INDUSTRIAL FINAL PRESENTATION FROM Lyd
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INDUSTRIAL FINAL PRESENTATION FROM Lyd
- 1. T. Nuttall, L. Jim, J. Stevenson, C. Grimshaw, R. Lee, A. Saunders & H. Owens PHY 346 TATA Group Industrial Project: Unglazed Transpired Solar Collectors
- 2. Design Brief How does surface microstructure affect the retention of the thermal boundary layer? Wind TSC Building Wall Fan Plenum Sun Hot Air What is the effect on performance of a heat reflecting wall?
- 3. Development
- 4. Surface Structure Stereolithographic Approach Adhesion Hydraulic Press
- 6. Method Efficiency: 𝜂 = 𝑣𝑠× 𝐴 𝑝𝑖𝑝𝑒 × 𝜌 × 𝐶 𝑝 × 𝑇𝑜𝑢𝑡𝑙𝑒𝑡 − 𝑇𝑎𝑚𝑏𝑖𝑒𝑛𝑡 𝐺 × 𝐴 𝑡𝑠𝑐
- 7. Lamp Stability 0 100 200 300 400 0 50 100 150 200 Irradiance (W/m^2) Time (minutes)
- 8. Lamp Stability 0 20 40 60 80 100 0 50 100 150 200 Lamp Temperature (◦C) Time (minutes)
- 9. Effect of Mass 0 20 40 60 80 100 848 852 856 860 864 % Efficiency Mass (g)
- 10. Wind Effect on Thermocouple Measurements 23.25 23.5 23.75 24 0 20 40 60 80 100 120 Temperature (◦C) Time (s) With Fan Without Fan
- 12. Different Backing Material 0 50 100 % Efficiency Matte Black Tape Avg 863.0g Aluminium Avg 863.0g Control 863.0g 94.7 ± 2.3 % 94.6 ± 2.3 % 95.1 ± 3.3 %
- 13. 0 50 100 % Efficiency Glue Channels Glue Channels Control blank Circles on Holes Circles on Holes Control blank Circles Out Circles Out Control Surface Structure with No Wind 92.3 ± 3.5 % 94.3 ± 3.5 % 90.4 ± 3.5 % 93.8 ± 3.5 % 92.1 ± 3.2 % 91.4 ± 3.2 %
- 14. 0 50 100 % Efficiency Wavy Wavy Control blank Cocktail Sticks Cocktail Sticks Control Surface Structure with No Wind 83.4 ± 2.5 % 90.4 ± 2.5 % 88.5 ± 2.5 % 91.1 ± 2.5 %
- 15. 0 50 100 % Efficiency Control Average Wavy Cocktail Sticks Circles on Holes Circles In Circles Out Surface Structure with Wind 46.1 ± 3.3 % 52.5 ± 3.1 % 52.5 ± 3.6 % 50.2 ± 3.4 % 44.5 ± 3.1 % 50.3 ± 3.1 %
- 16. Conclusion Reflective and absorbing wall covering – No significant difference Surface Structure without wind – Opaque objects reduced efficiency Surface Structure with wind – Improved performance for separated, curved structures Improvements
- 17. Questions?
Editor's Notes
- First is the microstructure of the surface of the solar collector. How does surface microstructure affect the retention of the thermal boundary layer? Tata have found that product that has a thin logo embossed onto the surface performs better than those without. 3D printing could be used to prototype different microstructures to better understand this effect. The second concerns the way heat is retained in the air space behind the solar collector surface. If the back surface of the this space reflects heat does it increase the overall performance of the system, or reduce it? A potential third line of investigation concerns the colour (and emissivity) of collector. Traditionally solar collectors have been black or very dark grey. An investigation into some specific new coating materials is required. The new coating will be made available later in the project from Tata.
- Original plan was to use 3D printing to create surface structure however the equipment available to us was deemed inappropriate for our purposes. The 3D printers in the physics lab here in Sheffield were unable to provide the resolution we needed. We looked into using some of the more advanced equipment in the mechanical engineering department, stereolithography machines used for commercial ventures were invented by Neil Hopkinson at Loughborough university who fortunately now works here at Sheffield, bringing his machines with him. Unfortunately he was of the persuasion while in principle it may be possible to adhere polymer powder to a metal substrate, the dimensions we were working with are much larger than any machine/build currently available at Sheffield and that in fact, in terms of bed size, the machine required to do this would constitute a rather large machine even in the commercial world, though they do exist, he was sure they wouldn’t be available for external projects. If the technology at Sheffield were apt, however, it wouldn’t have been available to us in the time frame we were afforded due to it being committed almost exclusively to PHD projects in that department. As such we have had to explore other options. Small objects, similar in size and consistency to those we intended to print were glued on to the surface of the steel sheets with epoxy resin, this obviously constricted us in what we were able to achieve. We have some examples of sheets tested in our rig. (SHOW SHEETS) It was important to take into account the mass increase and reduction in exposed surface area these additions offered and this was taken into account when comparing these sheets with controls, in that the controls were chosen to be of similar mass. The thermal capacitance of the sheet as a whole (protuberances included) is important and this, too, was taken into account. We wanted further variation in our test sheets and so looked to the workshop for assistance in distorting the steel sheets themselves, again, resources and time were limited but we were given access to a hydraulic press with which we stamped 18mm radius indentations 2mm deep to provide a change in surface structure whilst retaining thermal mass and surface exposure. We experimented with having the indentations come out from the surface and go in, over the holes and alongside them. All were tested and the results we’ll talk about later.
