In a message dated 10/22/2005 12:10:17 PM Central Standard Time,
tr3driver@comcast.net writes:
> I disagree. The thermodynamic equation for the heat dissipated by the
> surface
> of the radiator cares nothing for how fast the water is moving inside, only
> what
> the temperature at the surface is.
>
> Let's say you have a radiator dissipating 100,000 Btu/hr and 180F water is
> moving through it at 100,000 lbs/hr (about 185 gpm). That means the outlet
> temperature is 1 degree F lower than the inlet temperature, or 179F, giving
> an
> average water temp of 179.5F.
>
Let's approach this from a different angle. Since heat energy is neither
created nor destroyed (although it may be converted to mass but I seriously
doubt
that is what is happening here) allthe heat removed from the coolant is
absorbed by the air. If the coolant is entering the radiator at 180 deg at the
top
the air passing through the radiator at the top is heated up to 180 deg
(ignoring the approach factor of the coil). As the coolant cools as it passes
though the radiator it heats the air up to a lower temperature. Thus the air
passing though the lower part of the radiator absorbs less heat.
As the flow through the radiator increases the temperature differential
decreases and the air passing though the lower part of the radiator picks up
more
heat energy and the total amount of cooling increases.
>This works just fine until the condition is met where the thermostat is full
>open and yet there is inadequate cooling because a portion of the coolant is
>bypassing the radiator
So the question becomes, is this ever the case ? The answer depends on how
high
the relative flow is and the temperature drop across the radiator. If the
water
temperature drop across the radiator is large, then yes, a small change in
flow
will have a small effect on heat dissipation. But if the water temperature
drop
across the radiator is small, then a small change in flow will have an
infinitesimal effect on heat dissipation.
I don't know, I have had no experience with over heating in the TR3 but a
friend of mine claims that installing a restriction in his bypass solved his
overheating problem. Since the bypass is a shore piece of 1/2 inch heater hose
it
may represent a low enough impedance path for water flow that a significant
amount of flow may go that way instead of through the radiator - depending on
how restrictive the radiator is.
It could be significant or else why bother with the skirt on the thermostat?
Dave
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