| Absorption power cycle is an important energy saving technology that is driven by low grade heat. Instead of the condensation process by an absorption process and a separation process in the traditional Rankine cycle, absorption power cycle shows a higher thermodynamics consummating degree than the Rankine cycle. The thermophysical properties of the working pairs for absorption power cycle is very important in designing operation units and establishing operating conditions. However, most investigations of the absorption power cycle have concentrated on the optimization of cycle configuration and external conditions, with only a few studies focusing on the thermophysical properties of new working pairs. This paper focused on the research on the thermophysical properties of new working pairs, and he research contents are as follow:First, according to the previous study on the assessment methods of the working pairs for absorption power cycle, this study focus on the affinity of the binary mixture systems. Flory-Huggins theory and Wilson local composition concept were introduced to associate with the chemical affinity of binary mixed working pairs, and then the minimum excess Gibbs enthalpy value (GEmin) were considered to be a thermodynamic characteristics between absorption and absorber, and as a criterion of affinity for HFCs and organic solvent systems. Meanwhile, ten HFCs and nine organic solvents were selected, so 90 working pairs were formed as the studying objects. And the UNQUAC activity coefficient model was selected as the property method, the values of the GEmin of each working pairs at 303.15K, i.e. given absorption temperature in an absorption power cycle were calculated. According to the calculation results, HFC161/HFC152a+DMETEG systems were considered to be the preferable working pairs for absorption power cycle. In addition, the impacts law of the varieties and molecular structures of HFCs and organic solvents versus the GEmin were discussed.Second, based on the criterion of affinity for HFCs and organic solvent systems, three new working pairs,{fluoroethane (HFC161)+dimethylether tetraethylene glycol (DMETEG)}, {HFC161+dimethylether triethylene glycol (DMETrEG)} and {HFC161+dimethylether diethylene glycol (DMEDEG)}, are proposed for absorption power cycle. The working pairs are assessed from both thermodynamics and thermokinetic perspective. By combining the microcalorimetry and isothermal synthesis methods, an experimental apparatus was developed to simultaneously obtain the microcalorimetry and vapour-liquid equilibrium data. Then, the solubility and absorption enthalpy data of the three new working pairs were sync-measured at 303.15 K by this sync-measurement experimental apparatus. The thermodynamics data indicated that the affinities of the three working pairs increased from strong to weak in the following order: HFC161+DMETEG> HFC 161+DMETrEG> HFC 16+DMEDEG. Then the thermokinetic parameters of the absorption rate constant and activation energy were analysed based on the thermokinetic experiment at (303.15,313.15,323.15, and 333.15) K. As a result, the affinities of the three working pairs are consistent with the previous thermodynamics study. In addition, the intermolecular interactions within the three systems were analysed according to the intermolecular hydrogen bonds; overall, the HFC161+DMETEG system is considered to be the potential option for applications.Third, reviewing the previous vapor-liquid equilibrium (VLE) work, in this paper, VLE data of three systems, fluoroethane (HFC 161)+ dimethyl ether triethylene glycol (DMETrEG),1,1-difluoroethane (HFC152a)+DMETrEG, and HFC 152a+N-methyl-2-pyrrolidone (NMP), were measured from 293.15 to 353.15 K. The five-parameters nonrandom two-liquid (NRTL) model was selected to correlate the VLE data. For the HFC161+DMETrEG, HFC152a+DMETrEG, and HFC 152a+NMP systems, the average relative deviations of the pressure are 1.33%,1.43%, and 1.23%, respectively, and the maximum deviations of the pressure are 3.70%,3.66%, and 3.29%, respectively. The VLE behavior of HFC161/HFC152a+ethers, amides, and ketone systems were discussed by comparing the activity coefficient with the values for seven literature working pair systems and analyzing the interactions of the intermolecular hydrogen bonds. The results show that the HFC161+ absorbent systems exhibit negative deviations from Raoult's law and have a relatively good affinity compared to the HFC152a+absorbent systems. Moreover, the HFC 161+DMETrEG and HFC 152a+DMETrEG systems exhibit stronger affinity than the HFC152a+NMP system and can be considered as potential alternatives for working pair systems of the absorption power cycle.Finaly, the CO2+DME system were proposed as new working pairs of absorption power cycle. Based on the sub-cycle divided method, the "Chemical Heat Engine" theoretical model was introduced and absorption power cycle was divided into two sub-cycles:chemical heat engine sub-cycle and heat engine sub-cycle. Meanwhile, contrastive analysised the essential reason of trans-critical operating conditions is better than that of sub-critical and super-critical conditions. Then a typical CO2+DME trans-critical absorption power cycle simulation program was estabilished, and the PR equation was selected as calculation model based on the VLE data reported in literatures. Then the composition, flow rate, enthalpy value and entropy value of the cycle streams were calculated, respectively. According to the calculation data, the sub-cycle configuration effect and energy conversion mechanism were analysied by T-s, 1g p-h, energy flow digram and exergy flow digram, respectively. According to the parameter analysis method, the influence of the pressure to the heat conversion work efficiency for chemical heat engine sub-cycle were explored at different absorption temperature (25,30,35 and 40)?. The results show that reduces the operation pressure of chemical heat engine sub-cycle can increase the heat conversion work efficiency and improve energy utilization. |
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