Design And Performance Study Of Adsorption Water Purification And Refrigeration System

At present,there is a large amount of low-temperature waste heat discharge in China,and there is no effective way to use it,especially the low-grade waste heat below 100℃,which is basically discharged into the environment by water cooling.The discharge of low temperature waste heat not only causes energy waste,but also consumes a lot of water.As a new type of water purification and refrigeration technology driven by low-temperature heat source,adsorption water purification and refrigeration technology has the advantages of low energy consumption,low operation cost and less scale corrosion compared with the widely used water purification technology such as reverse osmosis(RO),multi-effect desalination(MED)and multi-stage flash(MSF).The adsorption water purification and refrigeration technology has attracted wide attention because of its unique advantages that it can produce refrigeration effect in the process of water purification of seawater or saline wastewater.At present,the main factors restricting the adsorption water purification and refrigeration technology are low energy utilization,large equipment,high initial investment,and the heat transfer performance and adsorption performance of adsorbent need to be improved.Therefore,looking for more efficient circulation methods,researching more efficient and compact adsorption beds,and improving the adsorption and heat transfer performance of adsorbents are the main research directions of adsorption water purification and refrigeration technology.In this paper,a continuous operation adsorption water purification and refrigeration system is designed.The system has two circulation modes:adsorption water purification and refrigeration cycle which can perform refrigeration and water purification at the same time,and adsorption water purification cycle which is dedicated to water purification process.The adsorption water purification refrigeration system adopts the way of two bed heat recovery cycle.The evaporator-condenser heat recovery circuit is set up to improve the adsorption water purification cycle.The condensation heat is recovered to the evaporator to improve the evaporation temperature,reduce the condensation temperature and save the power consumption of the water pump.The main components of the system are designed on the basis of adsorption water purification and refrigeration cycle.According to the design results,the evaporator,condenser,and adsorption bed are subjected to heat transfer coefficient calculation and thermal calculation to check the design results.In order to improve the heat transfer effect of the adsorption bed,the finned tube heat exchanger is used to expand the heat transfer area with silica gel.The evaporator adopts the form of horizontal tube falling film evaporation to improve the heat transfer coefficient of evaporation process.The condenser is a tubular condenser.Since the water vapor in the condenser has been cleaned by the evaporator and the adsorption bed after two purifications by the evaporation effect,the possibility of corrosion in the condenser is small,and it can be made of carbon steel and other cheap metals.The mathematical model of the designed adsorption water purification and refrigeration system is established by using the lumped parameter method.The steady state characteristics of the adsorption water purification and refrigeration cycle and the adsorption water purification cycle,as well as the effects of heat exchange fluid flow rate,temperature,cycle time and other parameters on the cycle performance are analyzed numerically,which provides a guidance scheme for the actual operation of the system.The system shows good steady-state characteristics under the two cycles,and the temperature time curve of each heat exchanger and heat exchange fluid,the water vapor uptake of silica gel and the adsorption rate curve all show periodic changes.Comparing the cooling performance at different operating temperatures,an estimation formula for the minimum cycle temperature difference is proposed.The effectiveness of the evaporator-condenser heat recovery cycle is analyzed,and the applicable conditions of the cycle mode are determined.An adsorption water purification and refrigeration experiment system was established on the basis of preliminary design.The system includes three subsystems:control system,test system and thermal system.The system runs automatically under the established control plan.The steady state characteristics of the adsorption water purification and refrigeration cycle and the adsorption water purification cycle were studied experimentally.The temperature and pressure change curves of the adsorption bed showed stable periodic changes.The effects of hot water temperature,cooling water temperature,and evaporation temperature on the adsorption and water purification and refrigeration cycle were explored.The water production of the system under the conventional cycle and the evaporator-condenser heat recovery cycle was studied.The design of the adsorption water purification and refrigeration system was verified by experimental results.The accuracy and applicability of the design scheme and numerical calculation of the adsorption water purification and refrigeration system are verified by the experimental results.The experimental results show that the adsorption water purification and refrigeration cycle can meet the design requirements at different operating temperatures,the accuracy of the minimum cycle temperature difference estimation formula is good,and it can provide guidance for the setting of operating temperature under different temperatures.