Study On Heat Transfer And Fluid Dynamics Performances Of The Finned Tube Heat Exchanger For Waste Heat Recovery

With China’s rapid development of economy, energy demand is growing rapidly too, soimproving energy efficiency is quite important for China’s energy work. Industrial waste heatrecycling is one important part of improving the energy efficiency and energy conservation.The gas from the industrial gas boiler with the low temperature waste heat (150to250°Cand above) emissions to the atmosphere, which not only wasting the energy, but also pollutingthe environment. Recycle and use of this part of the heat energy for heating water or boilerfeed water is a great significance to energy saving and emission reduction. The heatexchanger is the key equipment for industrial waste heat recovery. Finned-tube heatexchanger has good features as heat transfer performance, heat resistance, thermal shockproperties, and corrosion resistance, easy to clean up the dust and low pressure drop features,so they are widely used in industrial waste heat recovery.This paper by testing the existing finned tube heat exchanger for waste heat recovery ofthe gas boiler, and then set up three dimensional finned tube flow field model, use the testdata as boundary conditions, and use FLUENT software simulation to get finned tube of thegas flow velocity and temperature field and pressure field data. Then analysis the influenceparameters of the inlet speed, fin height and fin spacing on the heat transfer: Along with theincrease of the inlet velocity, when Re increases, the average heat transfer coefficient alsoincreases gradually, and making heat exchange strengthened, but the increase of flue gasvelocity that flow resistance increases, and the pressure drop loss also presents the growthtrend, so the working process need to consume more wind power; The highly increase of finscan increase unit length of finned tube heat exchange area, but will make fin efficiency drops,but this just small effect to the heat transfer; Spacing size of fin gaps on the heat transfer effectmuch bigger than the height of the fins, along with the increase of the fin spacing, heattransfer of finned tube weakened gradually, and the resistance coefficient reduce gradually.Comparing the experimental value to the simulation value of the heat exchanger, theresults show that the relative error of the outlet temperature was7.3%, total pressure drop ofrelative error is2.1%, simulation method can well described the working conditions of theheat exchanger.Change the flue gas imports speed and the structural parameters of the heat exchanger,formulate optimization scheme, through the simulation we can find the different effects of theoptimization schemes. Then use the comprehensive performance evaluation factors to calculate the most reasonable scheme for strengthening heat transfer. The results show thatwhen the flue gas inlet speed is6.8m/s, fin height is14mm, fins spacing is2mm and theheat transfer effect is the best. Using the principle of the cooperation analysis of the velocityvector and temperature gradient angle, we get the same result with the comprehensiveperformance evaluation factors.