Effects of Ventilation Fans and Type of Partitions on the Airflow Speeds of Animal Occupied Zone and Physiological Parameters of Dairy Pre-Weaned Calves Housed Individually in a Barn
Round 1
Reviewer 1 Report
General comments:
This manuscript employs isothermal steady CFD simulations as well as experimental tests to investigate the impacts of partitions on the thermal comfort and health of calves. Heat stress in calves is a crutial issue as it has adverse effects on the environment, animal welfare, productivity, and profitability. However, there is very limited empirical data and simulations that specifically evaluate the effects of different partition walls on air distribution in cow barns. Evaluating such effects will improve housing and management, thereby enhancing heat stress resiliency. This study contributes to the existing literature and provides valuable insights into this important topic. The results from this manuscript are informative and timely.
The organization of the manuscript is clear and flows logically between sections. References appear to have correct formatting and are complete. However, the language requires further improvements before being qualified as a research paper for this journal.
Detailed comments:
Lines 24-25: give the definitions of MP-LA, SP-LA, and SP-HA.
Line 47: forced convective heat is a consequence of high airspeed. It is not an intrinsic heat flow from the skin surface. Modify the sentence to make better sense.
Line 71-72: the sentence is unclear.
Line 131: ‘side view’, ‘floor plan’
Line 148-150: what does the source term refer to in your simulations? Why does d*/dt still present even though the simulations are time-independent? Eq. 1 and 2 do not align with what you mentioned in the context.
Line 155: k-e model can be used for simulating the indoor environment. However, it is not always the best choice for other engineering simulations. Please be strict with your opinions.
Line 182: a 2nd order formula does not fit eq. 4.
Line 231: why was the mesh partition modelled in detail? In which part did you implement the porous media?
Line 296: how are the P-values for models 1 and 2 calculated? Why are they so large?
Line 339: define the heat stress threshold associated with the selected THI in the methods section. The threshold should also be added to Fig. 6 (b) for better readability.
Line 394: what was circulated?
The language requires moderate editing.
Author Response
- Lines 24-25: give the definitions of MP-LA, SP-LA, and SP-HA.
We added. “The duration of treatment provided to the calves in the MP-LA (mesh partitions and subjected to a low-speed airflow) and MP-HA (mesh partitions and subjected to a high-speed airflow) groups, were both lower than the SP-LA (solid partitions and subjected to a low-speed airflow) and SP-HA (solid partitions and subjected to a high-speed airflow) groups. “
- Line 47: forced convective heat is a consequence of high airspeed. It is not an intrinsic heat flow from the skin surface. Modify the sentence to make better sense.
We modified the sentence. “To guard against heat stress, fans can be used to increase the speed of airflow and increase convective heat loss from the skin [7], and as long as the ventilation is sufficient (maintained air velocities above 3 m s-1) and directed so as to flow over the animals’ bodies, this measure can effectively reduce or alleviate heat stress [8].”
- Line 71-72: the sentence is unclear.
We modified the sentence. “ In an effort to increase the natural ventilation efficiency inside a small-scale calf barn, Norton et al. [14-16] was able to use CFD to predict that the system’s performance could be optimized by changing the eave opening and develop a CFD-generated heat transfer model of a dairy calf. ”
- Line 131: ‘side view’, ‘floor plan’
We added . “Figure 1. Schematic diagram of experimental calf barn cooled by natural ventilation augmented with axial fans. (a) Side view of experimental barn; (b) floor plan of experimental barn; (c) cross-sectional front view showing locations of the air velocity measurements taken in pens used in CFD model; (d) detailed plan of pens for housing calf groups (1-4). ”
- Line 148-150: what does the source term refer to in your simulations? Why does d*/dt still present even though the simulations are time-independent? Eq. 1 and 2 do not align with what you mentioned in the context.
We modified the Eq. 1 and 2.
- Line 155: k-e model can be used for simulating the indoor environment. However, it is not always the best choice for other engineering simulations. Please be strict with your opinions.
