Ventilation Operating Standard for Improving Internal Environment in Pig House Grafting Working Conditions Using CFD

Round 1

Reviewer 1 Report

In this work has been proposed a ventilation control standard that considers both the working environment and the breeding environment in a pig house simultaneously by efficiently reducing the concentration of harmful gases at the workers' height; the ventilation system has been evaluated trough CFD techniques. The research is attractive for engineering applications. The paper is quite of good quality, but some requests and suggestions have been provided to increase the quality of the work.

The introduction well understands the related problems, however the background on the CFD methodologies must be better expanded and described in more detail, not only a single phrase with [15-28]. Moreover, I suggest some references on the UQ techniques, very useful also for your application. For example:

- Cravero, C.; De Domenico, D.; Marsano, D. The Use of Uncertainty Quantification and Numerical Optimization to Support the Design and Operation Management of Air-Staging Gas Recirculation Strategies in Glass Furnaces. Fluids 2023, 8, 76.

-  Xia, L., Zou, Z. J., Wang, Z. H., Zou, L., & Gao, H. Surrogate model based uncertainty quantification of CFD simulations of the viscous flow around a ship advancing in shallow water. Ocean Engineering 2021, 234, 109206

- Cravero, C; De Domenico, D; Marsano, D. “Uncertainty Quantification Analysis of Exhaust Gas Plume in a Crosswind”. Energies, 2023, Vol. 16, Issue 8, p. 3549.

Moreover, similar studies by the previous author studies the ventilation system to reduce the COVID diffusion in indoor ambient.

The application case has been well described with the main data.

The numerical model must be further described by describing the computational domain used, the mesh (cell size, mesh sensitivity, y+), the model adopted, boundary conditions, numerical schemes and relative justifications. Then some figures on the mesh and on the boundary conditions must be provided.

A separated section with the governing equation for the fluid dynamics should be added too.

The tracer gas decay method is explained clearly, as well as the experimental procedure, however some details should be provided on the measurements techniques with the relative instrumentations.

The results analysis is well written, but some diagrams are difficult to read; moreover, the flow analysis must be enriched with some contour or streamlines to highlight the flow dynamics.

The conclusions are well supported by the results.

Minor typos

Author Response

Please see the attachment (major revised manuscript written in red) and responses for your recommendations as below; 

Response to Reviewer 1 Comments

Point 1:

The introduction well understands the related problems, however the background on the CFD methodologies must be better expanded and described in more detail, not only a single phrase with [15-28].

Moreover, I suggest some references on the UQ techniques, very useful also for your application. For example:

- Cravero, C.; De Domenico, D.; Marsano, D. The Use of Uncertainty Quantification and Numerical Optimization to Support the Design and Operation Management of Air-Staging Gas Recirculation Strategies in Glass Furnaces. Fluids 2023, 8, 76.

-  Xia, L., Zou, Z. J., Wang, Z. H., Zou, L., & Gao, H. Surrogate model based uncertainty quantification of CFD simulations of the viscous flow around a ship advancing in shallow water. Ocean Engineering 2021, 234, 109206

- Cravero, C; De Domenico, D; Marsano, D. “Uncertainty Quantification Analysis of Exhaust Gas Plume in a Crosswind”. Energies, 2023, Vol. 16, Issue 8, p. 3549.

Response 1: We deeply appreciate your precious reviewed in this manuscript, thus we can improve this research article. We corrected refer to your correction and comments.

Minor corrections (such as typos and diagram numbers) have been made without indicator in red.

Specific examples of CFD applications were presented in a detailed and categorized manner, based on cases involving breeding environments, thermal environments, and ammonia emissions.(line 85-98)

The papers you have provided related to UQ(uncertainty quantification) seem to be of great help for my future research. I will study them so that they can be applied in continuation of this paper.

Point 2: The numerical model must be further described by describing the computational domain used, the model adopted, boundary conditions, numerical schemes and relative justifications. Then some figures on the mesh and on the boundary conditions must be provided.

Response 2:

The numerical model was further described in the manuscript following your recommendation. The computational domain used, the mesh, cell size, mesh sensitivity and so on, were added to Table 1 and the manuscrips. The model validation was specifically discribed in the previous research on the same pig house, and key results were added in the manuscrips for understanding. (line 143-175).

Point 3: A separated section with the governing equation for the fluid dynamics should be added too.

Response 3:

The numerical model was further described in the manuscript following your recommendation. (line 143-162)

Point 4: The tracer gas decay method is explained clearly, as well as the experimental procedure, however some details should be provided on the measurements techniques with the relative instrumentations.

Response 4:

I have supplemented a detailed explanation on the application of the Tracer Gas Decay method. TGD method is measuring the concentration of tracer gases such as CO2, SF6, etc., at multiple points in field experiments to find ventilation efficiency. By using simulation, we can obtain more qualitative and quantitative data than in the field. In this research, the data obtained from the CFD were quantitatively analyzed for regional ventilation efficiency in pig house by region using the TGD method. (line 191-197)

Point 5: The results analysis is well written, but some diagrams are difficult to read; moreover, the flow analysis must be enriched with some contour or streamlines to highlight the flow dynamics.

