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Comparison of Environmentally Friendly Working Fluids for Organic Rankine Cycles
Published in Alina Adriana Minea, Advances in New Heat Transfer Fluids, 2017
Konstantinos Braimakis, Tryfon C. Roumpedakis, Aris-Dimitrios Leontaritis, Sotirios Karellas
The factor determining whether a fluid is wet, isentropic, or dry is its molecular complexity, which is defined as (Invernizzi et al. 2007) σ=TcritR(∂S∂T)Q=1,Tr=0.7 Since the value of the molecular complexity is directly proportional to the factor ∂S/∂T, it follows that it influences the inclination of the T–s saturation curve. That means that high σ fluids will have a more positively inclined vapor saturation curve. The molecular complexity of a fluid increases as the number of the atoms that form its molecule increases (Invernizzi et al. 2007). As a rule, the critical temperature and the acentric factor of fluids belonging to the same chemical group increase as the molecular complexity increases, while the critical pressure decreases (Bao and Zhao 2013).
Application of a non-cubic equation of state to predict the solid-liquid-vapor phase coexistences of pure alkanes
Published in Chemical Engineering Communications, 2022
José Manuel Marín-García, Ascención Romero-Martínez, Felipe de Jesús Guevara-Rodríguez
In the next step, the second virial coefficient is determined in such a way that equation of state is anchored to the acentric factor and boiling point temperature. In this work, the second virial coefficient is derived from the square-well potential (as described in Guevara-Rodríguez and Romero-Martínez (2013)), and this potential is defined as follows: where σ is the hard sphere diameter, λ is related to the width of the attractive part, ε is the square-well depth, and r is the radial distance between centers of two spheres. u(r) is a crude representation of a true molecular interaction, but describes the liquid-vapor coexistence, and the second virial coefficient has the following simple and exact expression: where NA is the Avogadro’s number.
Odorants for use with flammable refrigerants (1794-TRP)
Published in Science and Technology for the Built Environment, 2020
The Peng-Robinson equation of state (PR) is a cubic equation of state that was refined from the Soave modification (SRK) of the Redlich-Kwong equation of state (RK). The Peng-Robinson equation of state has the following form: Where Z is the compressibility, P is the pressure, v is the molar volume, R is the ideal gas constant, T is the temperature, Pr is the reduced pressure (P/Pc), Tr is the reduced temperature (T/Tc), Pc is the pressure at the critical point, Tc is the temperature at the critical point and w is the Pitzer acentric factor. The cubic nature of the PR equation of state yields up to three zeros with the maximum and minimum zeros corresponding to the vapor and liquid phases respectively and a single zero when only one phase is present. With the PR equation of state, it is possible to determine the pressure temperature and volume relationships and other thermodynamic properties of a fluid with only knowledge of the Pitzer acentric factor and the critical point of the fluid.
Investigation of wetting states and wetting transition of droplets on the microstructured surface using the lattice Boltzmann model
Published in Numerical Heat Transfer, Part A: Applications, 2020
The pseudopotential LB model for the flow field is coupled with the thermal LB model via a non-ideal EOS. In this work, the Peng-Robinson (P-R) EOS given below is used [39], where and ω is the fluid acentric factor; for water, ω = 0.344. Tc and pc are the respective critical temperature and critical pressure for the fluid. The values of a = 2/49, b = 2/21 and R = 1 are used in this study.