Since the intent is to more accurately assign an estimated friction
loss and the colder it gets, the greater the loss. Go with the lowest
temperature.
Now if you were attempting to use this for a wet pipe system instead
of Hazen-Williams then it is a great question and answers why we don't
otherwise use Darcy-Weisbach (loses the flaunted greater accuracy
since the variables are not constant).
Sure as the sky is falling, some sprinkler scientist will say when
using a tank, you have to calc for pipe size based on lowest temp but
tank size based on highest temp. Sometimes a good beating is called
for.
Roland
On Sep 18, 2008, at 11:06 AM, Travis Mack, SET wrote:
Ok..another viscosity question.
When using HydraCalc to calculate antifreeze systems using the Darcy
method,
it asks for viscosities of solutions. I have a data sheet with the
viscosities at various concentrations and various temperatures. My
question
is, do you use the average daily minimum temperature for an area, or
the
extreme daily minimum for an area? For this particular project, the
difference is 40°F in the 2 temperatures. With the average daily
minimum
temperature, the system works with the available pressure. With the
extreme
daily minimum, the city supply is not even close. There is a 100+
psi swing
in the demands.
So, do we go with average minimums, or extreme minimums?
There is always the option to go to a dry system, but the increased
design
areas and reduced c factor will also force a pump on this project. An
anti-freeze system at average daily minimum works without a fire pump.
However, we don't want to design/install an inadequate system.
Please feel free to call if you have any questions or comments.
Travis Mack, SET
MFP Design, LLC
2508 E Lodgepole Dr
Gilbert, AZ 85298
480-505-9271
[EMAIL PROTECTED]
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