Research And Development Of Fin-tube Fluoroplastic Heat Exchanger For Waste Heat Recovery Of Flue Gas

The recycling of industrial waste heat is one of the effective means to implement energy saving and emission reduction policies,and heat exchanger is commonly used in waste heat recovery systems.Gradually,the fluoroplastic heat exchanger is used widely in the fields of electric power,chemical industry and refrigeration for its excellent corrosion resistance and anti-scaling performance.Based on the actual needs of enterprises,this paper focused on the research and development of fin-tube fluoroplastic heat exchanger for power plant flue gas waste heat recovery.The thermal resistance analysis of fluoroplastic heat exchanger,the flow and heat transfer performances,thermal design calculation,application analysis and experimental test system design of fin-tube fluoroplastic heat exchangers were studied.Some meaningful research results were shown as follows:（1）The quantitative calculation and analysis of thermal resistance of fluoroplastic heat exchanger show that the main thermal resistance of fluoroplastic heat exchanger is the convection heat transfer outside tube and the thermal resistance of tube wall,under the calculation condition,the average proportion of total thermal resistance is more than 50%and 30%respectively,Fins and graphene-fluoroplastic composites can be used to strengthen the convective heat transfer outside tube and reduce the thermal resistance of tube wall.In order to reduce the contact thermal resistance between the fluoroplastic tube and fluoroplastic fin,a close contact connection method between fluorine plastic tube and fluorine plastic fin has been proposed,which lays a foundation for the research and development of fin-tube fluoroplastic heat exchanger;（2）Under the simulated conditions,the optimal range of air inlet velocity of fin-tube fluoroplastic heat exchanger is 6～8 m/s,the influence of fin thickness on Nu number and pressure drop（?）p can be ignored,and the influence of fin spacing is more obvious.Under the same inlet wind speed,with the increase of fin spacing,Nu number increases and（?）p decreases,with the increase of longitudinal spacing,Nu number increases andΔp decreases.Nu number decreases with the increase of tube transverse spacing,and（?）p remains almost unchanged with the increase of tube transverse spacing.Compared with tube transverse spacing,tube longitudinal spacing has a greater influence on the Nu number and（?）p.Through the comprehensive performance analysis,the comprehensive performance of fin-tube fluoroplastic heat exchanger is the best when fin spacing is 9 mm,fin thickness is 1.2 mm,tube transverse spacing is 10 mm and tube longitudinal spacing is 20 mm;（3）According to the design conditions,the logarithmic mean temperature difference method is selected to calculate the thermal design and calculation of fin-tube fluoroplastic heat exchanger.The thermal design calculation program of fin-tube fluoroplastic heat exchanger was compiled through Excel,and the structure size of heat exchanger that can meet the design conditions was obtained;（4）When fin-tube fluoroplastic heat exchanger is applied in waste heat recovery system,the thermal expansion of fluoroplastic fins should be concerned.The fin-tube fluoroplastic heat exchanger designed in this paper can save 1760 tons of coal and880,000 yuan according to the annual operation time of 8000 hours,and the investment recovery period is about 5 years.In addition,the waste heat recovery system of fin-tube fluoroplastic heat exchanger can reduce the emission of SO₂by15.84 tons and the emission of CO₂by 2425.16 tons per year,which has superior economic and environmental benefits;（5）According to the requirements of test conditions,the performance test platform of fin-tube fluoroplastic heat exchanger was designed,and the actual test scheme,data collection,experimental steps and experimental data processing methods ware determined,which laid the foundation for the test of fin-tube fluoroplastic heat exchanger,development of flow and heat transfer correlation and verification of existing typical flow and heat transfer prediction correlation.