A Flexible Heat Exchanger Network Synthesis Method Adapted to Multi-Operation Conditions

Round 1

Reviewer 1 Report

The authors proposed a flexible heat exchanger networks (HEN) synthesis method for the designing of HEM. The multiperiod operation conditions, uncertainty of parameters and phase changes in streams are considered. The method has several procedures, including initial HEN topology generation, critical points identification, multiperiod flexibility tests and improvement of HEN. An example of ammonia synthesis is used to validate the application of the proposed method. The flexible HEN synthesis method can be used for industrial multiperiod processes. The method has its novelty and is clearly described. I suggest the paper can be accepted after minor revision.

1) There are two symbol explanations in Section 7 and Appendix A. I suggest a nomenclature can be provided, which contains all the symbols appears in the paper. Although some symbols are explained flowing the equations, they should be also included in the nomenclature.

2) Will the phase change processes influence the heat transfer coefficient and how to consider it?

Author Response

Response to Reviewer 1 Comments

Point 1: There are two symbol explanations in Section 7 and Appendix A. I suggest a nomenclature can be provided, which contains all the symbols appears in the paper. Although some symbols are explained flowing the equations, they should be also included in the nomenclature.

Response 1: According to the suggestion, a new nomenclature has been created, which includes all symbolic interpretations. The symbol interpretations in the appendix have also been transferred to the new nomenclature.

Point 2: Will the phase change processes influence the heat transfer coefficient and how to consider it?

Response 2: In order to simplify the calculation, the effect of phase change on the heat transfer coefficient is not considered in this paper. However, in the actual process, the heat transfer coefficient of the stream with a phase change is greater than that without a phase change. I have mentioned this in my modified article too. More accurate computational models will be the next step in my research and will be considered in my next paper.

Reviewer 2 Report

The authors presented an interesting manuscript that discusses the problem of optimizing the heat exchanger network in an ammonia production plant. It seems to me that the text may be of interest to people who design such installations.

In general, I have no substantive comments to the text. However, it is required to introduce a few changes that will improve the readability of the presented material.

1. When the SI system of units is used, both temperature and its change are expressed in Kelvin, not degrees Celsius.

2. The list of symbols should be updated and include all symbols used in the work. For example, I have not found an explanation of all the symbols shown in Fig. 1 on a gray background.

3. The bibliography is incomplete, there are a few items missing which the authors refer to in the text.

4. All coefficients appearing in the equations and given in the manuscript should be accompanied by the source of the literature they come from.

5. The signum function should not be italicized.

6. The formatting of equations throughout the manuscript should be consistent. The multiplication sign (asterisk) is rather uncommon in scientific texts. In some equations the variables are in italics and in others they are not, this should be standardized.

Author Response

Response to Reviewer 2 Comments

Point 1: When the SI system of units is used, both temperature and its change are expressed in Kelvin, not degrees Celsius.

Response 1: According to the expert’s opinion, the symbolic unit of temperature in the text has been changed from °C to K, which includes a change in the temperature value in °C for the relevant formula. The revised location are partly marked in red in Nomenclature.

Point 2: The list of symbols should be updated and include all symbols used in the work. For example, I have not found an explanation of all the symbols shown in Fig. 1 on a gray background.

Response 2: A new list of symbols has been generated that includes all symbols used in the work, such as the explanation of all symbols in the grey background of Figure 1.

Point 3: The bibliography is incomplete, there are a few items missing which the authors refer to in the text.

Response 3: Thanks for the tip. After checking the references three places were missing, which have been updated and reconfirmed.

Point 4: All coefficients appearing in the equations and given in the manuscript should be accompanied by the source of the literature they come from.

Response 4: All sources of coefficients are labelled in the text clearly in case study. Some of them are from the actual process example, the others are from another case in the previous papers about heat exchangers network, which is mentioned in case study. Besides, the coefficients for the formulas are defined by the substance ammonia.

Point 5: The signum function should not be italicized.

Response 5: Adjustments and corrections have been made to the signum functions in the text and equations in the method part.

Point 6: The formatting of equations throughout the manuscript should be consistent. The multiplication sign (asterisk) is rather uncommon in scientific texts. In some equations the variables are in italics and others they are not, this should be standardized.

Response 6: Equations formatting throughout the manuscript are rechecked and confirmed to be consistent. All multiplication sign (asterisk) are omitted. In addition, the use of italics in the equations has been standardized.