# A Novel Generator Design Utilised for Conventional Ejector Refrigeration Systems

^{*}

## Abstract

**:**

_{2}transcritical refrigeration systems have inherently high working pressures and discharge temperatures, providing a large volumetric heating capacity. In the current research, the heat ejected from the CO

_{2}gas cooler was proposed as a driving heating source for the compression ejector system, representing the energy supply for the generator in a combined cycle. The local design approach was investigated for the combined plate-type heat exchanger (PHE) via Matlab code integrated with the NIST real gas database. HFO refrigerants (1234ze(E) and 1234yf) were selected to serve as the cold fluid on the generator flowing through three different phases: subcooled liquid, a two-phase mixture, and superheated vapour. The study examines the following: the effectiveness, the heat transfer coefficients, and the pressure drop of the PHE working fluids under variable hot stream pressures, cold stream flow fluxes, and superheated temperatures. The integration revealed that the cold fluid mixture phase dominates the heat transfer coefficients and the pressure drop of the heat exchanger. By increasing the hot stream inlet pressure from 9 MPa to 12 MPa, the cold stream two-phase convection coefficient can be enhanced by 50% and 200% for R1234yf and R1234ze(E), respectively. Conversely, the cold stream two-phase convection coefficient dropped by 17% and 37% for R1234yf and R1234ze(E), respectively. The overall result supports utilising the ejected heat from the CO

_{2}transcritical system, especially at high CO

_{2}inlet pressures and low cold channel flow fluxes. Moreover, R1234ze(E) could be a more suitable working fluid because it possesses a lower pressure drop and bond number.

## 1. Introduction

_{2}(denoted R744) transcritical refrigeration systems, and the compression ejector, where it replaces the compressor [1]. For the compression ejector refrigeration cycle (CERC), the generator’s heat source type is essential for improving the cycle coefficient of performance. Several studies considered different low-grade heat sources used to drive the cycle and perform the generation process, such as solar collectors, an absorption cycle, geothermal energy, and waste heat from power plants [2,3,4,5,6,7]. However, multiple eco-friendly solutions have been developed in the refrigeration sector, and the market is witnessing an increase in commercial CO

_{2}refrigeration systems worldwide. Therefore, utilising the gas cooler heat ejected at high discharge temperatures from the transcritical cooling system can represent an energy source for the compression ejector refrigeration system, which has not been identified in the open literature as a solution.

_{2}is used as a reference [23]. At present, the general allowable values of ODP and GWP are less than 0.4 and 2500, respectively [24,25]. The used HFOs and the R744 have values lower than the allowable ones with zero ODP and GWP < 4 [26,27,28]. Therefore, the early studies of evaporation heat transfer in PHEs were performed on refrigerants with high ODP and GWP [29,30,31]. In contrast, the recent studies have focused more on environmentally friendly refrigerants due to the restrictions imposed by the international regulations on the allowable ODP and GWP [25]. Huang et al. [32] presented correlations for two-phase heat transfer coefficients and the pressure drop of R134a and R507 with three different chevron angle combinations (28, 28/60, and 60). The mean absolute errors of the proposed correlations were 7.3% and 6.7% for the heat transfer coefficients and the frictional pressure drop, respectively. Longo and collaborators studied recently released HFOs [25,33,34,35] and investigated the heat transfer coefficients and frictional pressure drop during the evaporation process for different mass and heat fluxes, saturation temperatures, and outlet conditions. Their most essential conclusion was that the heat transfer coefficients are slightly dependent on the saturation temperature. The result indicated that the frictional pressure drop has a linear dependence on the refrigerant’s kinetic energy per unit volume and R1234yf has lower heat transfer coefficients and a lower frictional pressure drop than R134a. Moreover, R1234ze(e) substitutes for R134a and R1234yf as they have similar heat transfer coefficients and a slightly lower frictional pressure drop.

