Search

In this study, the solid–liquid equilibria of five binary systems containing refrigerants with low global warming potential, namely carbon dioxide (R744) + 1,1-difluoroethene (R1132a), R1132a + 2,3,3,3-tetrafluoropropene (R1234yf), R1132a + trans-1,3,3,3-tetrafluoropropene (R1234ze(E)), trifluoromethane (R23) + R1234yf, and R23 + R1234ze(E), was experimentally determined. Two experimental setups based on the cooling curve method were employed to measure the samples obtained from different sources. The results obtained using the two setups were in good agreement with the experimental uncertainty. In addition, the experimental data were compared with the values calculated using the Schröder equation, showing limited deviations. The accuracy of the experimental setups was tested by measuring the triple-point temperatures of the components of the studied binary systems, showing good agreement between the experimental data obtained for the pure refrigerants and the data available in the literature., International Journal of Refrigeration, 144, pp. 254-263; 2022

In the present work, an improvement of protocol widely used for reporting the thermal behaviour of solar cookers is communicated to the scientific community. The linear regression used to represent the standardised cooking power is based on the well-known Hottel-Whillier-Bliss equation written in dimensionless format. The authors’ new formulation procedure for estimating the standardised power includes a correction for the difference between the load temperature and the ambient air temperature of the procedure of ASAE S580.1 Standard. It is derived from a simple theoretical deduction, similar to the ones usually applied to solar thermal flat collectors. The correction factor relates itself with the ratio between the measured solar irradiance and the solar irradiance chosen as a standard value. As one example, test results of a funnel cooker loaded with water are used to show the impact of the improvement of the procedure for reporting performance of a solar cooker. The procedure is valid only for solar cookers evidencing a clear linear performance curve. info:eu-repo/semantics/submittedVersion

The triple point temperature of refrigerants is crucial because it serves as a reference for the lower limit of their use temperature in a refrigeration system. In this study, the triple point temperatures for recently proposed refrigerants with low global warming potential were experimentally determined. Ten hydro-fluoro-olefins, two hydro-chloro-fluoro-olefins, and trifluoroiodomethane were investigated. The triple point temperatures of the refrigerants were determined from the obtained cooling and heating curves. To improve measurement accuracy, measurements were conducted on samples obtained from different companies using two different measurement devices. The measured data were found to be in good agreement within the estimated measurement uncertainty., International Journal of Refrigeration, 133, pp.172-180; 2022

Solar radiation can be considered as one of the most suitable energy source to be used for cooking food. It is therefore important to promote advancement in solar cooking systems, in particular as concerns their efficiency and cooking times. In this work, we designed, realized and tested a novel low-cost solar cooker that uses a high-performance light-concentrating Fresnel lens, which is able to concentrate onto a small focal area a large amount of solar radiation. The radiation is then reflected by a mirror towards a cooking surface, where a pot can be located. The cooker has a geometrical concentration ratio of 40.97. In order to characterize the thermal performance of the cooker, we carried out several outdoor tests with a dedicated test setup, using water and silicone oil as absorbing media. Respect to other solar cookers, results show that the proposed cooker is able to reach high temperatures with good efficiency and reduced heating times: 3 kg of water can reach 90 °C in around 30 min, while 3 kg of silicone oil can be taken from 40 to 170 °C in less than one hour.

The comparison between I-V (current-voltage) curves measured on site and I-V curves declared by the manufacturer allows to detect decrease of performance and control the degradation of photovoltaic modules and strings. On site, I-V curves are usually obtained under operating conditions (OPCs), i.e. at variable solar radiation and module temperature. OPC curves must be translated into standard test conditions (STCs), at a global irradiance of 1000 W/m2 and a module temperature of 25 °C. The correction at STC conditions allows to estimate the deviation between the power of the examined module and the maximum power declared by the manufacturer. A possible translation procedure requires two correction parameters: Rs’, the internal series resistance, and k’, the corresponding temperature coefficient. The aim of this work is to determine the correction parameters carrying out specific experimental tests as indicated by IEC 60891. A set of brand-new photovoltaic modules was experimentally characterized determining their I-V curves by means of an indoor solar flash test device based on a class A+ AM 1.5 solar simulator. Using the OPC I-V curves, obtained at several conditions of irradiance and temperature, it was possible to determine the correction parameters of the photovoltaic modules being considered.

