| The general exhaust gas temperature of power plant boiler from 120℃ to 140℃, the heat loss accounted for all of the input heat power plant fuel from 3% to 8%, therefore, this part of the residual heat of the flue gas can be made full use of it, which can significantly improve the boiler efficiency and reduce the coal consumption. The current power plant boiler flue gas waste heat utilization of the most widely used mode is a heat exchanger installed in the tail flue (commonly known as the "low temperature economizer") using condensation water of low temperature flue gas heating steam turbine, saving part of extraction steam, increase the unit output, so as to achieve the effect of energy saving. The biggest obstacle in the low temperature flue gas waste heat utilization technology is serious corrosion problem, the problem of low-temperature corrosion of low temperature economizer is particularly serious. Plastic material corrosion resistance especially is good, plastic wall surface is smooth and have a modest one sex is not easy to scale, so it can work safely under fluid shock and vibration, which can effectively solve the problem of metal for corrosion in heat exchanger. Many scholars at home and abroad engaged in new plastic instead of metal as the research tail heating surface material, if can replace metal heat exchanger, it is a major reform of the power industry.In this paper, we research on performances of the conductive plastic finned tube heat exchanger, which provides the necessary reference and basis for this type of heat exchangers in the field of low-temperature flue gas waste heat recovery application. We carry on a thorough research on its performances through the designing and building the corrosion resistance test and the wind tunnel test. This paper build three-dimensional physical model of finned tubes based on FLUENT software and consider test data as boundary condition for numerical simulation,which gains velocity field, temperature field, pressure distribution of smoke flow outside finned tube. We simulate the heat exchanger by changing the spacing between elements, and find relatively reasonable structure type according to comprehensive performance evaluation. The results show that:(1) with the increased concentration of sulfuric acid and the elapse of soaking time, mass of heat transfer components changes in the range of 0.002-0.0031mg, but the overall quality do not changes significantly. The heat exchanger made of this plastic material can be used in low temperature flue gas heat recovery; (2) thermal plastic heat exchanger has a good performance. Improving air velocity can enhance heat transfer performance of heat exchangers, but the overall heat transfer coefficient increases slowly with the increasing wind speed, and the flow resistance rises significantly as the wind speed increases, so we should choose the appropriate operating wind speed. In addition, the flow rate of water side is small in the experimental conditions, and cooling water is in the laminar flow state, so increasing appropriately the flow rate of water side also contributes to the improvement of the heat transfer performance of the heat exchanger. (3) In order to consider the impact of the pressure drop and heat transfer, comprehensive performance evaluation index used in this paper shows that integrated heat exchanger performance that transverse spacing of heat transfer element is 3-9mm is superior than the original structure type of lmm transverse spacing, and the heat transfer element has the highest overall performance indicator when s5 is equal to 5mm, which indicating that the performance of finned tube heat exchangers under optimal spacing is best relatively. |
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