Hello All:
I am not an engineer, so I have not studied the subject of heat transfer
from that perspective, but I am a physicist and know at least some of the
fundamentals. It seems to me that the problem with regard to the cooling
system is to move a quantity of heat from where it is generated (i.e. in
the engine block) to the point where it is to be dumped to the atmosphere
(i.e. the radiator). Clearly, with no circulation of the coolant, the
process will not take place, so the coolant must be in motion, so then the
question is at what speed. As the engine comes up to its steady-state
operating temperature, the temperatures in the block and the radiator
outlet will assume more or less constant values. Since one of the
variables that will determine the increase in temperature of the coolant as
it picks up heat from the block is the mass available to absorb that heat,
it would seem that slowing the flow would increase the temperature of the
exiting coolant. That would, in turn, increase the temperature at the
radiator and make it more difficult for the radiator to dump the heat to
the atmosphere. Of course, the rate of heat rejection by the radiator will
be greater at the higher temperature but that will not necessarily mean
that the radiator outlet temperature will be lower. Speeding up the flow
would most likely lower the temperature of the coolant as it exits the
block and reaches the radiator, so the radiator my well end up operating at
a lower temperature, but, then again, maybe not. We have all heard the
admonition to not operate the engine without a thermostat in place, even if
it is just a gutted housing, which tells me that higher flow rates are not
necessarily a good thing. So the optimum operating circumstance depends on
the balance of the rate at which heat is absorbed by the coolant in the
block and the rate at which the heat is transferred to the atmosphere. The
Tiger's cooling system seems to be operating on the "edge" in many
situations, it has always seemed to me. Therefore, it may help in a
significant way under certain circumstances, to increase the flow of
coolant in the system, or it may not. YMMV, as they say. My analysis, I
am sure, has ignored a great many factors in attempting to simplify
something which is probably pretty complex. Developing a complete theory,
although perhaps an interesting exercise, would involve way too much time
and effort, IMHO, especially when what we are seeking is simple to quantify
(a cool running Tiger, what a concept!) It is probably more efficient to
simply do the experiment of trying out the various fixes that have been
proposed. The analysis done by TE/AE is a giant step in that direction and
helped me to make my Tiger run cooler and I would highly recommend that as
a starting point for anyone interested in making their Tiger run cooler.
Finally, it has always seemed to me that the main problem with cooling the
Tiger is the air flow through the radiator. Most of the problems with
Tiger cooling occur at low speeds, when the air flow through the radiator
is limited. Consequently, most of the problems can be cured by increasing
air flow through the radiator. A more efficient fan, an auxiliary fan,
blocking the horn holes, completing the shroud, venting the engine
compartment, and so forth are all, one way or another, an attempt to
increase air flow. If you have a Tiger that overheats at speed, then I
think we are dealing with a horse of a different color, in which case
increased coolant flow, again, might help but it also might help to have a
more efficient (i.e. more surface area) radiator to increase the rate at
which heat can be dumped.
My two cents.
Cheers,
Tod, in Maine (where temperature differences are a way of life)
B382002384LRXFE
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