Optimization of Hot-Water Drilling in Ice with Near-Bottom Circulation

Round 1

Reviewer 1 Report

Review of Manuscript ID: water-1485619

OPTIMIZATION OF HOT-WATER DRILLING IN ICE WITH NEAR-BOTTOM CIRCULATION

Gaoli Zhao, Pavel G Talalay *, Xiaopeng Fan, Nan Zhang, Yunchen Liu, Ting Wang, Yanji Chen

General comments

This manuscript focuses on the drilling of holes in ice using jets of hot water. The described experiments use a wide variety of water jet configurations and drill tip design to establish to optimum configuration for efficient drilling through ice in an ice test well. This follows the fieldwork experiments of Taylor 1984, where different water jets and drill tips designs were also used.

Here the application of the drilling is for the passage of a sonde type instrument rather than for the creation of deep access holes. The key difference is that melting is only required locally to the sonde rather than for an access hole where energy is required at all depths to maintain its size against refreezing. This should be emphasized more in the introduction.

The experiments conducted appear sound but the interpretation needs to be improved.

Main comments:

Throughout the manuscript, comments/figures that indicate the energy delivery by the jet(s) and an approximate jet velocity, in addition to the overall temperature and flow rate, MUST be added. This would make it easier to see the relative thermal efficiency of each nozzle and provide better explanations for the results obtained.

The jet velocity is important and MUST be considered, as this generates the turbulent heat transfer at the ice-water interface needed to melt the ice. More turbulence will increase the gradient of the thermal boundary layer, resulting in faster melting.

The above changes focusing on energy delivery and jet velocity will probably change the figures considerably and the final interpretation of the results. Hence comments are limited to points that will be useful to the changes to the next draft, rather than detailed text changes.

As a reference point, it would be very useful to calculate and plot the maximum theoretical ROP for the drill tips from the energy delivered and the volume of ice to be melted to allow passage of the drill head.  From this, an ROP efficiency can be calculated, therefore giving better context for each nozzle's performance.

Two different drill tips are used and the results from each differ, presumably as a result of the thermal condition differences between them when they come into contact with the ice. This was a key discussion point in Taylor 1984 and it shaped the design of the tips. This should also be discussed.

A fuller description of how the drill head was lowered into the ice would be helpful. Presumably, the head was allowed to rest on the ice to determine max ROP rather than a fixed assumed maximum lower rate. Use of load cell etc.

Plot 15 (and others) need to consider the energy input rather than just temperature. It is likely that the plots in 15 b are almost identical when this is considered.

In plots 11, 12, 15 the data should be smoothed to remove the high-frequency noise. This will make it easier to interpret the plots.

Units on axes need to be checked as some appear incorrect.

A fuller description of why some boreholes are uneven would be useful. Presumably related to poor head heat conduction.

Minor comments:

L24 change to ‘used to provide access holes for the observation’

Intro – emphasize the focus on sondes rather than drilled access holes, hence the big difference in equipment requirements.

Figures 1 and 2 – Add some basic dimensions and more labels for the items mentioned in the text. Is there a major difference between model and experimental setup? Add more labels. Including pt100 locations.

Table 2 text – do add the designations to this text.

Fig 5b and c missing?

Fig 6 highlight the void in the hollow cone with a different color. Why is the connection component in purple?

Fig15 text – add a referral to Fig6

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is devoted to the comparison of various nozzles when drilling the ice using jets of hot water. The article is written in a good and understandable language. The presentation is logical and well structured. 

I have only minor questions and comments. 

Figure 2: As I understand, the "internal" and "external" need to be changed in the figure caption

Why  the nozzles having  both forward and backward orifices  were not considered?

It was mentioned that the mathematical modeling is being under way. In my opinion, the results of mathematical modeling and optimization of nozzle design can greatly enhance the research. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf