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Re: [EnergyPlus_Support] About air to air heat exchanger input data
Charlie, an air-to-air heat exchanger's effectiveness varies much more
with changes in air flow from the manufacturers rating point than it
does with variations in temperature (or humidity when considering latent
effectiveness). The ARI 1060 Standard provides a fixed rating point so
that all manufacturers are reporting the same information to consumers.
You will notice from manufacturers data that the heating and cooling
effectiveness, although it does change, does not change dramatically.
This change is due to a change in the temperature difference between the
supply air and exhaust air streams. So the information you have is
probable adequate for simulation purposes as long as the delta T for
heating and cooling are similar to the ARI standard.
The ARI 1060 Standard uses a 19.3 C temperature difference (0.00408
kg/kg humidity ratio difference for latent effectiveness) for heating
and an 11 C temperature difference (0.00726 kg/kg humidity ratio
difference for latent effectiveness) for cooling. You can plot the
heating and cooling effectiveness versus delta T (or delta W for latent
effectiveness) for the data you have and then draw a line through these
points to extrapolate or interpolate and find the corresponding ARI
rating points. You will see that the effectiveness data do not change
significantly.
Since the variation in effectiveness is small for different delta T's
(or delta W's), EnergyPlus assumes a constant effectiveness in cooling
and heating. The cooling effectiveness inputs (100% and 75% air flow)
are used when the supply air temperature (usually outdoor air) is
greater than the exhaust air temperature (usually zone air). The cooling
effectiveness inputs are used for calculating exiting conditions until
the supply air temperature falls below the exhaust air temperature where
the heating effectiveness inputs are then used.
In addition, the effectiveness for air-to-air heat exchanger wheels is
impacted by leakage through the seals. If you choose to simulate a
wheel, use the "net" effectiveness values (~2 % lower than the thermal
effectiveness) provided by the manufacturer.
energypluser wrote:
> Dear all
> I wanna simulate the performance of the air to air heat exchanger based
> on manufacturer catalog.
> But I found that the rating conditons for the catalog data are
> different from that of the ARI standard.
> My question is :
> will E+ be able to mimic the actual performance of the exchanger with
> the effectivenesses calculated under different rating conditions£¿
> Thank you in advance
>
> Charlie
>
>
>
>
>
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--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL 32922-5703
Phone: (321) 638-1454
Fax: (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu
UCF - From Promise to Prominence: Celebrating 40 Years
[Non-text portions of this message have been removed]
The primary EnergyPlus web site is found at:
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The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
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