Exergetic and Energetic Analysis of an Ejector-Assisted Vapour Compression Refrigeration System Utilizing Ammonia, Propane, and Isobutane

Abstract

Over the last few years, the alarming rate of increase in greenhouse emissions across the world due to continuous growth in cooling and heating requirements has caused a rise in the global temperature. The use of energy-efficient systems, devices, and renewable energy systems are need of the hour as these can curtail greenhouse gas (GHG) emissions and will aid in sustainable development. In the cooling sector, most commercial and domestic refrigeration and air-conditioning systems run on the conventional vapour compression refrigeration (VCR) cycle. The irreversibility occurring in the capillary tube leads to significant energy loss. Also, hydrofluorocarbons (HFC) refrigerants, are being used in these systems, consuming more energy for the operation of the system and contributing larger GHG leading to enhanced climate change. The literature has demonstrated that deploying an ejector in lieu of the typical throttling valve can minimize the energy loss. In addition to this, the use of environment-friendly refrigerants in these systems will also keep a check on levels of emissions that lead to environmental change.

In the prevailing study, a parametric performance analysis is executed of the ejector-assisted vapour compression refrigeration system (EVCR) employing ammonia(R717), propane(R290), and isobutane(R600a) as refrigerants with a uniform pressure ejector model. I^st law and II^nd law analyses of the EVCR system are accomplished for a range of condenser temperature (T_cndr = 30°C to 60°C), evaporator temperature (T_evpr = 5°C, -5°C and -15°C), and pressure drop (δP = 0.01 to 0.50 bar) in the suction chamber. Variations in performance parameters such as coefficient of performance (COP_EVCR) & % improvement in COPEVCR (%COP_{EVCR, imp}), volumetric cooling capacity (VCC_EVCR) & % improvement in VCC (%VCC_{EVCR, imp}), optimum area ratios (AR_opt), pressure lift factor (PLF), total exergy destruction (E_{D, Total}), and II^nd law efficiency (η_exergetic) of the EVCR system for the above range of the operating parameters are reported in this study. It is observed from the results that at T_cndr = 40°C and T_evpr = 5°C, R600a yields the maximum COP_EVCR of 6.14 whereas the R290 gives the highest % COP_{EVCR, imp} of 12.78% and %VCC_{EVCR, imp} = 9.96% compared to the other two refrigerants. Also, it is observed from the II^nd law analysis that R717 gives the maximum ED, Total of 59.64 kW, and η_exergetic of 37.61% whereas R290 and R600a give values of η_exergetic as 36.90% and 37.56%.