Cycle Characteristics And Experimental Research On Heat Pump/Heat Pipes Compound Heating Equipment

As an efficient and clean heating device,the heat pumps have been playing an important role in energy conservation,emission reduction and haze management.At present,it has also played a more important role in domestic heating equipment ?Coal to Electricity? in the ?Beijing-Tianjin-Hebei? area.Domestic air source heat pumps have two main types: water circulation and direct refrigerant condensation.The water circulation air source heat pump system has two kinds of types: one is that indoor heat exchanger is placed indoors,which is called a split type;another is that with indoor heat exchanger placed outdoors,which is called integral type.The split type installation is mainstream installation modes.Water circulation heat pump has serious problems in practical use,such as inconvenient installation and maintenance.In particular,the anti-leakage and anti-freeze of waterways has always been a problem for heat pump users.In recent years,there has been a heating system that uses air source heat pumps to send refrigerant directly into the room,which is named as ?air source heat pump heat fan?.The heat pump heat fan places the heating terminal equipment on the indoor floor.Refrigerant discharged from the compressor with high-temperature and high-pressure dissipates the heat directly to the room through the fin heat exchanger and the fan.But this machine is not suitable to make a type of mainframe with multiple indoor machines.Compared with the conventional radiator heating based on convection heat dissipation,radiant heating has the advantages of good comfort,uniform indoor temperature distribution,and convenient maintenance and management.At present,commonly used radiant heating methods include floor radiant heating and radiator heating.Especially for home heating reconstruction projects in northern of China,radiator heating is the best choice.In order to improve the energy efficiency of traditional heat pumps and improve their practical problems such as the complexity of the system and low energy efficiency level encountered in the promotion,this paper proposes a heat pump/heat pipe combined heat supply device,and uses theoretical calculations and experimental methods to study its circulation mechanism,work characteristics and design methods.The specific research content is as follows:(1)Under the working condition of heat pump compound heat pipe,the theory of heat transfer and phase change heat transfer at the end of heat pipe was studied.A model of the heat transfer process in the the heat pipe radiator was established.The natural convection heat transfer and radiation heat transfer characteristics were studied in detail.According to the calculation,the radiation heat dissipation accounts for the total dissipated heat of 62%~76%,The convective heat accounts for 24%~38% of the total dissipated heat.(2)Combined with the working curve of steam compression heat pump,the joint working characteristics of heat pump and heat pipe heat radiater were studied.The matching characteristics between the end of heat pipe and the working characteristics of heat pump condenser were investigated,and the optimum working condition was found.(3)Heat radiator performances with different kinds of refrigerant and different refrigerant mass filling ratio of heat pipe have been experimentally investigated.This system can reach to stable running condition from startup in 30 minutes.Heat pipes radiator is capable of producing a good uniformity for surface temperature distribution,the difference between highest and lowest temperature value was less than 1.5 ?.The temperature difference between condensing temperature and heat pipes surface temperature is less than 2 ?.(4)The selection of the working medium of the heat pipe and the optimum mass filling ratio.A detailed study of different refrigerant cooling characteristics of heat pipe and the heating performance of the whole system influence,analysis of the refrigerant migration,and the transformation of energy transfer and the interaction mechanism,find the optimal mass filling ratio of working fluid in the heat pipe and the best matching refrigerants.As a result,R134 a obtained the highest heating capacity,and R32 obtained the highest heating COP.When the indoor temperature is 20 ? and the outdoor temperature is-20~5 ?,the heating COP range of the system is 2.37~4.36 when the heat pipe radiator is filled with R32.(5)The heat pump combined heat pipe radiator heating system was developed.Based on the conventional throttling device and the electronic expansion valve throttling device,experimental devices were established respectively,and the cycle characteristics and the heat transfer law were comprehensively experimentally studied.The experimental results were used to verify and modify the simulation model,and the design theory and method were improved.Based on the above research,the design theory and methods of the heat pump combined heat pipe radiator heating system are summarized.Popularizing the application of the heat pump air conditioner,which is an efficient and clean heating way to replace traditional coal-fired(gas-fired)heating,is a technical measure to fundamentally control smog.Therefore,the results of this study are expected to provide an effective governance measure for smog weather,and it is also a positive governance concept of "relying on technological progress to promote haze treatment".