Wow,
There are all sorts of neat ideas about cooling systems running around.
A good demonstration of the fact that different ideas, which all seem to
make sense, can lead to opposite conclusions.
I will have to lend my support to John Lupien's explanation of this
matter, (and thank him for running through this - that way I didn't have
to figure out a good way to explain it...)
It is often hard to reduce a mathematical understanding of a phenomena to
something which is concrete and simply demonstratable. I think that a
simple concept which may help some is this:
The greater the temperature difference between to items (radiator and
air flowing across radiator) the greater the rate at which heat (which is
not *temperature* but is energy) is transferred from the hotter to the
cooler item. Therefore the hotter the average temperature is of the
radiator, the more heat it transfers to the air. It is irrelevant (as
John has pointed out) why the radiator has a higher average temperature.
I think what may be confusing people is the "feedback" nature of the
cooling system. I would suggest that in a high flow system, while the
temperature of the coolant leaving the radiator is higher at steady state,
the average temperature of the coolant as a total system (and hence the
engine) is cooler than the low flow system, where the coolant enters at a
higher temperature but leaves the radiator at a lower temperature.
Want a schematic version? OK, what I am saying is that this:
High Flow Steady State Low Flow Steady State
Coolant in Engine (90C) Coolant in Engine (100C) (ouch!)
/\ | /\ |
Rad Out (80C) | Rad Out (70C) |
/\ | /\ |
Rad In (90C)<------ Rad In (100C)<-----
... is an example of what steady-state might be like.
By the way, I (disagreeing with M. Frankford) think there is some factual
basis for the reputation problems experienced by Lucas. I think my
Lucas problems have more to do with inept mechanical/materials usage. I
have a handful of parts (Turn signal switch, hazard switch, and headlamp
motor (must be a TR7 or 8 owner!)) which support this conclusion. Other
Lucas failures I have experienced are not Lucas' fault (one
starter solenoid and (separately) one starter moter fried due to proximity to
catalytic converter - the heat shield apparently disintegrated or fell
off ), or unassignable (one alternator failure).
BTW, I am not getting my PhD in thermodynamics, either, but I am getting
my PhD (very very soon, I hope) - and would welcome any information about
jobs for Chem. Eng. (Transport Phenomena and Polymers are my field)
Greg "tending to entropy... and can *prove* it" Fieldson
Dept. of Chemical Engineering krikor@jhunix.hcf.jhu.edu
The Johns Hopkins University or fieldson@jhunix.hcf.jhu.edu
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