Experimental Results
The operating conditions measured in terms of the
refrigerant temperatures and pressures, and air temperatures
and humidities, and compressor power are shown in Figures
2, 3, 4, 5, and 6, respectively. As expected in Figure 6, at
lower charge levels the compressor requires lesser power
input. Based on these measurements, the cooling capacity
is determined. Figure 7 clearly reveals that both air
enthalpy and refrigerant enthalpy methods yield similar
results at charge levels down to 90%. For further reduction
in charge level to 80% and below, while the refrigerant
enthalpy method shows a gradual decrease in the cooling
capacity, the air enthalpy method shows a drastic decrease
to zero and even negative values. The corresponding COP
is plotted in Figure 8.