1. Thermoelectric Cooling Team Members: Mark Campbell Peter Giles Andrew Smith Tom Strapps Nickolay Suther Team Supervisor: Dr. Prabir Basu Client: Greenfield Research

2. Our Problem Create an air bath using thermoelectric modules http://www.electracool.com

3. Project Requirements Temperature Range  +5°C to +25°C Temperature Control  +/- 0.2°C Cost  Less than $2,000

4. Construction Phases Frame Insulation Fibreglass inner box Panels Heat sink and fan arrangement Power supply Lid

5. Frame Constructed of ¾” square tubing 0.125 wall Crosspieces cut at 45° and arc welded Designed for rigidity and weight to resist vibration Dimensions:Width = 35 cm Length = 50 cm Height = 35 cm

6. Fibreglass Inner Chamber Used fibreglass because relatively high insulating value and water proof Styrofoam plug constructed 5 sided Fibreglass cube formed over plug

7. Insulation 2” Styrofoam SM™ 5 pieces cut and notched to fit inside frame and surrounding fiberglass chamber Cut using hot wire with jig

8. Panels Panels constructed of 22 gauge mild steel Cut and bent in machine shop Holes machined for good fit and appearance Aluminum expanded metal spot welded onto fan shrouds

9. Two thermoelectric modules 2 external and 2 internal heat sinks made from extruded aluminium Interior heat sinks each small (50mm) fan Exterior heat sinks each with 2 larger 12V fans (80mm) Heat Sinks and Fans

10. Power Supply and Display Back panel cut and power supply mounted Sheet metal tray fabricated and holes punched for ventilation Display panel bolted to top panel Coloured buttons also on top panel for programming and reset

11. Lid On top for simplicity and better sealing Three layers Sheet metal on top with handles Sealed with foam weather stripping

12. Testing Arrangement

13. Thermocouple Calibration Three Thermocouples Accurate thermometer Ice to 30 º C Sample every 20 sec for 2000 sec

14. Calibration Data Read TemperatureRecord Temperature

15. Thermocouple Calibration

16. Problem Points due to: Insufficient mixing Ice still not melted Different locations of thermocouples and thermometer bulb Thermometer Temperature Thermocouple Temperature 0 5 10

17. Thermocouple Calibration

18. Air Test Cool the empty volume Thermocouple locations  Both interior heat sinks  Suspended in the cooler

19. Air Test Data Interior Air Temperature 20ºC 5ºC 1.4 hours

20. Power Connections Ventilation Thermocouple locations Air Test Air and Heat Sink Temperatures Heat Sink 1Heat Sink 2Interior air ½ ºC difference Temperature ( O C) Time (Seconds)

21. Water Test 1L of water Thermocouple locations  Water  Heat Sink  Interior Air

22. Water Test Results WaterInterior heat sinkInterior air 9 hours 23.9ºC 5ºC

23. Forced or Natural Convection? Remove one set of fans Install thermocouples on both exterior heat sinks

24. We Need Fans HS w/o FanInterior Heat SinkHS w Fan 54ºC 36ºC Results 10 mins

25. Time Constants Time Constant, = 63.2% of temperature difference = 0.5 hours 20ºC 5ºC 10ºC ~ ½ hour Cooling of Air

26. Control Circuitry LCD Display Micro Controller Analog/Digital Converter User Input (3 Buttons) Temperature Sensor Precision Voltage Reference

27. Temperature Control WaterHeat Sink 2Heat Sink 1 1L Water Setpoint: 10 o C

28. Temperature Control WaterHeat Sink 2Heat Sink 1 Control

29. Temperature Control Precision 0.12 o C Water Temperature

30. Temperature Control Precision +/- 0.06 o C Water Temperature

31. Temperature Control Steady State 1hr 40minutes Water Temperature

32. Temperature Control WaterSet PointActual Accuracy 1.8 o C

33. Costs CategoryAmount ($) Construction581.24 Heat Transfer415.27 Control487.01 Total1,483.32 Budget2,000 Surplus516.68

34. Safety Features Solid State Relay –Isolates Power Supply from the Controller Thermal Switch –Protects from overheating Protective Shrouds Thermal Switch

35. Future Considerations

36. Recalibrate Set Point Present: Set point off by ~1.8 o C Future: Virtually no offset

37. Synchronize Fans to controller Present: Fans are always on Future: Fans turn on/off with TE modules –Less heat pumping into device –Increased efficiency

38. Additional Thermoelectrics Present: Two modules are in the device Future: More then two modules are used –Decrease cooling time –Increase temperature range

39. Heating the Device Present: Device can only be used for cooling Future: Heating and cooling will be possible

40. Special Thanks To Albert Murphy Angus MacPherson Stuart Carr Greg Jollimore Trisha Laws Dr. Prabir Basu Greenfield Research Source: www.dal.ca & www.greenfieldresearch.ca

43. Air Time Constant Average time constant ~ ½ hour

44. Water Time Constant Average time constant ~ 2.75 hours