Precision Ventilation for an Open-Plan Office: A Study of Variable Jet Interaction between Two Active Chilled Beams

Round 1

Reviewer 1 Report

The authors have presented on how Jetcone adjustment of active chilled beams (ACBs) affect air velocity and temperatures for precision ventilation in an open-plan office.

Major revision is recommended based on the following comments:

The theoretical framework/equations for determining the predicted mean vote (PMV) should be presented in the methodology section. It is unclear how the authors have computed the PMV and presented results in section 3.3 (PMV-PPD Calculations). The authors would also need to clearly present all the variables which were used to compute the PMV.

The methodology for the CFD simulation has to be explained very well. For CFD studies, it is important to show the methodology for grid independence study. The results should also demonstrate that your CFD solution does not depend on the grid size.

How did you measure the real-life response (thermal comfort), since you used electric bulbs to represent the occupants (human beings)? Explain how you were able to measure the thermal comfort – which is a state of mind of the occupant, if electric bulbs were used to represent the human beings. Explain to remove any ambiguity.

In the methodology, the authors have presented that electric bulbs were used to represent the sensible heat load from the occupants. However, in the results and discussion, the authors keep on mentioning “human body”. Please, can you clarify what “system” was actually used in your study and justification thereof.

The quality of Figure 13 should be improved. The writings on the figure are too small.

Also, the values for the PPD for Figure 13 cannot be clearly seen. For example, it is difficult to see the 10% PPD for Figure 13(a) as discussed by the authors.

 

Also, the writings on Figure 11 should be made more eligible.

It is suggested that the authors provide “Nomenclature” to define all variables used in the study.

 

 

 

 

Comments for author File: Comments.pdf

Author Response

The authors have presented on how Jetcone adjustment of active chilled beams (ACBs) affect air velocity and temperatures for precision ventilation in an open-plan office.

Major revision is recommended based on the following comments:

The theoretical framework/equations for determining the predicted mean vote (PMV) should be presented in the methodology section. It is unclear how the authors have computed the PMV and presented results in section 3.3 (PMV-PPD Calculations). The authors would also need to clearly present all the variables which were used to compute the PMV.

Additions: Pg: 7-8 Lines 203-234: Predicted Mean Vote (PMV) and predicted percentage dissatisfied (PPD) indices were….’
Figure modified: Pg. 8 Lines: 219. ‘Figure 4 PMV-PPD Measuring Graph with thermal comfort limits [9]’
Expressions Added: Pg. 8 Lines 230
Additions: Pg. 14, Lines 369-372 ‘The PMV and PPD were calculated from the equations shown in the Figure 4. The PPD is the function of PMV…..’

The methodology for the CFD simulation has to be explained very well. For CFD studies, it is important to show the methodology for grid independence study. The results should also demonstrate that your CFD solution does not depend on the grid size.

Additions: Pg. 5, Lines: 157- 159 ‘The grid independence test was carried out and tetrahedral….’
Additions with reference: Pg. 8-9, Lines: 237-247. ‘The experimental results were verified with CFD through data validity. The experimental air velocities…’
Additions: Figure 6 added Pg.10, Lines: 262-263. ‘Figure 6. Airflow Distribution from the ACBs (a) Case 1 (b) Case 2 (c) Case 3 (d) Case 4 (e) Case 5’.
Appendix A Added: Pg. 16-18 Lines: 439- 459 ‘Grid independence test was carried out with different mesh densities at line y1 = -0.5 y2 = -1.1 in the middle of the two desks. The variations after 3.67 million elements were not observed and this grid size was….’

How did you measure the real-life response (thermal comfort), since you used electric bulbs to represent the occupants (human beings)? Explain how you were able to measure the thermal comfort – which is a state of mind of the occupant, if electric bulbs were used to represent the human beings. Explain to remove any ambiguity.

Additions: Pg:4 Lines: 144-149. ‘The real office atmospheric environment was established…’
Additions: Pg:5 Lines: 167-168. ‘Four dummies (D1, D2, D3 and D4) were used as a heat source with heat flux adjusted with respect to changing metabolic rates in each case.’
Additions: Pg:7 Lines: 203-25. ‘Predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) indices were used to calculate thermal comfort for….’

In the methodology, the authors have presented that electric bulbs were used to represent the sensible heat load from the occupants. However, in the results and discussion, the authors keep on mentioning “human body”. Please, can you clarify what “system” was actually used in your study and justification thereof.

