Design And Numerical Simulation Of Ammonia Water Diffusion Absorption Refrigerator

The rapid development of our country’s economy,the increasing energy consumption and the continuous reduction of fossil energy storage media such as coal and oil have become one of the important issues facing mankind.At the same time,people’s living standards continue to improve,and the requirements for quality of life are getting higher and higher.The consumption of refrigerators,air conditioners and other refrigeration equipment is gradually increasing,and energy consumption is becoming more and more serious.In addition,the use of CFC and HCFC refrigerants that are harmful to the environment in these refrigeration systems can cause ozone layer destruction.Therefore,the search for renewable energy and the use of environmentally friendly refrigerants have become the focus of attention.Diffusion absorption refrigeration uses a ternary refrigerant of ammonia,water,and hydrogen,which is a refrigeration system powered by heat.Various low-grade heat sources,such as industrial waste heat,waste heat,and solar energy,can be used.The features of simple structure,stable operation,and long service life have attracted the attention of domestic and foreign scholars.According to the design requirements of the experiment,check the enthalpy concentration diagram of the ammonia solution,Determine the concentration,pressure and enthalpy value of the circulating working fluid at the point of generation,rectification,and condensation.And carry out structural design and load calculation for generators,rectifiers,condensers and other components.At the same time,a diffusion absorption chiller was made,and experimental research was carried out on it,and a mathematical model of the refrigeration box was established and numerically simulated using Fluent software.The main research contents and conclusions are as follows:1.In the experiment,the voltage is adjusted by the voltage regulator,and then the input power is adjusted,so that the input power of the refrigeration system is 37,44,48,52,57,65,72W respectively,Measure the change of refrigeration capacity and COP of the refrigerator under seven working conditions,The experimental results found:When the input power of the refrigeration system is less than 48W,the cooling capacity and COP increase with the increase of the input power;When the power exceeds 48W,the COP decreases as the input power increases,and the cooling capacity first decreases and then slowly increases;When the input power is 48W,the cooling capacity and COP both reach the maximum value,the cooling capacity is 6.03W,and the COP is 0.126.2.The occurrence temperature has a positive correlation with the input power,and the highest occurrence temperature is 172℃;The start-up time of the refrigerator is about 35min,and when the input power increases,the start-up time of the refrigerator is also shorter,but when the input power exceeds a certain value,the start-up time will increase.The start-up time of the refrigeration system under the optimal input power of 48 W is 26min.3.The inlet and outlet temperature of the condenser and absorber increases with the increase of the input power.When the input power increases,the evaporation temperature of the refrigeration system will drop faster,and the evaporation temperature will be lower,but when the power exceeds a certain threshold,it will cause the evaporation temperature to rise.In the experimental results,the evaporation temperature at the maximum input power of 72W is greater than the evaporation temperature at the power of 65 W.4.Use FLUENT software to establish a mathematical model for the refrigerated box of the diffusion absorption refrigerator,and set the boundary conditions according to the optimal input power,temperature and other conditions obtained from the experimental results.The simulation results show that the distribution of the flow field in the refrigeration box is uneven,and the temperature at the corners of the refrigeration box is high and the airflow velocity is slow;Through optimized design,after designing the corner of the refrigerating box into an arc shape,the simulation results and experimental measurement results are lower than the temperature at the corner before the optimized structure and the flow field distribution is relatively uniform,which proves that the structure optimization design plan of the refrigerating box is feasible.