Experiments Of Recovery Of Low Temperature Waste Heat From Combustion Products Of Natural Gas With Heat Pipe Exchanger

With the development of our country's economy,large consumption of fossil energy which has been reduced increasingly,so that energy saving has become an inevitable trend in the future.Natural gas is a kind of clean energy and the water vapor in the flue gas which released by burning natural gas is the most comparing with coal and oil.Therefore,it is very valuable to study the waste heat recovery of natural gas.However,low temperature flue gas belongs to low grade energy,which is more difficult to recover comparing with high temperature flue gas.As a kind of superconductor,the heat pipe has been widely studied and applied at home and abroad.Heat pipe is very suitable for recovery of low temperature flue gas because of its strong heat exchange ability and easy replacement and cleaning.At present,there are a lot of researches on the recovery of natural gas flue gas residual heat and the water vapor in the flue gas from the condensation heat pipe of the finned tube heat exchanger.However,the heat pipe heat exchanger which was used to recover the heat of the natural gas and the water vapor in the flue gas was seldom studied.In this paper,the double film theory is used to analyze the heat transfer process of the condensation of steam with a large amount of non-condensable gas.The heat pipe exchanger is arranged horizontally,and the flue gas of gas water heater and tap water were set as the heat source and cold source respectively.Then the length of the fin side and the tube side of the heat pipe is designed according to previous studies,in order to study the heat transfer effect of sensible heat and latent heat in flue gas.In this experiment,we used the finned tube heat exchanger with fin spacing of 1.5mm and 2.7mm,and compared the experimental results with the optimal theoretical ones.The theoretical calculation was based on the inlet temperature and flow rate of known flue gas and cold water,and the theoretical outlet temperature of the flue gas and cold water as well as the average wall temperature of the heat pipe were calculated by conservation of energy theorem.The results showed that amount of water vapor was condensed when the fin spacing was1.5mm,and some of the condensed water can not drop smoothly at the same time.The existence of condensation water increased the heat transfer resistance,and resulting in the experimental results of sensible heat exchange and latent heat exchange on the flue gas were quite different from the theoretical ones.The problem of condensation water drop was improved when the fin spacing was 2.7mm,and the experimental results showed that the sensible heat transfer effect was different from the theoretical one.The heat transfer effects of two kinds of fin spacing were compared and analyzed,and the results showed that the heat transfer effect of the sensible heat transfer and the latent heat transfer of the flue gas were much better when the fin spacing was 2.7mm.When the fin spacing was 2.7mm,the condensation ratio was higher than that of the fin spacing of 1.5mmTheoretical analysis and calculation method and experimental method were used in this paper.The effect of heat pipe exchanger on condensation heat transfer of natural gas was studied.In order to provide some new ideas for the research and application of the heat pipe,the follow-up works were prospected simultaneously.