Performance Characteristics of Custom Thermocouples for Specialized Applications
Round 1
Reviewer 1 Report
The manuscript entitled “Performance Characteristics of Custom Thermocouples for Specialized Applications” authored by Abdul-Sommed Hadi et al., is very interesting and describes the design and development of thermocouple with pyrolytic graphite (PG) in connection with aluminium, copper, steel and tungsten thermo elements, for use in elevated temperatures, metal casting operations. The paper is generally well written and structured. However, in my opinion the paper has some shortcomings regarding some data analyses and text, and I feel this unique dataset has not been utilized to its full extent. Below I have provided numerous remarks on the text as it is often vague and long-winded. In several instances I also suggested to cite more relevant and recent literature. Furthermore, I made additional suggestions for more in-depth analyses of the data. Key critical points are:
Q1. In the abstract, P1, L-17 the authors reported that “It is shown that hysteresis can affect the sensitivity of the thermocouples”. However, throughout the paper, the hysteresis effect is not mentioned anywhere even though there are thermoelectric potential data collected while heating as well as cooling. Draw the heating-cooling graphs together and explain the hysteresis effects on all PG-based thermocouples.
Q2. P2, L-76 crystallinity, types of defect, phonons, presence of impurities, and the carrier type and concentration [4].
Please remove one “and”
Q3.P2, L-87-91 Due to the extreme environments in which TCs operate, properties such as melting point, thermal conductivity, heat capacity and coefficient of thermal expansion electrical conductivity, corrosion resistance and density for weight regulation were paramount for selecting the materials.
A lack of discussion on the effect of coefficient of thermal expansion on the performance of the sandwiched thermocouple samples? Address the post analysis of the thermocouple on this perspective.
Q4. P3, L-109-110” Alloys of aluminum and their pure forms are highly corrosion resistant because of the forming of an oxide layer that protects them, and are therefore used for high strength and critical applications”
Change forming into “formation”
Q5. P3, L-136 Tungsten is a refractory material and has the highest melting point (> 3000oC) among all the variable thermoelements
Please change material into “metal”
Q6. P4, L-146 preparation prior to SEM imaging is a critical step to obtaining quality images.
Please change obtaining into “obtain”
Q7. P5, L-174 used as the second thermoelement, whiles flat Cu wires of dimensions 26 × 15 × 0.35 mm 174
Please change whiles into “while”
Q8. How well the thermocouples respond to real time? Show the longevity of the thermocouples on a voltage vs Time Graph? How accurate the performance of the new thermocouple compared to a commercial K-type thermocouple? What is the response time?
Q9. The test results of all the PG//Al, PG//Cu and PG//W thermocouple indicate a near linear responses from 0-450°C. Describe how these thermocouples are superior or better than a commercially available K-type thermocouple or RTD? Could you compare the cost because already there are K-type thermocouples (-200° to 1250°C) and RTD (up to 850°C) available in the market.
Q10. In the manuscript, P7, L-208 and 209 the author mentioned that “The thermopower of all four thermocouples compares favorably with commercial thermocouples used in the industry for metal casting purposes” Please explain how these thermocouples favour casting industries?
Q11. Elaborate Figure 2. Caption with thermocouple type used
Q12. Elaborate Figure 3. caption and the Seebeck coefficients of the sensors under heating and cooling cycles are determined from experimental data up to 500℃. List the fitting parameters and the R-square values of the Seebeck coefficients evolved from the linear regression analysis on a table.
Q12. Elaborate Figure 4. Caption and indicate the fitting parameters of the linear regression analysis with R-square values on a table.
Q13. Show the cycling graphs Voltage-Temperature plots that indicates the repeatability of the performance of PG based thermocouple.
Comments for author File: 
Comments.pdf
Author Response
Responses
Q1-- This was addressed by removing the discussion of hysteresis that was discussed in prior work, but not applicable to the data shown.
Q2,Q4,Q5,Q6,Q7 -- These changes were made. Thank you
Q3 Discussion was added near line 87 of the manuscript
Q8,Q9, and Q10 These were addressed near line 230 to discuss the topics of longevity, comparison of other thermocouples, and how these are favorably compared.
Q11,Q12 Figure captions and figure have been revised
Q13. A new figure was added to show the temperature and voltage differential over time for one of the test runs as an example on page 7.
Reviewer 2 Report
The authors presented a customized thermocouple design using pyrolytic graphite for specialized applications. Please address following questions before it can be considered for publication:
- After read through the manuscript, I didn’t find the specific reason that PG benefit the performance of TCs. Please make it clearer.
- How’s the influence of different thermoelement is excluded from the consideration? The Seebeck coefficient of Cu, Al, W and steel is different, and the difference of Seebeck shown in Table 2 is also close to each other.
- The PG part is made by compressing graphite flakes without a binder. So it seems like it is not a robust one. How’s this would be used for a real TC demonstration further?
- In Table 1, what the “other (wt%)”? And how these “others” will influence the results?
Author Response
Q1 These are addressed in a new paragraph at line 230 as well at line 91.
Q2 Addressed at line 69 in the updated manuscript
Q3 Addressed in the comments on line 96 as well as brief discussion.
Q4 Addressed in the comments at line 166 for the figure.
Round 2
Reviewer 1 Report
Thank you very much for the corrections.