During their lifetime, photovoltaic (PV) plants are subject to a normal degradation of their components, and they are consequently characterized by decrease of the expected production. In order to prevent and evaluate failures and loss of production, specific tests can be carried out on the PV modules. Non-destructive methods, such as visual inspection and infrared thermography, can be performed in order to determine production failures or defects on the PV modules. I-V curves allow to estimate the performance of photovoltaic modules and strings, estimating the deviation between the power of the examined module and that declared by the manufacturer. The aim of this work is to evaluate the efficiency loss of photovoltaic modules associated to specific defects, causing in a systematic way some faults on a set of brand-new modules and assessing the relative decrease of power. The set of brand-new photovoltaic modules, after being damaged, was experimentally characterized determining their I-V curves by means of an indoor solar flash test device based on a class A+ AM 1.5 solar simulator. Using the I-V curves as a dataset, it was possible to estimate the incidence of different defects on the power of the photovoltaic module being considered.

This paper presents a literature survey of the experimental thermal conductivity data for environmentally friendly refrigerants, namely HydroFluoroOlefins (HFOs) and HydroChloroFluoroOlefins (HCFOs), in the liquid phase. A total of 2073 experimental data for six alternative refrigerants, i.e. R1233zd(E), R1234yf, R1234ze(E), R1234ze(Z), R1224yd(Z), and R1336mzz(Z), was collected in the temperature range from 203.18 K to 434.99 K and in the pressure range from 0.10 MPa to 66.62 MPa. Literature correlations not considering the pressure dependence were compared for reduced pressures lower than 1. Di Nicola et al. (2014a) correlation was re-fitted and new coefficients expressly dedicated to low global warming potential refrigerants were given. The proposed equation gives an overall deviation of 1.78% for the data measured at reduced pressure up to 1. The liquid thermal conductivity dependence on pressure was also considered adding new terms on Di Nicola et al. (2014a) correlation and on Latini and Sotte (2012) correlation. The proposed equations give overall deviation of 1.45% and 1.99%, respectively, for the complete dataset.

This paper provides 84 two-phase and 66 vapor phase PvTx measurements for binary blends comprising difluoromethane (R32) and cis-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(Z)). The data are for seven i...

Solar radiation is a variable energy source and the mismatch between the availability of such source and the domestic energy demand is a paramount challenge to deal with. For this reason, in this work a 4.08 concentration ratio portable solar box cooker coupled with a thermal energy storage (TES) based on a phase change material (PCM) was characterized through outdoor experimental tests. The TES is a double-wall stainless steel vessel, with the annular volume filled with 2.5 kg of erythritol. The portable solar box cooker was tested under 4 different experimental conditions: without load, with water, with silicone oil, and with silicone oil inserted in the erythritol-based TES. The load tests were divided into a heating and a cooling phase, in order to evaluate the cooker performance in absence of solar radiation. Results showed that equipping the portable solar box cooker with the erythritol-based TES allowed to extend the average load cooling time, in the range 125–100 °C, of around 351.16%.

In this paper, 182 pvTz data (28 data in the two-phase region and 154 data in the superheated vapor region) of mixtures containing difluoromethane (R32) and trans-1,3,3,3-tetrafluoroprop-1-ene (R12...

Sugar alcohols have interesting thermodynamic properties that make them good options as heat storage materials (HSMs) to be used in solar cookers. Among sugar alcohols, xylitol is affected by severe supercooling that can significantly alter its usefulness in thermal energy storage (TES) systems. To overcome the supercooling issue, in this work the thermal behavior of a xylitol-based TES installed in a portable solar box cooker was investigated experimentally. The solar cooker has a 4.08 concentration ratio and the TES is a double-pot system filled with 2.5 kg of commercial-grade xylitol. The TES includes a manual mixing device that can be used to trigger the nucleation of xylitol. The effectiveness of the TES system with and without triggering was assessed through several outdoor tests, divided into heating and cooling phases, using silicone oil as absorbing media. It was found that the average load cooling time, in the temperature range of the test fluid from 110 to 80 °C, increased by about 346% when the solar cooker was equipped with the xylitol-triggered TES. The mixing device can therefore be considered an effective solution for regarding xylitol as an actual and performing phase change material.

