Physical properties of alternatives to the fully halogenated chlorofluorocarbons

Presented here are recommended values and correlations of selected physical properties of several alternatives to the fully halogenated chlorocarbons. The quality of the data used in this compilation varies widely, ranging from well-documented, high accuracy measurements from published sources to completely undocumented values listed on anonymous data sheets. That some of the properties for some fluids are available only from the latter type of source is clearly not the desired state of affairs. While some would reject all such data, the compilation given here is presented in the spirit of laying out the present state of knowledge and making available a set of data in a timely manner, even though its quality is sometimes uncertain. The correlations presented here are certain to change quickly as additional information becomes available

Working fluid selection for space-based two-phase heat transport systems

The working fluid for externally-mounted, space-based two-phase heat transport systems is considered. A sequence of screening criteria involving freezing and critical point temperatures and latent heat of vaporization and vapor density are applied to a data base of 860 fluids. The thermal performance of the 52 fluids which pass this preliminary screening are then ranked according to their impact on the weight of a reference system. Upon considering other nonthermal criteria (flammability, toxicity, and chemical stability) a final set of 10 preferred fluids is obtained. The effects of variations in system parameters is investigated for these 10 fluids by means of a factorial design

Vapor-Phase (<i>p, ρ, T, x</i>) Behavior and Virial Coefficients for the (Methane + Propane) System

The (<i>p, ρ, T, x</i>) behavior of three (methane + propane) mixtures was measured with a two-sinker magnetic suspension densimeter over the temperature range of (248.15 to 373.15) K with pressures up to the dew-point pressure or 6 MPa, whichever was lower. The compositions of the gravimetrically prepared mixtures were (0.74977, 0.50688, and 0.26579) mole fraction methane. A detailed uncertainty analysis is presented. The relative combined expanded uncertainty (<i>k</i> = 2) in density considering all effects, including the uncertainty in composition, was 0.05 % or lower for most points, except it was larger at densities less than 5 kg·m^–3. Comparisons to the GERG-2008 equation of state for natural-gas mixtures showed significant deviations in density (as large as −1.3 %) that increased with decreasing temperature, with increasing pressure, and with increasing propane fraction in the mixture. The experimental values were also used to calculate interaction virial coefficients <i>B</i>₁₂(<i>T</i>) for this system. The <i>B</i>₁₂(<i>T</i>) agreed well with literature values. They were constant (within experimental uncertainty) with composition, as expected from theory. In contrast, the <i>B</i>₁₂(<i>T</i>) calculated with the GERG-2008 equation of state varied with composition

Computational Design of New Refrigerant Fluids Based on Environmental, Safety, and Thermodynamic Characteristics

We present a systematic search for new classes of refrigerants that would possess low values of global warming potential (GWP), along with low- to moderate flammability and suitable thermodynamic characteristics. We have developed new methods for estimating, solely from the molecular structure, the radiative efficiency (RE, a measure of radiative climate forcing) and atmospheric lifetime; the combination of RE and lifetime yields an estimate of the GWP. We also developed an estimate of the lower flammability limit (LFL) based on the enthalpy of formation. These estimation techniques, along with a previously developed technique for estimating critical temperature (<i>T</i>_c), are applied to a library of over 56 000 candidate molecules. We select fluids with GWP < 200; 300 K < <i>T</i>_c < 550 K; and LFL > 0.1 kg·m^–3. Filters for toxicity and chemical stability based on functional groups are also applied to arrive at 1234 candidates for further study. The candidates that would be suitable for use in present types of refrigeration equipment (those having critical temperatures less than 400 K) are dominated by halogenated alkenes; additional chemical classes, including halogenated ethers and cyclic compounds, are identified among fluids with higher critical temperatures

Computational Design of New Refrigerant Fluids Based on Environmental, Safety, and Thermodynamic Characteristics

We present a systematic search for new classes of refrigerants that would possess low values of global warming potential (GWP), along with low- to moderate flammability and suitable thermodynamic characteristics. We have developed new methods for estimating, solely from the molecular structure, the radiative efficiency (RE, a measure of radiative climate forcing) and atmospheric lifetime; the combination of RE and lifetime yields an estimate of the GWP. We also developed an estimate of the lower flammability limit (LFL) based on the enthalpy of formation. These estimation techniques, along with a previously developed technique for estimating critical temperature (<i>T</i>_c), are applied to a library of over 56 000 candidate molecules. We select fluids with GWP < 200; 300 K < <i>T</i>_c < 550 K; and LFL > 0.1 kg·m^–3. Filters for toxicity and chemical stability based on functional groups are also applied to arrive at 1234 candidates for further study. The candidates that would be suitable for use in present types of refrigeration equipment (those having critical temperatures less than 400 K) are dominated by halogenated alkenes; additional chemical classes, including halogenated ethers and cyclic compounds, are identified among fluids with higher critical temperatures

