Drying Behavior of Hardwood Components (Sapwood, Heartwood, and Bark) of Red Oak and Yellow-Poplar

Round 1

Reviewer 1 Report

Wood drying is the most important process and key technology not only for making wood products but also for quality control. Wood physical properties affect the drying characteristics, according the research of this paper are meaningful for wood drying study and application. 

Comments for author File: Comments.pdf

Author Response

Dear chief editor,

We would like to appreciate the candid suggestions and constructive comments from reviewers that enhanced our manuscript’s quality. Changes and corrections are highlighted in yellow in the uploaded files.

First Reviewer

1. Line 109. Why were the samples used in different sizes? (17.69, 16.47, and 19.30). These dimensions are the average values of all sapwood and heartwood species in this study. Total surface area (A) is a contributing factor in drying flux (equation 7 and Figure 3), but not in drying rate. If authors used the exact same size for all samples, drying rate curves would have resembled drying flux rates because of the same total area (A) values for all samples. For this reason, the dimensions for different samples were slightly different. A brief explanation has been added (line 117).
2. Line 122. The accuracy of 0.01g of the balance is accurate enough for the small sample

weighing? Thank you for your valid comment. Authors fully agree with the reviewer that more decimals could have improved the accuracy. However, in this study, the authors used two decimals for all physical measurements as a matter of consistency.

3. Line 131. Why did the samples were dried above 100 °C? the conventional kiln drying is

conducted usually at less than 100 °C. And why the temperature intervals are 10 °C, the dryings

between 105 and 125 °C are significantly different? Further explanation is added to clarify this part (lines 141-147).

4. Line 170. What is moisture ratio, it should be moisture content or not, the same question is

also, in other Figures for the horizontal axis. Moisture ratio is different than moisture content. The unit for moisture content is (%) while moisture ratio is unitless. The equation to evaluate moisture ratio is added to the manuscript. Explanations and attributed equation have been added (lines 186-192).

5. Line 250. Why the specific gravity of sapwood and heartwood of red oak was almost equal.

Please explain the reason. Rationale and justification have been added (lines 275-283).

6. Line 288. Changes in moisture ratio drying period, the sentence may be misses ‘during’. It has been corrected accordingly (Line 317).
7. Line 303. The initial moisture ratio was the same in Figure 2? And the drying rate in this

Figure seems different from that in Figure 4. As pointed out in comment 4, moisture content and moisture ratio are different. Figure 2 shows moisture ratio vs. time while figure 4 (a and b) represents drying rate as a function of moisture ratio.

8. Line 346. The temperatures were the values of the surfaces of all samples? Did you measure

the temperature of all samples and how to confirm the samples have the same temperature in

surface and inner locations? As mentioned in the caption of Figure 5, these curves represent the temperatures of three drying runs, not the temperatures of the wood. In fact, these temperatures are setpoints for the ambient inside the TGA equipment. A brief explanation has been added in this regard (lines 377 and 378).

9. Try to explain the reasons in all discussion sections corresponding to the results obtained. Broader and deeper discussions have been added to the manuscript.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors

I had the opportunity to review the extensive (16 pages) research proposed for Forests under the name "Drying Behavior of Hardwood Components (Sapwood, Heartwood, and Bark) of Red Oak and Yellow-Poplar". 

Despite interesting topic and analyses, I present some suggestions/questions which should be considered in my opinion for this article.

Review:

Dear Authors

I had the opportunity to review the extensive (16 pages) research proposed for Forests under the name "Drying Behavior of Hardwood Components (Sapwood, Heartwood, and Bark) of Red Oak and Yellow-Poplar". The article deals with the very interesting topic which investigated presents differences in the drying behavior of red oak and yellow-poplar sapwood, heartwood, and bark and their relationship with selected physical characteristics. Results showed that volumetric and cellular shrinkages of sapwood were greater than that of heartwood for both species. For red oak, the specific gravity of sapwood and heartwood was not significantly different. Additionally, the total porosity of heartwood was lower than that of sapwood in red oak. Results also indicated that yellow-poplar was dried faster than red oak.

Despite interesting topic and analyses, I present some suggestions/questions which should be considered in my opinion for this article:

• Authors stated extensive used references (40) but in discussing the results were used only 13 references so that extensive of critical discussion is lacking. Authors have to more discussion with other similar articles. Please, add missing discussing.
• Material and Method: more detailed information on the place of logging of wood is missing, such as: altitude, type of forest, region of logging etc.
• Incorrect stated citation. Lines such as 366, 390, 417 etc. Correct is [number]. Please correct this lines.
• The conclusions are general, short and should relate more directly to the values obtained in the experimental tests.

Author Response

Second Reviewer

1. Authors stated extensively used references (40) but in discussing the results were used only 13 references so extensive critical discussion is lacking. Authors have to have more discussions with other similar articles. Please, add the missing discussion. Further citations and more comparisons to the previous studies have been added to the text.
2. Material and Method: more detailed information on the place of logging of wood is missing, such as altitude, type of forest, region of logging, etc. Further information has been added accordingly (Lines 109-111).
3. Incorrectly stated citation. Lines such as 366, 390, 417, etc. Correct is [Number]. Please correct these lines. References (citations in the text) have been corrected accordingly.

Author Response File: Author Response.docx