Enhancing energy efficiency and sustainability in ejector expansion transcritical CO2 and lithium bromide water vapour absorption refrigeration systems

This paper presents a comprehensive and in-depth exploration of the energy and exergy efficiency of a hybrid refrigeration system, combining an Ejector Expansion Transcritical CO2 (EETC) cycle with a single-effect lithium bromide Water Vapor Absorption Refrigeration System (VARS). The EETC cycle employs a high-temperature carbon dioxide compressor to generate thermal energy, which is utilized to initiate the absorption refrigeration cycle by releasing heat. The system is evaluated and analyzed in accordance with the fundamental principles of the first and second laws of thermodynamics. Numerical simulations are conducted using the EES software to derive various performance parameters. By considering factors such as temperature, pressure, and energy exchange rates, the optimal cooling pressure and Suction Nozzle Pressure Drop (SNPD) are calculated under different system conditions. These calculations provide valuable insights into the system's energy efficiency and identify potential areas for improvement. The novelty of this work lies in the integration of these two distinct technologies to enhance overall system performance and efficiency and aims to contribute to the better understanding and development of hybrid refrigeration systems, offering more sustainable and energy-efficient cooling solutions. Results reveal significant improvements in the hybrid system's cooling capacity, Coefficient of Performance (COP), and exergy efficiency compared to the standalone EETC cycle. For instance, at an evaporator outlet temperature (T4) of -25 degrees C and a cooling temperature of 40 degrees C, the EETC cycle achieves a COP of 39.7% compared to the Transcritical CO2 Refrigeration System (TCRS). The combined system exhibits enhancements of 17.22%, 17.28%, and 4.8% in cooling capacity, COP, and exergy efficiency, respectively, outperforming the EETC cycle.