_{2}is preferably used for refrigeration systems because of its low critical temperature and pressure, which overcome the inefficiency problems [36]. Heat transfer coefficients and the pressure drop of CO

_{2}have been analysed in many types of research. However, most of the mentioned studies in the literature were applied to channel or tube heat exchangers [37]. In contrast, Zendehboudi et al. [12] experimentally investigated supercritical CO

_{2}as a hot fluid in brazed PHEs of a tri-partite gas cooler. The authors found that the correlations mentioned in the literature for the Nusselt number were not applicable for their case. These correlations are either based on a different supercritical fluid or derived for a channel or tube heat exchanger. Moreover, their results proved that buoyancy forces significantly influenced the heat transfer process and they proposed a new correlation for the Nusselt number with a relative error of 11.61% and 12.82% for a one-pass and a two-pass PHE, respectively. Therefore, a correlation to estimate the fanning friction coefficient and the Nusselt number of CO

_{2}should be chosen carefully since the thermophysical properties of R744 change nonlinearly in the supercritical region [37].

_{2}transcritical system as the driving energy source based on a local analysis. The two cycles were emphasised and discussed by Elbarghthi et al. [38,39,40]. Matlab software was used to develop the PHE analytical model and integrated the NIST database for real gas properties [41]. The supercritical CO

_{2}represented the hot stream in the heat exchanger, while two cold streams were studied and compared as the working fluids (R1234yf and R1234ze(E)) flowing from subcooled liquid to superheated vapour. Moreover, the total pressure drop, Nusselt numbers, Reynold numbers, and effectiveness were determined and are discussed at various channel mass fluxes, superheating temperatures, and plate sizes.

## 2. System Description

_{2}as the hot working fluid that supplies the ejected heat to the generator from the refrigeration cycle as the heat sink. The generator side uses HFO refrigerants (1234ze(E) and 1234yf) for three different phases of flow: subcooled liquid, a two-phase mixture, and superheated vapour.

- the heat exchanger operated under steady-state conditions and was considered as one-pass counterflow;
- heat losses to the environment are negligible;
- the maldistribution phenomenon inside the PHE was neglected;
- for the cold stream with a phase change, the plate was divided into three portions;
- a linear temperature difference was considered between the two flow streams;
- the cold stream was modelled at a saturation temperature of 87 °C and an inlet temperature of 25 °C;
- effectiveness was estimated using the ϵ-NTU method; and
- all the thermophysical properties were estimated based on the NIST fluid database (REFPROP v.10).

_{2}refrigeration cycle, a semi-hermetic reciprocating compressor model, manufactured by the Dorin company (Dorin CD1400H), was employed [46]. The compressor’s electric power supply and the discharge mass flow rate were determined according to polynomial functions provided by the manufacturer at a nominal frequency of 50 Hz.

## 3. Theoretical Analysis

#### 3.1. Data Reduction

_{2}side of the setup. This is because the R744’s thermophysical properties change nonlinearly with temperature. In comparison, the LMTD considers that both cold side fluids have a constant specific heat. Therefore, the actual temperature difference was estimated as mentioned by Zendehboudi et al. [10] as follows:

#### 3.2. Calculation Procedures

- The inputs are the hot stream pressure (${\text{P}}_{\text{h}}$) and the superheat difference ($\mathrm{\u2206}{\text{T}}_{\text{sh},\text{c}}$). Afterwards, the saturation pressure (${\text{P}}_{\text{c}}$) was calculated according to the refrigerant name ($\text{Ns}$) at 87 °C.
- The enthalpies were estimated for all artificial inlets and outlets of the cold stream.
- The total heat rate (${\text{Q}}_{\text{k}}$) was evaluated for each artificial section according to the enthalpy difference multiplied by the mass flow rate of the cold stream, Equation (1).
- The inlet enthalpy and the temperature of the hot stream (${\text{H}}_{\text{h}3\text{i}}$ and ${\text{T}}_{\text{h}3\text{o}}$ ,respectively) were estimated using the compressor model and the hot stream pressure (${\text{P}}_{\text{h}}$). Subsequently, the other enthalpies and temperatures were evaluated using the corresponding heat rate (${\text{Q}}_{\text{k}}$) from each artificial section.

