Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] cooling hints



The student misconception probably comes from some concept they alread have
and are misapplying. It might be instructive to try to figure out what that
concept might be. At this moment I can not think of one.

John M. Clement
Bellaire, TX


Years ago, during 70s energy crisis (la plus sa change, la
meme la chose!) I
did a simulation in lab with a variac and a homemade AC box that was
connected to a simple immersion heater placed in a an
insulated beaker and
an uninsulated beaker. Part of the lab was to compare energy
consumption
between complete AC turn off and reducing the set point
temperature. A
complete cycle was run to simulate a constant AC setting, a
temp reduction
setting and a complete AC off by starting all runs at a fixed
temperature
and running through the 3 cycles for fixed times and then
returning to the
initial temperature. Invariably, minimum energy consumption for the
complete cycle was lowest with the complete turn off cycle.
Probably not
terribly applicable to today's units, but students found it very
surprising. Most students believed you used more energy to
"catch up" if
you turned off the heater.
James Mackey

On Wed, Aug 24, 2011 at 3:31 PM, John Clement
<clement@hal-pc.org> wrote:

I know someone who was working for the Army and in the
winter they used to
open the windows to combat the overheating of their work
space. But during
one year when there was a jump in energy prices the Army
sealed the windows
shut to prevent this. Why they didn't just turn down the heat is an
unsolved mystery. So the employees found they could have comfort by
turning
on the AC.

John M. Clement
Houston, TX


Ah! Bitten by the "Law" of Unintended Consequences.


_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l

_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l