| With the rapid development of society,the efficient use of clean energy and the improvement of the comprehensive utilization of low-grade energy will bring great benefits to the entire industrial sector and society,and at the same time have a certain positive effect on energy conservation and emission reduction.The traditional compressed refrigeration system consumes high grade electrical energy,while the absorption refrigeration system uses industrial waste heat,solar energy and geothermal energy as heat sources to drive the system operation,consuming only a small amount of electrical energy.R134 a as the refrigerant and DMF as the absorber binary work pair can be well applied in absorption refrigeration.The main research of this thesis for R134a-DMF absorption refrigeration system is as follows:(1)The simulation system of R134a-DMF absorption refrigeration was built,and the system was analyzed under varying conditions.Based on Aspen Plus software,according to the design parameters of R134a-DMF absorption refrigeration and the physical properties of R134a-DMF binary working medium pair,a simulation system of R134a-DMF absorption refrigeration was built to study the effects of condensation temperature and R134 a mass ratio change on the system performance under different temperature.In view of the high mass ratio and absorption temperature of R134 a in the binary solution,R134 a gas is easy to appear at the outlet of the absorber,which leads to the impossibility of simulation.The original R134a-DMF absorption refrigeration simulation system is improved,and a gas-liquid separator is added behind the absorber.The effects of R134 a mass ratio and absorption temperature on the system performance were studied.(2)The R134a-DMF absorption refrigeration system test platform was used to carry out the test,and the test data were analyzed.The operation mode of each circulating system,the detailed parameters of the main equipment,the circulating process and the operating flow of the experimental platform are introduced in detail.According to the temperature and pressure information detected by the experimental platform,the analysis combined with the third chapter shows that:The temperature and high pressure of the experimental platform are lower than that of the simulation condition,the main reason is that the heat source temperature is low,which can improve the high temperature protection of the water heater as the heat source.Because the absorption temperature is high,the air cooler of the absorber can be changed to the water cooler of the absorber to increase the cooling effect of the absorber.The undercooling degree analysis of condenser can show that:In order to ensure that R134 a gas does not exist at the condenser outlet,the maximum opening of electronic expansion valve EEV1 is 130 pulses,which leads to the cooling capacity and COP not reaching the design value.The main reason is that the condensing pressure of the system is low.The influence of hot water inlet temperature and chilled water outlet temperature on the evaporator load and performance coefficient COP of the experimental platform was studied,and the relative error was compared with the corresponding data of the simulation system.The simulation system in Chapter 3 was verified.(3)In order to improve the operating performance of the system,two kinds of parallel and series R134a-DMF absorption-compression composite refrigeration simulation system was built,and the variable condition analysis was carried out.In order to solve the problem that refrigerant R134 a gas is prone to appear at the outlet of the absorber,the R134a-DMF absorption and compression parallel refrigeration simulation system is established.The evaporator load is7.758 k W,the thermal drive performance coefficient is 0.451,and the power saving rate is 0.963.The effects of different condensation temperatures and absorption temperatures of different R134 a mass ratios on the evaluation indexes of system performance were studied.In order to expand the thermal drive temperature range of the system and avoid the problem of low high pressure in the absorption refrigeration system,the R134a-DMF series absorption-compression refrigeration simulation system is built.The evaporator load of the system is 7.182 k W,the thermal drive performance coefficient is 0.269,and the power saving rate is 0.57.The influence of temperature and compressor outlet pressure variation on system performance evaluation index under different evaporation temperature was studied.In summary,this thesis based on Aspen Plus software,according to the design parameters of R134a-DMF absorption refrigeration and the physical properties of R134a-DMF binary working medium pair,set up R134a-DMF absorption refrigeration simulation system,and carried out variable condition analysis;R134a-DMF absorption refrigeration system experiment platform was used to carry out experimental testing and data analysis,and compared with simulation values;In view of the above problems in simulation and experiment,two forms of R134a-DMF absorption-compression complex system in parallel and series are proposed,and the corresponding simulation system is built for variable condition analysis;The above research provides some theoretical support for the application of R134a-DMF working medium in absorption refrigeration industry. |
PDF Full Text Request