- How the rig works air-tight chamber with mounting for TSC under test fan pulls air through the TSC, and past thermocouple, which outputs temp to LabView External lamp and fan provide environmental conditions LabView reads ambient temp and outlet temp Use Excel to calculate difference and then efficiency…
- 𝐶 𝑝 is the specific heat capacity (Jkg-1K-1) , 𝑇 𝑜𝑢𝑡𝑙𝑒𝑡 is the cavity exit air temperature (K) , 𝑇 𝑎𝑚𝑏𝑖𝑒𝑛𝑡 is the ambient air temperature (K) and 𝐺 is the solar radiation (Wm-2) incident on the tsc. suction velocity 𝑣 𝑠 at the out;et, where 𝐴 𝑝𝑖𝑝𝑒 is the area of the pipe (m2), 𝜌 is the air density (kgm-3) and 𝐴 𝑡𝑠𝑐 is the area of tsc exposed to solar radiation. How we used the rig Bang sheet in Switch lamp on Press Go in Labview Present Formula Used Efficiencies calculated may not be accurate but is repeatable so allows us test performance relatively. Explanation of comparison method (every experiment was carried out with a control experiment on the same day since lab conditions varied from day to day)
- Pre-Test aim: find out how much the lamp light output varies with time. Method: Place Irradiance meter at the rig distance from the lamp and measure the irradiance over time. Results: Lamp output fluctuates by 2% with time. Discussion: Hence it was reasonable to state that the lamp gives a steady output. -> The irradiance on the tscs during tests will not be affected by how long the lamp will be on for.
- Pre-Test aim: find out how much the lamp temperature output varies with time because the lamp heating will contribute to black body radiation. Method: Place thermocouple on the lamp and measure the temperature over time after the lamp temperature has reached an equilibrium. Results: Lamp temperature fluctuates by 0.4% with time. Discussion: Hence it was reasonable to state that the lamp temperature remains constant with time. -> The blackbody radiation incident on the tscs during tests will not be affected by how long the lamp will be on for.
- Context: The tsc sheets give to us were of varying masses. Heavier tscs may store more heat. Method: Measure the efficiencies of un-altered tscs of varying masses. Additionally a doubled up tsc was tested. Results: The results lie in the range 89.3% to 94.7 % with 2.5-3.5% error. The doubled up tsc had an efficiency of 91%. Discussion: Results are consistent with each other. No significant difference due to mass difference.
- Context: In the test rig, thermocouples will be used to measure the temperature of the outlet air; wind due to the extraction fan will be incident on thermocouple. Aim: To observe if the incident wind on the thermocouple will have a significant effect on the temperature measurement. Method: A thermocouple was situated above a 6cm diameter fan with variable wind speed (approx. 7m/s -13m/s, measured at the point of the thermocouple). Another thermocouple was placed some distance apart with no incident wind. Results: The mean temperature difference was 0.24±0.03 degrees. Discussion: The temperature fluctuations for the two thermocouples are very similar and the mean temperature difference is small compared to the difference in temperature between the ambient air and the outlet air. This supports that the incident windon the thermocouple in the outlet will not significantly affect the thermocouple measurement with respect to the tsc tests.
- Aim: Find if covering the back wall of the cavity with an absorbing or reflective material affects the efficiency Method: Test a tsc with no additional materials as a control and then repeat the test with the back wall of the cavity covered in matte black tape and aluminium tape seperately. Results:. Black Tape: (94.7 ± 2.3) % Aluminium (9 4.6 ± 2.3) % Control (95.1 ± 3.3) % Discussion: Results agree well with each other. No significant effects.
- Aim: Find if surface structure affects efficiency Method: Test an unaltered tsc as a control and then repeat the test with the altered tsc. The control and the altered tsc were tested on the same day to minimise systematic errors due varying conditions in the lab Results: As displayed. Discussion: All altered tsc except the tsc with wavy surface structures had results that agree well with their controls. The tsc with wavy surface structures appear to perform worse than its controls.
- Aim: Find if surface structure affects efficiency Method: Test an unaltered tsc as a control and then repeat the test with the altered tsc. The control and the altered tsc were tested on the same day to minimise systematic errors due varying conditions in the lab Results: As displayed. Discussion: All altered tsc except the tsc with wavy surface structures had results that agree well with their controls. The tsc with wavy surface structures appear to perform worse than its controls.
- Reflective and absorbing wall covering were tested with a control. There was no significant difference in performance. Tscs with surface structure were tested without wind with controls. The tscs with pressed and epoxy channels surface structure did not a significant difference in performance. The tscs with objects adhered to the surface showed inferior performance when compared to the control sheets. We suspect that this is because of the reduction of the exposed surface area of the TSC, since the objects had lower specific heat capacity. The TSCs with surface structure were tested with wind, and compared with controls. Those with separated, curved surface structure performed significantly better than the controls. This could be due to the separated, curved surface structures aiding the retention of the thermal boundary layer in windy conditions; this hypothesis could be tested using a thermal imaging camera to see the regions around the curved surface structures are warmer than the surrounding regions in windy conditions It should be recognised that a comparison method was used to obtain the results and the efficiencies determined using the test rig may not be an accurate representation of the true efficiencies of the tested tsc systems. More controlled environment: room temperature changed with time, background light, open windows Better ambient temperature.