Compressed liquid density and speed of sound measurements and correlation of the binary mixture {carbon dioxide (CO 2 ) + 1,1-difluoroethene (R1132a)} at temperatures from 220 K to 350 K

The blend of carbon dioxide and R1132a has been suggested as a feasible alternative to R23 in lowtemperature devices. In this work, we present new experimental data for compressed-liquid density, vapour density and compressed-liquid speed of sound for the binary system CO2 + R1132a by means of a two-sinker densimeter and a pulse-echo-type instrument, respectively. The measurements cover the temperature range of 220 K to 350 K with pressures to 30 MPa for density; the speed of sound measurements cover the range 230 K to 350 K with pressures to 55 MPa; for both properties two mixture compositions were measured. Finally, we present an Equation of State (EoS) correlation for the experimental data based on a Helmholtz free energy model, which shows a good agreement with the measurements. The mixture strongly absorbed the sound pulse, and the usual dual-path analysis was not possible; thus, we developed a method using only the short-path signal

Thermodynamic Properties of <i>trans</i>-1-Chloro-3,3,3-trifluoropropene (R1233zd(E)): Vapor Pressure, (<i>p</i>, ρ, <i>T</i>) Behavior, and Speed of Sound Measurements, and Equation of State

We present experimental measurements of the density, speed of sound, and vapor pressure of <i>trans</i>-1-chloro-3,3,3-trifluoropropene, which is also known as R1233zd­(E). Densities were measured over the temperature range from (215 to 444) K, with pressures from (0.3 to 24.1) MPa. Sound speed data were measured at temperatures between (290 and 420) K, with pressures from (0.07 to 2.1) MPa. Vapor pressures span the temperature range from (280 to 438) K. The experimental data cover the saturation curve, the vapor and liquid phases, and also the vicinity of the critical point. Densities and vapor pressures were measured in a two-sinker densimeter with a magnetic suspension coupling. Sound speed data were measured with a spherical acoustic resonator. An equation of state written in terms of the Helmholtz energy was developed; it represents the present experimental data with relative root-mean-square deviations of 0.020 % for densities, 0.223 % for vapor pressures, and 0.131 % for speeds of sound

Properties and Cycle Performance of Refrigerant Blends Operating Near and Above the Refrigerant Critical Point, Task 1: Refrigerant Properties

The main goal of this project was to investigate and compare the performance of an R410A air conditioner to that of an R22 air conditioner, with specific interest in performance at high ambient temperatures at which the condenser of the R410A system may be operating above the refrigerant's critical point. Part 1 of this project consisted of measuring thermodynamic properties R125, R410A and R507A, measuring viscosity and thermal conductivity of R410A and R507A and comparing data to mixture models in NIST REFPROP database. For R125, isochoric (constant volume) heat capacity was measured over a temperature range of 305 to 397 K (32 to 124 C) at pressures up to 20 MPa. For R410A, isochoric heat capacity was measured along 8 isochores with a temperature range of 303 to 397 K (30 to 124 C) at pressures up to 18 MPa. Pressure-density-temperature was also measured along 14 isochores over a temperature range of 200 to 400 K (-73 to 127 C) at pressures up to 35 MPa and thermal conductivity along 6 isotherms over a temperature range of 301 to 404 K (28 to 131 C) with pressures to 38 MPa. For R507A, viscosity was measured along 5 isotherms over a temperature range of 301 to 421 K (28 to 148 C) at pressures up to 83 MPa and thermal conductivity along 6 isotherms over a temperature range of 301 to 404 K (28 to 131 C) with pressures to 38 MPa. Mixture models were developed to calculate the thermodynamic properties of HFC refrigerant mixtures containing R32, R125, R134a and/or R125. The form of the model is the same for all the blends considered, but blend-specific mixing functions are required for the blends R32/125 (R410 blends) and R32/134a (a constituent binary of R407 blends). The systems R125/134a, R125/143a, R134a/143a, and R134a/152a share a common, generalized mixing function. The new equation of state for R125 is believed to be the most accurate and comprehensive formulation of the properties for that fluid. Likewise, the mixture model developed in this work is the latest state-of-the-art for thermodynamic properties of HFC refrigerant blends. These models were incorporated into version 7 of NIST REFPROP database