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Re: [EnergyPlus_Support] Purchased Air Question

In a real system, there is often a minimum air flow rate imposed by a 
ventilation rate. The flow rate will not go below the minimum 
ventilation requirement.
The Purchased Air option in EnergyPlus is an ideal system design to meet 
the heating
or cooling load in all circumstances. The Purchased Air system is 
constant temperature,
variable volume. As an ideal system the variable flow rate is allowed to 
approach zero
(in order to meet a very small load). The outside air input is not 
treated as a minimum
ventilation requirement; instead the requirement to meet the load by 
varying the air flow
overides the outside air specification. For this reason Purchased Air is 
not a good
way to calculate real-world ventilation loads.

Fred Buhl

energypluser wrote:

>Dear all
>When I looked the user news of building energy simulation in 
>Jul/Aug,2004,I found a statement about the purchased air coupled with 
>outside air. The asker has a question about the difference between the 
>purchased air total cooling energy and the purchased air sensible 
>cooling energy.
>The answer in the file explain why the total cooling energy is less 
>than sensible cooling energy when the purchased air is mixed with 
>outside air. But the following sentence in the explain section makes me 
>"If the purchased air flow rate is less than the outside air flow rate, 
>then the purchased air flow rate is used and is 100% outside air"
>Can you explain it for me?
>Thank you in advance.
>The primary EnergyPlus web site is found at:
>The group web site is:
>Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.
>Yahoo! Groups Links

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