Response 5:

Following your suggestions, I have revised the diagram and supplemented the text.

Firstly, Table 2, which had duplicative meanings, was deleted and merged with Table 3 (Table 2, line 385).

The manuscrips was revised and added to the explanation of the table, and improved Table 4 to enhance readability (Table 3, line 400).

The appropriate ventilation volume and ventilation time were represented in a single diagram. I revised the title of the chart and the detailed description (Figure 10, line 457 / manuscript line 421-427).

Author Response File: Author Response.pdf

Reviewer 2 Report

A brief summary

The research presented showed an exciting study of the working and breeding environments simultaneously with computational fluid dynamics (CFD) to develop ventilation operation management plans.

General concept comments

Did you find any studies in the field of both environments? If there are any, please refer.

How did you consider the shape and envelope of the building and the external environment in simulations?

Are there any future works?

Did you run RANS or the LES simulations? Was it the steady or unsteady simulation?

Were the CFD results from the ventilation efficiency and thermal environment compared with experimental and field data?

The authors have put in significant effort and achieved considerable results. The conclusion needs to highlight the key findings for practical application.

Specific comments

The quality of the figures must be improved.

Sections 2.4.2 and 2.4.3 have the same title.

Author Response

Please see the attachment (major revised manuscript written in red) and responses for your recommendations as below; 

Response to Reviewer 2 Comments

Point 1: Did you find any studies in the field of both environments? If there are any, please refer.

Response 1: We deeply appreciate your precious reviewed in this manuscript, thus we can improve this research article. We corrected refer to your correction and comments.

Minor corrections (such as typos and diagram numbers) have been made without indicator in red.

I have added and organized detailed references to livestock environment studies (lines 85-98). However, upon reviewing existing research, it appears that studies in the field of livestock environment primarily deal with the breeding environment only, while those in the field of health environment separately deal with the working environment only. It was quite difficult to find papers that deal with both. Nevertheless, I have added two papers that mention both environments (mainly focused on livestock environment) to the references (lines 90-92).

Point 2: How did you consider the shape and envelope of the building and the external environment in simulations?

Response 2:

The shape and boundary conditions of the CFD simulation model were designed following the actual specifications of the experimental pig house. The model validation and boundary conditions were referenced from the previous research conducted directly by us. I though the manuscrips was insufficient, so I added more details in the manuscrips. (line 164-175)

Point 3: Did you run RANS or the LES simulations? Was it the steady or unsteady simulation?.

Response 3:

We used the RANS (Reynolds-Averaged Navier-Stokes) model. Using LES (Large Eddy Simulation) was deemed excessive due to the large scale (targeting the entire pig house), so it was decided that RANS was sufficient as it was targeting relatively stable environmental conditions. And the model validation was also shown in good agreement in the previous research considering same experimental pig house.

The modeling was initially initialized in Steady state, then modeled in Unsteady state for regional ventilation efficiency analysis using the TGD method. I have added this information to the main text (lines 213-215).

Point 4 : Were the CFD results from the ventilation efficiency and thermal environment compared with experimental and field data?

Response 4:

In this study, we focused on creating ventilation operation standards that consider both the breeding environment and working environment using the validated model by myself, Oh et al. (2019). We used the model that was validated based on the velocity and temperature between field experimental data and CFD data in previous research targeting the same structure.

As the manuscript was not enough to explain about model validation, I added and improved this. (line 164-175)

Point 5&6 : The results analysis is well written, but some diagrams are difficult to read; moreover, the flow analysis must be enriched with some contour or streamlines to highlight the flow dynamics.

The authors have put in significant effort and achieved considerable results. The conclusion needs to highlight the key findings for practical application.

Response 5&6:

Following your suggestions, I have revised the diagrams.

Firstly, Table 2, which had duplicative meanings, was deleted and merged with Table 3 (Table 2, line 388).

The manuscrips was revised and added to the explanation of the table, and improved Table 4 to enhance readability (Table 3, line 400).

The appropriate ventilation volume and ventilation time were represented in a single diagram. I revised the title of the chart and the detailed description (Figure 10, line 457 / manuscript line 421-427).

I have supplemented the conclusion so that the key finding can be further emphasized.

The key point of this study is that when operating ventilation, both the breeding environment and working environment should be considered simultaneously. For this, it is important to appropriately adjust the ventilation volume and ventilation time, along with improvements in the ventilation structure. It is difficult to analyze this in real time on-site, and it is necessary to create standards for control for automatic control. Since the control standard always changes depending on the structure, it is important to set standards according to the structure. In this study, a single diagram that can be evaluated on-site for the existing structure and three improved structures was presented. (Conclusion)

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The quality of the work is increased. My requestes have been integrated in the paper a part the references suggested.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf