How to run with AMS in horizontal position

On ground, because of the effects of gravity, depending on AMS' orientations in horizontal position, one must be aware of different procedures to run the TTCS.

Essentially, when AMS in horizontal position, one must always operate with the lowest loop as the heat will then be rejected to the bottom of the Tracker radiators. The heat pipes in the radiators will work as thermo-syphon, thus avoiding the heat pipes to dry out. This explains why one must use:

  • The Primary Loop when the Port Side facing down.
  • The Secondary Loop when the Starboard side facing down.

One should always keep the set-point to a value <= 26 C because higher values would be too close to the critical 31 C limit. Close to this point, the latent heat becomes smaller and smaller and the amount of vapour per watt will thus increase. This could cause dry-out.

High pump speeds are used (~ 7500 rpm) to avoid instabilities in the evaporator due to gravity. The evaporator is vertical so vapour tends to go up by buoyancy forces. At low pump speed this would cause instabilities. If you increase the pump speed, annular flow is enforced in the tubes and the instabilities then disappear.


Running TTCS with AMS Port side facing down.

Start-up Procedure (see also TTCS Procedures):

  • Switch On TTCE
  • Set-point to 26 C and switch on GAC
  • Wait until set-point of 26 C is reached.
  • Check sub-cooling:
    • Pt1 > Pt2 + 3C
  • Switch on primary pump with speed set to 7500 rpm
  • DAQ shifters can switch on Tracker (power-step 3).


Configuration Summary:

  • Operation With the TTCS Primry Loop
  • Operation with the GAC heater.
  • Set-point fixed to <= 26 C.
  • Pump's speed set to 7500 rpm.


Running TTCS with AMS Starboard facing down


Start-up procedure (see TTCS Procedures):

  1. * Switch on TTCE
  2. * Set-point to +26 C and switch on the FAC heater.
  3. * Wait until the 26 C set-point is reached.
  4. * Wait 10 minutes to be sure all vapour in the loop is condensed.
    • Check Pt2, DS1, DS2, DS17 and DS18 are under 26 C.
  5. * Give Ok signal to DAQ shifters for switching ON tracker (Power Step 3).
  6. * Wait for 2-3 minutes
  7. * Check sub-cooling * Pt1 > Pt2 + 3 C
  8. * Switch on pump to 7500 rpm.


Configuration Summary:

  • Operation with the Secondary Loop.
  • Operation with the FAC (as the GAC is on the top-side of the accumulator and not heating efficiently the liquid any more).
  • The set-point remains <= 26 C.
  • The pump's speed is set to 7500 rpm.
  • The operations in dT/dt < 0 must be carefully checked:
    • CO2 could be pushed from from the accumulator in the loop.
    • There could be a flow of vapour to the pump.
    • DS1 (or DS2 depending on the pump) must be checked.
    • DS7 and DS8 first sensors dowstream the pump must be checked.

-- MatteoDuranti - 15-Aug-2010

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Topic revision: r5 - 2010-11-15 - MatteoDuranti
 
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