Thermophysical Properties of Low GWP Refrigerants: An Update

Abstract

In the last decades, the industry of HVAC&R has faced continuous changes trying to identify environmentally friendly refrigerants for the numerous applications of the sector. However, the amount of low GWP fluids still available as potential refrigerants is limited to some natural fluids and, among synthetic chemicals, to hydrofluoroolefins (HFO). The knowledge of the thermophysical properties of these compounds and the evaluation of their energy efficiency in experimental apparatuses is essential to properly address the selection of the most suitable fluids. However, regarding the wide majority of HFOs, the information on the thermophysical properties, especially for the blends, are still scarce and require further research. In this work, an analysis of the possible substitutes and the available experimental data sets on their thermophysical properties was carried out to find out for which fluids further studies are needed to obtain an accurate representation of their thermophysical properties. Specifically, for 21 pure refrigerants, an overview of the thermodynamic (critical point, psat, PVT, heat capacity and speed of sound) and transport properties (λ, μ, σ) data published in the peer reviewed literature was provided. In addition, a more comprehensive analysis was carried out for four fluids (R1243zf, R1233zd(E), R1336mzz(Z), and R1224yd(Z)), for which major efforts have been made in the last 4 years to investigate the above thermophysical properties. Although an increasing amount of data sets on thermophysical properties have been compiled in recent years, the present study indicates that research efforts are still needed, especially on transport properties, as only 4 of the fluids of interest for the present research have been fully investigated (R1234yf, R1234ze(E), R1233zd(E), R1243zf), while other 4 (R1234ze(Z), R1336mzz(Z), R1224yd(Z), R1336mzz(E)) have been almost completely characterised.

Solubility Measurements of R1234ze(E), R1243zf, and R1234yf in POE46 at Temperatures from 283.15 to 343.15 K

“…2 Although the drawbacks existed, 3,4 natural refrigerants (for example hydrocarbons, carbon dioxide, and ammonia) and synthesized hydrofluoroolefin (HFO) refrigerants are generally identified as promising substitutes. Moreover, the thermo-physical properties of pure HFO and the blends with HFCs or HCs were studied extensively in the past few years, and the research progress has been summarized by Bobbo et al 5 and Fedele et al 6 recently.…”

Thermal conductivity measurements for the hydrochloroolefin R1130(E)

“…This knowledge, based on reliable experimental data, plays a pivotal role in the design of efficient energy systems and the selection of suitable refrigerants for practical applications and simulations. As pointed out by Fedele et al [11], while the properties of R1336mzz(Z) have been extensively researched [12], leading to its inclusion in the REFPROP 10.0 software [13], R1130(E) remains relatively unexplored, with no publicly available fluid equation of state despite its recent addition to ASHRAE Standard 34 [10]. A summary of the fundamental properties of R1130(E) is shown in Table 1.…”

Surface Tension and Parachor of cis- and trans-1,1,1,4,4,4-Hexafluorobutene [R-1336mzz(Z) and R-1336mzz(E)]

“…Hydro-fluoro-orefins (HFOs), with their short atmospheric lifetime and low GWP, are expected to be next-generation refrigerants. Furthermore, physical property, performance, and safety assessments are currently being conducted, including for mixtures with stable substances. HFO-based substances R1336mzz­(E) and R1336mzz­(Z), which are cis- and trans-1,1,1,4,4,4-hexa-fluoro-butene, respectively, have relatively high boiling points and can be utilized in waste heat recovery systems and solar–thermal systems , or mixed with other refrigerants to reduce the GWP .…”

“…The parachor method was empirically determined by Macleod 25 and used to estimate the surface tension from saturated vapor and liquid densities. According to Sugden, 26 the surface tension obtained using this method can be expressed in terms of the molar densities ρ̂Land ρ̂V (in mol cm −3 ) as follows: (4) where [P] is an inherent substance parameter known as the "parachor." Fowler 27 and Boudh-Hir and Mansoori 28 attempted to rationalize this simple correlation using a statistical approach.…”