Multi-objective Optimization And Heat Transfer Enhancement Performance Analysis Of Hot Blast Stove Heat Exchanger

As an important energy conversion equipment for heat exchange in hot air stoves,the heat exchanger has an important impact on the overall efficiency of the hot air stoves.Parameter optimization and performance analysis of heat exchangers not only contribute to improve production efficiency,but also have a very important significance in reducing energy consumption and improving economic benefits.A response surface optimization method combining structural parameters and flow parameters is proposed for the multi-parameter multi-objective optimization of the heat exchanger with the 5LW-20 biomass pellet hot air stove heat exchanger as the research object.The twisted tube and finned tube are designed based on two ways of disturbing the flow and changing the heat transfer area,and the reinforced tube is analyzed for single-factor,multi-factor and field synergy,and the heat transfer characteristics of the single tube are studied experimentally according to the analysis results.The specific research is as follows:(1)The heat exchanger model of the hot blast furnace was established.The heat exchanger performance evaluation method is studied carefully,and the Nusselt number,friction factor,and comprehensive performance coefficient are determined as the evaluation criteria of the heat exchanger.The whole model of the hot blast stove is established,the heat exchanger model is reasonably simplified,the fluid domain of the heat exchanger simulation calculation is extracted by using Design-Modeler,and the material properties of the fluid domain are determined.According to the heat design requirements of the hot blast stove,the boundary conditions of the model simulation are calculated,the model mesh is verified to be irrelevant,and the correctness of the heat exchanger simulation is verified by comparing the errors between the test conditions and the simulation results.(2)Numerical simulation and multi-objective optimization of the hot blast stove heat exchanger.A numerical simulation study of the heat exchanger in Fluent was carried out to analyze the distribution laws of the temperature,velocity,and pressure fields of the heat exchanger in the shell and tube processes under the calculated boundary.The results showed that the air-side outlet temperature of 88.33°C,which is 10.41% error compared with the design value of 80°C.The structural parameters affecting the heat exchanger(heat pipe diameter,transverse pitch,and longitudinal pitch)were also analyzed as a single factor,and the multi-objective optimization of the heat exchanger structural parameters as well as the flow parameters was performed using response surface optimization.The optimization results show that the optimal design points are P1=74.91 mm,P2=104.23 mm,P3=121.37 mm,P4=4.83 m/s,and P5=8.48 m/s.The Nusselt number is increased by 9.55%,the friction factor is reduced by 15%,and the comprehensive performance coefficient Pec is increased by 16.11% compared to the performance parameters under the initial structure.(3)Analysis of heat transfer enhancement performance.The twisted tube and finned tube structures were designed based on disturbing the flow and changing the heat transfer area,and the single-factor and multi-factor analyses were performed on different influencing factors of the twisted tube(ratio of short to the long axis and conductivity)and finned tube(number of fins,thickness of fins and height of fins).Based on the synergistic field theory,the synergistic angles of the common circular tube,twisted tube,and finned tube were compared,and the synergistic angles were 85.26°,85.19°,and 84.80°,res Pectively,with the finned tube having smaller synergistic angles.The synergy between velocity and temperature fields is better.(4)Heat transfer performance experiment of finned tube.Based on the results of heat transfer enhancement analysis,a single-tube test platform is built,and the heat transfer of the finned tube structure is all greater than that of the common circular tube structure.Comparing the test values with the simulated values,the average error of Nusselt number is9.63% and the average error of outlet temperature is 7.88%.