Performance mapping of the R744 ejectors for refrigeration and air conditioning supermarket application: A hybrid reduced-order model

Haida, Michał; Smołka, Jacek; Hafner, Armin; Ostrowski, Ziemowit; Palacz, Michał; Madsen, Kenneth B.; Försterling, Sven; Nowak, Andrzej J.; Banasiak, Krzysztof

doi:10.1016/j.energy.2018.04.088

Cited by 29 publications

(23 citation statements)

References 34 publications

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“…The same expression for the total ejector efficiency was presented by Elbel et al deriving by different approach as shown in Equation (5) [36]. This formula was used in many other literatures, as in [37][38][39]. It was defined as the ratio of the amount of the recovered ejector expansion work rate with maximum possible expansion work rate recovery potential.…”

Section: Ejector Efficiencymentioning

confidence: 98%

CFD Based Design for Ejector Cooling System Using HFOS (1234ze(E) and 1234yf)

Elbarghthi

Mohamed

et al. 2020

Energies

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The field of computational fluid dynamics has been rekindled by recent researchers to unleash this powerful tool to predict the ejector design, as well as to analyse and improve its performance. In this paper, CFD simulation was conducted to model a 2-D axisymmetric supersonic ejector using NIST real gas model integrated in ANSYS Fluent to probe the physical insight and consistent with accurate solutions. HFOs (1234ze(E) and 1234yf) were used as working fluids for their promising alternatives, low global warming potential (GWP), and adhering to EU Council regulations. The impact of different operating conditions, performance maps, and the Pareto frontier performance approach were investigated. The expansion ratio of both refrigerants has been accomplished in linear relationship using their critical compression ratio within ±0.30% accuracy. The results show that R1234yf achieved reasonably better overall performance than R1234ze(E). Generally, by increasing the primary flow inlet saturation temperature and pressure, the entrainment ratio will be lower, and this allows for a higher critical operating back pressure. Moreover, it was found out that increasing the degree of superheat for inlet primary flow by 25 K improved the entrainment ratio by almost 20.70% for R1234yf. Conversely, increasing the degree of superheat to the inlet secondary flow has a relativity negative impact on the performance. The maximum overall ejector efficiency reached was 0.372 and 0.364 for R1234yf and R1234ze(E) respectively. Comparing the results using ideal gas model, the ejector entrainment ratio was overestimated up to 50.26% for R1234yf and 25.66% for R1234ze(E) higher than using real gas model. systems relying on fossil fuels and the use of harmful substances such as chlorofluorocarbons (CFCs) as refrigerants. In fact, the emissions from these systems also contribute to ozone depletion which is most likely to increase the demand for air-conditioning, especially for thermal comfort [2].Compared with conventional systems, ejector refrigeration systems (ERS) are more attractive, especially as we become more energy conscious. ERS come with advantages such as simple mode of function, lack of moving parts in construction, low cost, long lifespan, in addition to simplicity of installation and maintenance. This refrigeration system utilizes an ejector, generator and a liquid pump in place of the compressor which is electricity driven [3]. For a low-grade heat source, the liquid pump may consume up to 1% of the supplied heat to the ejector system. Compared to other conventional systems of the same refrigerating capacity, the ejector system may consume only one fifth of electricity consumed by the other systems [4,5].Coefficient of performance (COP) is one of the main parameters for measuring ejector efficiency. The cooling systems of the refrigeration system may be analyzed from the COP. There exists a healthy relationship between the COP and the entrainment ratio in ejector cooling systems such that systems with high COP have high entrainme...

