The Study Of Computational Optimization And Experimental Research For Longitudinal Shell-and-tube Heat Exchanger

It will be beneficial for civil applications as well as strategy of domestic sustainable development because of the global trend of improving energy-utilizing efficiency, reducing carbon emission, lowering greenhouse effect and domestic trend of industrial capacity adjustment, reducing carbon emission per GDP, and developing techniques of energy-saving and emission-reducing. As one of the most energy-consuming and material-consuming equipments in engineering industry, heat exchangers draw lots of attention from academic field. Improving the energy-utilization efficiency, reducing pumping power, extending its longevity, inventing novel heat exchangers, and optimizing design heat exchanger are crucial for the goal of energy-saving and emission-reducing.The present thesis conducts research on rod-baffle heat exchanger, summarizes different numerical simulation methods and builds unit model, periodic model, porous model and whole model. The present thesis also verifies the numerical simulation with experimental verification. The numerical results indicate that unit model is not capable of predicting pressure drop in general. Unit model predicts heat transfer performance in an acceptable accuracy. But unit model can predict heat transfer precisely when the heat transfer tube bundle number is large. The results also indicate that periodic model is not capable of predicting pressure drop. Periodic model predicts heat transfer performance accurately, and more accurate if the ratio of shell length to shell diameter is big. The results also indicate that porous model can precisely predict heat transfer and flow performance, however, it needs empirical correlation and user-defined-functions during the calculation process. The results also indicate that whole model is the most accurate model and is applicable for all situations when the above three models cannot be utilized. But whole model also consumes the most computational resource. Based on the results and analysis, the present thesis provides a standard to guide researchers to choose the most appropriate model for different circumstances.Based on the convective heat transfer optimal theory of minimum dissipation, the principles of core-flow heat transfer enhancement and multi-fields synergy principles, the convective heat transfer processes in heat exchanger are theoretically analyzed. The present thesis infers the change of total available potential inside a shell-and-tube heat exchanger. For the tube-side, longitudinal rotation flow with single or multi vortexes will improve thermal-hydraulic performance when the irreversible dissipation and power consumption are set as the objective function and constraints. On the basis of this, the present thesis proposes a novel spiral tube and applies it into shell-and-tube heat exchanger. The novel spiral tube eliminates baffles in heat exchanger thus reduces fluid vibration and fouling issues. Based on the standard that the present thesis proposed, the numerical whole model for the novel shell-and-tube heat exchanger is proposed with experimental verification. The results indicate that the performance evaluation criterion value is 1.15-2.1 for the tube-side in comparison with rod-baffle heat exchanger. For the shell-side, the heat transfer performance reduces 14.6-24.9%, and the pressure drop decreases 32.7-35.8%, thus the performance evaluation criterion value is 0.9-0.95. But in general, the novel heat exchanger has a better comprehensive performance compared to rod-baffle heat exchanger when tube-side and shell-side are both taken into consideration. Combining the advantages of rod-baffle heat exchanger and whole plate baffle heat exchanger, the present thesis proposes a novel whole plate heat exchanger. The whole model is established and the results indicate that shell-side heat transfer performance increases 28.4?38.7% and pressure drop increases 39.5-49.7% when Reynolds number ranges from 5000 to 14,000. Overall, the performance evaluation criterion value is 1.15?1.22. What's more important, the novel whole plate heat exchanger is easy to be manufactured thus has a broad industrial application.The present thesis proposed a novel optimization design method based on constructal theory by regarding the whole heat exchanger as the combination of different sub-heat exchangers connected in parallel or series path. The mathematic formulation for constraints and objective function is given and genetic algorithm is utilized to design shell-and-tube heat exchanger. The results indicate that the novel design method is able of expanding the optimal range and has a great advantage on the realization of objective function. Meanwhile, this original method consumes lots of computation resources during the model formulation and calculation procedure. Therefore, the novel design method is simplified into two methods. And one of the two simplified methods is applied for the shell-and-tube heat exchanger design. The results indicate that the simplified method demonstrates good advantages than all other design methods in the open literature. Besides, the present thesis optimizes a shell-and-tube heat exchanger using a genetic algorithm regarding the minimization of total exergy loss as the objective function. The results indicate that the inreversibilities and power consumption reach minimum and the efficiency reaches maximum when the total available potential change reaches minimum.