This work presents a dynamic model for a CO₂ heat pump gas cooler. The gas cooler model is based on the conservation equations of energy, mass, and momentum. Due to the importance of an expansion device and a compressor for heat exchanger modeling, detailed mathematical treatment is also given to those devices. The spatial variations of temperature, pressure, specific volume, and mass flow rate are predicted at each time step. The model is validated by comparing simulation results and experimental data for transient and steady conditions. It observes a reasonably good agreement between these results, with a maximum deviation of 2°C (3.6°F) between the mathematical model and experimental data, with the test data exhibiting a fairly similar trend. The developed model is therefore presented as a useful tool for analyzing the dynamic behavior for the gas cooler of a heat pump operating with CO₂.

Given the growing demand for sustainable energy solutions, this study addresses the challenge of improving the efficiency and environmental performance of residential water heating systems. This work presents the design and implementation of a controller aimed at regulating the outlet water temperature of a direct-expansion solar-assisted heat pump operating with propane. A dynamic model was experimentally identified using the AutoRegressive with eXogenous input methodology and used to design a Proportional–Integral–Derivative controller via the direct synthesis method. To regulate the outlet water temperature, the controller acts on the water flow rate. The effectiveness of the controller was evaluated through computer simulations and experimental tests. Its robustness was assessed by considering parametric variations of ±15%, during which the system maintained stability and performance. The controller demonstrated good accuracy and performance, keeping the desired temperature stable even in the presence of disturbances, both in simulations and experimental evaluations.

EXPERIMENTAL VALIDATION OF A DYNAMIC MODEL FOR A RESIDENTIAL HEAT PUMP WITH IMMERSED CONDENSER