In the present work, the results of testing panel and box solar cookers are used to investigate the suitability of using the linear regression for estimation of the performance parameters of a solar cooker. The panel cooker and the box cooker were experimentally tested with glycerine and peanut oil, respectively. An exponential fitting to the plot of measured load temperature versus time is used to derive the linear regression between the instantaneous efficiency and the specific difference of temperature. The linear regression curve is compared with the corresponding experimental curve. Minor deviations are observed in the case of the panel cooker, but only in the middle part of the test. In the case of the box cooker, the deviations are very significant during the whole test. The present work presents the simplified formu-lation associated with the physical problem. It points out the importance of performing further research to develop a more accurate procedure. The determination of parameters based on the linear regression cannot be seen as a universal procedure applicable to all types of cookers. The opto-thermal ratio and the maximum achievable load temperature are overestimated. info:eu-repo/semantics/publishedVersion

In this paper, the solid – liquid equilibrium of the binary system containing difluoromethane (R32) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) was experimentally evaluated. An experimental setup was used to measure 20 different compositions of the binary system in the temperature range from 168.2 K to 132.00 K. The studied binary system showed an eutectic point which was estimated at the temperature of 132.00 K. The results for the solid – liquid equilibrium of the studied system showed a general agreement with the prediction provided by the Schroder equation, showing deviations generally within 2 – 3 K. In addition, in order to test the validity of the experimental setup, the triple point temperatures of the components of the binary system and four well described refrigerants (namely R125, R152a, R143a, and R41) were measured. The experimental results for the pure refrigerants agreed with reliable values available in the literature.

The Boyle temperature represents the temperature at which a real gas behaves more like an ideal gas. It is an useful thermodynamic parameter but it is difficult to measure experimentally. Thus, in this work we provide the Boyle temperatures of 16 pure gases, namely: argon, carbon dioxide, carbon monoxide, deuterium, helium-3, helium-4, hydrogen, krypton, methane, neon, nitric oxide, nitrogen, oxygen, tetrafluoromethane, tritium and xenon. The Boyle temperatures of the gases were determined by setting to zero their second virial coefficient (B) functions. Starting from 1663 available experimental data of B, an artificial neural network (ANN) was trained to correlate the second virial coefficient of the gases to two parameters: the reduced temperature and the critical molar volume. In order to obtain results as accurate as possible, different ANN configurations were tested, with variable numbers of neurons/hidden layers and up to 10000 iterations. It was found that the best configuration consists of 2 hidden layers with 24 neurons each. The ANN root-mean-square error was compared to those of other correlations available in literature and resulted to be very low, being equal to 2.74 cm3/mol. The temperatures determined by setting the ANN mapping of B to zero are comparable to those obtained from accurate curve fittings and, by virtue of their low deviations, can be adopted for calculation and as reference for experimental measures.

This study presents a method to calculate the surface tension of a wide variety of organic carboxylic-based acids molecules starting from the experimental data of the liquid viscosity. The first step of this research was a data collection and then an accurate selection of experimental sources for the calculation of surface tension. Besides, in order to build two different but comparable databanks, the experimental points were regressed with simple equations at the same reduced temperature range, spanning from 0.35 to 0.75. As a final step, the original relationship of Pelofsky between the natural logarithm of surface tension and the inverse of viscosity was changed to better describe the property under investigation. The simple modification of adding the reduced temperature allowed to achieve an AAD of 1.24% for the whole dataset that contains 22 fluids with 170 surface tension data and 379 liquid viscosity experimental data.

In this study, it is aimed to design an efficient and sustainable solar tunnel dryer to be used in drying process of sewage sludge. In the first step of this study, heat and flow structure of three tunnel dryers including rectangular tunnel (RSTD), quonset tunnel (QSTD) and quonset tunnel with fins (QSTD/F) have been numerically surveyed to determine the effective design. Based on CFD results, quonset-type tunnel designs have been fabricated, experimentally analyzed and compared with numerical findings. In this work, different from previous studies on quonset-type solar-thermal systems, top surface of quonset geometry was made from sheet metal as an absorber to enhance heat transfer area. The drying tests have been performed in different months of the year (June and January) by applying two different air velocities to evaluate the performance of tunnel dryers at various climatic conditions. Integrating fins to the quonset tunnel had considerable positive effects on both thermal and drying performances. According to the experimental findings, specific moisture extraction rate (SMER) value was attained on June and January in the range of 0.50–0.89 and 0.39–0.65 kg/kWh, respectively. The results indicated the successfulness of quonset solar tunnel dryer design in the dehumidification process of sewage sludge.