- If the outlet temperature of the hot stream’s second section (${\text{T}}_{\text{h}2\text{o}}$) is higher than the cold stream saturation temperature (${\text{T}}_{\text{c}.\text{sat}}$), then the required dimensionless numbers of each stream can be evaluated directly except for the boiling number (Bo), as it requires information on the heat flux between the hot and cold streams (${\text{q}}_{\text{k}}$). Based on Amalfi’s review [22], the average between the maximum and the minimum Boiling number was taken as an initial guess with a value of 0.002.
- In the next step, the overall heat transfer coefficient (${\text{U}}_{\text{k}}$), the heat flux (${\text{q}}_{\text{k}}$), the number of transfer units (NTU), and the effectiveness (${\mathsf{\epsilon}}_{\text{k}}$) will be estimated. When all the data are calculated, the boiling number (Bo) will be updated according to the new heat flux (${\text{q}}_{\text{k}}$) as well as the overall heat transfer coefficient (${\text{U}}_{\text{k}}$), the number of transfer units (NTU), and the effectiveness (${\mathsf{\epsilon}}_{\text{k}}$). Then, the mass flow rate (${\dot{\text{m}}}_{\text{c}}$) will be updated.
- Alternatively, if the outlet temperature of the hot stream’s second section (${\text{T}}_{\text{h}2\text{o}}$) is lower, then the calculation will be stopped for the current cold stream mass flow rate, and the name (Ns) will be updated to the next step.
- Finally, the output is stored as the effectiveness, the convection coefficients, and the pressure drop matrices at various channel mass fluxes.

## 4. Discussion

#### 4.1. Effect of Hot Stream Inlet Pressure

_{2}was operating in the supercritical region. This is explained by the idea that the CO

_{2}temperature is relatively high and far from the critical value at which the thermophysical properties change linearly in this region.

#### 4.2. Effect of Superheat

#### 4.3. Effect of Heat Exchanger Size

_{2}temperature is relatively high and far from the critical one. In addition, the peak of both HFOs is more apparent than the one illustrated in Figure 8 because of the wider range of the y-axis. This peak represents the point at which the viscosity changes its tendency from a decrease to in increase in the supercritical region. Additionally, it was observed for the Reynolds number at the same temperature. The hot stream convection coefficients were 20% higher for size A due to the difference in the Grashof number and the Reynolds number since size A has a higher hot channel mass flux. We maintained an identical hot channel mass flux for both sizes, which was possible because the hot stream flow rate was estimated using the compressor model. Moreover, the number of plates was chosen to maintain equivalent cold channel mass fluxes for both sizes.

_{2}temperature is higher than the HFO saturation temperature. Once a good flow range is specified, a stable and smooth variation in the convection coefficient would be observed for the three different phases, resulting in a smooth operation of the overall combined cycle. For the gas-cooler side, the relatively high temperature of the CO

_{2}negates the nonlinearity in the CO

_{2}’s properties, making it a suitable driving heat source for the generator in the combined cycle.

## 5. Conclusions

_{2}transcritical refrigeration systems have inherently high working pressures and discharge temperatures, providing a large volumetric heating capacity. Therefore, the heat ejected from the CO

_{2}gas cooler was proposed to be utilised as a driving heating source for the compression ejector system, representing the energy supply for the generator in a combined cycle. The study was based on the local theoretical approach to a brazed plate heat exchanger. The theoretical model was constructed by a Matlab code with analysis procedures illustrated through flow chart stages. The main parameters for the assessment of the heat exchanger, including the convection coefficients, the effectiveness, and the pressure drops, were evaluated and discussed at various CO

_{2}inlet pressures, different cold-side refrigerant superheat temperatures, and two different plate sizes.

- when increasing the hot stream inlet pressure from 9 to 12 MPa, the two-phase convection coefficients of the HFOs increase significantly with a range of 20–50% and 20–200% for R1234yf and R1234ze(E), respectively;
- increasing the cold stream superheat temperature difference from 5 K to 20 K allows the two-phase convection coefficients of the HFOs to increase steeply with a value of 1–20% at low cold channel flow fluxes;
- the two-phase convection coefficient is significantly influenced by the boiling and bond numbers. The working fluid type affects the bond number, while the heat flux dominates the boiling number;
- increasing the plate size influenced both the two-phase convection coefficient and the effectiveness significantly. The two-phase convection coefficients of the HFOs increased with a range of 1–20% and 1–50% for R1234yf and R1234ze(E), respectively. In contrast, the effectiveness increased by 10% for R1234yf and 5% for R1234ze(E);
- the two-phase convection coefficient dominates the frictional pressure drop as the flow is turbulent even at a low vapor quality.

