Experimental Study On Special Heat Exchanger For Waste Heat Recovery Of Sewage

The development and utilization of renewable energy is an inevitable choice to reduce fossil energy consumption,environmental pollution,energy saving and emission reduction,and heat pump technology has long-term and practical significance for the use of low-grade renewable energy.The development and utilization of new cold and heat sources should meet the requirements of energy saving,environmental protection and healthy development,and urban sewage as a low-level heat source for heat pumps can meet the above requirements.However,there are still many key technologies that need to be researched and solved in terms of improving the comprehensive heat exchange performance of the sewage source heat pump system and the descaling and inhibition of the sewage heat exchanger.Based on the research of a large number of documents at home and abroad,this article focuses on the development and experimental research of new sewage heat exchangers.This paper first proposes two types of heat exchangers that are antifouling and easy to decontaminate: deflector-type sewage total heat exchangers(belonging to indirect heat exchangers)and pillow-plate heat exchangers(belonging to direct heat exchangers).The heat exchange principle of the deflector-type sewage total heat exchanger can be briefly described as the total heat exchange between sewage and air.This form of heat exchange can effectively reduce the impact of dirt accumulation on the heat exchange effect,and at the same time can obtain a certain amount of sewage condensate.The heat exchange principle of the pillow plate heat exchanger can be briefly described as: the refrigerant flows through the inner channel of the pillow plate heat exchange fins,and the sewage passes through the wide channels on both sides of the heat exchange fins.The device can reduce the degree of dirt and impurities blocking the heat exchanger.After building an experimental platform and setting up an automatic control and data acquisition system,a performance test experiment was conducted for a deflectortype sewage total heat exchanger.Test experiments show that: The effects of sewage temperature and air-sewage flow ratio on the amount of waste heat recovery,COP,and heat transfer rate are different.The COPu of the improved deflector sewage tower is more compatible with the system COPs;in terms of heat transfer rate,its capacity is larger and it has greater heat recovery capacity.From the perspective of pressure drop,actual water consumption and condensate water quality,the effect of energy saving and water saving is remarkable.Finally,this paper explores the heat exchange performance and energy saving of pillow-plate sewage heat exchanger.The results show that: The heat transfer coefficient K is greatly affected by the temperature of the sewage,and is relatively less affected by the flow of sewage;the coefficient of heat transfer on the sewage side of the pillow plate heat exchanger is 1.73 times that of the traditional immersion heat exchanger.Pillow plate type sewage source heat pump system can obtain greater heat transfer,higher COP and higher energy saving rate when recovering waste heat of higher temperature sewage.Waste heat recovery of the system can be increased by properly increasing the sewage flow,which can obtain greater heat transfer,higher COP and higher energy saving rate.From the perspective of the flow resistance on the sewage side and the actual water use,the energy saving of the heat exchanger and its heat pump system is obvious.The research in this paper is of great significance to people's understanding of the operating characteristics of the new sewage heat exchanger,and provides reference basis and theoretical support for the in-depth study of anti-scaling and easyto-descale heat exchange equipment.