Desenvolvimento do modelo dinâmico e sistema de controle para uma bomba de calor a R290 assistida por energia solar com expansão direta: eficiência no aquecimento de água residencial

Abstract

Given the growing demand for sustainable energy solutions, this research addresses the challenge of improving the efficiency and reduce the environmental impact of residential water heating systems. This work presents a dynamic moving boundary mathematical model of the condenser of a direct expansion solar-assisted heat pump operating with propane, along with the design of a controller aimed at regulating the final water temperature. The mathematical model was developed based on mass, momentum, and energy conservation equations and validated by comparing the water flow rate step responses with 121 experimental data points, with a maximum mean relative deviation of 6.5%. The designed controller is of the PID type and was implemented on a microcontroller. To regulate the output water temperature, the controller acts on the water flow rate. The controller effectiveness was evaluated using computer simulations and experimental tests. The developed mathematical model accurately describes the behavior of the heat pump, and the main results of the simulations show that both water flow rate and inlet temperature significantly influence the final water temperature and the system coefficient of performance (COP). The highest water temperature, 68.5 °C, was achieved with an inlet temperature of 30 °C and a flow rate of 0.25 L/min, while the highest COP, 2.3, occurred with an inlet temperature of 10 °C and a flow rate of 0.80 L/min. In addition, increasing the compressor inlet pressure raised the water outlet temperature by 17.8% and the COP by 55.0%. The controller demonstrated high accuracy and robustness, ensuring the stability of the water temperature under external disturbances in both simulations and experimental validations.