Search

In this study, the pressure drop of automotive refrigerant pipes with the refrigerant R1234yf is investigated in detail. For this purpose, 1D and 3D simulations are compared with respect to prediction accuracy using liquid lines from a production car. It is shown that for a combined approach of the methods a very good agreement with the measured values can be obtained, whereas simplified modeling of the line as a straight pipe of equal length significantly underestimates the experimental values. The transition pieces between the pipe and the hose are of particular importance, since they account for up to 85 % of the total pressure drop and therefore result in major errors if neglected. If hoses were eliminated, the lines could be designed smaller, resulting in a charge reduction of up to 56 %.

Polymer ejectors manufactured with injection molding offer a low cost and lightweight design for automotive applications compared to traditional metal designs. New materials need to be resistant against the refrigerant R1234yf and withstand the pressure under operating conditions of a mobile air conditioning. In this paper, a material research selects possible material candidates for a polymer ejector. A FEM simulation investigates the stability and deformation of the ejector when using a polymer material instead of the usual stainless steel solution. A selective laser sintering (SLS) printed polyamide 12 ejector is benchmarked in an enhanced vapor-compression refrigeration cycle against a stainless steel prototype on a test bench. Both ejectors implement the expected pressure levels and show a good pressure recovery rate. However, the new polyamide 12 ejector has a faster decrease of performance from its maximum efficiency. The difference in the ejector performance is expected to be caused by a larger manufacturing tolerance in the SLS printing, leading to a larger nozzle diameter. The design of a polymer ejector is successfully tested, offering new applications for the ejector technology in the automotive industry.

HFC refrigerants as R134a, R404A, R407C and R410A are commonly used in heating, air conditioning and refrigeration (HACR) systems since Kyoto protocol. However, they are phased-out due to their high global warming potential (GWP). There are various options to replace high GWP refrigerants, among all hydrofluorolefin (HFO) fluids, such as R1234yf, represents an excellent alternative. With GWP

In the present paper, the experimental results of the use of R1234yf and R1234ze(E) as drop-in alternatives of R134a in a water-to-water heat pump are discussed. The heat pump is firstly tested with R134a, to establish the baseline performance, and, then, is tested with the two above-mentioned refrigerants considering the same compressor shaft rotational frequency and the same outlet temperatures of the secondary fluids from the evaporator and the condenser. The obtained results show that, compared to the R134a, the use of R1234yf leads to a reduction of the heating capacity and of the COP up to 9.80% and 7.39% respectively, whereas with the use of R1234ze(E) the capacity reduction achieves a maximum of 33.82% while a COP variation in the range −12.27% to +4.32% is found. A second group of tests is carried out varying the rotational frequency of the compressor shaft with the aim of matching the baseline R134a heating capacity. The results indicate an increase in the shaft rotational frequency up to 16% with R1234yf and up to 50% with R1234ze(E) which, however, leads to a maximum reduction of the heat pump COP respectively equal to 7.38% and to 18.11%.

In the present work, an absorption-compression cascade refrigeration system (ACCRS) has been analyzed theoretically for low temperature cooling applications. It comprises of a triple effect H2O-LiBr series flow vapor absorption refrigeration system in higher temperature section associated with vapor compression refrigeration (VCR) system using R1234yf refrigerant in lower temperature section. The cascade system provides lower temperature i.e. 223.15–263.15 K for freeze drying, pharmaceuticals, chemical and petroleum industry at lower running cost using waste available from the exhaust of gas turbine or steam turbine to run the triple effect vapor absorption refrigeration system which reduces the overall high grade energy (electricity) consumption of the cascade system. Moreover, the use of R1234yf protects the environment from global warming and ozone depletion. Energetic and exergetic analysis have been performed for the parametric investigation of the system. An EES software based computational model has been formulated for the computation of performance parameters. The analysis determines the effect of generator temperature (448.15–473.15 K), absorber temperature (298.15–313.15 K) and evaporator temperature (223.15–263.15 K) on the energetic (COP) and exergetic (exergetic-efficiency, exergy destruction rate and exergy destruction ratio performances of the system. The results illustrate that the electricity savings of triple effect cascade system are 45.84% in comparison to conventional VCR cycle. The COP and exergetic-efficiency of VCR circuit in the cascade system boost up by 85.26% and 85.28% respectively. The COP and exergetic efficiency of triple effect cascade system are higher than that of single and double effect absorption compression cascade refrigeration systems. The system circulation pump and absorber are the sites of lowest and highest irreversibility in comparison to the other system components.

