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[EnergyPlus_Support] Re: modelling misters
Help - just bumping this back up in the hope I'll get a good
response - I'm pretty desperate for some help here!
thanks in advance (hopefully:-)
Danny
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Danny Bishop"
<bish.dj@...> wrote:
>
> Hi All
>
> As a follow up to my previous post (I've been working on it today
seemingly
> in a different time zone from most of you all), I just wanted to
get some
> more feedback on the approach to modelling cooling effects of water
misters
> in a fresh fruit market overnight.
>
>
>
> The recommendation I got for doing it in Ecotect was basically to
have an
> appliance with a negative heat output. This sort of works (but the
calcs for
> the power seem obscene, see footnote), but it obviously doesn't
account for
> the following:
>
>
>
> 1) Effect on humidity
>
> 2) You need to assume some sort of percentage of evaporation,
and this
> needs to be the amount that changes to and stays as vapour, ie
doesn't
> condense anywhere.
>
>
>
> If I did this in E+ using the recommendations I've been given (see
below),
> would they model the two above effects, instead of rely on me to
estimate
> them?
>
>
>
> Secondly, another option that occurred to me (that should minimise
my
> interaction with E+ as I am very green) is to include a large latent
> internal gain for each zone. However, when I export these to E+
(Ecotect
> doesn't use the latent part in the calculation) I get only the
slightest
> change in the temperature. I have uploaded these two files to the
online
> file location, one named "Market export to E+-no latent", and the
other
> "Market export to E+-latent". Perhaps the difference is the pesky
HVAC loads
> which seemed to have activated themselves! If anyone can shed some
light on
> why the difference is so small that would be great!
>
>
>
> Cheers and thanks
>
> Danny
>
> ____________________
>
> Footnote: latent power calculation of 1 litre of water vaporising
per
> minute:
>
>
>
> Latent vapour heat of H20: 2270kJ/kg
>
>
>
> Power = 2270 (kJ/kg) x 1 min/60s x (1kg/min)/(1L/min)
>
> =2270kJ/60s per L/min
>
> =38kW per L/min
>
>
>
> This seems huge! Can anyone tell me if I've made a silly error?
>
>
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Josh K
> Sent: Wednesday, 23 January 2008 4:29 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: Re: [EnergyPlus_Support] modelling misters
>
>
>
> I've used ECOTECT to create geometry for EnergyPlus simulations. It
doesn't
> do a whole lot more than that; there are some options to create
schedules,
> infiltration, and internal gains objects within ECOTECT, but
frankly I've
> found it easier just to do these things within EnergyPlus.
>
> That being said, it does a reasonably good job of creating
geometry, as long
> as the geometry isn't excessively complicated -- when it is, ECOTECT
> sometimes has a hard time calculating adjacency properly, which
results in
> the OutsideFaceEnvironment field of the SURFACE:HeatTransfer objects
> sometimes being specified incorrectly. In one instance, I created
what was,
> in retrospect, excessively complicated geometry, and using the most
> sensitive settings for ECOTECT's inter-zonal adjacency
calculations, I ended
> up with about 8% of the surfaces' OutsideFaceEnvironment field being
> specified incorrectly. In my opinion, if one were to simplify the
geometry
> to the extent that simulation accuracy wouldn't be affected, this
number
> would be pretty close to 100%. Unfortunately, I don't have enough
experience
> at this point to state definitively if that's the case or not; what
I can
> tell you is that after using the two systems together for a while,
you
> definitely begin to get a sense of what geometric features ECOTECT
will deal
> with correctly and which ones might be troublesome.
>
> The biggest annoyance when using ECOTECT to create EnergyPlus
geometry is
> the surface naming conventions. To my knowledge, there is no way to
directly
> name surfaces in ECOTECT; they are all automatically assigned
object numbers
> by the software. This wouldn't even be too bad, but these object
numbers
> aren't static. That is, if you go in and modify your geometry in
ECOTECT and
> re-export it to ECOTECT, it's possible that an unmodified surface
could have
> a new object name. If one is importing and exporting entire
geometries en
> masse, this isn't really a problem, but it can be really annoying
if you
> have a big model and you just want to export chunks of it.
>
> Anyways, if you learn to cope with the idiosyncrasies, ECOTECT is a
usable
> tool for creating geometry for EnergyPlus. However, that's about
all it does
> -- no HVAC.
>
> Hope that helps,
>
> Josh
>
> On Jan 22, 2008 10:05 AM, Griffith, Brent <brent_griffith@...
> <mailto:brent_griffith%40nrel.gov> > wrote:
>
> > If you know a water flow rate and schedule for the misters, then
it
> > should work to use the Water Use Equipment input object with a
high
> > latent fraction. I suggest using a Water Mains Temperatures
object for
> > your location to model the mister's inlet water temperatures.
> >
> > Hopefully someone else out there knows more about Ecotect ...
> >
> > ________________________________
> >
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com>
> <EnergyPlus_Support%40yahoogroups.com>
> > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com>
> <EnergyPlus_Support%40yahoogroups.com>]
> > On Behalf Of Danny Bishop
> > Sent: Monday, January 21, 2008 5:48 PM
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com>
> <EnergyPlus_Support%40yahoogroups.com>
> > Subject: [EnergyPlus_Support] modelling misters
> >
> >
> > Hi All
> > I want to do a simulation modelling the use of misters to cool a
fresh
> > food
> > market overnight. I want to see the benefit to the temperature,
and also
> > the
> > effect on humidity. I would prefer to do import this to e+ via
Ecotect,
> > but
> > suspect that I may need to do some post processing on the IDF. Can
> > anyone
> > tell me how to get my teeth into this, any examples perhaps?
> > Cheers
> > Danny
> >
> > [Non-text portions of this message have been removed]
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
>
> --
> Josh Kjenner, EIT, LEED AP
> Manasc Isaac Architects Ltd.
> 10225 100 Avenue :: Edmonton, AB T5J 0A1
> 780.429.3977
>
> [Non-text portions of this message have been removed]
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
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