Additions: Pg:5 Lines: 167-168. ‘Four dummies (D1, D2, D3 and D4) were used as a heat source with heat flux adjusted with respect to changing metabolic rates in each case.’
Additions: Pg:7 Lines: 203-25. ‘Predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) indices were used to calculate thermal comfort for….
Updated:
Pg. 12 Lines 295- 299. ‘…..low-velocity zones according to the rates set for the human dummy. Figure 6 shows the basic case where all dummies had the same metabolic rates….’
Pg. 12 Lines 301-303. ‘In Figures 8 and 9, the high-velocity colliding jets are directed from the center to (zones 1 and 2) the dummies with a metabolic rate….’
Pg. 12 Lines 307-308. ‘…individual thermal comfort of the dummies with metabolic rates (higher heat release) of 1.6 met.’
Pg. 12 Lines 312-315. ‘The pin positions were adjusted to have air velocities of 0.15m/s, 0.45 m/s, and 0.55 m/s in the specific zones with human dummies having metabolic rates…’
Pg. 12 Lines 316-317. ‘….in different combinations by targeting the airflow according to the metabolic occupant’s requirements.’
In Conclusion: Pg. 16 Lines: 403-404 ‘The human dummies with low metabolic rates (1.2 met) could be exposed to air velocities as….’

The quality of Figure 13 should be improved. The writings on the figure are too small.

Updated Figure: Pg: 15 Lines:373-374 ‘Figure 14 PMV and PPD (a) Case 1 (b) Case 2 (c) Case 3 (d) Case 4 (e) Case 5 ‘

Also, the values for the PPD for Figure 13 cannot be clearly seen. For example, it is difficult to see the 10% PPD for Figure 13(a) as discussed by the authors.

Modifications in Figure 14: Pg: 15 Lines:373-374 ‘Figure 14 PMV and PPD (a) Case 1 (b) Case 2 (c) Case 3 (d) Case 4 (e) Case 5 ‘

Also, the writings on Figure 11 should be made more eligible.

Modifications in Figure 12: Pg: 13 Lines: 331-332 ‘Figure 12 Measured Vertical Air Temperature Distribution (a) Case 1 (b) Case 2 (c) Case 3 (d) Case 4 (e) Case 5’

It is suggested that the authors provide “Nomenclature” to define all variables used in the study.

Nomenclature Added: Pg. 18, Lines: 475-476.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors of this article built Precision Ventilation to enhance the thermal comfort of office residents. The current work uses variable jet interaction among two Active Chilled Beams to achieve individual thermal comfort for residents with varying metabolic rates and airflow variations. Full-scale experiments and computational fluid dynamics (CFD) models were performed for five office room cases. Experimental and simulation results demonstrated that diverse microclimate zones might be created by repositioning the JetCones concerning the colliding jets.

 

The authors should address the following comments and minor revisions:

 

11. The abstract needs to be rewritten so that the reader easily spot the aims/objectives of the study. It should reflect the novelty of the work.

22.   Ensure that any acronyms used are defined.

33. Please enhance your literature review to include more papers in 2021/2022. Several papers are available relating indoor conditions to thermal comfort, energy use, infection control, etc.

4. Please specify the site location and climatic conditions of the case study.

55. The validation technique needs to be clarified and clearly stated.

66. Please mention the CFD simulation tool name.

77. Is the simulation tool licenced? Using an unauthorized version is prohibited.

88. Use more illustrative figures, but not limited to, a graphical flowchart for the study.

99. Figures need to be added in higher quality for publishing. E.g. Figure 13 is totally unclear.

110. Did the authors consider the relationship between air velocity, airflow patterns, and temperature distribution to indoor infection transmission?

111. Please get its English revised very well. Various grammatical and punctuation errors occur.

112  Avoid merging British and American English in your writing.

11   Detailed comments and discussion of the results are required.

 

1 . The conclusion should be restructured to highlight the essential findings concise y. You may use bullet points for the ease of the readers.

Comments for author File: Comments.pdf

Author Response

The abstract needs to be rewritten so that the reader easily spot the aims/objectives of the study. It should reflect the novelty of the work.

Abstract Rewritten: Pg: 1 Lines: 12-29 ‘Precision Ventilation is developed to achieve thermal comfort for occupants in an office by creating micro-climate zones. The present study aims to achieve individual thermal comfort for occupants with different metabolic rates using higher airspeeds for enhancing heat transfer. The variable jet interaction….’

22.  Ensure that any acronyms used are defined.
    
    All acronyms highlighted in Nomenclature defined in text.
23. Please enhance your literature review to include more papers in 2021/2022. Several papers are available relating indoor conditions to thermal comfort, energy use, infection control, etc.

References Additions: [4],[6],[10],[12],[22],[24],[44],[47]

4. Please specify the site location and climatic conditions of the case study.

Additions: Pg: 3-4 Lines: 123-125. ‘The experiments were carried out during summers (between the months of May to September).’

