TMT - Test Demonstration of Thermal Control Hardware
Team: Marshall Benson, Marlee Jacobs and Carson Rebar
Project Description
Thermal Management Technologies partnered with Utah State University to design and build custom fixtures and heaters for testing a thermal switch in a vacuum (TVAC) environment. The project tested for thermal resistance, evaluated performance across survivable temperatures from —60℃ to 85℃, and included thermal cycling and vibration testing to assess durability. These results validated the switch's performance for space-like operating conditions.
Thermal Design Overview
- Test Fixture mounts switch to TVAC plate in vacuum chamber and regulates switch temperature.
- PID-controlled heaters regulate temperature.
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Top heater provides constant heat input for resistance testing.
- 39.7 Ω flexible heater used on top plate
- DC power supply enables adjustable heat rates.
- TVAC plate is maintained at —80 °C using liquid Nitrogen and PID temp controller.
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10 PT-100 thermistors monitor temperature and provide PID feedback.
- Show locations of PT-100 thermistors for temperature monitoring
- Show locations of PT-100 thermistors used for PID controllers
Vibration Design Overview
Performance Review
| Requirements/Constraints/Goals | Target | Threshold | Predicted Performance | Actual Performance |
|---|---|---|---|---|
| Cool switch to -60 °C inside vacuum | -60 °C | ≤ 60 °C | -60 °C | -65.55 °C |
| Heat switch to 80 °C inside vacuum | 80 °C | ≥ 80 °C | 80 °C | 88.929 °C |
| Maximum rate of change of temperature of switch: 6 °C/min | NA | ≤ 5.5 °C/min | 11.37 °C/min | TBD |
| Maximum temperature of heater element: 150 °C | NA | < 150 °C | 147.254 °C | TBD |
| Maximum current through temperature controller: 3 A | NA | < 2.5 A | 0.96 A | 0.947 A |
| Natural frequency of test fixture needs to be 2X that of the thermal switch | 200 Hz | >190.6 Hz | 441 Hz | TBD |
| Connected mass for vibration test: 2kg | 2 kg | 1.9 kg ≤ m ≤ 2 kg | 1.99kg | 1.99 kg |
| CM of vibration testing mass 5-10cm from the top of switch | 7 cm | 5 cm < d < 10 cm | 7.36 cm | 7.3 cm |
Not all values were able to be tested because the thermal switch was not functional. See conclusions
Resistance Testing Results
During resistance testing the fixture is held at a constant temperature and the top heater provides a constant heat input. The temperature across the switch is measured and plotted against the power input from the top heater plate (shown in conductance testing graph). The slope of the line created is the tested thermal resistance.
Temperatures and Heat Input for Full Resistance Test Period
Conclusion
The maximum rate of temperature change was predicted to exceed the maximum; however, it was only predicted to exceed the maximum for a short period and was deemed acceptable by Thermal Management Technologies. The natural frequency was not verified as the test was not able to be completed. The maximum temperature of the heater elements was not able to be verified as cyclic testing was not completed, but it is predicted that they should not exceed the maximum temperature. All other requirements constraints and goals were met
The lessons learned from this project was the importance of documentation, tolerancing and circuitry.
We recommend that Thermal Management Technologies replace damaged parts, use test data to make appropriate thermal switch modifications, and conduct vibration testing once changes are implemented