Thermodynamic process control of compression-assisted absorption refrigeration using ocean thermal energy

Abstract

An efficient control method is crucial for the safe and reliable operation of compression-assisted absorption refrigeration using ocean thermal energy. In this study, a dynamic model of 10 kW compression-assisted absorption refrigeration system is developed, and four integrated control strategies containing two cooling-capacity control approaches (Single input control and Cooperation control) and two temperature glide control approaches (Valve-based control and Compressor-based control) are proposed to control thermodynamic process. The proposed control strategies are evaluated in terms of both control and refrigeration performances. The results indicate that the refrigeration system can operate with stability at 50 % cooling load under the proposed control strategies. Moreover, the cooperative control of the flow rates for both warm-seawater and concentrated solution can significantly speed up cooling-capacity regulation. The rotational speed of compressor is a more suitable manipulated variable for regulating the evaporator temperature glide. The equivalent COP for the compressor-based control strategies is greater than 0.12 at 50 % cooling load, while the equivalent COP for the valve-based control strategies is only 0.064.