 Actual enthalpy at compressor outlet at LTC. ${\eta }_{\text{isen}}=\frac{{h}_{2s}-{h}_{1}}{{h}_{2}-{h}_{1}}$ Equation (1)  Actual enthalpy at compressor outlet at HTC. ${\eta }_{\text{isen}}=\frac{{h}_{6s}-{h}_{5}}{{h}_{6}-{h}_{5}}$ Equation (2)  Mass flow in LTC (heat balance over LTC evaporator) ${\stackrel{˙}{m}}_{\text{LTC}}=\frac{{Q}_{cc}}{{h}_{1}-{h}_{4}}$ Equation (3)  Mass flow rate in HTC (heat balance over intermediate heat exchanger) ${\stackrel{˙}{m}}_{\text{HTC}}={\stackrel{˙}{m}}_{\text{LTC}}\ast \frac{{h}_{2}-{h}_{3}}{{h}_{5}-{h}_{8}}$ Equation (4)  Work of LTC compressor (energy balance over LTC compressor) ${W}_{LTC,Comp}={m}_{LTC}\ast \left({h}_{2}-{h}_{1}\right)$ Equation (5)  Work of HTC compressor (energy balance over HTC compressor) ${W}_{\text{HTC},\text{Comp}}={m}_{\text{HTC}}\ast \left({h}_{6}-{h}_{5}\right)$ Equation (6)  Heat transfer in intermediate heat exchanger (energy balance over entire LTC) ${Q}_{\text{int}}={Q}_{\text{cc}}+{W}_{\text{LTC},\text{Comp}}$ Equation (7)  Heat rejected by the upper cycle condenser (energy balance over entire HTC) ${Q}_{\text{rej}}={Q}_{\text{int}}+{W}_{\text{HTC},\text{Comp}}$ Equation (8)  Coefficient of performance (COP) ${\text{COP}}_{\text{LTC}}=\frac{{Q}_{\text{cc}}}{{W}_{\text{LTC},\text{Comp}}}$ Equation (9) ${\text{COP}}_{\text{HTC}}=\frac{{Q}_{\text{int}}}{{W}_{\text{HTC,Comp}}}$ Equation (10) ${\text{COP}}_{\text{CRS}}=\frac{{Q}_{\text{CC}}}{{W}_{\text{HTC,Comp}}+{W}_{\text{LTC,Comp}}}$ Equation (11)