[TR] water pump

[dave]

In the last few weeks there was some discussion about the new vs old water
pumps.  Someone postulated that the newer water pumps move water faster
through the radiator, which results in less cooling and a hotter engine.  I
asked my nephew, a mechanical engineer who is also a car person, about this.
here is his reply:

 

I think the point of confusion is the notion that increasing flow rate is a
bad thing. I get the basic thought of it spending less time in the radiator
but it's one of those things that sounds correct without having any real
science to back it up. One of the rules of thermodynamics is that flow rate
and heat transfer are directly proportional. If you increase flow rate and
all other things remain constant then you will reduce temperature.

 

For your specific use case, you're improving the efficiency of cooling
because the fluid is moving more quickly through the engine. It's better to
keep fluid at as low of a temperature as possible and moving it very quickly
means that each molecule is exposed to the heat for less time. When it gets
to the radiator there isn't as much heat to be removed so spending less time
in the radiator becomes a moot point.

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