_{2}transcritical cycle operates at a relatively high temperature far from the critical point, causing a smooth variation in the thermophysical properties. This effect provides stable operation and distinguishes the use of supercritical CO

_{2}as a heat source.

_{2}transcritical cycle can be used efficiently as a heat source for the CERC generator since the heat transfer coefficients, the effectiveness, and the pressure drops have smooth variations at different flow fluxes, superheat temperature differences, and plate sizes.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Nomenclature

Units and Symbols | |

$\dot{\text{m}}$ | Mass flow rate (Kg/m^{2}) |

A | Area (m^{2}) |

b | Mean channel gap (m) |

Bd | Bond number (-) |

Bo | Boiling number (-) |

C | Heat capacity (KW/K) |

Cp | Specific heat (Kj/Kg.K) |

D | Diameter (m) |

f | Fanning friction coefficient (-) |

F | Fouling Factor (m/s^{2}) |

g | Gravity acceleration (m/s^{2}) |

G | Mass flux (Kg/m^{2}·s) |

Gr | Grashof number (-) |

H | Enthalpy (Kj/Kg) |

I | Enthalpy of vapourization (Kj/Kg) |

h | Convection coefficient (-) |

L | Effective flow length (m) |

NTU | Number of transfer units (-) |

Nu | Nusselt number (-) |

p | Plate pitch (m) |

P | Pressure (MPa) |

PHE | Plate heat exchanger (-) |

Pr | Prandtl number (-) |

q | Heat flux (KW/ m^{2}) |

Q | Heat rate (KW) |

Re | Reynolds number (-) |

t | Thickness (m) |

W | Plate width (m) |

Greek symbols | |

∅ | Enlargement factor (-) |

µ | Dynamic Viscosity (kg/m.s) |

β | Corrugation Angle (°) |

Δ | Difference (-) |

ε | Effectiveness (-) |

κ | Conductivity (-) |

λ | Corrugation Pitch (kg/m^{3}) |

ρ | Density (kg/m^{3}) |

$\mathsf{\sigma}$ | Surface tension. (N/m) |

Subscripts | |

* | Reduced |

a | Martin first constant |

1 | First partition |

b | Martin second constant |

2 | Second partition |

3 | Third partition |

c | Cold |

ch | Channel |

eff | Effective |

h | Hot |

hy | Hydraulic |

i | Inlet |

k | Artificial partition index |

l | Liquid |

lo | Liquid only |

lv | Liquid vapour difference |

m | Mean |

o | Outlet |

p | Plate |

s | Refrigerant type index |

sat | Saturated |

SH | Superheated |

sp | Single phase |

tp | Two phase |

v | Vapour |

vo | Vapour only |

w | Wall |

## References

- Tashtoush, B.M.; Al-Nimr, M.A.; Khasawneh, M.A. A comprehensive review of ejector design, performance, and applications. Appl. Energy
**2019**, 240, 138–172. [Google Scholar] [CrossRef] - Besagni, G.; Inzoli, F. Computational fluid-dynamics modeling of supersonic ejectors: Screening of turbulence modeling approaches. Appl. Therm. Eng.
**2017**, 117, 122–144. [Google Scholar] [CrossRef] - Chen, X.; Omer, S.; Worall, M.; Riffat, S. Recent developments in ejector refrigeration technologies. Renew. Sustain. Energy Rev.
**2013**, 19, 629–651. [Google Scholar] [CrossRef] - Charalambous, P.G.; Maidment, G.G.; Kalogirou, S.A.; Yiakoumetti, K. Photovoltaic thermal (PV/T) collectors: A review. Appl. Therm. Eng.
**2007**, 27, 275–286. [Google Scholar] [CrossRef] [Green Version] - Nehdi, E.; Kairouani, L.; Elakhdar, M. A solar ejector air-conditioning system using environment-friendly working fluids. Int. J. Energy Res.
**2008**, 32, 1194–1201. [Google Scholar] [CrossRef] - Spallina, V.; Romano, M.C.; Chiesa, P.; Lozza, G. Integration of Coal Gasification and Packed Bed CLC process for High Efficiency and Near-zero Emission Power Generation. Energy Procedia
**2013**, 37, 662–670. [Google Scholar] [CrossRef] - Li, C.; Wang, R.; Lu, Y. Investigation of a novel combined cycle of solar powered adsorption–ejection refrigeration system. Renew. Energy
**2002**, 26, 611–622. [Google Scholar] [CrossRef] - Amalfi, R.L.; Vakili-Farahani, F.; Thome, J.R. Flow boiling and frictional pressure gradients in plate heat exchangers. Part 1: Review and experimental database. Int. J. Refrig. Rev. Int. Du Froid.
**2016**, 61, 166–184. [Google Scholar] [CrossRef] - Zohuri, B. Compact Heat Exchangers; Springer International Publishing: Cham, Switzerland, 2017; Volume 58. [Google Scholar]
- Kakaç, S.; Liu, H.; Pramuanjaroenkij, A. Heat Exchangers: Selection, Rating, and Thermal Design, 2nd ed.; Taylor & Francis: Abingdon, UK, 2002. [Google Scholar]
