A Novel Capacitive Model of Radiators for Building Dynamic Simulations

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The text presents a study focusing on the challenge of accurately calculating
energy savings in buildings by optimizing heating systems. Despite the
significance of the topic, the paper exhibits structural and methodological
weaknesses that should be addressed to enhance its scientific value.

From the very beginning, there is a noticeable discrepancy with the
formatting required by academic journals. The standard information about the
authors, including their affiliations and emails, is missing, which is a significant
omission. Additionally, the "Author Contributions" section (lines 419-432) is not
structured according to the required standards.

Content-wise, the study addresses an important aspect of building energy
efficiency by proposing a new zero-dimensional capacitive radiator model
integrated into the TRNSYS simulation environment. The finding that ignoring
the capacitive effect leads to an underestimation of heating energy consumption
by approximately 20% is particularly noteworthy. However, the analysis of the
obtained results remains limited, as there is no statistical processing of the data.
Including statistical tests would be crucial to confirm the significance of the
observed differences between the capacitive and non-capacitive models.

The figures in the paper also require improvement. The captions in Figures
3-10 are excessively large and visually unappealing, making it difficult to read
and accurately interpret the presented data. Reducing the font size would enhance
the clarity of the information and improve the overall aesthetics of the paper.
Moreover, incorporating more visual comparisons, such as graphs illustrating
temperature dynamics over different time periods, would make the presentation
more intuitive for the reader.

Another issue lies in the structure of the text, specifically the merging of
the "Discussion" and "Conclusion" sections. This makes it difficult to distinguish
between the interpretation of results and the study's final conclusions. Separating
these two components would help readers better follow the argumentation and
logical sequence of the paper.

Beyond structural and visual aspects, the references also require revision.
It is unclear whether they are formatted according to the journal's requirements,
which poses a risk of non-compliance with academic publication standards. It is
recommended that all cited sources be aligned with the template, ensuring
complete accuracy in the formatting of bibliographic data.

In conclusion, while the study makes a valuable contribution to
understanding the energy efficiency of heating systems, it requires substantial
improvements in both methodological and structural aspects. Adding statistical
analyses, refining the visual elements, separating the discussion and conclusion
sections, and adhering to the formal requirements of academic journals would
significantly enhance the quality and scientific credibility of the presented work.

Author Response

The authors are grateful to the reviewers for the comments provided which were useful to further improve the quality of the Manuscript. Each comment of the has its dedicated reply which is marked by a number (R1.1, R2.3..) and the integration of each comment within the Manuscript has a pinned comment with the same number labelled. Modified parts are highlighted in yellow for the sake of clarity.

 

Reviewer #1

The text presents a study focusing on the challenge of accurately calculating energy savings in buildings by optimizing heating systems. Despite the significance of the topic, the paper exhibits structural and methodological weaknesses that should be addressed to enhance its scientific value.

1. From the very beginning, there is a noticeable discrepancy with the formatting required by academic journals. The standard information about the authors, including their affiliations and emails, is missing, which is a significant omission. Additionally, the "Author Contributions" section (lines 419-432) is not structured according to the required standards.

R1.1: Thank you for the comment. The formatting has been checked and modified according to the guidelines. The author contributions list at the end of the manuscript has been removed and replaced by the (†) symbol at the beginning of the Manuscript linked to the authors’ names, according to the guidelines.

2. Content-wise, the study addresses an important aspect of building energy efficiency by proposing a new zero-dimensional capacitive radiator model integrated into the TRNSYS simulation environment. The finding that ignoring the capacitive effect leads to an underestimation of heating energy consumption by approximately 20% is particularly noteworthy. However, the analysis of the obtained results remains limited, as there is no statistical processing of the data.
   Including statistical tests would be crucial to confirm the significance of the observed differences between the capacitive and non-capacitive models.

R1.2: Thank you for your insightful comment. We appreciate the reviewer’s suggestion regarding statistical validation. While we agree that statistical tests as χ², t-students, or ANOVA could be useful for quantifying discrepancies between models in studies involving stochastic variability, our study is based on a deterministic mathematical model. The governing equations describe heat transfer phenomena without random variability, and thus, statistical tests—typically used to assess uncertainty or variability in empirical studies—are not applicable in this context. The observed 20% difference in heating demand arises directly from the thermal inertia effect, a phenomenon well-established in heat transfer theory. This effect results in a slower increase in the radiator temperature, leading to a smoother evolution of the heat transfer rate to the ambient. Moreover, our sensitivity analysis systematically explores the impact of key parameters, further confirming the consistency of the results across different conditions. An experimental analysis of the radiator performance is planned for future work. In the meantime, we have validated our model by comparing its simulated design performance—using the manufacturer's technical data—with that of a real radiator, as described in the Results section. Moreover, we have revised the Discussion section to explicitly state why statistical validation is unnecessary in this context, also following comment number 4 of the reviewer.

