Development And Research On Low Temperature Air Source Heat Pump Using Refregerant R32

R32 has become one of the long-term alternative refrigerants of R22 in the refrigeration and air conditioning industry of China due to its good comprehensive properties.Low ambient temperature air source heat pump(ASHP)also becomes popular because of its energy saving,environmental protection features in the northern heating market popular.However,the combination of the two in the practical application is facing some problems,such as low temperature environment,high discharge temperature,low heating capacity.It is thus important to research the discharge temperature control and performance improvement of ASHP using R32 in low ambient temperature.The contents of this thesis are as follows.According to the features of ASHP using R32 in low ambient temperature,a design combining vapor injection and discharge temperature control is proposed to reduce the discharge temperature and enhance the heating performance.An ASHP using R32 with this design is developed after the theoretical calculation.The performance with and without vapor injection are both tested under different conditions.And the features of ASHP using R32 under low ambient temperature are concluded.Finally,this newly developed ASHP using R32 is applied and tested in a demonstration project for coal-fired boiler alternative.The conclusions are as follows:The discharge temperature keeps safe with and without vapor injection in all cooling conditions.The cooling capacity and input power increase,and the discharge temperature decreases by vapor injection.However the cooling COP keeps almost constant.The contribution of vapor injection enlarges with the outdoor temperature rising,and the differences of these parameters between with and without injection increase.The heating capacity,input power and heating COP increase greatly,and the discharge temperature reduces with vapor injection under heating conditions.With the decrease of outdoor temperature,the heating capacity,input power and heating COP decrease,and the discharge temperature rises for both with and without vapor injection.The discharge temperature without vapor injection reaches 125℃at outdoor temperature-5℃,which is the limit value.However,the discharge temperature is less than 115℃with vapor injection at outdoor temperature-15℃.In the field testing,the indoor temperature keeps nearly constant under different outdoor temperature during the whole heating season.The indoor temperature is higher than 20℃at the lowest outdoor temperature-17℃.The operating cost is 21.7 RMB/m~2,cheaper than the municipal heating charges in Beijing 24 RMB/m~2.ASHP using R32 is much better than coal-fired boiler in energy conservation and emission reduction.