- Zendehboudi, A.; Ye, Z.; Hafner, A.; Andresen, T.; Skaugen, G. Heat transfer and pressure drop of supercritical CO
_{2}in brazed plate heat exchangers of the tri-partite gas cooler. Int. J. Heat Mass Transf.**2021**, 178, 121641. [Google Scholar] [CrossRef] - Amalfi, R.L. Two-Phase Heat Transfer Mechanisms within Plate Heat Exchangers:Experiments, Modeling and Simulations; EPFL: Lausanne, Switzerland, 2016. [Google Scholar]
- Kumar, H. The Plate Heat Exchanger: Construction and Design. In Proceedings of the First U.K. National Conference on Heat Transfer, Leeds, UK, 3–5 July 1984; pp. 1275–1288. [Google Scholar]
- Martin, H. A theoretical approach to predict the performance of chevron-type plate heat exchangers. Chem. Eng. Process. Process. Intensif.
**1996**, 35, 301–310. [Google Scholar] [CrossRef] - Focke, W.; Zachariades, J.; Olivier, I. The effect of the corrugation inclination angle on the thermohydraulic performance of plate heat exchangers. Int. J. Heat Mass Transf.
**1985**, 28, 1469–1479. [Google Scholar] [CrossRef] - Hayes, N.; Jokar, A.; Ayub, Z.H. Study of carbon dioxide condensation in chevron plate exchangers; heat transfer analysis. Int. J. Heat Mass Transf.
**2011**, 54, 1121–1131. [Google Scholar] [CrossRef] - Hayes, N.; Jokar, A.; Ayub, Z.H. Study of carbon dioxide condensation in chevron plate exchangers; pressure drop analysis. Int. J. Heat Mass Transf.
**2012**, 55, 2916–2925. [Google Scholar] [CrossRef] - Jokar, A.; Hosni, H.M.; Eckels, S.J. Dimensional analysis on the evaporation and condensation of refrigerant R-134a in minichannel plate heat exchangers. Appl. Thermal Eng.
**2006**, 26, 2287–2300. [Google Scholar] [CrossRef] - Lockhart, R.W.; Martinelli, R.C. Proposed Correlation of Data for Isothermal Two-Phase, Two-Component Flow in Pipes. Chem. Eng. Prog.
**1949**, 45, 9–48. [Google Scholar] - Chisholm, D. A theoretical basis for the Lockhart-Martinelli correlation for two-phase flow. Int. J. Heat Mass Transf.
**1967**, 10, 1767–1778. [Google Scholar] [CrossRef] - Amalfi, R.L.; Vakili-Farahani, F.; Thome, J.R. Flow boiling and frictional pressure gradients in plate heat exchangers. Part 2: Comparison of literature methods to database and new prediction methods. Int. J. Refrig. Rev. Int. Du Froid.
**2016**, 61, 185–203. [Google Scholar] [CrossRef] [Green Version] - Finlayson-Pitts, B.J.; Pitts Jr., J.N. Scientific Basis for Control of Halogenated Organics. Chem. Up. Low. Atmos.
**2000**, 727–761. [Google Scholar] [CrossRef] - Vallero, D.A. Air pollution calculations: Quantifying pollutant formation, transport, transformation, fate and risks; Elsevier: Amsterdam, The Netherlands, 2019; pp. 377–428. [Google Scholar]
- Wuebbles, D.J. Ozone Depletion and Related Topics: Ozone Depletion Potentials, Encyclopedia of Atmospheric Sciences, 2nd ed.; Elsevier: Amsterdam, The Netherlands, 2015; Volume 4, pp. 364–369. [Google Scholar] [CrossRef]
- Longo, G.A.; Mancin, S.; Righetti, G.; Zilio, C. HFC32 vaporisation inside a Brazed Plate Heat Exchanger (BPHE): Experimental measurements and IR thermography analysis. Int. J. Refrig.
**2015**, 57, 77–86. [Google Scholar] [CrossRef] - ASHRAE. 2018 ASHRAE Handbook-Refrigeration; ASHRAE: Atlanta, GA, USA, 2018. [Google Scholar]
- Nekså, P.; Walnum, H.T.; Hafner, A. Keynote: CO
_{2}—A refrigerant from the past with prospects of being one of the main refrigerants in the futurer. In Proceedings of the 9th IIR-Gustav Lorentzen Conference on Natural Working Fluids, Sydney, Australia, 14–15 April 2010. [Google Scholar] - United Nations Development Programme. Montreal Protocol on Substances That Deplete the Ozone Layer. 20 Years of Success; United Nations Development Programme: New York, NY, USA, 2007; p. 50. [Google Scholar]
