Research On Fouling Discipline And Online Cleaning Device Of Sewage Heat Exchanger

As a method of energy recycling by transforming sewage into resources, sewage-source heat pump (hereafter for short SSHP) air-conditioning system is an air-con device which takes urban sewage, industrial waste and so on as heat source or cold source for heating or cooling. Compared with the traditional air-conditioning systems, SSHP air-conditioning system has the characteristics of energy saving, water saving, economy and environmental protection. While the working effect of the SSHP air-conditioning system is always affected by fouling in actual operation. Therefore, the growth discipline and online cleaning technology of fouling in the heat exchanger becomes the key point of study on SSHP air-conditioning system.Sewage can be divided into original sewage and reclaimed water in accordance with the different sources of sewage. Herein we took Shandong Jianzhu University reclaimed water station as the experimental base, analyzed the composition of the school domestic sewage, obtained the growth discipline of fouling on the surface of PE tube sunk in original sewage, and then got the maximum thickness of fouling growth through electron microscope.SSHP systems can be divided into direct and indirect heat pump systems according to whether the sewage will flow into the heat pump unit. Generally, the heat pump system with original sewage sourced will adopt indirect heat exchange system due to the restrictions of water quality. In such system, immersed, shell-and-tube or spray sewage heat exchangers are usually adopted.In this paper, we established a heat transfer model for the immersed sewage heat exchanger, developed a corresponding simulation program, and then made a simulation calculation for heat transfer coefficient of the immersed sewage heat exchanger under different working conditions. Through the simulations, we have got the changing disciplines of heat transfer coefficient with circulating water flow rates, sewage temperature and sewage flow rates. This model has been verified in our SSHP system test bench.With the growth of fouling, the performance of sewage heat exchanger will drop drastically, so removing of fouling in time is one of the key solutions in order to guarantee the performance of heat exchanger. In this paper, we summarized the online mechanical cleaning technology for the fouling of heat exchanger, proposed an optimization strategy for fouling prevention and fouling dissolution of bio-fouling. Aimed at that the bio-fouling is dominant in sewage fouling of heat exchanger, we have developed an inner spring-brush online cleaning device. This device can clean tube fouling repeatedly with spring's own elastic which expands back and forth, and the cleaning effect is excellent. This device has the advantages of low equipment investment, simple being manufactured, and no damage to the heat exchanger, which can be popularized to SSHP system.