Systematic assessment of the dynamic behavior of ecofriendly refrigerants used in dual vapor compression chiller

This paper investigates the dynamic behavior of dual vapor compression Refrigeration (VCR) chillers, considering nine ecofriendly refrigerants such as R134a, R32, R1234yf, R1234ze(E), R717, R600, R600a, R290, R410a and compared to R22. Disturbances are introduced to the secondary loop of the VCR as sudden and ramp increases of the inlet cooling and chilled water temperatures and their impact on the dynamic responses of the condensing, evaporating and chilled water outlet temperatures, and Coefficient of Performance (COP) are discussed. The duration of the dynamic responses, the rise in temperatures and the change in COP are used as criteria to evaluate the fluids through a combination of rank-ordering and multi-criteria assessment approaches. R290 and R410a exhibit lower transient response time than the other options. Refrigerants R290 and R717 exhibit the lowest rise in the condensing temperature, R717 exhibits the minimum rise in the evaporating temperature, whereas R717 and R1234yf indicate the lowest rise in the chilled water temperature among others. R717 further exhibits very low change in COP under disturbances, whereas it exhibits the optimum tradeoffs among all fluids between robustness in dynamic operation and steady-state efficiency. It is recommended to introduce disturbances in a ramp manner instead of a sudden increase.