Additions: Pg. 4 Lines: 128-135. ‘The constant airflow of 50 L/s was supplied from the each ACB, such that 100 l/s of total airflow (w) was…’

55. The validation technique needs to be clarified and clearly stated.

Additions with reference: Pg. 8-9, Lines: 237-247. ‘The experimental results were verified with CFD through data validity. The experimental air velocities…’

66. Please mention the CFD simulation tool name.

Modifications: Pg: 5 Lines: 155-159. ‘Figure 2(b) shows the geometry of the actual experimental setup made in Solidworks 2020 version. The geometry was imported to ANSYS 17.1 to conduct simulations for different cases [33].’

77. Is the simulation tool licenced? Using an unauthorized version is prohibited.

Response. ANSYS 17.1 and Solidworks 2020 software were used licensed by Aalborg University, Denmark.

88. Use more illustrative figures, but not limited to, a graphical flowchart for the study.

Illustrations Addition: Pg: 10 Lines: 263. Figure 6(a).6(e)
Description Added: Pg 9-10. Lines:  251 - 379. ‘Optimal airflow is the need of maintaining the heat balance between the human body and the surrounding environment [43]. The higher metabolic rates occupants require the need of higher air velocities to accelerate….’

99. Figures need to be added in higher quality for publishing. E.g. Figure 13 is totally unclear.

Updated Figure 14: Pg: 15 Lines:373-374 ‘Figure 14 PMV and PPD (a) Case 1 (b) Case 2 (c) Case 3 (d) Case 4 (e) Case 5 ‘
Updated Figure 4: Pg. 8, Lines: 219. ‘Figure 4. PMV-PPD Measuring Graph with thermal comfort limits [9]’
Updated Figure 3: Pg. 7, Lines 202. ‘Figure 3. Velocity and Temperature Measuring Points (a) Vertical (b) Horizontal’
Updated Figure 12: Pg: 13 Lines: 331-332 ‘Figure 12 Measured Vertical Air Temperature Distribution (a) Case 1 (b) Case 2 (c) Case 3 (d) Case 4 (e) Case 5’

110. Did the authors consider the relationship between air velocity, airflow patterns, and temperature distribution to indoor infection transmission?

Highlight/Response: Pg: 1 Lines: 13-16 ‘The present study aims to achieve individual thermal comfort for occupants with different metabolic rates using higher airspeeds for enhancing heat transfer. The variable jet interaction between two ACBs by ACB JetCone adjustments cause higher velocity jets to reach different regions of the occupied zone.’

111. Please get its English revised very well. Various grammatical and punctuation errors occur.

The manuscript is updated and proofread without grammatical and punctuation errors as highlighted

112  Avoid merging British and American English in your writing.

The manuscript is updated and proofread with American English.

11   Detailed comments and discussion of the results are required.

Additions with reference: Pg. 8-9, Lines: 237-247. ‘The experimental results were verified with CFD through data validity. The experimental air velocities…’
Additions with references: Pg: 9-10 Lines: 251- 279 ‘Optimal airflow is the need of maintaining the heat balance between the human body and the surrounding environment [43]. The higher metabolic rates occupants require the need of higher air velocities to accelerate the heat transfer [44]. Earlier studies have shown that local air velocity…’
Additions with references: Pg: 13 Lines: 319- 324. ‘Vertical air temperature difference plays an important while considering local discomfort. The problem…’
Additions with references: Pg: 13-14 Lines: 342- 346. ‘Literature shows that more airflow results in lower vertical temperature…’
Additions with references: Pg: 14 Lines: 352- 354. ‘One of the main characteristics of mixing ventilation, to maintain thermal uniformity, was fulfilled…’
Additions with references: Pg: 14 Lines: 359- 363. ‘Room temperatures can be raised in cooling modes to save energy while maintaining thermal comfort by utilizing higher air velocities. This reduction in energy use..’
Additions: Pg: 14 Lines: 369- 372. ‘The PMV and PPD were calculated from the expressions (2) and (3). The PPD is the function…’

1 . The conclusion should be restructured to highlight the essential findings concise y. You may use bullet points for the ease of the readers.

Conclusion Rewritten: Pg: 16 Lines: 392-416 ‘The occupants with higher metabolic rates working in offices require higher air velocities to balance the body heat. In this regard, the precision ventilation technique  is used to maintain individual…’

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper focuses on precision ventilation to achieve thermal comfort for occupants in an office by creating micro-climate zones. However, some descriptions are not clear. Some revisions are necessary in the manuscript.

1.       This paper takes case as the core part, and the overall analysis is based on specific cases. Please add more general content.

