Study on Multi-Measures Joint Optimization Regulation of Temperature Control and Ice Melting for Water Conveyance Projects in Cold Regions

Round 1

Reviewer 1 Report

In this paper, two kinds of ice-melting measures are optimized to achieve ice-free water transmission in channels. The model and method have a good guiding significance for the actual ice-free water transmission project in winter, and provide another innovative idea for other projects to avoid the occurrence and solve the ice condition. This paper has good publication value, and there are still some that need to be improved, I list some as follows, and hope the authors go through the manuscript carefully once more:

Line 45-50：“.. and daily life along the line”. The background narration is more, the introduction of the main idea of the article is slower, and the content unrelated to the main idea can be appropriately deleted.

Line 62-214: In this part, the description of the research status of hydraulic measures, thermal measures (heat preservation, temperature increase, new energy utilization) and optimization regulation of ice-free water transmission is redundant, and the sentences or contents can be simplified.

Line 247：The scope of application of the two ice melting measures should be supplemented, and the universality of their calculation formulas should be explained.

Line 253: The titles of 2.1.1 and 2.1.2 are the same and need to be modified.

Line 283：The first line is not indented; Please check and modify the same parts below.

Line288-289：Is the reason for the active circulation system "for better heat transfer"? What idea does the author want to convey? Please describe in detail.

Line 293：”” The variable font should be italic.

Line316：”” This parameter is not involved in eq. (2), Should be deleted.

Line319: In the sentence "... without ice concentration..” The first half of the sentence can be changed to "for open waters without floating ice,..." .

Line324 and line336：As described in the article, "suppose that the interval length from the calculated point at the entrance of the channel to the point where the water temperature of the channel is equal to 0℃ is the non-icing length", but why is the water temperature of the cut-off section 0.4℃ shown in the figure?

Line 324-361:"the non-freezing length", "ice-free length", "the freeze-free length" in the figure and the article should be used in the same way.

Line 370: "S" is not represented in eq.(8).

Line 385：Genetic algorithm has been widely recognized, and it can be properly simplified and reduced in length when describing it.

Line 431: “m3/s” The format of the quantity unit is modified.

Line 545 and Line 548：Figure 10.(a) horizontal radiation unit please check, is it W or KJ?

Line661: The article describes "... and the change range of flow is greater than the change range of cost ". Whether this conclusion can show the specific value.

Line740 and Line784：The scope of application of the fitting formula should be described briefly.

Author Response

I have modified it according to your suggestion. Please see the revised paper and the attachment for the specific modification content.

Author Response File: Author Response.pdf

Reviewer 2 Report

REVIEW OF : Study on multi-measures joint optimization regulation of temperature  control and ice melting for water conveyance projects in cold regions

This study describes an investigation of the feasibility of providing ice-free open channel flow throughout the winter for the mid-latitude section of the North-South Water Transfer Project in China. 

There are two major objectives for the study. The first objective is to demonstrate the advantages of a muti-measure approach to ice-free winter operations employing both solar heating galleries and heated storage tanks. The second objective is to evaluate the overall benefit/cost ratio for ice-free operations compared to winter operation with an ice cover.

The study as presented contains a competent analysis of the advantages of using a multi-measure approach over a single-measure approach. However the study results for overall benefit/cost comparison of ice-free versus ice-cover operations as currently presented are not acceptable for publication.

The following are the changes I regard as necessary to the submitted manuscript.

Correction of error in benefit/cost summary

The study as presented contains the following major error in lines 797-800. Assuming the  most extreme case, that is the 90-day water transfer flow  in the winter operation period is 180 m³/s, and the comprehensive satisfaction rate is 100%, the operating cost is nearly 720 million yuan, and the comprehensive total benefit is nearly 220 million yuan, which is far greater than the costs.

There are three major deficiencies in this summary statement:

·        The stated benefit of 220 million yuan is not “far greater” than the costs of 720 million yuan, it is much smaller.

·        The comparison is made for operating costs only whereas a proper benefit/cost comparison must also include capital costs which are very large for the ice-free system

·        The numerical value of operating costs and comprehensive total benefits have not been presented and justified in the body of the paper that precedes this statement.

This erroneous statement must be corrected to make the study publishable. I suspect the costs have been misstated at 720 million yuan.  I have calculated the 90 day costs from data given in Tables 5 and 6 and get figures of 52 million yuan and 56 million yua n. Costs are presented in different forms throughout the paper. The full set of units for cost should be stated each time i.e. per hour. Per day or per 90-d period.

 However even if operating costs are lower than benefits this does not justify changing to ice-free operations.  Capital costs must be included. If caital costs are not available then no statement should be made about the relative value of ice-free versus ice-cover operations.

Improved explanation of procedure used to calculate longitudinal temperature profiles

Another major defect of the present paper is the inadequate presentation of the calculating procedure that generates the relationship between water temperature and distance along the canal as shown in Figures 14, 18, 19, 21, 22.

The most direct way to calculate the variation of temperature with distance along the flow path is to express the heat transfer fluxes as functions of distance and time and solve these equations as a continuous-in-time model with short time steps (hourly) for the entire 90 day period using input files for the varying meteorological variables of solar radiation, air temperature and wind speed. The authors should explain why continuous-in-time modelling was not done in this study.

