[EnergyPlus_Support] Re: Circulation-only Fans: Zone Equipment?

["JV Dirkes II" <jvd2pe@xxxxxxx>]

Dear Kristin,

46% sounds reasonable to me; most smaller fans don't have very high
efficiency.  If, however, EPlus is not able to model the breeze
created by your fans, it begs the question of whether it's not simpler
just to add electrical load to the zone...


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Kristin Field"
<fieldkm@...> wrote:
>
> Thanks for the response!  From the manufacturer and mech. schedule
> data, it looks like the fans are about 46% total efficiency.  Feel
> free to tell me if that doesn't sound reasonable.  To answer your
> question, I'm not using the airflow network for this model.
> 
> --Kristin
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "JV Dirkes II" <jvd2pe@>
> wrote:
> >
> > Dear Kristin,
> > 
> > If you model the fans as unit heaters (which seems like a reasonable
> > choice to me), make sure that you've got the fan efficiency properly
> > defined so that the KW calculated by the Fan object is appropriate.  I
> > don't know typical efficiency for the circulation fans you're
> > modeling, but it can be derived from the air flow rate, delta Pressure
> > and motor data.
> > 
> > Although not very familiar with the EPlus algorithms, I wonder if it
> > even "cares" about airflow from fans in any of its convection
> > calculations; there's not enough information provided in the IDF
> > objects such as Unit Heaters, to describe airflow patterns....  Maybe
> > you're using Airflow Network for that (which I'm unfamiliar with)
> > 
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Kristin Field"
> > <fieldkm@> wrote:
> > >
> > > Hi, I'm trying to model a set of greenhouses that are heated
only with
> > > fin tube radiators.  The only "cooling" is through natural
ventilation
> > > and intake fans, which I have modeled using AirFlow objects.  I
don't
> > > have a question about this part of the model, just providing this
> > > info. as background.
> > > 
> > > The question I have is about modeling the circulation fans that run
> > > continuously in the greenhouse.  I thought of doing them as zone
> > > equipment, but the I/O Reference lists the types of zone equipment
> > > allowed, and plain "fans" are not among them.  Another option I
> > > considered is modeling them as unit heaters with the heating cool
> > > never enabled, but I was hoping for an easier solution.  The cfm is
> > > high and, I would think, will have a big effect of the
convection part
> > > of the heat balance.  Without the effect on convection, I would
> > > otherwise just input the fan heat as an electric internal gain.
> > > 
> > > Any thoughts?
> > > 
> > > Thanks,
> > > Kristin Field
> > >
> >
>




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