| The end of the carbon neutral runway is still 40 years away.It is necessary to implement renewable energy substitution actions,implement low-level energy reuse actions,build a clean,low-carbon,safe and efficient energy system,control the total amount of fossil energy,and focus on improving utilization efficiency.Our country is rich in low-grade flue gas waste heat resources.In the energy expenditure of various industrial furnaces,the waste gas waste heat accounts for about15% to 35%.The heat loss of flue gas is the largest of all heat losses,generally from5% to 8%,especially in coal and other industries.Waste heat resources account for about 17% to 67% of its total fuel consumption,of which the recovery rate is 60%.The utilization of low-grade flue gas in China is still immature.At this stage,the amount of waste heat resources is huge,the energy utilization rate is low,and the heat loss is large.Based on the above problems,this paper designs and develops a boiler exhaust waste heat recovery system based on micro heat pipe technology.The system includes heat exchange system,data monitoring system,intelligent control system,experimental analysis and evaluation of heat exchanger performance.Combined with the environmental conditions of the flat plate micro heat pipe array in the actual project of boiler flue gas waste heat recovery,the micro heat pipe selection scheme is designed and an experimental bench for the performance test of the micro heat pipe is built.The heat transfer performance of the flat micro-heat pipes with different liquid-filled working fluids and different liquid-filled rates under different cold and heat sources is analyzed.It is found that in a fixed heat source range,the heat transfer performance of the micro-heat pipe array filled with acetone-methanol 2:1 is better than that of acetone-methanol 1:1 and acetone-methanol 1:2,in which the acetone-methanol 2:2 with 35% liquid filling rate2:1.The overall heat transfer performance is the best in the experiment.The micro heat pipe was treated with anti-corrosion treatment and the corrosion test was carried out in the air duct in front of the desulfurization tower,and it was found that the anti-corrosion performance was good.The paper presents a gas water heat exchanger based on the technology of a micro heat pipe.The heat exchanger parameters such as inlet and outlet temperature of flue gas,wind speed,inlet and outlet temperature of the water were measured in practice.The analysis data showed that the temperature difference between the flue gas and the flue gas before and after heat exchange increased with the inlet temperature.At the same time,the water temperature difference remained unchanged.This paper analyzed the influence of different inlet temperatures and wind speed on heat transfer using the control variable method.It was found that the inlet temperature of flue gas was 190°C and the heat transfer efficiency was stable above 0.7 when the heat transfer was maximum,which was higher than the national standard.The irreversibility of the heat transfer process was analyzed by introducing the dimensionless equivalent thermal resistance R* and the thermal conductivity N*,which were derived from the dissipation number of the entransy.It was found that the heat exchanger operated stably when the flue gas temperature and the wind speed were constant.However,when the flue gas temperature or wind speed was increased,it was appropriate to use a lower wind speed to maintain the heat transfer performance before the temperature reached the critical temperature.After getting the critical temperature,the heat transfer performance was compared with the effective degree-NTU method and the effective degree-thermal conductivity method. |
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