Study On The Enhancing Heat Transfer Performance Of The Heat Exchanger In Sewage-Source Heat Pump Units And Its CFD Design

In the world’s growing energy crisis, energy conservation and environmental protectionis the responsibility that we should assume. Specific to the HVAC industry, We try to find away that not only to achieve the comfort of the living environment, but also to save energyand reduce pollution and protect the environment. Sewage source heat pump is such a waythat it is a device which transfer the cold and the heat of sewage to the air conditioning system.The use of resources is the urban sewage, and urban sewage is in every day production andinexhaustible. Because sewage is bound to be discharged into the environment, it isenvironmentally friendly and energy-efficient in the application of the wastewater re-use.Sewage source heat pump will inevitably become the hot trend of energy saving.Of course the sewage pump system has the great advantage, but if the quantity andquality of the heat transfer in heat pump units is not in a good situation, everything is of nopractical significance. Then we need to looking for a way to enhance the heat transfer processwhich could make the highest utilization of the heat and cold extracted from sewage, while atthe same time it is to achieve the purpose of energy saving and environmental protection.The power of heat pump operation will be electricity and heat. Consumption ofheat-powered absorption heat pump has the advantages of energy saving and environmentalprotection compared to the electricity-powered compression heat pump. Using thecombination of sewage source driven absorption heat pump unit makes energy-saving andenvironmental effects betterThe heat exchanger of absorption sewage source heat pump is mainly occur in theevaporator and absorber. To strengthen the heat transfer in order to maximize the energyutilization, we must make optimum design in the form of heat exchanger and heat transfertube. With the contrast analysis we found that the spray heat exchanger enables fluid totop-down flow of the liquid film in the form and the effect of heat transfer is the best in themembrane flow situation. However, if the heat exchange tubes are smooth surfaces, the liquidfilm which formed from the liquid distributor uniform flow into the heat exchanger fluid willuneven on area and liquid holdup,it will affect the heat transfer performance.If we coated with a layer of copper mesh in the heat transfer tube surface, the role ofsurface tension will lead to liquid flow through the mesh surface to form part of the liquidfilm to enhance the effect of heat transfer. However, copper wire diameter, mesh density andmesh area will affect the holding liquid area and liquid holdup continuity in coated liquidmembrane, and thus affect the influence of heat transfer. So we need to use CFD design, making use of the numerical simulation to calculate and analysis under what circumstancesthe heat exchanger is the best. The inlet velocity of the fluid in the liquid distributor can alsoaffect the liquid film formation between the heat transfer tube, and thus affect the influence ofheat transfer. Then we from the fluid inlet velocity, copper diameter and the number of wiremesh to analyze their influence on heat transfer, and finally we get the theoretical results toguide the application in practical engineering.