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Section: Ejector Efficiencymentioning

confidence: 98%

CFD Based Design for Ejector Cooling System Using HFOS (1234ze(E) and 1234yf)

Elbarghthi

Mohamed

et al. 2020

Energies

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“…Some miscellaneous theoretical cycles of the two-phase ejector are summarized in Table 8. Recently, Haida et al [197] proposed a performance mapping of four CO 2 ejectors installed in a multi-ejector module to be integrated with supermarket refrigeration systems. The proposed model was generated by use of experimental data together with CFD model results.…”

Section: Theoretical Studiesmentioning

confidence: 99%

Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors

et al. 2019

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Two-phase ejectors play a major role as refrigerant expansion devices in vapor compression systems and can find potential applications in many other industrial processes. As a result, they have become a focus of attention for the last few decades from the scientific community, not only for the expansion work recovery in a wide range of refrigeration and heat pump cycles but also in industrial processes as entrainment and mixing enhancement agents. This review provides relevant findings and trends, characterizing the design, operation and performance of the two-phase ejector as a component. Effects of geometry, operating conditions and the main developments in terms of theoretical and experimental approaches, rating methods and applications are discussed in detail. Ejector expansion refrigeration cycles (EERC) as well as the related theoretical and experimental research are reported. New and other relevant cycle combinations proposed in the recent literature are organized under theoretical and experimental headings by refrigerant types and/or by chronology whenever appropriate and systematically commented. This review brings out the fact that theoretical ejector and cycle studies outnumber experimental investigations and data generation. More emerging numerical studies of two-phase ejectors are a positive step, which has to be further supported by more validation work.

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“…The numerical model of the ejector used in this paper is a hybrid ROM of the R744 two-phase ejector taken from the scientific work done by Haida et al [32]. The aforementioned model was developed based on a POD approximation of the CFD results and experimental data.…”

Section: A Hybrid Reduced-order Modelmentioning

confidence: 99%

“…The CFD results used to build the hybrid ROM were performed using the modified HRM [27] within the operating regime presented in Figure 2 with a defined pressure difference step of 1 bar and a temperature difference step of 5 K. Therefore, the total number of the CFD points was 5380, which were combined with approximately 200 experimental data points to generate the hybrid ROM. Then, the hybrid ROM was validated for all two-phase ejectors installed in the multi-ejector module [32]. The use of experimental data with the CFD results to generate the hybrid ROM allowed the prediction of the MFR of both nozzles with an accuracy level within ±1% at each validated point.…”

Section: A Hybrid Reduced-order Modelmentioning

confidence: 99%

“…The single case computational time of ROM was shown to be below 0.05 s, which allows its utilisation in dynamic simulations. The low-order model of the R744 two-phase ejector was also enhanced by hybrid combination of the CFD results together with the experimental data by Haida et al [32]. The hybrid ROM maintained high accuracy and fast simulations at a very wide operational envelope for the R744 Heat, Ventilation, Air-Conditioning and Refrigeration (HVAC&R)supermarket system.…”

Section: Introductionmentioning

confidence: 99%

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An Object-Oriented R744 Two-Phase Ejector Reduced-Order Model for Dynamic Simulations

et al. 2019

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The object-oriented two-phase ejector hybrid reduced-order model (ROM) was developed for dynamic simulation of the R744 refrigeration system. OpenModelica software was used to evaluate the system’s performance. Moreover, the hybrid ROM results were compared to the results given by the non-dimensional and one-dimensional mathematical approaches of the R744 two-phase ejector. Accuracy of all three ejector models was defined through a validation procedure for the experimental results. Finally, the dynamic simulation of the hybrid ROM ejector model integrated with the R744 refrigeration system was presented based on the summer campaign at three different climate zones: Mediterranean, South American and South Asian. The hybrid ROM obtained the best prediction of ejector mass flow rates as compared with other ejector models under subcritical and transcritical operating conditions. The dynamic simulations of the R744 ejector-based system indicated the ejector efficiency variations and the best efficiency at the investigated climate zones. The coefficient of performance (COP) varied from 2.5 to 4.0 according to different ambient conditions. The pressure ratio of 1.15 allowed a more stabilised system during the test campaign with an ejector efficiency from 20% to over 30%.

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Performance mapping of the R744 ejectors for refrigeration and air conditioning supermarket application: A hybrid reduced-order model

Cited by 29 publications

References 34 publications

CFD Based Design for Ejector Cooling System Using HFOS (1234ze(E) and 1234yf)

CFD Based Design for Ejector Cooling System Using HFOS (1234ze(E) and 1234yf)

Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors

An Object-Oriented R744 Two-Phase Ejector Reduced-Order Model for Dynamic Simulations

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