Fouling Generation Laws Of Sewage Source Heat Pump Heat Exchanger And Its Impact On System Performance

The sewage source heat pump air-conditioning system is an effective method forsolving the current energy crisis and reducing the environmental pollution.ComParedwith the traditional air-conditioning systems,sewage source heat pump system has theadventures of energy saving,environmental protection and eeonomy.But in actualoperation,due to the particularity of sewage water,the working effect of the sewagesource heat pump system is always effected by fouling.Therefore the study of thefouling growth discipline in heat exchangr of sewage source heat pump system and theinfluence on the system performance is particularly important.According to the different sources of sewage,sewage can be divided into originalsewage and reclaimed water.And according to whether the sewage will flow into theheat pump unit,sewage source heat pump systems can be divided into direct andindirect heat pump systems.The direct sewage-source heat pump system for sewagedirectly into the unit, no intermediate heat transfer temperature loss, can improve thecoefficient of performance of the unit, and reduce the investment, so the developmenttrend of sewage-source heat pump system transforms to direct type gradually. Butwhen sewage directly into the heat exchanger unit, sewage side fouling coefficientincreases significantly, the evaporator or condenser heat transfer efficiency is reduced,affect the unit performance. Taking sewage plant secondary effluent as hot and coldsource of the direct sewage-source heat pump system as the research object, the growthof fouling in heat exchanger and the formation of fouling impact on the performance ofthe unit are discussed in this paper after the sewage directly into the unit. In this paper, taking sewage-source heat pump system engineering of awastewater treatment plant in xi’an as experiment object, its winter operatingparameters are acquised, and the heat exchanger surface fouling growth characteristicof the sewage-source heat pump has carried on the full cycle of monitoring by themethod of fouling heat resistance, which concluded the changes of fouling heatresistance with time and reveals the mixed fouling formation process mainly ofmicrobial fouling. Combined with the experimental results, the dirt accumulationprediction model of the direct sewage-source heat pump heat exchanger is establishedusing the least squares, which use the sewage treatment plant secondary effluent ascold and heat source. And the fouling growth rules of plate heat exchanger in theindirect sewage-source heat pump system has carried on the contrast, points out thedirt growth differences caused by different conditions. At the same time,combiningwith the test data,the performance of sewage-source heat pump system is analyzed indetail, the influence of fouling on the heat exchanger heat transfer performance andunit performance have obtained.As the growth of the dirt, heat exchanger heat transfer performance willdeteriorate, so the inhibition and clean of dirt is one of the most main method to ensurethe high-efficiency and stable operation of the heat exchanger.In this paper,the heatexchanger fouling cleaning technology are reviewed, and puts forward to theoptimization strategies of the dirt inhibiting and cleaning for microbial foulingproduced by sewage,which can inhibit and control the growth of dirt effectively,realized the efficient and stable operation of sewage-source heat pump system.Thestudy has important significance for the reasonable operation and application ofsewage-source heat pump system.