Thermodynamic properties of (R1234yf + R290): Isochoric pρTx and specific heat capacity cv measurements and an equation of state
Introduction
In recent years, with global warming and ozone depletion, looking for alternative refrigerants that are efficient and environmentally friendly is of much significance. The positive azeotrope (R1234yf + R290) mixtures [1] is a potential alternative refrigerant for its zero ozone depletion potential, ultra-low global warming potential, lower flammability than pure R290 and much better volumetric refrigeration capacity than pure R1234yf. Knowledge of reliable thermophysical property of refrigerant is essential for evaluating the performance in the refrigeration cycle. In our previous work, we measured the gaseous pressure-density-temperature-mole fraction (pρTx) property from (265.546 to 300.268) K [2] and saturated liquid pρTx property from (255.048 to 300.135) K [3] for (R1234yf + R290) mixtures using a compact single-sinker densimeter. Additional, we studied the vapour–liquid equilibrium (VLE) property [1] from (253.150 to 293.150) K using an apparatus based on the recirculation method. Brown et al. [4] obtained its gaseous density at temperatures from (268.15 to 363.15) K by the constant-volume method.
Among the above studies, truncated virial equation of state (EOS), PR-VDW model (Peng-Robinson EOS [5] combined Van der Waals [6] mixing rule) and PT-VDW (Patel-Teja EOS [7] model combined Van der Waals mixing rule) were used to correlate the gaseous density data [2], [4], empirical VDNS [8] and modified Rackett [9], [10] equations were applied to fit the liquid density data [3], and PR-VDW model and PR-HV-NRTL model (PR EOS with non-random two liquids [11] activity coefficient model involving Huron–Vidal [12] mixing rule) were used to present the VLE data [1]. However, these equations are not accurate enough to present the experimental data of many different properties simultaneously. The virial EOS is only suitable for gaseous state and the cubic EOSs are hard to describe liquid properties.
This work measured the isochoric pρTx and specific heat capacity cv of compressed liquid (R1234yf + R290) mixtures. The pρTx data were obtained at temperatures from (254.28 to 348.30) K and the cv data were obtained at temperatures from (255.48 to 347.55) K with mole fractions of R1234yf at (0.825, 0.607, 0.521 and 0.285). What’s more, a Helmholtz energy EOS based on the multi-fluid approximations model was developed for (R1234yf + R290) using the present and available experimental data. The Helmholtz energy EOS calculates the density, VLE and isochoric specific heat capacity properties with sufficient accuracy for technical applications.
Section snippets
Chemicals
Table 1 contains the critical temperatures, critical pressures, critical densities and acentric factors for the measured samples of R1234yf [13] and R290 [14]. R1234yf was supplied by Honeywell with a stated mole fraction purity of no less than 0.999, while R290 was supplied by Beijing AP BAIF Gases Industry Co. Ltd. with a claimed mole fraction purity of no less than 0.999. All the samples were used without further purification.
Experimental apparatus and uncertainty
As shown in Fig. 1, the adiabatic batch calorimeter that was used
Compressed liquid density and isochoric specific heat capacity results
Compressed liquid density data for (R1234yf + R290) binary mixtures are presented at temperatures ranging from (254.28 to 348.30) K with mole fractions of R1234yf from (0.285 to 0.825). The experimental results are listed in Table 2.
The Tait equation [16] was used to correlated the density data, it has the following form:with B given by Eq. (5). The saturation pressure ps and saturation density ρs were calculated from the developed PR-vdW model and modified Rackett equation
Conclusions
In this work, isochoric pρTx and specific heat capacity cv for (R1234yf + R290) binary mixtures were experimentally determined by an adiabatic batch calorimeter. The compressed liquid density data were measured at temperatures ranging from (254.28 to 348.30) K and pressures up to 14.239 MPa, while the isochoric specific heat capacity data were obtained at temperatures from (255.48 to 347.55) K and pressures up to 13.803 MPa. The compressed liquid density data, isochoric specific heat capacity
Acknowledgement
The supports provided by the National Natural Science Foundation of China (Grant No. 51676200), Beijing Nova Program (Grant No. Z181100006218022) and Beijing Natural Science Foundation (Grant No. 3171002) for the completion of the present work are gratefully acknowledged.
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