Instead of continuous-in-time modelling a probability based approach of the combined probability of occurrence of set values of the three meteorological variables was used. This was combined with an assumption of a set pattern of hourly variation in meteorological parameters rather than the actual pattern of variation in these parameters from hour to hour and day to day.

The authors need to make clear how equation 3 for free-free length has been used to determine the variation of water temperature with distance as shown in

Figures 14, 18, 19, 21, 22.  This explanation should also justify the fixed hourly pattern of heating need that is used instead of basing hourly pattern of heating on the actual observed pattern of hourly variation in the meteorological variables.

Limitation on optimization of ice-free system

The authors should explain that it was not their intent to optimize the types and locations of heating equipment to achieve ice-free operation.  Optimization was performed on a specific set of heating equipment at set locations to determine the best operational mode for the heating tanks by varying temperature and flowrate.

Relation of Comprehensive Satisfaction Rate to actual winter-period flow rate

In practical terms the operators of the transfer system need to know what flowrate can be achieved by the ice-malting system.  The authors need to state the relationship between Comprehensive Satisfaction Rate and average 90-day flowrate achieved.  For example 100 % corresponds to the full intended flowrate – is there a linear relation between Comprehensive Satisfaction Rate and achieved increase in flowrate above 78 m³/s ?

I list below some additional defects that should be attended to before the paper is published.

(1) The discussion of the use of groundwater warming at the Hongshanzui Power Station found between Lines 81 and 89 and in Figure 1 should not be included unless this discussion is based on published studies or represents studIes done by the authors.  Also the label of Figure 1 says it is a schematic diagram but it is not a diagram it is a photograph and there must be photograph credit given if it is to be included.

(2) Figure 2 as included in this version of the paper is a repeat of Figure 1.  If the correct version of Figure 2 is a photograph it must show a photo credit.

(3) Is Figure 3 created by the authors of this paper or is it taken from another publication – if from another publication  permission must have been obtained.

(4) In Line 352 there is a discussion of the effect of “a certain distance between the water conveyance channels”   I do not understand what feature of the conveyance channel is being discussed.  Does this discussion relate to changes in the cross-section area of the channel  ?  also are the “unit channel sections” arranged in series or in parallel ?

(5) Figure  24 as presented does not show effect of downstream depth and should be replaced with the correct figure.

(6 )In Table 8 - What is the calculation equation for “single heating charge”  also What is the time unit for costs – is it per day ?

(7) In Figures 12-14 and in the text Line 592 the assumption is made that between the hours 12:00 and 14:00 no heating is required for the water storage tank. This assumption is applied to all days no matter how cold or how cloudy a day might actually be. This assumption does noy represent conditiond during days of extreme cold – why is this assumption made ?

OTHER EDITING COMMENTS

Line 32                      PV/T should be moved to start Line 33

Line 48                      The introductory description of China’s water problems and solutions needs a reference publication.

Line 51                      projects in cold regions with low latitudes in the north affected by cold weather in winter, ….

Line  108                   Reference needed for the statement on green power in China and USA

Line 122-125           Reference needed for NEXUS project.

Lines 184-187         This sentence must be revised to list what data and analyses must be combined “to achieve the goal of ice-free water conveyance”.

Line 216                    conveyance of channels in winter, and THERE IS A lack of research……

Line 332                    In equation 3 what are the units for the coefficient of channel slope n_{rou ?}

Line 347                    I understand that the flow through the heating water storage tank is pumped out of the canal, heated, and returned to the canal. If this is correct the second term in the numerator of equation 6 should be (Q- aQ_inc) T_w  and the denominator should be simply Q.

Line 430                    In Table 1 slope is not defined as to whether it is longitudinal slope or the side slope of the cross section and the units for slope are missing. Also length is not defined – is it the wetted perimeter  or the top length of the gate ?

Line 570                    In the label for Figure 14 what are the % values of 100%, 79% 56%, 37% referring to ???  Also what does the upward sloping line referring to in each graph ?

Line 602                    The label for Figure 16 says different satisfaction rates are involved.  The figure as show has no satisfaction rates and must be corrected.

Line 604                    In Table 5 are the average hourly flow rates shown for the flow from the heating water storage tank ?

Comments for author File: Comments.pdf

English language is adequate

Author Response

I have modified it according to your suggestion. Please see the revised paper and the attachment for the specific modification content.

Author Response File: Author Response.pdf

Reviewer 3 Report

The study is devoted to a pressing issue - increasing the efficiency of water transfer taking into account the winter period.

The scientific novelty of the research is beyond doubt.

The manuscript is well structured, the results of the study are logically presented, the analysis is carried out at a modern level, and various methods of data analysis are used.

The results obtained by the authors can be used by other researchers when choosing data analysis methods and for developing similar water transfer projects.

A small number of typos in the text of the manuscript do not spoil the overall good impression of this important study, but in some places it makes it difficult to understand the results presented.

I can recommend this manuscript for publication after making minor changes.

Please, see some comments in attached file/

Comments for author File: Comments.pdf

Author Response

I have modified it according to your suggestion. Please see the revised paper and the attachment for the specific modification content.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The revised paper is now free of deficiencies and is ready for publication .