 

3. The figures in the paper also require improvement. The captions in Figures 3-10 are excessively large and visually unappealing, making it difficult to read and accurately interpret the presented data. Reducing the font size would enhance the clarity of the information and improve the overall aesthetics of the paper. Moreover, incorporating more visual comparisons, such as graphs illustrating temperature dynamics over different time periods, would make the presentation more intuitive for the reader.

R1.3: Thank you for the comment. Font size in Figures 3-10 has been reduced to improve readability and enhance the overall aesthetics of the paper. Additionally, the visual presentation has been improved by incorporating clearer graphical comparisons to better illustrate temperature dynamics over different time periods and ensure a more intuitive and accessible interpretation of the results.

 

4. Another issue lies in the structure of the text, specifically the merging of the "Discussion" and "Conclusion" sections. This makes it difficult to distinguish between the interpretation of results and the study's final conclusions. Separating these two components would help readers better follow the argumentation and logical sequence of the paper.

R1.4: To improve clarity and readability, the Discussion and Conclusion sections have been separated, ensuring a clearer distinction between the interpretation of results and the study’s final conclusions.

 

5. Beyond structural and visual aspects, the references also require revision. It is unclear whether they are formatted according to the journal's requirements, which poses a risk of non-compliance with academic publication standards. It is recommended that all cited sources be aligned with the template, ensuring complete accuracy in the formatting of bibliographic data.

R1.5 : We appreciate the reviewer’s feedback on the references. The formatting has been carefully checked to ensure full compliance with the journal’s requirements, aligning all cited sources with the specified template and verifying the accuracy of the bibliographic data.

In conclusion, while the study makes a valuable contribution to understanding the energy efficiency of heating systems, it requires substantial improvements in both methodological and structural aspects. Adding statistical analyses, refining the visual elements, separating the discussion and conclusion sections, and adhering to the formal requirements of academic journals would significantly enhance the quality and scientific credibility of the presented work.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The paper shows a novel radiator model implemented in TRNSYS. I think the paper and the topic are interesting. I have some comments.
1. The introduction should be more concise. The references from [12] to [16] are TRSNSY simulations mainly oriented on generation equipment, not radiators.
2. I am missing some model validation.
3- Types with ODE  are time-consuming and have convergence problems; could you provide some information on this?
4 In lines 337-338, Figures 8,9, 10, and 11I think they are incorrectly numbered.

Author Response

The authors are grateful to the reviewers for the comments provided which were useful to further improve the quality of the Manuscript. Each comment of the has its dedicated reply which is marked by a number (R1.1, R2.3..) and the integration of each comment within the Manuscript has a pinned comment with the same number labelled. Modified parts are highlighted in yellow for the sake of clarity.

Reviewer #2

The paper shows a novel radiator model implemented in TRNSYS. I think the paper and the topic are interesting. I have some comments.

1. The introduction should be more concise. The references from [12] to [16] are TRSNSY simulations mainly oriented on generation equipment, not radiators.

R2.1: Thank you for the comment. The introduction has been rewritten in a more concise way by streamlining the discussion while maintaining the necessary context. Therefore, the discussion of the references from [12] to [16] have been revised to ensure relevance on the focus on radiators and dynamic heat transfer modelling.

 

2. I am missing some model validation.

R2.2: Thank you for the comment. While our study primarily focuses on developing a novel capacitive radiator model and demonstrating its dynamic behaviour through theoretical and numerical analysis, we acknowledge that direct experimental validation is essential for confirming the model accuracy. For the current work, we relied on a rigorous sensitivity analysis and a comparative evaluation against a well-established non-capacitive model in TRNSYS. These comparisons serve as an indirect validation by showing that our model more accurately captures the transient dynamics observed in realistic heating scenarios. We recognize that incorporating experimental data would further strengthen the validation of our approach. However, to validate the model, its performance was compared to the design performance of a real radiator, as specified by the manufacturer's technical data and in accordance with Reviewer 1's comments.

 

3. Types with ODE  are time-consuming and have convergence problems; could you provide some information on this?

R2.3: Thank you for your comment. While it is true that ODE solvers can be time-consuming and may present convergence challenges, the proposed model was developed with computational efficiency in mind. We used a 0D approach in order to minimize computational burden and employed a numerically stable solver (ode15s in MATLAB), which is well-suited for stiff differential equations. In the simulations performed, the computational time remained reasonable, and no significant convergence issues were observed. A brief discussion has been added in the Model section of the manuscript to clarify this aspect and provide insights into the solver selection and performance.

4. In lines 337-338, Figures 8,9, 10, and 11. I think they are incorrectly numbered.

R2.4: Thank you for the comment. We appreciate the reviewer’s careful review and attention to detail. The numbering of all the Figures has been verified and corrected.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

After reviewing the revisions made, I consider that the manuscript has been sufficiently improved to justify publication in Thermo. I accept the manuscript with the corrections made, but the references need to be formatted according to the journal's template requirements.