This topic was discussed previously on the list and somebody (whose name
I can't remember) gave a good explanation of the process. It seems that
the current explanations are digressing a bit so I'll try and recall some
of the basics presented before. I am not familiar with the bypass
arrangement on the TR3 so I will stick to general fundamentals.
1) While the analogy to an air conditioning system seems ok on some
levels, there really is little similarity. An AC system involves phase
change (i.e. evaporation and condensation) and a compressible fluid.
Water is incompressible and its ability to accept or reject heat varies
little with pressure.
2) Removing the thermostat does increase the speed at which water runs
through the radiator which reduces the time for heat to be lost from a
given volume of water. But with this argument, it must also hold that
the same volume of water passes through the engine quicker and thus has
less time to pick up heat. The total amount of heat transferred from the
engine to the water or from the water to the air is a function of the
heat gained/lost per volume of water times the number of *volumes* of
water that pass through per second. If the thermostat is removed, the
heat transferred per volume is less but the speed of the water (i.e. the
number of *volumes* per second) is greater so the total heat transfer is
more or less the same.
3) One benefit of increasing the speed of the water running through the
engine and radiator is that the heat transfer process from the water to
the surrounding metal is more efficient. This is why we blow on things
to cool them faster, etc. This may explain why some people see their
engine temperatures go down when they remove the thermostat.
4) The MAIN point that was made when this topic was discussed previously
is that if the water runs through the engine TOO fast there is the chance
that as it runs around a sharp edge or tight corner in the engine it will
not flow efficiently around the backside of the edge/corner. This is the
problem of flow separation which can be seen as water tries to flow
around a sharp rock in a stream. If the water is running slowly the
water will follow the backside of the rock, if it is running too fast the
backside will be covered with swirling eddies which are not good for heat
transfer. Thus, if you remove the thermostat and you do get this flow
separation problem it will create a local hot spot which may not show up
on your temperature gauge, but could create big problems for your engine.
I hope this clarifies some of the issues and I certainly hope I did not
offend any of the people who offered other explanations.
Santa Clara, CA