Hydrodynamics of Direct Contact Condensation Process in Desuperheater

Round 1

Reviewer 1 Report

Dear authors,

below some aspects to be better explained for a possible publication in Fluids:

1. To compare the results with some teorethical models. The experimental work should include an analytical comparison;

2. The load drops calculation would be interesting; In the study of flow dynamics, the calculation of load drops along the duct would be an interesting point. A focus on the friction or other dissipative mechanisms is suggested.

3. The novelty aspects need to be detailed. Both the introduction and conclusions to be extended with considerations about the impact in the engineering community.

Author Response

Respected Reviewer: Below are the some aspects which we have explained as guided by you for the possible publication of our article in the journal "Fluids":

1. To compare the results with some theoretical models. The experimental work should include an analytical comparison;

Reply: To our knowledge, no comprehensive analytical or theoretical model exists for the work carried out in the present paper. Therefore, these experimental results can be used to validate modeling and simulation works.

2. The load drops calculation would be interesting; In the study of flow dynamics, the calculation of load drops along the duct would be an interesting point. A focus on the friction or other dissipation mechanisms is suggested.

Reply:The load drop pointed out by the esteemed reviewer is not clear. However, keeping in view the fact that the steam being inserted mixing and condenses rapidly with the liquid stream, it is clear that the pressure drop and friction factor can be assumed to be solely incurred by the liquid stream. However, two phase pressure drop and friction drops may become significant if the steam fraction being inserted becomes significant. That not being the case in current work, it is reasonable to approximate the pressure drop and friction factor as calculated by single phase correlations. For the case of accuracy, reader may use two-phase homogeneous equilibrium model for calculation of pressure drop and friction factor.

3. The novelty aspects need to be detailed. Both the introduction and conclusions to be extended with considerations about the impact in the engineering community.[Please Refer to Page 1]

Reply: Direct contact condensation (DCC) play significant role in heat and mass transfer equipment design such as condensers, contact feed water heaters, cooling towers and deaerators. It has recently been extensively used where vapor is made to contact directly with a liquid at ambient temperature and condenses [Effects of External Oscillations on Cocurrently Flowing Steam–Water in Pipes, DOI: 10.1007/s42417-022-00626-5]. DCC differs from other modes of condensation as DCC does not require a solid surface for energy exchange between the phases. DCC offers the benefit of large contact surface area for heat exchange, simplicity of design, less scaling and corrosion problems and low cost of maintenance. In line with the above-mentioned advantages, the authors focused on using the high-pressure steam that is available to be discarded into atmosphere. Major novelty of the current work is thorough investigation of two-phase hydrodynamics that take place when steam is introduced into a flowing liquid for condensation thereby recovering the availably energy instead of wasting into atmosphere. In doing so, it is important to analyze the details of heat and mass transfer that occur when the work is undertaken. This is what has been the goal of current work.

Reviewer 2 Report

1. Along with Fig.1, It is strongly recommended to show complete figure of whole experimental setup for better understanding. The figure can be either schematic representation or real photograph of complete experimental setup.  

2. What is the temperature of subcooled water? Is Water temperature constant throughout the experiment? If yes, then how it is ensured?

3.  Has author perform uncertainty test and repeatability test in the study. Can refer this as an example (https://doi.org/10.1016/j.ijthermalsci.2022.107714). 

4. The subcooled water velocity will have a significant impact on the circulation zone length. This parameters should also be considered in the study.

5. Fig.2 (b) can be drawn in better way for clear and distinct visualization.  

6. The authors should carefully proof read the whole manuscript for Grammatical and language mistakes. Like spelling of solar water heaters in line 54.

7.  The literature related to present work is missing in the introduction section. So, enrich it by recent work.

Author Response

Respected Reviewer: Below are the some aspects which we have explained as guided by you for the possible publication of our article in the journal "Fluids":

1. Along with Fig.1, It is strongly recommended to show complete figure of whole experimental setup for better understanding. The figure can be either schematic representation or real photograph of complete experimental setup. 

Reply: In this article the DCC phenomena has been discussed which occurs inside the body of the Desuperheater. It is therefore the region of the main interest is the body of the Desuperheater itself which has been shown in the cross-sectional view form to better understand the position of the steam jet injection and the region where this phenomena takes place. The diagram of the whole experimental setup is useless to our view as by including such figure we will not be able to see the region in 3D  as it is shown now.

2. What is the temperature of sub-cooled water? Is Water temperature constant throughout the experiment? If yes, then how it is ensured?

Reply:The water temperature that enter the pipe is at 15 °C and is drawn from the chiller into the pipe. In order to prevent heat losses or gains from the surroundings, the whole assembly is insulated with local insulating material mostly made of cotton and wrapped by aluminum foil. One of the shortcomings of the current work is that separate local temperatures were not noted. However, the temperature profiles are essential and will be measured in future work using thermo-couples in the mixing zones.

3. Has author perform uncertainty test and repeatability test in the study. Can refer this as an example (https://doi.org/10.1016/j.ijthermalsci.2022.107714).[Page 3]

Reply:As the reviewer highlighted, it is important that uncertainty analysis and repeatability of any experimental work is essential for identifying the deviations in the measurements. Before executing the experiments, all the testing setup was calibrated. In almost all the measurements made, an error of no more than 3% was observed. A detailed uncertainty analysis of all the parameters involved was not calculated in the current work. However, we plan to include in upcoming works. We have included the recommended paper (Influences of tip clearance on flow and heat transfer characterstics of open type micro pin fin heat sink, DOI: https://doi.org/10.1016/j.ijthermalsci.2022.107714) in our manuscript for reference.

4.The subcooled water velocity will have a significant impact on the circulation zone length. This parameters should also be considered in the study.[Page 3]

Reply: The impact of the subcooled water velocity has been considered towards circulation zone length through HFA measurements of interfacial steam-water fluctuating velocities.

5. Fig.2 (b) can be drawn in better way for clear and distinct visualization.  

Reply: The Figure 2(b) has been redrawn as advised with more magnification and in the larger size as can be seen in the attached manuscript. (Please draw one figure below the text body not two figures side by side).

6. The authors should carefully proof read the whole manuscript for Grammatical and language mistakes. Like spelling of solar water heaters in line 54.

Reply: The manuscript has been read very carefully and mistakes relating to spelling, grammatical and language have been corrected.

7. The literature related to present work is missing in the introduction section. So, enrich it by recent work.[Page 1]

Reply:Wehave included the following text in the introduction section.

Direct contact condensation (DCC) play significant role in heat and mass transfer equipment design such as condensers, contact feed water heaters, cooling towers and deaerators. It has recently been extensively used where vapor is made to contact directly with a liquid at ambient temperature and condenses [Effects of External Oscillations on Co-currently Flowing Steam–Water in Pipes, DOI: 10.1007/s42417-022-00626-5]. DCC differs from other modes of condensation as DCC does not require a solid surface for energy exchange between the phases. DCC offers the benefit of large contact surface area for heat exchange, simplicity of design, less scaling and corrosion problems and low cost of maintenance. In line with the above-mentioned advantages, the authors focused on using the high-pressure steam that is available to be discarded into atmosphere. Major novelty of the current work is thorough investigation of two-phase hydrodynamics that take place when steam is introduced into a flowing liquid for condensation thereby recovering the availably energy instead of wasting into atmosphere. In doing so, it is important to analyze the details of heat and mass transfer that occur when the work is undertaken. This is what has been the goal of current work.

Round 2

Reviewer 1 Report

Dear authors,

the paper is fine for me. 

my best regards.

Reviewer 2 Report

The article can be accepted for further publication process.