Refrigerant mixture composition determination with different methods during dynamic start-up, charging, and enforced leakage events in a laboratory high-temperature heat pump.

This paper investigates the performance of several inline composition measurement methods for refrigerant blends in high-temperature heat pump applications. Methods evaluated were density, speed of sound, temperature change during isenthalpic expansion, and dew point temperature. The results show that these methods are effective for almost instantaneous real-time monitoring of the refrigerant composition traced during start-up, charging or leakage events. A detailed analysis of steady-state data emphasizes the importance of selecting the right methods with steep property gradients, which vary by refrigerant mixture. For instance, the expansion valve method performed well for the R-1336mzz(E)/1336mzz(Z) mixture, while the density method was more accurate for the mixture consisting of R-1234ze(E)/1336mzz(Z).