Design And Performance Study Of Ejector Refrigeration System With Water-cooled Condenser For Ship

Marine products caught by fishing vessels need to be refrigerated in time to keep fresh.Marine ice maker,refrigerator and air conditioner rely on marine refrigeration system.Therefore,the study of marine refrigeration system energy saving and improving fuel efficiency has important theoretical significance and application value.This paper compares the feasibility of several heat-driven refrigeration technologies applied to fishing vessels.A water-cooled two-stage ejector refrigeration system for fishing vessels is proposed.The main contents include:1.Firstly,the adsorption refrigeration system,absorption refrigeration system and jet refrigeration system are compared and analyzed.The application of adsorption refrigeration system in fishing boats is limited by its low coefficient of performance.Absorption refrigeration has a high coefficient of performance.But the absorption refrigeration system is filled with liquid,which is susceptible to the swaying of fishing boats.Because of its high coefficient of performance and insensitive to vessel swaying,ejector refrigeration system is an effective alternative to traditional compression refrigeration system.2.A two-stage ejector is designed to improve its boosting capacity.There have been many studies on the application of jet refrigeration system in the field of air conditioning.However,due to the limited boosting capacity of the ejector,the temperature of the evaporator is difficult to reach subzero.Two-stage ejector is proposed to connect the diffuser exit in first stage with the entrance of section chamber in second stage so that the boost ability can be enhanced.The proposal of two-stage ejector makes the ejector refrigeration system applicable to subzero refrigeration.3.Apply water-cooled condenser to ejector refrigeration system.As the outlet temperature of the ejector,the temperature of the condenser effectively affects the performance of the ejector.Water-cooled condenser has higher heat transfer efficiency and lower condensation temperature and pressure.Lower condenser temperature means lower pressure difference,which enables the ejector to reach lower evaporation temperature.4.An optimization scheme of two-stage ejector is proposed.The entrainment ratio of the ejector is optimized by adjusting its Ar and NXP.As the key variable of the two-stage ejector,the intermediate pressure avoids the coupling problem in the optimization process.The results show that:(1)the boosting capacity of the ejector is effectively improved by two-stage ejector.Two-stage ejector refrigeration system can realize sub-zero refrigeration.(2)The ejection ratio of the two-stage ejector is related to the temperature of the generator.The optimum performance of the two-stage ejector is achieved when the generator temperature is 80 C.(3)The optimized water-cooled two-stage ejector can operate efficiently at a lower evaporator temperature of-25 C.(4)The entrainment ratio of the optimized two-stage ejector can reach 0.1119.Compared with the air-cooled two-stage ejector with evaporation temperature of-18 ℃ and-22 ℃,the entrainment ratio increases by 37.6%and 52%respectively at even lower evaporation temperature.