Study On Thermal Properties Of Organic Absorbent/carbon Dioxide Binary Working Fluid

In recent years,China has begun to vigorously develop energy conservation and consumption reduction projects to improve current energy efficiency.The absorption power cycle utilizes industrial waste heat,geothermal energy and other medium and low-grade energy efficiently,and converts them into useful work.So,the absorption power cycle is of great importance for improving the comprehensive utilization efficiency of energy.In this paper,the working fluids pairs of absorption power cycle system was studied.Firstly,according to the performance requirements of the absorption power cycle system and the matching principle of the absorbent/CO₂ working fluids pairs,8 pairs of working fluids pairs were selected for further performance research and optimization,including n-nonane/CO₂,1-pentanol/CO₂,1-octanol/CO₂,acetone/CO₂,2-pentanone/CO₂,butyl ether/CO₂,amyl ether/CO₂ and hexyl formate/CO₂.Then,the maximum Gibbs function(G^E_max)was used as the thermodynamic criterion to evaluate the affinity of 8 pairs of organic absorbent/CO₂ working fluids pairs.And using PR equation and fugacity coefficient method to calculate the thermodynamic properties of organic sorbent/CO₂ working fluids pairs,including T-x-y,P-x-y,enthalpy and entropy of bubble state,enthalpy and entropy of super-cooled liquid,enthalpy and entropy of superheated steam for working fluids pairs.And the curves to show the relationship of thermodynamic parameters and transfer properties with the mole fraction of CO₂ are obtained in this thesis.The enthalpy of working fluids pairs decreases with the increase of mole fraction of CO₂.Whenx_{CO 2}?(0,0.05],the entropy of bubble point and supercooled liquid decreases gradually.when x_{CO 2}?(0.0 5,1],the entropy of bubble point and supercooled liquid increases gradually.while the entropy of superheated steam increases with the increase of the mole fraction of CO₂.And the transfer properties of organic sorbent/CO₂ working fluids pairs were calculated by empirical correlation,including dynamic viscosity,thermal conductivity,dynamic viscosity and surface tension.And the curves to show the relationship of transport properties with the mole fraction of CO₂ are obtained in this thesis.when x_{CO 2}?(0,0.95],the dynamic viscosity of the gas increases gradually;whenx_{CO 2}?(0.9 5,1],The dynamic viscosity of the gas decreases gradually.With the increase of the mole fraction of CO₂,the change trend of the hydrodynamic viscosity is quite different.whenx_{CO 2}?(0,0.9],the thermal conductivity of the gas decreases gradually;when x_{CO 2}?(0.9,1],the thermal conductivity of the gas decreases quickly?The thermal conductivity of liquid increases with the increase of the mole fraction of CO₂.when x_{CO 2}?(0,0.1],the surface tension gradually increases;while inx_{CO 2}?(0.1,1],The surface tension decreases gradually.Finally,the performance of acetone/CO₂ absorption power cycle was modeled with the help of Aspen Plus.The effect of CO₂ molar concentration on cycle efficiency was investigated by the calculation of thermal efficiency and exergy efficiency in different ratio of acetone/CO₂ absorption power cycle.The results show that with the increase of CO₂ mole fraction,thermal efficiency and exergy efficiency increase firstly and then decrease,and there exists a maximum at mole fraction of CO₂ in 0.8.