Experimental and Numerical Investigations on the Local Direct Leakage Process of Rotary Regenerative Air Preheater

Round 1

Reviewer 1 Report

The manuscript investigates the effect of various parameters on the leakage process through the rotary regenerative air preheater. Among the parameters considered are the pressure differences between the hot and cold sides, number of sealing sheets, etc and makes use of the experimental observations to compare them with the predictions made by the various numerical models employed.  

 

The manuscript lacks richness in detail and is generally quoting the observations made, in the literal sense. Little or no inference is made about the observations in light of the literature surveyed. The manuscript is not recommended for publication until the following issues are addressed, the break down of which is given  as follows

 

Minors: 

1 The language of the script should be improved. I  highlighted, on a number of occasions, the errors I could see. After a while, I gave up. And I am sure there are many apart from those highlighted, that need to be addressed

2 Figure captions should be revised. Their structure is not correct.

 

Majors

1    The authors claim that the flow is in "turbulent state" but they do not state this with regard to any quantifiable parameter (Re etc) that tells how "turbulent" the flow actually is. The authors should shed more light on this.

 

2  What do the authors mean by "fluid thermodynamics imbalance"?  what thermodynamic quantities is the author measuring and referring to in this context?

 

3   Flue gases are far from being ideal. How come then Eq. 6 makes reasonable predictions about the pressures and the pressure differences  used to parametrize the leaking effects? A reasonable adjustment should be made for the non-ideal nature of the gases. Flue gases comprise of various oxides (SOx and NOx). The van der Waal constant is an attempt to make up for this but no values are actually reported

 

4  Authors, by visualizing the streamlines, conclude on how and where vortices are formed. This is a very crude inference and even less likely to be plausible. 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper presents an experimental and numerical study on the local direct air leakage of rotary regenerative air preheater, investigating how it is affected by the leakage gap, the number of sealing sheets, the spacing between the adjacent sealing sheets, the bending angle of sheeting sheets, and the pressure difference on direct air leakage and orifice coefficient. The study shows that the used three-equation Transition k-kl-ω model presents good agreement with the experimental data.

The study seems to present a satisfying scientific and engineering relevance with the journal, describing the current state-of-the art and demonstrating the correctness of the approach. Therefore, this reviewer would like to suggest this paper for publish, after some significant improvements.

The following lot of major changes may be used to improve the quality of the manuscript:

The abstract should include an extra sentence (maybe from the intro), showing why this study concerns the current state-of-the art and should be investigated. The abstract and the conclusions may present how important is each parameter that affects the leakage by presenting a number that shows the engineering importance. Fig 1a could show which is the rotating and the stationary part. Which numerical tool was used for the simulation and which is its solver method? Regarding Fig 4, the differences between each model and the experiments should be referred. “… agreed well…” does not show the engineering interest. Same comments for the next paragraphs describing the effect of each parameter. Maybe a table showing the measured parameter, the used device and its range, accuracy and the corresponding uncertainty should be added for the Uncertainty Analysis.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have responded to the comments and improved the quality and scientific soundness of the manuscript. 

Reviewer 2 Report

It is accepted for publication after the corrections.