- Karayiannis, T. EHD boiling heat transfer enhancement of R123 and R11 on a tube bundle. Appl. Therm. Eng.
**1998**, 18, 809–817. [Google Scholar] [CrossRef] - Aprea, C.; Greco, A.; Maiorino, A. An experimental evaluation of the greenhouse effect in the substitution of R134a with CO 2. Energy
**2012**, 45, 753–761. [Google Scholar] [CrossRef] - Kruse, H. European research concerning CFC and HCFC substitution. Int. J. Refrig.
**1994**, 17, 149–155. [Google Scholar] [CrossRef] - Huang, J.; Sheer, T.J.; Bailey-McEwan, M. Heat transfer and pressure drop in plate heat exchanger refrigerant evaporators. Int. J. Refrig.
**2012**, 35, 325–335. [Google Scholar] [CrossRef] - Longo, G. Vaporisation of the low GWP refrigerant HFO1234yf inside a brazed plate heat exchanger. Int. J. Refrig.
**2012**, 35, 952–961. [Google Scholar] [CrossRef] - Longo, G.A.; Mancin, S.; Righetti, G.; Zilio, C. HFO1234ze(E) vaporisation inside a Brazed Plate Heat Exchanger (BPHE): Comparison with HFC134a and HFO1234yf. Int. J. Refrig.
**2016**, 67, 125–133. [Google Scholar] [CrossRef] - Longo, G.A.; Mancin, S.; Righetti, G.; Zilio, C. Boiling of the new low-GWP refrigerants R1234ze(Z) and R1233zd(E) inside a small commercial brazed plate heat exchanger. Int. J. Refrig.
**2019**, 104, 376–385. [Google Scholar] [CrossRef] - Lorentzen, G.; Pettersen, J. A new, efficient and environmentally benign system for car air-conditioning. Int. J. Refrig.
**1993**, 16, 4–12. [Google Scholar] [CrossRef] - Ehsan, M.M.; Guan, Z.; Klimenko, A. A comprehensive review on heat transfer and pressure drop characteristics and correlations with supercritical CO 2 under heating and cooling applications. Renew. Sustain. Energy Rev.
**2018**, 92, 658–675. [Google Scholar] [CrossRef] - Elbarghthi, A.F.; Hafner, A.; Banasiak, K.; Dvorak, V. An experimental study of an ejector-boosted transcritical R744 refrigeration system including an exergy analysis. Energy Convers. Manag.
**2021**, 238, 114102. [Google Scholar] [CrossRef] - Elbarghthi, A.F.; Mohamed, S.; Nguyen, V.V.; Dvorak, V. CFD Based Design for Ejector Cooling System Using HFOS (1234ze(E) and 1234yf). Energies
**2020**, 13, 1408. [Google Scholar] [CrossRef] [Green Version] - Elbarghthi, A.F.; Dvorak, V.; Hafner, A.; Banasiak, K. The potential impact of the small-scale ejector on the R744 transcritical refrigeration system. Energy Convers Manag.
**2021**, 249, 114860. [Google Scholar] [CrossRef] - Lemmon, E.; Huber, M.; McLinden, M. NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 9.1.; Natl Std. Ref. Data Series (NIST NSRDS); National Institute of Standards and Technology: Gaithersburg, MD, USA, 2013. [Google Scholar]
- The European Parliament and the Council of the European Union. REGULATION (EU) No 517/2014. Off. J. Eur. Union
**2014**, 57, 195–230. Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=uriserv:OJ.L_.2014.150.01.0001.01.ENG&toc=OJ:L:2014:150:TOC (accessed on 15 November 2021). - Minor, B.; Spatz, M. HFO-1234yf Low GWP Refrigerant Update. In Proceedings of the Purdue University International Refrigeration and Air Conditioning Conference, West Lafayette, IN, USA, 15–17 July 2008; Pap. No. 937; pp. 1–8. [Google Scholar]
- Kracik, J.; Dvorak, V.; Van, V.N.; Śmierciew, K. Experimental and Numerical Study on Supersonic Ejectors Working with R-1234ze(E). EPJ Web Conf.
**2018**, 180, 02047. [Google Scholar] [CrossRef] - Smierciew, K.; Gagan, J.; Butrymowicz, D.; Łukaszuk, M.; Kubiczek, H. Experimental investigation of the first prototype ejector refrigeration system with HFO-1234ze(E). Appl. Therm. Eng.
**2017**, 110, 115–125. [Google Scholar] [CrossRef] - Dorin Software Version: 20.12. 2020. Available online: https://www.dorin.com/en/Software/ (accessed on 31 August 2021).
- Incropera, F.P. Fundamentals of Heat and Mass Transfer; John Wiley & Sons, Inc.: Hoboken, NJ, USA, 2006. [Google Scholar]