This work reviewed the state of the art concerning solar cookers and dryers used in food processing. The general description of solar cookers and dryers was presented, with a specific attention to the equipment where the cooking takes place with the contribution of the direct sunlight. Some insight about the history of design and development of devices that use solar light to process food were provided. The possibility to store the heat produced by solar light using Phase Change Materials was analyzed. Moreover, some “case-studies” were revised and discussed, in which solar light is efficiently used to dry or cook food, focusing on the quality of the food in terms of nutraceuticals content. The analyzed literature points out the necessity for further research about the effects produced by direct solar rays on different foods. The reliable data on this aspect will allow assessment of the quality of food transformation by solar cookers and dryers, adding a strong incentive to the development of such devices, up to now primarily motivated by energy-saving and environmental issues.

Heat pumps are high-efficiency heat transfer devices with different usages, which can work by using various energy sources. This helpful device can be mixed with multiple technologies to make more efficient systems. In this study, a combination of heat pump and shower drain water is proposed to utilize wastewater deriving from the high-rise building's bathroom. This heat pump system uses waste heat of bathroom-drained water, which is a cheap energy source compared to fossil fuel in Turkey. The mentioned heat pump system can also use wastewater from sauna, public bath, building bath, etc. to be effectively applied not only for water heating but also for space heating. In this work, it is proposed to utilize wastewater as heat source for heat pump system. In this regard a heat recovery system has been designed and combined with a heat pump system to utilize the available energy in the drained shower water. Accordingly, a wastewater gathering tank has been designed and manufactured to reuse the waste heat of the drain water. In addition, a conventional boiler has been used in the designed system to meet intended heat demand. Then the performance of the heat pump was analyzed in different wastewater temperatures. As a result, COP approximately improved by 55% when the drain water temperature increased from 15 degrees C to 33 degrees C. The obtained experimental results in this study showed that shower drain water thermal energy can be used successfully as a heat source for heat pump systems.

Ninety-seven vapor-phase PvTx measurements are reported for six binary blends of cis-1,2,3,3,3-pentafluoroprop-1-ene (R1225ye(Z)) and isobutane (R600a), and sixty-six vapor-phase PvTx measurements ...

An algorithm is presented for the estimation of the UNIQUAC interaction parameters for liquid-liquid equilibrium of ternary systems. The algorithm is based on two optimization levels. In the inner level the algorithm performs the minimization of an objective function based on the isoactivity conditions. The outer level aims to minimize the error between calculated and experimental compositions. The Common Tangent Plane condition is checked at the end to guarantee a thermodynamically consistent representation of the phase behavior of ternary liquid systems. The algorithm is challenged with a historical Type 1 ternary liquid-liquid equilibrium system from the seminal study of Anderson and Prausnitz in which the authors showed the limitations of the original UNIQUAC model and justified its amendment in the modified UNIQUAC model. The present algorithm makes available single temperature and temperature-dependent interaction parameters enabling accurate and thermodynamically correct description of the experimental data with the original UNIQUAC model, therefore without the need of any model modification. This outcome does not change when the interaction parameters from the binary partially miscible constituent pair are first regressed and kept constant during the estimation of the remaining parameters on ternary equilibrium data. This investigation confirms that a model cannot be judged if the correctness of the model parameters has not been proved first.

Different Cubic Equations of State (CESs) were used to represent Vapor-Liquid Equilibrium (VLE) of binary systems containing low Global Warming Potential (GWP) refrigerants. The calculated VLE data from some of the widely used CESs were compared with the experimental data collected from the literature. To extend CESs to binary systems, van der Waals one-fluid mixing rules with a single binary interaction parameter were used. Although the deviations between the experimental and calculated values are generally low, a comparison of the results was performed to find the most accurate CES for VLE of the studied binary systems.