2.       There are also revisions in the paper, such as the second line of Section 2.3.

3.       Please explain whether the conclusions obtained in the paper are generalizable.

4.       Please supplement the analysis of the simulation results.

5.       In this study the authors have focused on mixing ventilation systems with heat transfer, which involves multi-energy coupling and conversion. More comparison and analysis on energy conversion are suggested to supply to indicate advantages of your work, which can refer to：[a] IEEE Trans. Ind. Inf. vol. 18, no. 2, pp. 835-846. 2022; [b] IEEE Trans. Smart Grid, vol. 10, no. 3, pp. 3236-3247, 2019; [c] IEEE Trans. Ind. Inf., vol. 15, no. 14, pp. 2008-2022, 2019.

Author Response

This paper focuses on precision ventilation to achieve thermal comfort for occupants in an office by creating micro-climate zones. However, some descriptions are not clear. Some revisions are necessary in the manuscript.

1. This paper takes case as the core part, and the overall analysis is based on specific cases. Please add more general content.

Additions with references: Pg: 9-10 Lines: 251- 279 ‘Optimal airflow is the need of maintaining the heat balance between the human body and the surrounding environment [43]. The higher metabolic rates occupants require the need of higher air velocities to accelerate the heat transfer [44]. Earlier studies have shown that local air velocity…’
Additions with references: Pg: 13 Lines: 319- 324. ‘Vertical air temperature difference plays an important while considering local discomfort. The problem…’
Additions with references: Pg: 13-14 Lines: 342- 346. ‘Literature shows that more airflow results in lower vertical temperature…’
Additions with references: Pg: 14 Lines: 352- 354. ‘One of the main characteristics of mixing ventilation, to maintain thermal uniformity, was fulfilled…’
Additions with references: Pg: 14 Lines: 359- 363. ‘Room temperatures can be raised in cooling modes to save energy while maintaining thermal comfort by utilizing higher air velocities. This reduction in energy use..’
Additions: Pg: 14 Lines: 369- 372. ‘The PMV and PPD were calculated from the expressions (2) and (3). The PPD is the function…’

2. There are also revisions in the paper, such as the second line of Section 2.3.
   
   Revisions removed: Pg: 6 Lines: 193-194 ‘The vertical velocity measuring points were taken at the heights of…’
3. Please explain whether the conclusions obtained in the paper are generalizable.

Conclusion Rewritten: Pg: 16 Lines: 392-416 ‘The occupants with higher metabolic rates working in offices require higher air velocities to balance the body heat. In this regard, precision ventilation technique is used to maintain individual…’

4. Please supplement the analysis of the simulation results.
   
   Additions with reference: Pg. 8-9, Lines: 237-247. ‘The experimental results were verified with CFD through data validity. The experimental air velocities…’
   Additions: Pg. 5, Lines: 178- 180 ‘The grid independence test was carried out and tetrahedral….’
   Additions with illustrations and references: Pg: 9-10 Lines: 251- 279 ‘Optimal airflow is the need of maintaining the heat balance between the human body and the surrounding environment [43]. The higher metabolic rates occupants require the need of higher air velocities to accelerate the heat transfer [44]. Earlier studies have shown that local air velocity…’
   Additions: Figure 6 added Pg.10, Lines: 262-263. ‘Figure 6. Airflow Distribution from the ACBs (a) Case 1 (b) Case 2 (c) Case 3 (d) Case 4 (e) Case 5’.
   Appendix A Added: Pg. 16-18 Lines: 439- 259 ‘Grid independence test was carried out with different mesh densities at line y1 = -0.5 y2 = -1.1 in the middle of the two desks. The variations after 3.67 million elements were not observed and this grid size was….’
   Additions: Pg: 14 Lines: 352- 363. ‘One of the main characteristics of mixing ventilation, to maintain thermal uniformity, was fulfilled…’
   
   
5. In this study the authors have focused on mixing ventilation systems with heat transfer, which involves multi-energy coupling and conversion. More comparison and analysis on energy conversion are suggested to supply to indicate advantages of your work, which can refer to：[a] IEEE Trans. Ind. Inf. vol. 18, no. 2, pp. 835-846. 2022; [b] IEEE Trans. Smart Grid, vol. 10, no. 3, pp. 3236-3247, 2019; [c] IEEE Trans. Ind. Inf., vol. 15, no. 14, pp. 2008-2022, 2019.
   
   Additions with new references: Pg: 14 Lines: 359- 363. ‘Room temperatures can be raised in cooling modes to save energy while maintaining thermal comfort by utilizing higher air velocities. This reduction in energy use..’

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addressed the questions raised in the first review. However, the quality of the figures presented can be improved, further.  

 

 

Author Response

Additions: Figures 1, 2, 3, 7, 8, 9, 10, 11, 12, 13, and 14 from the manuscript have been replaced with new Figures with further improved quality.

Author Response File: Author Response.pdf