Heat Transfer Analysis And Experimental Study Of Cold-end Efficiency Improving Technology With Cool Storage Model In Air-cooling Unit

Air-cooling technology in power plant is the key cooling mode in northern area in China that is rich in coal but short of water;however,the long-term operation causes serious problems such as the ash fouling in the tube bundle.Besides,due to the increase of high temperature weather and the influence of strong winds in spring,the heat transfer capacity of the air-cooling system reduces seriously,the back pressure of the unit rises,and the power generation load is limited.In order to improve operation safety and economy of the unit,and accomplish the energy saving and emission reduction targets of China's power industry,it is imperative to improve the cold-end efficiency in air cooling unit.Taking a 600MW air-cooling generation unit as an example,according to the operating and environmental conditions of the unit,a cold-end efficiency improving system with cool storage model is adopted,which is composed of a mixed type condenser,a forced draught air cooler and a cool storage device.The principle,operation mode of the system and its heat matching with the original direct cooling system of the unit are expounded.In terms of the cool storage system composed of cool storage tank and forced draught air cooler,the mathematical model is established through the heat balance equation and heat transfer equation of the air-cooled heat exchanger.And the heat transfer analysis and calculation of the cool storage process,the cool water storing process and the cool water mixing process are carried out.The calculation of the back pressure reduction caused by the system under the average monthly temperature and the actual high temperature conditions is carried out,and the back pressure declining effect of the cool storage system is obtained.Based on the design conditions of the unit,a simulation experiment system for cold-end efficiency improving technology with cool storage model was established.The nighttime cool storage experiment and the daytime cool water mixing experiment were carried out.The influence of the ambient temperature,air face velocity and velocity of the circulative water on temperature reduction of the cooling water were studied.Besides,the impact of different cool water mixing conditions on the back pressure reduction were studied.Through heat transfer calculation and analysis and experimental research,it is concluded that the cold-end efficiency improving system with cool storage model has a good back pressure reduction effect,and the cool storage system could further reduce the back pressure without increasing the cooling area,and help the unit pass the summer peak period safely.A reference for the cold-end efficiency improving and energy saving of the air cooling unit was provided.