculated. The influence of heat transfer and resistance performance of shell-side on the different cutting forms of baffle slabs was analyzed. What’s more, the traditional helical baffle heat exchanger was optimized in structure in order to get more superior performance. The main work was as follows:1. A helical baffle heat exchanger calculation model was established by use of numerical simulation software ANSYS. Grid independence validation was used to obtain both effective and economic grid. Rational turbulence model selected, physical parameters modified, boundary condition and solver control properly defined were carried out to guarantee the credibility of the calculation. And the definition of Re number and characteristic velocity on shell-side was calculated in detail, which served as the basis of data processing.2. The influence on the heat transfer and pressure drop performance of shell-side was investigated under the condition of different cutting forms of baffle slabs. The results indicate that elliptic slab shows a better comprehensive heat performance at the small spiral angle (β=20°), while the sector slab performs better at the large spiral angle (β=40°). The results are instructive for baffle slabs structure selection in engineering application.3. A novel helical baffle heat exchanger of heat transfer augmentation with low penalty of pressure drop was proposed. Distinct from other researches, this paper replaced traditional circular tube bundle with elliptical one to enhance the heat transfer. Results show that under the condition of β=30°and2000<Re<7000, the heat transfer performance of helical baffle heat exchanger with elliptical tubes is equal or superior to that of the circular one. And elliptical tubes can greatly reduce the pressure drop of shell-side, which improves32～40%of the comprehensive heat transfer performance. The enhanced effects of elliptical tubes are situated in the third quadrant of PECD, illustrating a rare condition which both enhances heat transfer and reduces resistance performance. This may because elliptic tubes have advantages in three field synergy principle.4. In order to optimize the comprehensive heat performance of shell-side, simulations under different spiral angle and axis ratio of elliptic tubes helical baffle heat exchanger were carried out separately. The optimal structural parameters were obtained at: β=35°,X=2.5.