Dan, just 1 question on your point #4- for flow separation to ocurr,
wouldn't there have to be air trapped in the water jacket? How would that
happen? Sorry, that's 2 questions :-)
Bob K
>Fellow Listers,
>
>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.
>
>Dan Pruzan
>71 Stag
>Santa Clara, CA
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