Numerical Characterization of the Flow Dynamics and COP Estimation of a Binary Fluid Ejector Ground Source Heat Pump Cooling System

Round 1

Reviewer 1 Report

 

The main objective of the present study is to estimate the COP of an ejector GSHP cooling system using CFD modeling for the entrainment ratio estimation. In addition, a proper selection of binary fluids is performed to improve the efficiency of the binary fluid ejector compared to a conventional single fluid ejector. The topic is important. The results of various CFD modeling are presented. However, identifying the previous research gap related to the numerical characterization of the paper topic needs to be explained. The computation methods, validation, and data verification in this manuscript version are limited. The discussion and analysis need to be more profound.

Therefore, the recommendation for the publication is a major revision, and provide the following comments for correction.

 1.       I would strongly advise the author to add the literature related to the main topic and rewrite their introduction by identifying the previous research gap. Moreover, the paper's novelty could be well stated.

2.       The paper uses a computational simulation to analyze the result. Therefore, the numerical model should be explained in detail, including the figure of computational meshes geometry. Moreover, the numerical setup and boundary condition need to be presented.

3.   The CFD model's limitation should be stated because only the 2D model was used for the analysis.

4.       The grid independence test procedure and results should be presented in detail. The validation of the simulation has been described in detail, including numerical error between the experiment and simulation.

5.        The results and discussion should describe the research's major findings and compare them to previous studies. In addition, the current research area's gaps must be highlighted, and future study directions must be presented.

6.       Position x (m) range is different between schematic view and dimensions in Figure 2 and simulation result in Figure 4,5,6. Please explain why?

7.       The conclusions should be written technically.

Author Response

Please see attached

Author Response File: Author Response.pdf

Reviewer 2 Report

The author presented an estimation of the thermal coefficient of performance for a binary fluid ejector ground source heat pump cooling system. The work lacks novelty and originality. I have the following comments:

 1. The English of the text needs revision. Proofreading by a native speaking is recommended.

2. The abstract should contain the problem, its solution and the main results.

it is recommended that the abstract be rewritten to make appealing for readers.

3. The acronyms must be defined when they are first used.

4. The introduction is very weak and do not explain the problem and the gap in the research and the justification of this work.

5. Summing references in the introduction is not a good way of presenting research work ([1-4], [5-7], [8-12] etc. It is recommended to write at least a statement about the work and what they have achieved so that the author can present the gap and justify the need for this work.

6. The introduction need s improvement. more recent works on the ejector need to be added to show a good literature review.

7. A schematic and a description of the system is missing.

8. There is only two equations !! Is that enough for the thermodynamic analysis of the system? Why do need the shear force? It has to be explained by the author.

9. What is Tbiol? Is it the boiler temperature? A nomenclature is needed for all symbols mentioned in the text.

10. What is the parameter fh? Is it a new parameter? What physical value does it have? HAs it been used previously?

11. The COP is the acronym  for the coefficient of performance and not C.O.P.!

12.  In table 1, why the author did not mention the symbol for the refrigerant. Scientific community got used for the refrigerant symbols (R12, R134a, etc. The chemical formula is not widely used and it might confuse the reader.

13. What is CR in Table 2? Is it compression ratio? Please define before use in the Table.

14. In Figure 4b, is possible to reach Mach number of 4?What would be the supply and back pressures for this case?

15. The differences in the performance as can be seen from figures 4-6 is very minimal. Was worth the investigation?

16. The conclusion as stated by the author "A wide range of primary molecular masses (M1) are considered in the CFD modelling. It is found that M1 affects the flow momentum of the primary jet and thus the entrainment ratio. On the other hand, the shear forces become stronger when the secondary molecular mass increases leading to a decrease in the entrainment ratio. With methanol as the secondary fluid, the mass entrainment ratio presents a peak for M1/M2 ≃ 3 ". This a well known fact for researchers who works with ejectors. A good look into the published literature will show this easily.

 

 

 

 

 

Author Response

Please see attached

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper discusses a numerical study of an ejector used for a binary fluid heat pump. The author investigates the resultant COP for different binary fluid pairs. It appears that the study has been performed well and that the results are valid.

1.    This paper has relatively little to do with ground source heat pumps. Yes, the binary fluid ejector heat pump can be tied to a ground heat exchanger as your condenser, but that’s pretty much where it ends with regards to the contents of this paper. I recommend removing that from the title and making it application-agnostic. Although valid, I think people searching for “ground source heat pump” in the scientific literature are likely not looking for this type of work.

2.     A figure is warranted when describing how these binary fluid heat pumps function. I suggest you add one.

3.     Page 1: “On-site use of natural gas typically yields reductions in primary energy use and GHG emission over electrical appliances, due to large losses in generation and transmission processes for main grid electricity.” Really? Then why is the world transitioning to the electrification of all things? I think this deserves a citation or two if you plan to make this assertion. I’m skeptical of the veracity of this statement without something to back it up.

4.     Figure 2 appears to be nearly identical to Figure 3 in the report by May (https://www.eralberta.ca/wp-content/uploads/2017/05/F101124-MRT-Binary-Fluid-Injector-Final-Report-Public.pdf), yet I don’t see a citation to this report. Perhaps it came from another one of your references. I suggest you cite this report and potentially state that the figure was used with permission.

Author Response

Please see attached

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

There are a lot of improvements in the revised version. I think the paper can be accepted now.

Reviewer 2 Report

The work lacks novelty.