Simulation and experimental study on dynamic characteristics of R290 split heat pump during start-up

As a new generation of heat pump refrigerant, R290 (propane) not only has advantages in environmental protection, but also has the good performance. However, reliability problems remain in the start-up process of R290 heat pumps, and hence it is necessary to study the dynamic characteristics of the start-up process. This paper establishes a mathematical model based on the physical properties of R290 and the system characteristics of R290 split heat pumps. The model is used to calculate the dynamic start-up characteristics. The proposed mathematical model is validated by experiments, and an error analysis of the heating start-up is carried out, and the mechanism of continuous low suction pressure during start-up is analysed. Taking a variable frequency rated heating condition as an example (indoor and outdoor temperature 20/7 degrees C), the maximum deviation between the calculated pressure and the experimental value is within 5% during stable process. The refrigerant mass in the compressor shell is 164.76 g at most and the liquid separation process lasts 370 s during heating start-up process. The continuous suction of low pressure in the R290 split heat pump is attributed to the accumulation of liquid phase refrigerants in the accumulator and the presence of refrigerant condensation in the compressor shell.