Application Research Of Double Stage Coupling Heat Pumps In Severe Cold Area

It is one of the major issues on the economy and the society to conserve energy,to reduce the consumption of resources and to control the emissions of pollutants.While the technology of heat pump is a kind of effective method to save energy and protect the environment.Utilizing reverse Carnot cycle,heat pumps transfer heat energy from low grade heat source to heat consumers.With the advantages of saving high-grade energy and reducing the emissions of carbon dioxide,it can also guarantee higher operational efficiency,which meets the current policy of coal-to-electricity and has a wide application prospect.Air source heat pumps has been widely used in southern areas of China.While in the northern areas,they are difficult to develop rapidly due to the problem of the high pressure ratio and the high discharge temperature when working in the low temperature.So the questions of air source heat pumps,surface water source heat pumps,under-ground water source heat pumps,ground source heat pump and solar assisted heat pumps in severe cold area are analysed in this article.According to characteristics of the climate in severe cold area,double stage coupling heat pumps are researched,which will expand the application's scope of air source heat pumps.Throughout the research and application of double stage coupling heat pumps in recent years,projects of it in severe cold area are relatively rare.Whether air source heat pumps run stably is the key of double stage coupling heat pump systems used in severe cold area.So in this article,the numerical simulation on performances of air source heat pumps is conducted.Then one double stage coupling heat pump system in Jiuquan City is monitored.The performance of operation and the effect of supply heat are analysed.In the end,according to the investment of the heating system in this project,economic benefits and energy-saving benefits of double stage coupling heat pumps and air source heat pumps are analysed comparatively which guides the promotion and application of double stage coupling heat pumps.The main contents and conclusions are shown below:(1)Mathematical models of core components in double stage coupling heat pumps have been built,which provides theoretical basis for subsequent calculation.And the results indicate that the heating capacity and the compressors' power consumption of air source heat pumps in the double stage coupling heat pumps are almost the same as them in the single stage air source heat pumps.However the pressure ratio and the discharge temperature of air source heat pumps in the double stage coupling heat pumps substantially drop.And what is more,COP is also higher than single stage air source heat pumps.So the double stage coupling heat pumps have better adaptability to low temperature.(2)The field tests on one double stage coupling heat pumps in Jiuquan City prove that no matter what the weather is,the temperature of supply and return water in the air source heat pump and the water source heat pump remains relatively stable and doesn't fluctuate according to the weather.In addition,the indoor temperature of test users can reach the requirements of design,which indicate that types of heat sources of this system are reasonable and that it can satisfy the demanding of users for heating.(3)During the test,the COP of the air source heat pump,the water source heat pump and the double stage coupling heat pump is reasonable,which shows that the double stage coupling heat pump system in this project runs steadily and has good properties of energy conservation and economy.(4)Firstly,several economic methods of scheme comparison are introduced.Then the economical efficiency of the double stage coupling heat pump system and the air source heat pump system are detailly calculated and comparatively analysed by using the method of annual cost.After comprehensively considerating the initial investment and the operating cost,the double stage coupling heat pump system is a better heating mode.