[FRIAM] Naïve physics question

[Nick Thompson]

All—

 

Can I piggy back on to Gary’s question with one of my own.  Much more naïve.
Even tho I am an ardent conservationist, I believe that claims for energy
saving from light bulbs that don’t spill heat only approach truth in the
warmest parts of our country.  Where yearly annual temperature average is
less than human comfort, the cost from heat loss from incandescent bulbs is
compensated by a diminishment in the cost of heating by other means.  This
works particularly well with a reading lamp, which is warming you while it
lights you.  Now in summer, the loss of heat from bulbs is actually a very
bad thing because it has to be compensated for with airconditioning.  But
summers in most of the country are way shorter than winters.  

 

I am sure I am going to get some sort of a lecture on the second law, here.
Spilled heat from inefficiently deployed light sources is STILL more
expensive than heat directly extracted from gas or oil.  Not sure how to
think about that. 

 

Nick

 

Nicholas S. Thompson

Emeritus Professor of Psychology and Biology

Clark University

 <http://home.earthlink.net/~nickthompson/naturaldesigns/>
http://home.earthlink.net/~nickthompson/naturaldesigns/

 

From: Friam [mailto:friam-bounces at redfish.com] On Behalf Of Robert J.
Cordingley
Sent: Tuesday, February 14, 2017 11:11 PM
To: The Friday Morning Applied Complexity Coffee Group <friam at redfish.com>
Subject: Re: [FRIAM] Naïve physics question

 

Seems like from a thermodynamics question you can first think of having two
identical systems with identical energy inputs. Unless one of the systems is
capable of storing energy in some form differently from the other the
equilibrium temperatures should be the same.

Now CFBs emit more of the their input energy as light which since the
containers are transparent (presumably to the same light that's emitted,
visible, UV, infrared) it will escape more easily. Incandescents generate a
lot of heat for the same energy input which may not escape as easily as the
light energy. It will depend on the thermal conductivity of the container's
materials etc. If the CFB were 100% efficient all it's energy will leave
immediately in a container that is 100 % transparent to its 'light' and show
no temperature increase. If the incandescent's heat is transmitted as
infrared energy at 100% efficiency along with any light then its temperature
will show no increase either.  So the answer may have more to do with the
properties of the containers than the properties of the lights. Practically,
I'd expect A to warm up more than B because B's light energy will escape
more easily with materials we are familiar with.

If both containers are opaque to all light (UV, visible and IR) and have the
same thermal conductivity properties we are back to the first paragraph.

2c

Robert C

 

On 2/14/17 8:01 AM, Gary Schiltz wrote:

Since there are some non-naïve, i.e. professional physicists, as well as
just gererally smart people in FRIAM, I pose the following fun question.
Given: two transparent, sealed containers filled with air - one contains an
incandescent light bulb A that consumes 100 watts of energy; the other
container contains a fluorescent light bulb B that also *consumes* 100 watts
of energy. Since B is of a more efficient design, it will produce more light
than A. Assuming the same color temperature light is produced by A and B,
and ignoring any feedback effects of rising temperatures inside the
respective containers, will the temperatures inside the containers reach the
same temperature? Naïve physicist G (me) thinks that since more light is
escaping from the container containing B, that its temperature will rise
less. G also thinks that if the containers are opaque, that the temperatures
will rise by the same amount. But G is besieged with doubts. Please help G.






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