VLE calculation of carbon dioxide+n-alkanes binary mixtures with MHV2 mixing rule

Khodakarami, Behzad; Naderifar, Abbas

doi:10.1007/s11814-008-0244-6

Cited by 2 publications

(4 citation statements)

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“…Michelsen-Huron-Vidal second order (MHV2) mixing rule with zero reference pressure combined with a Peng-Robinson-Stryjek-Vera (PRSV) equation of state has been shown to be adequate in the calculations of VLE of asymmetric mixtures [130]. This mixing rule is shown in Equation (9): The values of and in Equation (9) are recommended as -0.478 and -0.0047, respectively [130][131][132].…”

Section: Model Descriptionmentioning

confidence: 99%

“…This mixing rule is shown in Equation (9): The values of and in Equation (9) are recommended as -0.478 and -0.0047, respectively [130][131][132].…”

Section: Model Descriptionmentioning

confidence: 99%

“…To predict phase equilibria of polar mixtures, the Michelsen-Huron-Vidal second order (MHV2) mixing rule with reference pressure zero has been shown to be adequate in the calculations of the VLE of mixtures [130], and which can reproduce low temperature data with a better accuracy for solving [130] and the molar co-volume as shown in Equation (37) to Equation (41):…”

Section: Mhv2 Mixing Rulementioning

confidence: 99%

“…The values of and for the SRK equation of state are recommended as -0.478 and -0.0047, respectively [130].…”

Section: Mhv2 Mixing Rulementioning

confidence: 99%

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Mixed-Fluid Organic Rankine Cycles for Low Temperature Power Conversion

Zhang¹

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The purpose of the thesis is to investigate and optimize refrigerant fluid mixtures for applications in low-temperatures ORC in order to maximize brine effectiveness ( ) rate for geothermal energy conversion in organic Rankine cycles. An in-house developed Matlab program interfaced with the Simulis TM thermodynamic database software was used to ascertain the performance of cycles having various mixture compositions. Brine effectiveness (the ratio of net work to geofluid mass flow rate) was used as the main metric to measure the performance of the Organic Rankine Cycle according to mixture composition, turbine inlet temperature and pressure. The optimum mixture concentrations have been found to depend on the plant design. There is an optimal pressure at different composition. The results highlight that it is not possible to obtain the maximum brine effectiveness, the maximum thermal efficiency, the smallest exergy destruction in the condenser and minimum turbine size factor simultaneously. For a geothermal plant, it is significant to maximize the power generated per unit flow of the geothermal fluid. The first-law efficiency is of secondaryimportance. These results demonstrate the importance of using brine effectiveness as the main performance metric rather than the thermal efficiency, which may not always describe the cycle that makes optimal use of the available energy. Similar optimization goals are presented in waste heat recovery, and the methods and findings of this thesis may be of interest in waste heat recovery applications.Based on the results obtained so far, selection of working fluids should depend on the specific conditions for each application, most notably the temperature of the resource. Working fluid critical temperature is very important in selecting the optimal working fluid. It is better to use a fluid with a critical temperature lower or a little bit higher than the heat resource temperature for cycles without superheating. The fluid's critical temperature then tends to determine the optimal cycle pressure.Mixed fluids have some advantages over pure working fluids. Most importantly, temperature glide (non-isothermal phase change) improves the performance in power cycle heat exchangers, especially the condenser, improving the performance of the overall power cycle.According to the fluid selection criteria, this thesis will focus on isentropic and dry fluids, which have higher thermal efficiencies because the turbine's expansion process terminates in the superheated region. 17 pure fluids were identified for low-moderate temperature power conversion and the performances of their mixtures were simulated at various ratios at 90 , 110 and 130, respectively. and for the optimization of the binary interactions parameters of the Non-Random-Two-Liquid (NRTL) model used for the calculation of the Gibbs Free Energy of Excess inside of the Michelsen-Huron-Vidal-second-order mixing rule (MHV2) used in combination with the Soave-Redlich-Kwong (SRK) equation of state. At the very least that the VLE...

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