UCSB 4Hybrid Thermal Test System Status

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UCSB 4-Hybrid Thermal Test System Status
Peltier T/E Element Failures 3 September 2004
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Peltier Failures

• Two peltier thermoelectric units have failed over
  the past year.
• February 2004
• August 2004
• Units exhibited reduced thermal efficiency
  resulting in longer hybrid test cycle times
• 65 min vs 40 min
• Distorted tygon exit hose
• Replacing with new units restores short thermal
  cycle time.

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Heat Exchange

• Cooling Water Flow Rates
• 4 L/m suggested by Supercool
• 1.3 L/m current use
• Measured cooling water exchange rate
• 6 deg C at 1.3 L/m at full power

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Peltier Failure Mode

• Degradation of thermoelectric element due to
  overheating
• Nominal Input Power (24v12A)290 watts
• Current Usage (24v14a) 336 watts (16)
• 80 deg C Thermal Interlock currently in use
• need to test functionality
• It should not be possible to power up Peltier
  element without cooling water flow.

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Future Plans

• Current Peltier Interlocks
• 80 deg C thermal switch on unit
• Software has peltier current locked to water flow
• Need additional hardware interlock in the event
  of a software or PC failure.

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Flow Interlock

• Peltier power will be locked to cooling water
  flow
• Use existing flow sensor
• Electronic threshold on flow sensor output set to
  gt1 L/m, if lower then power relay drops out
• Comparitor/Relay board to mount on existing
  sensor interface panel.

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Flow Interlock
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Other Plans

• Use rigid Peltier exit line back to chiller
• Reduce temperature of cooling water
• Consider reduction of peak current by 5