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In article ,
what says...
On Tue, 14 Feb 2006 11:42:46 -0500, the renowned Keith Williams
wrote:

In article ,
says...
On Tue, 14 Feb 2006 11:03:19 -0500, the renowned Keith Williams
wrote:

In article .com,
says...
In the original post I was speaking in Fahrenheit not Celcius or
Kelvin. An increase from 160 to 200 is 25 %, no matter where you are in
the world. Jeez, lighten up.........

All right. My temperature scale is (F-160)*5/4. Now what's the
(percentage) rise? Hint: It's still 6.4%.

Jeez, wise up.....

Is this still a sci group (or a practical group in the case of rcm)???

Heat loss is a function of temperature *difference* to the ambient, so
you are all wrong. So there. It's more like 100%. Of course heat
engines get more efficient when they have a larger temperature
difference to work with, so the total heat loss, all other things
being equal, would be less.

Engine (Carnot Cycle) efficiency is related to absolute temperature
difference, not some man-made scale.

Yes. Though I think an IC gas engine is Otto cycle, no?

In undergrad physics we were taught Carnot, but they may have been
lieing to give us a reason to care. ;-)

Temperature difference is only one
factor-- a Maglite(tm) flashight bulb runs much hotter than a range
element, but uses only a tiny fraction of the power.

Because its temperature is *higher* more energy is radiated in the
visible range.

And because it's so much smaller and better insulated less total
energy per unit time is radiated, convected or conducted.

The point is that more of the energy in in the visible range, thus
more efficient. How you make it hotter is a design detail.

It's not really that hard to figure out.

There are people out there who think big trucks are less efficient
than small trucks just because they look huge and guzzle more gas.
Of course when you calculate the gasoline consumption per unit of
freight (volume or weight) you find the bigger ones are better if you
can keep them reasonably full.

Sure, I wouldn't want to pay the fuel bill for a DE locomotive
pulling 100 coal cars (unless I was getting paid to haul coal). Of
all the bad ways to do things, some are less bad.

Was the "mileage" of 747s (?) discussed in this group today? They
drink a lot of fuel too, though not too bad when you consider
moving 400 people the same distance by other means.

--
Keith