Due to the entry into force in 2014 of the European F-Gas Regulation n° 517/2014 and the subsequent Kigali amendment, the phase-out of the medium and high-GWP refrigerants has speeded up in all refrigeration fields. The effect on the plug-in or stand-alone systems has meant that other environmentally friendly refrigerants must replace the R134a with low or ultra-low GWP maintaining the same operating conditions and reducing the energy consumption. Extended examples of these fluids are the hydrocarbons R600a and R290 and the inorganic fluid R744 (CO2). However, there are other alternatives to the HFCs R152a and R1234yf or the hydrocarbon R1270 that have hardly been analysed and can make a positive contribution to this sector. Accordingly, this work aims to evaluate the behaviour of a commercial beverage cooler experimentally when it is optimised with six alternatives to the HFC R134a: R152a, R1234yf, R290, R1270, R600a and R744. Results demonstrated that fluids R290, R1270, R152a, R744 and R600a reduce the energy of R134a in 27.5%, 26.3%, 13.7%, 3.9% and 1.2%, respectively, while the use of R1234yf increases the energy usage to 4.1%. Funding for open access charge: CRUE-Universitat Jaume I

R134a, one of the most commonly used refrigerants especially for air conditioning (AC) systems, will be banned in automotive air conditioners after 2022 due to a high global warming potential (GWP). R152a and R1234yf are considered as two potential low GWP drop-in alternatives to R134a due to similar thermodynamic properties. In this paper, the performance of R152a, R1234yf, and R134a in an oil-free vapour compression refrigeration (VCR) system is investigated. The absence of oil lubricant enables a wide range of refrigerant selection and highly efficient refrigeration cycle. Experiments for R152a, R1234yf, and R134a were conducted over wide range of operating conditions. The results show that R1234yf is similar to R134a in terms of operating pressure and temperature, but R1234yf has an 11% and 16% deterioration in cooling capacity and coefficient of performance (COP) respectively. The higher volumetric efficiency, adiabatic efficiency and cooling capacity of R152a contributes to a 13% and a 6% higher cooling capacity and COP respectively than that of R134a. At an evaporator temperature of 0 °C, the COP of R152a, R1234yf, and R134a are 2.8, 1.8, and 2.3, respectively. Though flammability restricts the use of R152a in conventional automotive air conditioners, R152a can be considered as a more promising alternative to R134a for oil-free automotive air conditioning than R1234yf due to its high efficiency, low cost, and reasonable safety level benefiting from the absence of oil lubricants.

This work presents experimental critical heat flux (CHF) values for a low environmental impact synthetic refrigerant and their comparison with well-known correlations from scientific literature. Tests were performed with HFO-1234yf in an aluminum heat sink made up of seven mini-channels, each of them 2 mm wide and 1 mm high. The heated length was 25 mm. Experiments have been obtained in a variety of thermodynamic condition: the R1234yf saturation temperatures T sat ranged from 25 up to 65 °C (corresponding to medium-to-high reduced pressures), whilst the mass fluxes G had been fixed to 150 up to 300 kg/m 2 s. The tests have been carried out by increasing the heat dissipated by the boiling refrigerant until the thermal crisis occurred and the corresponding heat flux value was recorded as CHF. The experimental results were finally compared to the well-known correlations of Wojtan et al. [1] , Kuan [2] , Katto-Ohno [3] , Zhang et al. [4] and Anwar et al. [5] to investigate their effectiveness with the present data. The latter correlation was found to better predict the experimental values.

The growing of the energy consumption, in particular from buildings, both residential and commercial has induced a major interest for the analysis of the seasonal performance of heat pumps. The same considerations are effective for the well-known environmental problems related to direct and indirect emissions of carbon dioxide into the atmosphere and the incentives to support energy efficiency. In this work an air to water heat pump working with R290 and HFO1234yf has been modeled and simulated using the software package IMST-ART in order to evaluate the seasonal performance. Two different types of applications were considered: fan coils and radiant heat floor panels. Different types of building are considered. The seasonal performance in heating mode, SCOP, is calculated by coupling the performance of the heat pump in different operative conditions to a heating demand curve, in two different climate zones (average and colder). The results of the simulations show better performance of the heat pump with propane in both climates and applications, which is probably due to the state of current technology of the different components. In particular, the global performance of the compressor working with R1234yf is not yet optimized. At the same time a new design of the evaporator is desirable to reduce the pressure drops with R1234yf.

This paper reports an experimental investigation of the heat transfer performance of the new low-GWP refrigerants, R1234yf and R1234ze(E), during flow boiling heat transfer inside a horizontal high porosity copper foam with 5 Pores Per Inch (PPI). Metal foams are a class of cellular structured materials consisting of a stochastic distribution of interconnected pores; these materials have been proposed as effective solutions for heat transfer enhancement during both single and two-phase heat transfer. R1234yf and R1234ze(E) refrigerants are appealing alternatives of the more traditional R134a by virtue of their negligible values of GWP and normal boiling temperatures close to that of R134a, which make them suitable solution in several different applications, such as: refrigeration and air conditioning and electronic thermal management. This work compares the two-phase heat transfer behaviour of these new HFO refrigerants, studying the boiling process inside a porous medium and permitting to understand their effective heat transfer capabilities. The experimental measurements were carried out by imposing three different heat fluxes: 50, 75, and 100 kW m −2 , at a constant saturation temperature of 30 °C; the refrigerant mass velocity was varied between 50 and 200 kg m −2 s −1 , whilst the mean vapour quality varied from 0.2 to 0.95. The two-phase heat transfer and pressure drop performance of the two new HFO refrigerants is compared against that of the more traditional R134a.

