Model based performance analysis of a transcritical combined heating and cooling CO₂ cycle for a school cantina in India

To demonstrate and promote natural refrigerants for the future HVAC&R sector in India, a 140 kW
transcritical CO₂ heat pump will be installed at the demonstration side at the Akshaya Patra Foundation in
Bangalore, India. The unit will cover both the heating and cooling load, typical for school kitchen facilities. To
investigate and analyse the system performance both in rated conditions and in part load, the heat pump is
modelled using Dymola/Modelica. The simulation operates with water as heat source and sink with
return/supply temperatures of 13/4°C and 29/90°C, respectively. The system is configured as a second generation CO₂-booster system, featuring an ejector-supported operation mode as an option. It consists of
two-stage cooling with a low-temperature evaporator at 37.5 bar (2.8°C saturation temperature) and a
medium-temperature evaporator at 42.5 bar (7.6°C saturation temperature). For the high-pressure side, the
operational pressure limit is set to ca. 120 bar. The initial estimate of the overall combined COP reaches 5.1.
Keywords: Carbon Dioxide, Booster System, Combined Heating and Cooling, Heat Pump, Refrigeration,
Ejector