[TR] Fan Hookup

[levilevi]

After a drive my electric fan will run for awhile when the engine is off until
the water at the top of the radiator is cooled to below my thermostat setting
(which is somewhere around 200-210 degrees if I remember correctly).  The
sensor is stuck in the fins at the top of the radiator right below the upper
hose.  Often times the fan kicks back on for a bit which worried me but I
figured that the "cold" air in the radiator sunk which pulled hot water (hot
enough to go above my thermostat setting) in from the engine and start the
process again.  This happens more in the summer than the winter and I've seen
it cycle like this twice on some occasions...in the summer.

Bud Rolofson

71TR6 CC57365 (Good 6)
66TR4A CTC57806 (The Wreck-Almost Parts)
66TR4A CTC57529 (The Project)
71F-250 Camper Special (Triumph Support Vehicle)
Z-50A Hardly Davidson 1977 Honda Mini-Trail Bike (Triumph Pit Bike)
  ----- Original Message -----
  From: Jim Muller
  To: triumphs at autox.team.net
  Sent: Sunday, November 11, 2007 7:55 PM
  Subject: Re: [TR] Fan Hookup


  On 11 Nov 2007 at 21:24, DLylis at aol.com wrote:

  > I ain't no scientist, but when a temperature gradient is set
  > up does the coolant not do it's level best to become all the
  > same temperature?

  Well, yes, but it's a question of how fast.  And what other things
  are going on.

  The only physical connections between coolant in the radiator and the
  coolant in the block are the narrow diameter radiator hoses.  When
  the engine is running the heat transfer due to water convection is
  very much greater than the heat flow through the water itself, which
  is how it keeps the block cool at all.  Meanwhile, air convection
  happens within the engine compartment.   This carries heat away from
  the block so that eventually it will cool down by itself.  Depending
  on various engineering values (i.e. specific features of each car)
  rather than science per se, either of these phenomena could be
  faster.  Certainly keeping the fan on could help air flow around the
  block if the air can't convect by itself.  But neither of these
  phenomena is fast compared to the water flow when the engine is
  running.  Yes, keeping the fan on would cool things down a little
  faster, but only just a little and nothing under a Triumph bonnet
  would benefit from it.

  --
  Jim Muller
  jimmuller at rcn.com
  '80 Spitfire, '70 GT6+



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