We modified the sentence. The k-ε models are widely used for simulating the indoor environment because they can be robust and most likely achieve convergence.”
- Line 182: a 2ndorder formula does not fit eq. 4.
We modified the sentence. “ After obtaining the results of a test conducted to ascertain the fan-performance curve, the data were fitted to an equation that describes the relationship between the fan pressure rise and the wind speed.”
- Line 231: why was the mesh partition modelled in detail? In which part did you implement the porous media?
We tested the wind speed of the mesh partition under the fan, and established the mesh partition model in ANSYS according to the wind speed. Since the mesh partition needs to occupy a large amount of mesh in the simulation, in order to reduce the amount of mesh used and improve the calculation speed, the mesh partition was set as porous medium.
- Line 296: how are the P-values for models 1 and 2 calculated? Why are they so large?
The P-value was the significance analysis of the air speed simulated by CFD and direct measurements, and the results were both greater than 0.05, which means that there was no significant difference between them.
- Line 339: define the heat stress threshold associated with the selected THI in the methods section. The threshold should also be added to Fig. 6 (b) for better readability.
We added the define the heat stress threshold.
- Line 394: what was circulated?
We modified the sentence. “Zhao et al. [10], such a low air circulation rate can adversely affect respiratory rate and rectal temperature during warm seasons.”
Reviewer 2 Report
1. For the simulation mesh in the ANSYS of the CFD (not the mesh as partitions of the barn), please explain the following:
- What is the type of mesh used in this simulation?
- Could you add the ANSYS image of the mesh that was used in this simulation?
- Did you test this mesh?
2. Add a flowchart describing the steps of the simulation.
3. Add a schematic drawing describing the experimental test (locations of the measuring devices, connecting the measuring devices, …., etc.).
4. If possible add the ambient conditions (ambient temperature, wind speed, humidity, …, etc.) outside the barn during the test.
5. In Figure 3, what are the dimensions of the holes in the mesh?
6. In Figure 1 a, please add the dimensions of the chimney.
7. Are the materials of the roof, walls, and floor of the barn affect the simulation? If yes please add the specifications of the materials used in the simulation.
8. Could you add a simulation for a full year using the recorded weather data?
9. what are the optimum weather condition that must be in the barns and suitable for the livestock.
Author Response
- For the simulation mesh in the ANSYS of the CFD (not the mesh as partitions of the barn), please explain the following:
- What is the type of mesh used in this simulation?
An unstructured mesh
- Could you add the ANSYS image of the mesh that was used in this simulation?
We added the image in figure 4.
- Did you test this mesh?
Yes, the results was shown in 2.2.4
- Add a schematic drawing describing the experimental test (locations of the measuring devices, connecting the measuring devices, …., etc.).
Figure 1 described the experimental test.
- If possible add the ambient conditions (ambient temperature, wind speed, humidity, …, etc.) outside the barn during the test.
The test calf barn was an open barn, there was little difference in temperature and humidity between inside and outside the barn, so no separate graph was made and only the temperature and humidity outside the barn was described in words.---“The average daily temperature and relative humidity outside fluctuated between 17.32 °C to 30.46 °C and 48.46% to 96.08%.”
- In Figure 3, what are the dimensions of the holes in the mesh?
In the mesh partition, the dimensions of the hole is 0.05m×0.05m
- In Figure 1 a, please add the dimensions of the chimney.
We added the dimensions of the chimney in Figure 1a.
- Are the materials of the roof, walls, and floor of the barn affect the simulation? If yes please add the specifications of the materials used in the simulation.
In simulation, the materials of the roof, walls, and floor of the barn set as no-slip, adiabatic wall.
- Could you add a simulation for a full year using the recorded weather data?
In the next step, we can consider conducting a full year simulations to explore the appropriate management of calf barn at different temperatures.
- what are the optimum weather condition that must be in the barns and suitable for the livestock.
The weather conditions in the spring and fall are more suitable for calf growth than summer and winter.
Round 2
Reviewer 2 Report
I recommend that this manuscript is ACCEPTED for publication without further review.
