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Re: [EnergyPlus_Support] Fan Power Minimum Flow Rate Input Method



As I understand it, the minimum flow fraction sets the fan to always supply at least the design airflow rate x min airflow fraction (if the availibility is non-zero). As most AHU Frequency converter / motor combinations can throttle down the air flow to a certain amount (about 25%) and then no more. Else, it must switch off completely. If the system does not bring the minimum ODA rates you expect, then I think the problem lies elsewhere. Be careful of which fields have priority in the controller:outdoorair object. Simply leaving previous settings in, the wrong fields can mess it up.

Mit freundlichen GrüÃ?en- Sent from my iPhone (excuse the brevity)

i. A.
Jean Marais
b.i.g. bechtold
Tel.   +49 30 6706662-23

On 25.06.2014, at 18:37, "fpasserini.tn@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

As for the object Fan:VariableVolume I don't understand clearly the meaning of the fields "Fan Power Minimum Flow Fraction" and "Fan Power Minimum Air Flow Rate". 

In the "I/O Reference" I read:


Field: Fan Power Minimum Flow Fraction

The minimum air volumetric flow rate for fan power, specified as a fraction of maximum

system air flow rate. Must be between 0 and 1. Note that this field is only used to calculate

the fan power. This field does not enforce the system air flow rate during simulation. The

default is 0.25.


Does it mean that the "Fan Power Minimum Flow Fraction", in combination with the "power coefficients", determines the fan power at the minimum Flow fraction? How?

I read that "This field does not enforce the system air flow rate during simulation" but in my model if I write 0 as "Fan Power Minimum Flow Fraction" the AHU is not able to supply the outdoor air that I specified in Controller:OutdoorAir (it supplies a lower flow rate), while if I write 1 as "Fan Power Minimum Flow Fraction" the AHU can supply the outdoor air that I want.

Regards



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Posted by: "jeannieboef@xxxxxxxxx" <jeannieboef@xxxxxxxxx>


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