A DYNAMIC MODEL FOR A MULTI-STAGE CO2 THERMAL COMPRESSOR HEAT PUMP APPLICATION

Thermally driven heat pumps primarily use thermal energy to drive a compression cycle. The thermal
energy can be in the form of waste heat, combustion of natural gas, or solar energy, contributing to the
demand for increased efficiency and reduced greenhouse gas emissions. A thermal compressor heat
pump is one type in which the compressors are driven by heat as a primary source instead of electricity
to deliver heat. Like any vapor compression cycle, a thermally driven heat pump cycle needs to be
dynamically modeled for control and optimization purposes. A finite volume method is used to
discretize the main heat exchangers (evaporator and gas cooler) into several control volumes, and mass
and energy balance equations are applied to each. The connecting components, such as thermal
compressors and high- and low-pressure valves, are statically modeled due to the difference in the rate
of change compared to the heat exchangers. The important system performance indicators are validated
at steady state and dynamically by varying key cycle inputs. This validated model serves as a reference
for our thermal compressor heat pump application, which we aim to use for control law development
and performance optimization.