A Hybrid Dynamic Model for the Thermal Compressor Heat Pump and Validation with Experimental Data^†

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents a well-structured and technically sound study on the development and validation of a hybrid dynamic model for a three-stage thermal compressor heat pump (TCHP) using CO₂ as the refrigerant. The work is novel in its application of a finite-volume (FV) based hybrid modeling approach implemented in Python, and its validation against both steady-state and transient experimental data is thorough and convincing. The model demonstrates good predictive accuracy and is well-suited for control-oriented applications. I recommend acceptance after minor revisions.

1. The manuscript occasionally uses incomplete sentences or abrupt transitions . A thorough proofreading is recommended
2. The authors note that the model does not fully capture the coupling between low-pressure valve changes and high-pressure dynamics. This limitation should be more explicitly discussed in the conclusion or model validation section.
3. The assumption of negligible pressure drops in heat exchangers should be justified with respect to its impact on model accuracy, especially in a multi-stage system
4. The authors claim the framework is transferable to other systems. It would be helpful to briefly suggest how the model structure or tuning process might adapt to different refrigerants or cycle configurations.
5. It is recommended to more clearly indicate the unique contributions of this review compared to existing reviews in the introduction or conclusion, such as the summary of the latest numerical simulation methods and the exploration of two-phase flow mechanisms.For example, . A novel in-situ sensor calibration method for building thermal systems based on virtual samples and autoencoder. 2. A coupled LBM-LES-DEM particle flow modeling for microfluidic chip and ultrasonic-based particle aggregation control method

Author Response

Comments 1: The manuscript occasionally uses incomplete sentences or abrupt transitions . A thorough proofreading is recommended

Response 1: A full proofreading has been done and the incomplete sentence and abrupt transitions have been corrected.

Comments 2: The authors note that the model does not fully capture the coupling between low-pressure valve changes and high-pressure dynamics. This limitation should be more explicitly discussed in the conclusion or model validation section.

Response 2: This limitation is now explicitly discussed in both the model validation section and the conclusion.

Comments 3: The assumption of negligible pressure drops in heat exchangers should be justified with respect to its impact on model accuracy, especially in a multi-stage system

Response 3: A justification has been added explaining why pressure drops were neglected in the model.

Comments 4: The authors claim the framework is transferable to other systems. It would be helpful to briefly suggest how the model structure or tuning process might adapt to different refrigerants or cycle configurations.

Response 4: A short explanation has been added describing how the model can be adapted to other working fluids or cycle architectures.

Comments 5: It is recommended to more clearly indicate the unique contributions of this review compared to existing reviews in the introduction or conclusion, such as the summary of the latest numerical simulation methods and the exploration of two-phase flow mechanisms.For example, . A novel in-situ sensor calibration method for building thermal systems based on virtual samples and autoencoder. 2. A coupled LBM-LES-DEM particle flow modeling for microfluidic chip and ultrasonic-based particle aggregation control method

Response 5: A paragraph has been added at the end of the introduction highlighting the main contributions of this work.

 

Detailed version is found in PDF!!

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Title:

A Hybrid Dynamic Model for the Thermal Compressor Heat Pump and Validation with Experimental Data

 

Contribution:

The manuscript presents a dynamic model of a CO₂ heat-pump system that uses heat-driven, Stirling-type thermal compressors (nominal ~8 kW). The model is positioned for control/optimization studies and performance benchmarking. Validation against experiments reports ~6 % MAPE at the system level with R² ~ 0.80; component heat-rate errors are within 20 % MAPE. Under transient step tests (expansion-valve opening and burner-fan speed), thermal COP and total recovered heat track within 4 % MAPE (R² up to 0.96); pressures show ≤1.5 bar MAE; evaporator heat rate has 14–22 % MAPE.

 

Comments:

1. In the abstract, please summarize your validation results, and clearly state (a) the novelty (heat-driven Stirling compressor, CO₂, transient validation), (b) the gap in prior models, and (c) your contribution.
2. Page 5, line 156, “With a small contribution of electricity compared to heat”, is the small electricity can be quantified? Or please add justification for this claim.
3. Is there any control design in this work? Or is it just model development and validation?
4. Typo: page 3 line 112, “steay-state” should be “steady-state”.
5. Typo: Figures 16 and 17: Total “recoverd” should be “recovered”.  

Author Response

Comment 1: In the abstract, please summarize your validation results, and clearly state (a) the novelty (heat-driven Stirling compressor, CO₂, transient validation), (b) the gap in prior models, and (c) your contribution.

Response 1: This was addresses and abstract is modified.

Comment 2: Page 5, line 156, “With a small contribution of electricity compared to heat”, is the small electricity can be quantified? Or please add justification for this claim

Response 2: I fixed this by adding a reference to this where this was dicussed in more details.

Comment 3: Is there any control design in this work? Or is it just model development and validation?

Response 3: This papaer offers only model development and validation. Control design is provided in another submitted paper still under review.

Comment 4: Typo: page 3 line 112, “steay-state” should be “steady-state”.

Response 4: Fixed

Comment 5: Typo: Figures 16 and 17: Total “recoverd” should be “recovered”.

Response 5: Fixed

 

Extended version is found in the PDF!!

 

Author Response File: Author Response.pdf