Add them. So the "less efficient" heat exchanger would have
a thermal resistance of 1/5+1/12K+1/5 = 0.4000833 h-F-ft^2/Btu
vs the "more efficient" 1/5+1/24K+1/5 = 0.4000417 h-F-ft^2/Btu,
with 0.01% less thermal resistance :-)
Scrubbing surfaces for better heat transfer IS the industries
proverbial _Let's Build a Better Mouse Trap_. Combustion efficiency
design and integration is already well established and has many choices
to meat a criteria.
What was interesting to watch is the Discovery Channel's Lance Armstrong
saga. Specifically, detailing the interaction of air to the surface of his
It went from researching golf ball dimples to mother natures design of a
ISTR, dimpled and scaly surfaces were the focal points.
As relating to heat transfer, a couple of years ago there was a program
showing the advances of ancient peoples, and how their levels of
achievement ranked to modern times.
How interesting that a properly hammered Wok was shown to have the best
heat transfer of all other kinds of modern designed woks.
My point is there's room for improvement.
On Jan 23, 3:38 am, firstname.lastname@example.org wrote:
Well how high is the air film resistances in forced convection?
You have a lot of radiant heat transfer initially on the inside of the
HX, then perhaps in the tubular HXs , the tubes tend to taper down once
past the line of sight of the flame to enhance convection by making
the products of combustion more turbulent.
You then have one of your favourite issues, thermal capacitance, heat
needed to get the HX hot enough in the first place to start driving
heat into the air.
Old octopii are still in existance, utilizing this capacitance and some
old heavy duty clamshells still around too. The forced air clam shells
worked off of a fan/limit control, and would take some time before the
fan would engage.
Newer, thin wall HX's the fans are timing on maybe in 30 seconds tops
after ignition, and the heat stored in the HX s is gone in a short
period of time as well. Not like a heat anticiaptor shuts the heat off
5 minutes before the home is up to temperature.
So, I seriously doubt you ever desiogned a forced air furnace in your
life, so perhaps you could go stay at a Holiday Inn Express and then
after a good night's sleep, you can derive non-intinsic PI yet one more
time, and wow us with all the calculations involved in this simple heat
It will most likely end up like your futile attempts to model a cooling
gain on a home as a simple "Conductance" based on indoor and outdoor
temperatures, and be 'completely out to lunch', yet one more time.
Well, the verdict is in. I called a Goodman authorized HVAC
dealer/contractor (in Denver Metro), and their technician told me that
the reason that return air temp must not be less than 55F is because of
the possibility of excess condensation.
BTW, I first called the Goodman hotline, but they told me that, for
liability reasons, they didn't provide tech support directly to
individuals. However, they told me to call one of their authorized
dealers with any questions. They gave me three names, and I called one
On Jan 18, 10:12 pm, email@example.com wrote:
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