Analytical and computer modelling of a thermo-mechanical vapour compression system for space air conditioning in buildings

Abstract

Air conditioning in buildings is essential for providing indoor thermal comfort, but it imposes a significant electrical power load and carbon footprint, particularly when using traditional vapor compression systems. This study investigates an innovative design and thermodynamic analysis of a cooling system that integrates an ejector device into a basic vapour compression cycle and incorporates a thermally driven second-stage compressor, forming the proposed thermo-mechanical vapor compression cooling system. The second-stage compressor operates at constant volume, utilizing thermal energy from an external heat source, such as a thermal solar collector. A MATLAB® model was developed to evaluate key energy performance indices of the cycle for selected commercially available refrigerants, and the effect of external heat source temperature and condenser temperature on the cooler’s thermodynamic performance was studied in detail. Results showed a marked reduction in mechanical compressor work using refrigerants such as R161, R1270, R1234yf, and R1234zeE. For instance, the mechanical energy consumption was reduced by 30.54 %, and the Coefficient of Performance improved by 43.98 % compared to the basic vapor compression cycle, at a condenser temperature of 65 °C and a superheated refrigerant temperature leaving the thermal storage of 100 °C using R1234yf. These findings indicate that the thermo-mechanical vapour compression cooling system offers a promising solution for reducing energy consumption and carbon emissions in buildings, particularly in hot climates.