In this paper we present two different analyses of R1234yf and R1234ze(E) as drop-in replacements for R134a in a small power refrigeration system. The first analysis is based on equal evaporation and condensation temperatures before and after the refrigerant replacement. The second analysis is carried out for equal cooling medium conditions in the condenser, so that the transport properties and the heat transfer features in the condenser are considered for the three refrigerants. In order to perform the analyses, a simulation model was developed, that takes into account specific data, characteristics and dimensions of the main components of a small power refrigeration system. The model was validated with experimental data for R134a and later used to predict the behavior with R1234yf and R1234ze(E). Results show that different conclusions may be drawn if the drop-in analysis is carried out for equal condensation temperatures or for equal temperatures of the cooling medium in the condenser, as well as that these results are affected by the condenser design. In general, R1234yf seems as an adequate drop-in refrigerant for R134a, but R1234ze(E) may perform better when an overridden compressor can be used to match the refrigerating system cooling power.

Heat management by means of two-phase mechanically pumped loop (TMPL) possesses promising advantages such as long-distance heat transport, high heat density and good temperature control. Knowledge of the fluid charge has great importance for TMPL system efficiency. The present work is a theoretical/experimental study on the refrigerant charge in TMPL system using R134a and R1234yf refrigerants. The mass of refrigerant in the TMPL system was measured for several cooling capacities. The effects of vapor quality in the evaporator (varying from 0.1 to 1), mass flux (300 kg s−1 m−2 and 400 kg s−1 m−2), and saturation temperature (25 °C and 30 °C) on refrigerant charge in the TMPL were experimentally investigated. About 70 experimental points were analyzed and compared with a theoretical model employing eight different prediction tools for the determination of the void fraction. The best results were obtained by Zivi and Hughmark correlations with mean absolute errors of 12% and 13%, respectively.

This paper presents an experimental analysis of the influence of an internal heat exchanger on the performance of a vapour compression system using R1234yf as a drop-in replacement for R134a. In this work, we compare the energy performance of a monitored vapour compression system using both refrigerants, R134a and R1234yf, with and without the presence of an internal heat exchanger under a wide range of working conditions. A set of experimental tests are carried out varying the condensing temperature, the evaporating temperature and the internal heat exchanger use. From the experimental results, reductions in cooling capacity and COP between 6 and 13% have been observed when R134a is replaced by the drop-in fluid R1234yf, although the presence of an IHX can help to lessen these reductions between 2 and 6%. Finally, the experimental results obtained agree with the theoretical evaluations developed neglecting the pressure drops.

[EN] This paper presents an experimental analysis of a vapor compression system using R1234yf as a drop-in replacement for R134a. In this work, we compare the energy performance of both refrigerants, R134a and R1234yf, in a monitored vapor compression system under a wide range of working conditions. So, the experimental tests are carried out varying the condensing temperature, the evaporating temperature, the superheating degree, the compressor speed, and the internal heat exchanger use. Comparisons are made taking refrigerant R134a as baseline, and the results show that the cooling capacity obtained with R1234yf in a R134a vapor compression system is about 9% lower than that obtained with R134a in the studied range. Also, when using R1234yf, the system shows values of COP about 19% lower than those obtained using R134a, being the minor difference for higher condensing temperatures. Finally, using an internal heat exchanger these differences in the energy performance are significantly reduced., This study was sponsored by Fundacio Caixa Castello-Bancaixa under the project P11B2010-24 "Aplicacion de nuevos refrigerantes con bajo potencial de efecto invemadero en sistemas de frio comercial y climatizacion".

Group contribution methods are used to predict the critical temperatures, critical pressures, critical densities, acentric factors, and ideal gas specific heats at constant pressure for eight fluorinated olefins, namely: R-1225ye(E), R-1225ye(Z), R-1225zc, R-1234ye(E), R-1234yf, R-1234ze(E), R-1234ze(Z), and R-1243zf. For the same eight refrigerants, the Peng–Robinson equation of state is used to predict thermodynamic properties, which are presented in pressure-enthalpy and temperature-entropy state diagrams. To provide the reader with some sense of the predictive capability of the methodology, property predictions for R-134a are compared to known data. Property predictions for R-1234yf are compared, where possible, to the open literature.