Clear-sky conditions are an essential need to allow proper high-temperature solar cooking. Moreover, it is not an easy task to accomplish evening cooking, especially during wintertime when solar radiation is available only for a few hours. A solution to bypass these drawbacks lies in adopting a cooker provided with a thermal storage unit. The storage unit proposed in this work is a double-walled vessel composed by two stainless steel cylindrical pots assembled concentrically. The annular space between the pots was loaded with 4 kg of phase change material (PCM) based on a ternary mixture of nitrite and nitrate salts (solar salt: 53 wt% KNO3, 40 wt% NaNO2, 7 wt% NaNO3). The thermal storage unit was characterized by means of a test rig including a high-concentration-ratio (10.78) solar box cooker. Four different sets of 14 experimental tests, divided into a heating and a cooling phase, were carried out to assess the performance of the solar cooker with the storage unit. It was found that the PCM thermal storage significantly improves the load thermal stabilization when solar radiation is not available: the load cooling time in the range 170–130 °C was determined to be from 65.12% to 107.98% higher than that without the solar-salt-based PCM thermal storage, proving the effectiveness of the proposed solution.

In the present work, a large number of compounds described in the publicly available literature have been reviewed with the aim to identify possible substitutes for high-GWP HFCs in HVAC&R and organic Rankine cycle (ORC) applications. Taking into account various criteria (particularly low toxicity, low flammability, low GWP, and high energy efficiency), only a few single-component compounds are suitable for many of the relevant applications. In particular, in addition to natural fluids, studies have shown that there are only a few HFCs and a dozen or so HFOs, i.e. halogenated olefins characterized by the presence of a C C double bond in the molecule, that are potentially suitable for a number of relevant applications. Here, a review of the present state-of-the-art of experimentally-determined thermophysical properties of a number of HFOs working fluids and their mixtures also with other categories of refrigerants is presented, with particular emphasis placed on saturation and critical properties, vapor phase PVT data, liquid density, specific heat capacity, thermal conductivity, viscosity, and surface tension.

This work presents a method to calculate the surface tension of the inorganic family of silicon-based molecules starting from the knowledge of the liquid viscosity. As a first step, the raw experimental data of silanes were collected from the data available in the DIPPR database, both for surface tension and liquid viscosity. After the data analysis, a selection of experimental data was considered for the calculations. Furthermore, to create two homogeneous databanks, the original experimental data were regressed at the same reduced temperature range, spanning from 0.3 to 0.8. The original Pelofsky empirical relationship between the natural logarithm of surface tension and the inverse of viscosity was modified to represent the surface tension of silanes starting from the viscosity of liquids. The obtained results produced an AAD = 1.13% calculated on the entire dataset.

In this paper, a literature survey of the available experimental surface tension data of both low global warming potential (GWP) refrigerants and binary systems containing low GWP refrigerants is provided. The experimental data were collected for 14 halogenated alkene refrigerants and 5 blends. The data were analyzed with the most reliable semi-empirical correlation models designed for pure refrigerants and blends, based on the corresponding states principle (CSP). Recent scaled correlations based on the CSP and developed for other kinds of fluids were re-fitted and tested, too. The coefficients of these equations were subdivided for ethylene derivative refrigerants, propylene derivative refrigerants and blends. The absolute average deviations (AADs) of the new re-fitted equation for the ethylene derivatives are in agreement with the AADs of the correlations existing in the literature, while the proposed equations for the propylene derivatives and the binary systems give a considerable improvement respect to existing relations.

A viscosity model based on the Patel–Teja equation of state has been applied to pure refrigerants and their liquid mixtures. 7490 data points, containing 6481 points for pure refrigerants and 1009 points for binary, ternary and quaternary mixtures, have been used. First, 29 pure refrigerants are selected and the pure-component parameters of the model are then fitted. Subsequently, seven binary mixtures have been used to regress the binary interaction parameters of the model. The resulting binary interaction parameters and pure-component parameters are then used to predict the viscosity of two ternary and one quaternary mixtures. The results show that deviations are generally low for all analyzed compounds and mixtures. (Overall AADs% are 7.44 for pure compounds, 3.37 for binary mixtures, 3.77 for ternary mixtures and 3.36 for a quaternary mixture). This model does not require the property of density, which is one of its main advantages.

