Optimization of Co2 Booster Refrigeration Cycle With Flooded Evaporators and Parallel Compressor by Using the Bees Algorithm

Abstract

Energy supply is one of the most significant issues in modern society. So, energy saving becomes important in systems used frequently in daily life. Due to these energy saving concerns, there are numerous studies in literature to make supermarket refrigeration systems consume less energy. Among these studies, CO2 booster refrigeration system with flooded evaporators and parallel compressor (BFP) seems as an energy-saving and nature-friendly choice. In this study, BFP was selected as the system of concern and the Bees Algorithm optimization was applied to get minimum power consumption (maximum COP). Gas cooler pressure (P-gc), intermediate pressure(P-int), and medium temperature (MT) level evaporator outlet quality(x(14)) were chosen as optimization parameters. According to the optimization results, the Bees Algorithm converged well, and these three parameters were found worthy to optimize as they brought significant energy saving in total (up to 8.7% in comparison with constant intermediate pressure and MT evaporator outlet quality). As a result of this analysis, the optimal P-gc values were found to be between 7600 kPa and 12000 kPa at ambient temperatures ranging from 28 to 46 degrees C. The optimal Pint values were found to be around 3500 kPa below ambient temperature of 14 degrees C and around 4500 kPa above this temperature. The optimal values for x(14) ranged between 0.62 and 0.69. Additionally, annual energy consumption (AEC) and total equivalent emission (TEE) for 15 years were calculated for four different climate types. The highest AEC and TEE were obtained at tropical climate with 728.56 MWh and over 10000 tons, respectively. The lowest AEC and TEE were found at continental conditions as 380.01 MWh and almost 6000 tons of emission.