Transient response of different refrigerants used in single-pass dual chiller

A number of process parameters can affect the performance of the district cooling plant, in which the vapor compression refrigeration (VCR) cycle has been widely employed. Two major process disturbances are: the end-user daily varying cooling demand (temperature of the received chilled water) and the seasonal changes in environmental conditions (cooling water temperature). This paper aims to investigate the effect of the selected refrigerants (R134a, R32, R717, R1234yf, R410a) on the transient response of dual chillers. It considers the cooling water temperatures as the process disturbances and disturbance are introduce in two fashion; namely sudden temperature increase and ramp temperature increase. The dynamic behavior of the process dependent variables, namely, the condensing temperature, evaporating temperature, and the coefficient of Performance (COP) are investigated. It is observed that the transient time that is needed for the given refrigerant to reach the new steady-state follows the following rank of refrigerants, starting with the fastest to the slowest: R410a, R32, R134a, R1234yf, and R717. Further, it is observed that the least reduction in COP upon the disturbance occurs in the chillers that run with R717, while the highest is associated with the one that has R134a.