**Figure 2.**Schematic view of the chevron plate heat exchanger with the basic dimensions on the left side and a photograph of the two sizes on the right side.

**Figure 5.**Cold stream liquid-phase and gas-phase convection coefficients at various cold channel mass fluxes.

**Figure 6.**Cold stream liquid-phase and gas-phase convection coefficients at various cold channel mass fluxes.

**Figure 12.**Cold stream two-phase convection coefficient at various cold channel mass fluxes and different superheat temperature differences.

**Figure 13.**Effectiveness at various cold channel mass fluxes and different superheating temperatures.

**Figure 14.**Cold stream two-phase convection coefficient at various cold channel mass fluxes and different plate sizes.

**Figure 15.**Hot stream convection coefficient at different plate sizes: size A (marked with solid lines) and size B (marked with dashed lines) at various mean hot stream temperatures.

**Figure 16.**Effectiveness at different plate sizes: size A (marked with solid lines) and size B (marked with dashed lines) at various cold channel mass fluxes.

Geometry Parameters | Plate Size | |
---|---|---|

PHE#A | PHE#B | |

Effective flow length, L (mm) | 485 | 250 |

Plate thickness t_p (mm) | 0.60 | 0.60 |

Port diameter D_p (mm) | 55 | 30 |

Corrugation angle, β (°) | 60 | 60 |

Plate Pitch, P (mm) | 2.8 | 2.50 |

Mean Channel Gap, b (mm) | 2.2 | 1.90 |

Plate width, W (mm) | 245 | 95 |

Corrugation pitch, λ (mm) | 6.80 | 6.80 |

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Elbarghthi, A.F.A.; Hdaib, M.Y.; Dvořák, V.
A Novel Generator Design Utilised for Conventional Ejector Refrigeration Systems. *Energies* **2021**, *14*, 7705.
https://doi.org/10.3390/en14227705

**AMA Style**

Elbarghthi AFA, Hdaib MY, Dvořák V.
A Novel Generator Design Utilised for Conventional Ejector Refrigeration Systems. *Energies*. 2021; 14(22):7705.
https://doi.org/10.3390/en14227705

**Chicago/Turabian Style**

Elbarghthi, Anas F. A., Mohammad Yousef Hdaib, and Václav Dvořák.
2021. "A Novel Generator Design Utilised for Conventional Ejector Refrigeration Systems" *Energies* 14, no. 22: 7705.
https://doi.org/10.3390/en14227705