The diploma thesis deals with the calibration of thermal conductivity measurements in vacuum and analyzes an existing thermo-vacuum measurement setup. The topic is practically relevant for laboratory verification of thermal hardware and low-conductivity samples.

The student worked on the thesis continuously during the semester and consulted mainly the text, structure, formatting, and formal expectations. The experimental and technical work was performed primarily at the Faculty of Mechanical Engineering under the guidance of a consultant.

The main strength of the thesis is the practical analysis of the measurement system. The author verified the heating loop, analyzed the temperature dependence of heating resistors, investigated heat-loss mechanisms, tested insulation improvements, and assessed the behavior of temperature and heat-flux sensors. These results provide useful input for further development of the laboratory setup.

During the work, limitations of the existing equipment were identified. The thesis shifted from a direct calibration procedure toward a diagnosis of the measurement chain and proposal of future modifications, which can be justified. However, the relation between the original assignment and the final direction of the thesis could have been described more explicitly, so that the reader is guided more clearly through this reasoning. Additionally, some parts could be improved by clearer terminology or more consistent explanation of abbreviations.

Overall, the student demonstrated a good understanding of the measurement problem and produced useful practical results. I recommend the thesis for defense with grade 89/B. Points proposed by supervisor: 89

The student submits a master’s thesis written in English dealing with the calibration of thermal conductivity measurements in vacuum, more specifically with the analysis and verification of the current measurement system in a thermo-vacuum chamber. The topic is highly relevant for laboratory measurements at the Institute of Aerospace Engineering, Brno University of Technology.

The thesis provides a very detailed analysis of the current state of the instrumentation and correctly identifies the main shortcomings of the measurement chain. I positively evaluate in particular the systematic verification of the heating loop, the temperature dependence of the resistors, the accuracy of the current source, the influence of radiative and conductive losses, the repeatability of the FHF02 heat flux sensor measurements, and the properties of the temperature sensors used. The student demonstrated good understanding of the topic and approached the work in a comprehensive manner. The experimental reduction of part of the heat losses, consultations with experts, and the proposal of modifications to the measurement system for future use are also valuable. From this point of view, the results are well applicable in laboratory practice.

The weaker aspect of the thesis is its relation to the original assignment and instructions. The assignment was primarily focused on the development of a calibration methodology, a calibration plan, and experimental verification of measurements at the level of 10⁻² W/K. However, the thesis ultimately represents rather a thorough diagnosis of the limitations of the current apparatus and a proposal for a new measurement system concept. This shift is technically understandable and valuable for the further development of the laboratory, but it should have been described, justified, and related to the individual points of the assignment more clearly in the text. Measurement uncertainties are not presented as a complete quantitative uncertainty budget. The experimental verification of the proposed procedure on samples is therefore only partially fulfilled.

In terms of graphical, stylistic, and formal quality, the thesis is prepared at a good level. I have minor reservations regarding the use of the abbreviation TCR with multiple meanings, and the less clear distinction between verified results and recommendations for future modifications of the apparatus. Despite the partial fulfilment of the assignment, I appreciate the scope of the work performed, the student’s own contribution, and the practical applicability of the conclusions. I recommend the thesis for defence and evaluate it with grade B (very good). Topics for thesis defence:

1. 1) Could you estimate the percentage share of the main potential heat losses in the original measurement setup for 2 W and 4 W heating? Please include radiation, conduction, cable/harness losses, and possible input power error. Where experimental data are missing, provide an engineering estimate and explain your assumptions.
2. 2) Did you observe any influence of ambient temperature or chamber wall temperature on the measurements, especially with respect to steady-state conditions, repeatability, and radiative heat losses?
3. 3) Could you propose a calibration procedure for the FHF02 heat flux sensor, assuming the sensor itself is functional and stable?

Points proposed by reviewer: 87