The Research Of Control Strategies Of The Heat Storage Evaporator For The Air Scource Heat Pump System

For the poor performances of air source heat pump(ASHP) in the low-temperature environment, our team has been studying ASHP for 3 years and designed the phase change heat storage evaporator system of the ASHP. Compared to the traditional ASHP systems, this new heat pump system adds the phase change heat storage evaporator(PCHSE). When the environment temperature is higher than the balance point temperature, the phase change material(PCM) can store heat; when the environment temperature is lower than the balance point temperature, the PCM can release heat and support heat to the users, transferring the heat according to the time and solving the problems of the ASHP in low temperature. At the same time, using the storage heat to defrost, it can shorten the defrost time and avoid the phenomenon of blowing the cold air to the rooms, significantly improving the heating quality and operating performances.This paper provides the system scheme of combining the condenser, evaporator and PCHSE through series and parallel connections. The PCHSE can accumulate the storage time by putting the PCHSE in reasonable place after the condenser as a post-condenser and using the latent heat to store heat. The PCH adopts 80%Na2SO4?10H2O+20%Na2HPO4?12H2O as the PCM after the experiments. This paper proposes a kind of effective heat transfer calculation method of the PCHSE, accurately calculating each moment of heat storage and heat release. In order to control the heat pump system well this paper provides the relationships between the electronic expans ion valves and medium flow rate; This paper designs the phase change heat storage evaporator system of the ASHP system and it can realize the automatic operation among those models of the heat-storage model, heat-releasing model, defrosting model and safety protection programs; The system designs the human-computer interaction interface through the DOPsoft software, it can make a real-time display, set parameters and monitor system parameters; The system can read and store data by connecting PC; For the working stability of the heat pump system and the requirements of environmental adaptability, a hysteres is control method is proposed based on PI control. That is the temperature control links embedded in the return difference control method, solving the problems of system operating mode switching frequently, implementing the smooth transition b etween the different working conditions to prolong the service life of the system.Through the test of the related authority institution, the designed system COP at 15 ℃ can be at 4.8; when the temperature is-15℃, the COP can be 1.94. The system can defrost efficiently and the defrosting time is about 230 s.The phase change heat storage evaporator system of the ASHP can replace the traditional coal heating ways to provide the technical support for heating improvement of the green, high efficiency, energy saving and low carbon.