Study On A Solution Dehumidification Evaporative Cooling Air Conditioning System Driven By Residual Heat From Ships

As an essential device in modern ship navigation,the air conditioning system not only affects the normal use of instruments and equipment and the physical health of crew members,but also consumes a large amount of energy.The refrigerant containing chlorofluorocarbons is used in the vapor compression refrigeration cycle of traditional ship air conditioners,which will cause environmental pollution and greenhouse effect,and the compressor operation will consume a lot of electricity.In order to improve the utilization rate of marine energy,a new type of marine air conditioning system was constructed by combining the clean and efficient advantages of solution dehumidification and evaporative cooling technology with ship waste heat.The system uses ship waste heat as a regenerative heat source,treated indoor exhaust air as the regenerative air during the solution regeneration process,and fully utilizes seawater as a natural cold source.The heat and humidity load of the air conditioning system of a5000 DWT class multi-purpose ship in summer was calculated,and the parameters of the supply air volume and supply air status point were determined.A comprehensive comparison was made on the surface vapor pressure,corrosiveness,and economy of lithium chloride solution,lithium bromide solution,and calcium chloride solution.Finally,lithium chloride solution was selected as the dehumidifier.Based on the laws of energy conservation and mass conservation,establish the physical parameter equations of lithium chloride solution and wet air,establish mathematical models of various components of the system,and use Simulink software to construct a simulation model of the system.In order to verify the correctness of the established model,the main modules in the system were validated.The simulated values of the dehumidifier module,regenerator module,and direct evaporative cooling module were compared with the experimental values in relevant literature.The results showed that the average maximum error of each outlet parameter of the dehumidifier was 9.5%,and the reasons for some errors were analyzed.The maximum error of each outlet parameter of the regenerator was 12%.The maximum error of the air outlet parameters of the direct evaporative cooler is 9%.By numerical simulation,the effects of solution temperature and flow rate,ambient air temperature and moisture content,and regeneration air temperature and moisture content on system performance are studied.The thermal coefficient of the system is positively correlated with solution temperature,environmental temperature,and environmental moisture content,while negatively correlated with solution flow rate.Under the operating conditions of an outdoor temperature range of 30℃～40℃ and an outdoor moisture content range of 20g/kg～26g/kg,the system can meet the dehumidification demand,with an average thermal coefficient of 1.32.The heating amount required for the regeneration process gradually decreases as the temperature of the regeneration air increases and the moisture content of the regeneration air decreases.Analyze the effective energy of the system,study the loss rate and efficiency ratio of various components of the system under basic operating conditions,and study the impact of various parameter changes on the efficiency of the system and the cooling capacity obtained by the system’s fresh air.The simulation results show that the component with the highest loss rate is the regenerative heat exchanger,with a loss rate of 38.78%.The dehumidifier with the highest efficiency ratio is the dehumidifier,with an efficiency ratio of 0.08.Optimizing the heat and mass exchange process of solution dehumidification and regeneration and using low-grade heat sources as regenerative heat sources are the main directions to improve the performance of the system.