Efficiency of energy systems can be improved in different ways. One of these consists in adopting heat transfer fluids with better thermo-physical properties, e.g. thermal conductivity and dynamic viscosity, which can improve convective heat transfer coefficient. Being mixtures of high-conductive nanoparticles and common base fluids, nanofluids have the potential to increase the efficiency of a large number of energy systems. Thus, great importance should be dedicated to a correct and reliable estimation of the thermophysical properties of these fluids. In this work, the thermal conductivity of 11 nanofluids, for a total of 239 experimental points, was analyzed in detail: 7 nanofluids have water as base fluid (Ag, Al2O3, CuO, Fe2O3, SiO2, TiO2, ZnO), while 4 nanofluids have ethylene glycol (Al2O3, CuO, SiC and SnO2). All nanofluids’ thermal conductivity data derive from experimental measurements available in literature, carried out with samples characterized by stable preparation methods. The thermal conductivity of the nanofluids was estimated with 13 well-known correlations, in order to verify their accuracy. A new semi-empirical, scaled equation for predicting the thermal conductivity of nanofluids was also proposed. The equation requires the use of six parameters (volume fraction, temperature, base fluid critical temperature, nanoparticle diameter, nanoparticle thermal conductivity, base fluid thermal conductivity) and shows small deviations respect to the experimental data, having an average absolute relative deviation of 2.60%. This value was found to be the lowest among the other studied correlations. The study also highlights some issues and limitations that the research field related to nanofluids should overcome.

This paper provides eighty-four PvTx data points for binary blends of trans-1-chloro-3,3,3-trifluoroprop-1-ene (R1233zd(E)) and isobutane (R600a) in the vapor phase and ninety-seven PvTx data points for binary blends of cis-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(Z)) and R600a in the vapor phase. The R1233zd(E)/R600a data were recorded along six isochores (0.0499, 0.0536, 0.0927, 0.1263, 0.1431, 0.1744) m3·kg–1 for temperatures (303 < T < 383) K for six R600a mole fractions (0.125, 0.453, 0.564, 0.644, 0.746, 0.865). The R1234ze(Z)/R600a blends were recorded along five isochores (0.0759, 0.0907, 0.1272, 0.1288, 0.1520) m3·kg–1 for temperatures (303 < T < 383) K for six R600a mole fractions (0.118, 0.222, 0.427, 0.510, 0.658, 0.725). The data were regressed using several equations of state.

This work presents a new formula to calculate the liquid viscosity of the inorganic family of silicon-based molecules. As a first step, the raw viscosity experimental data of silanes were collected...

The paper presents 96 PνTx vapor phase data values for binary blends of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) and isobutane (R600a) and 102 PνTx vapor phase data values for binary blends of trans-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(E)) and R600a. The R1234yf/R600a blends were measured for five isochores (0.0751, 0.0944, 0.1280, 0.1666, 0.1701) m3·kg–1 for (303 < T < 383) K for six R600a mole fractions (0.234, 0.400, 0.472, 0.606, 0.772, 0.850) mol·mol–1. The R1234ze(E)/R600a blends were measured for four isochores (0.0852, 0.0894, 0.1006, 0.1064) m3·kg–1 for (303 < T < 383) K for six R600a mole fractions (0.290, 0.428, 0.516, 0.612, 0.685, 0.755) mol·mol–1. The data were fitted with a fundamental Helmoltz equation of state (EoS), a Peng–Robinson EoS, and a truncated virial EoS.

This study investigates the applicability of artificial neural networks (ANNs) as an efficient tool for the description of thermal conductivity of liquid alcohols for a broad range of temperatures. The proposed multilayer perceptron has 1 hidden layer with 43 neurons, determined according to the constructive approach. The model developed was trained and validated on the set of data gathered, showing that the accuracy of the ANN model is higher than that of other approaches proposed in the literature. The experimental or experimental and predicted thermal conductivity data of alcohols were taken from the database due to the ‘DIPPR Database’. The ability of the ANN method to reproduce the original data was tested for 26 alcohols in the liquid phase at reduced temperatures ranging from 0.30 to 0.90. The maximum absolute deviations between experimental and calculated thermal conductivity data points are generally less than 0.0110%, while the average absolute deviations are usually less than 0.0016%. T...

This work presents a literature survey of the available data regarding the thermal conductivity of refrigerants. About 31 pure refrigerants that contain 7127 data points are selected for th...

