Re: [EnergyPlus_Support] outside minimum flow

["Michael J. Witte" <mjwitte@xxxxxxxx>]

The minimum outside air flow rate input should reflect the desired minimum OA 
flow when the system is at its full flow rate.

With FIXED MINIMUM, the OA flow rate will equal the "minimum outside air flow 
rate" multiplied by the current "Minimum Outside Air Schedule Value" (if 
specified).  However, if the total system supply flow rate falls below this 
value, the OA flow will be reduced to match the supply flow rate.  It is up to 
the user to set the VAV minimum flow rates to deliver enough total flow to meet 
the desired OA minimum flow.

With PROPORTIONAL MINIMUM, the OA flow rate will equal the "minimum outside air 
flow rate" multiplied by the current "Minimum Outside Air Schedule Value" (if 
specified) multiplied by the ratio of the current system supply flow rate 
divided by the design full system supply flow rate.

We will try to add a clear explanation of this to the Input/Output Reference.

Mike


On 16 Feb 2005, at 13:06, Zhen Tian wrote:

> 
> Hi, All:
> 
> I have a question for using the object "Controller: outside air".  In this
> object, I am not sure how to input the field "minimum outside flow rate"
> combined with "minimum limit" field(fixed or proportional), even I looked up the
> reference.
> 
> The following is what I am thinking:
> Assuming the system design maximum airflow rate is 6 m3/s; with 80 occupants;
> each zone minimum airflow ratio 0.3 (VAV system); the sum of total maximum
> airflow rate for all zones is 7 m3/s (it is bigger than system airflow rate).
> Set minimum airflow rate for each occupant 8L/s
> 
> If I use "fixed minimum", then the minimum outside air flow rate should be:
> 80*0.008=0.64 m3/s. The maximum outside flow is 6m3/s.  Is this correct?
> 
> If I chose "proportional minimum", and set the ratio of outside air flow rate to
> system air flow rate also as 0.3.  What should be the minimum outside air flow
> in this field?  To my understanding, it should be 7 (sum of total air flow)* 0.3
> (zone minimum air flow)* 0.3 (outside airflow to system airflow ratio)=0.63
> m3/s.  So should input 0.63 into the "minimum outside air flow rate" field. Is
> this method correct?
> 
> Any response will be highly appreciated.
> 
> Regards,
> 
> Zhen
> 
> 
> 
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx




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