This work presents 24 vapor pressures and 131 vapor-phase pvT properties for 1,1-difluoroethene (R1132a) measured using an isochoric apparatus. This fluid is a hydrofluoroolefin with a GWP less than 3 and it is considered to be a potential component for low-GWP refrigerant mixtures for ultralow temperature applications. The saturated pressure data were obtained in the temperature range from (223.15 to 280.65) K and pressure range from (0.471 to 2.675) MPa. The vapor-phase pvT measurements were performed in the temperature range from (223.15 to 303.15) K, pressure range from (0.312 to 2.340) MPa, and specific volume range from (0.013226 to 0.086770) m3 kg−1. The saturated pressure data were compared with the experimental values available in literature and fitted to extended Antoine-type and Wagner-type vapor-pressure correlations. The vapor-phase pvT data were compared with the values available in literature. In addition, the pvT properties were used to develop a truncated virial equation of state.

The values of thermal conductivity at different temperatures for organic and inorganic compounds in the liquid phase is required in the study of several processes, but experimental data are often not available with acceptable reliability or not available at all; since rigorous theoretical or semi-theoretical models of the liquid state are usually of poor practical use for engineering purposes (the errors can be very high and the mathematical difficulties generally lead to excessive simplifications) empirical or semi-empirical methods are used to estimate with reasonable accuracy. In this work a simple equation already proposed by the authors for the estimation of the liquid thermal conductivity of alcohols is generalized in order to allow the calculation of for the compounds belonging to the families of n-alkanes, ketones and silanes. The proposed equation requires for each compound the knowledge of the critical temperature Tc and the molecular weight M and contains three parameters: the ‘golden r...

This work proposes an equation useful for engineering purposes and requiring the critical temperature T c , the molecular weight M and three parameters: the “golden ratio” Φ, a factor h characteristic of the organic family and an exponent a linked with the number of carbon atoms. The investigation is based on the available experimental or experimental&predicted thermal conductivity data of alcohols from the database due to “The DIPPR Information and Data Evaluation Manager”. The important family of alcohols represents the first example of the method, which is compared with other existing methods. The method was developed for 26 alcohols in the reduced temperature ranging from 0.30 to 0.90, the average absolute deviations between calculated and DIPPR thermal conductivity data are generally very low, being less than 5% and the maximum absolute ones less than 8%, for most of the alcohols.

cis-1,2,3,3,3-Pentafluoroprop-1-ene (R1225ye(Z)) is a non-flammable potential working fluid possessing low global warming potential. Toxicity testing has uncovered some concerns with sub-chronic and chronic exposures. In this paper, ninety-six vapor pressure data points for a saturation temperature range from approximately 233 K to 366 K from two different laboratories are presented. These data are regressed using Wagner and extended Antoine correlations. The root mean square errors of the Wagner and Antoine correlations relative to the measured data are 0.084% and 0.094%, respectively. The vapor pressure curve of R1225ye(Z) is shown to be similar to trans-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(E)). The normal boiling temperature, critical temperature, critical pressure, critical density, acentric factor, and ideal gas specific heat at constant pressure at a temperature of 300 K of R1225ye(Z) are estimated to be 253.62 K, 380.05 K, 3529 kPa, 517.17 kg m−3, 0.3256, and 101.9 kJ kmol−1 K−1, respectively.

The paper presents 86 PvTx measurements in the vapor phase for blends of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) and propane and 62 PvTx measurements in the vapor phase for blends of cis-1,2,3,3,3-pentafluoroprop-1-ene (R1225ye(Z)) and propane. The R1234yf and propane blends were measured along four isochores (0.047, 0.048, 0.072, 0.095) m3·kg–1 for (268 < T < 363) K for four propane mole fractions (0.230, 0.505, 0.611, 0.709) mol·mol–1. The R1225ye(Z) and propane blends were measured along five isochores (0.032, 0.038, 0.042, 0.067, 0.090) m3·kg–1 for (303 < T < 363) K for five propane mole fractions (0.225, 0.516, 0.593, 0.690, 0.855) mol·mol–1. The data are well-predicted when fitted (1) with Fundamental Helmoltz Equations of State (EoS), Peng–Robinson EoS, and Extended Corresponding States EoS when each are coupled with a modified van der Waals one-fluid linear mixing model, and (2) with a truncated Virial EoS.