Re: [EnergyPlus_Support] Re: Pools in E+

2013/7/16 Chien Si Harriman <chien.harriman@xxxxxxxxx>

That is way more than two cents worth Rui!

I ended up finding a research paper funded by the DoE that claims the ASHRAE equation overestimates evaporation loss by about 25%. They only had one experimental data set to make this claim though.

My general feeling after doing all the research was that you just have to find a model and go with it. So many variables to predict, the best we can do is make the closest prediction of these variable estimates and go.

From there, just engineer the system well.

What I didn't find appropriate about shah's work for my calculation of an outdoor pool's heat loss, is it seems to be most applicable to indoor pools? That is something I an not sure about. Can his work be used for outdoor pool calculations? I agree that his work is the most comprehensive though, by far.

Maxime, I don't have a sheet I have a python script. I don't know if this is what you mean. It isn't a spreadsheet.

On Jul 16, 2013, at 6:12 AM, "Rui" <ruiigreja@xxxxxxxxx> wrote:

Hi,

Here are my 2 cents to the discussion:

- This work by Randy Jones has no references to Shah's works because it's from 1994, previous to most of Shah's works dealing with evaporation from swimming pools. Jones' article is also available on the the Solar Energy journal: http://www.sciencedirect.com/science/article/pii/S0038092X94905975 (but here Charles Smith is the main author).

- As far as I know there are two more papers by Smith and Jones on evaporation from swimming pools: Energy Requirements and Potential Savings for Heated Indoor Swimming Pools (1993) and Rates of Evaporation from Swimming Pools in Active Use (1998) .

- There are various works on evaporation from very different water surfaces: small tanks, swimming pools, big reservoirs or lakes, etc; some deal with occupied swimming pools where it seems evaporation can be 2-3 times higher than when they are unoccupied; some deal with evaporation caused by natural convection, some by forced convection, some by mixed convection, some don't even mention it!
The prediction of the evaporation rate by different models/formulas can vary widely.
There are some works that resume models and formulas by other authors. For example: A critical review on equations employed for the calculation of the evaporation rate from free water surfaces (2000) , Evaluation of Available Correlations for Rate of Evaporation from Undisturbed Water Pools to Quiet Air (2002) , Experimental comparison of the ability of Dalton based and similarity theory correlations to predict water evaporation rate in different convection regimes (2012) .

- I think the differences between different models is due to: 1) experimental results been obtained in particular circumstances, and therefore aren't valid outside those conditions; and 2) evaporation isn't easy to measure, and experimental measurements usually suffer of big uncertainties, specially if done in real situations (pool, reservoirs) outside the lab.
Myself am trying to do some measurements in indoor swimming pools and there are some things I just can't control and uncertainties I don't even know how to quantify.

- I think the most widely used formula to predict evaporation from swimming pools is the one from the ASHRAE - Hvac Applications Handbook. But it's very vague, it includes an activity factor, ranging from 0.5 to 1.5, depending on the type of pool, and doesn't take into account the occupancy level.
I think Shah's works have something no one else has, he compares his, and other's, analytical and empirical models with experimental results. And, he manages to achieve very good levels of deviation from the experimental results. His publications can be found here: http://www.mmshah.org/publications.html

I'd love to hear what you think and your comments about these points.

Regards,

Rui

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Chien Si Harriman wrote:
>
> Thanks Jim-
>
> Have fun at the wedding. I can share what I've learned when you get back.
> I ended up being pretty fed up with what I could find out there for hourly
> calculations of outdoor pools, so I've begun to write my own python script
> for the calculation, based on this reference. I'd be happy to let people
> take a look at it.
>
> Have fun at your daughter's wedding.
>
>
> On Sat, Jul 13, 2013 at 5:47 PM, Jim Dirkes jim@...
> > wrote:
>
> > **
> >
> >
> > Dear Chien,****
> >
> > The article is an interesting one and deals specifically with outdoor
> > pools. I scanned it just now and the methodology looks reasonable, but
> > I'll have to take a closer look later on. One of my daughters will be
> > married next Saturday and I will be thinking of other things than energy
> > analysis for the next week!****
> >
> > Thanks for sending the link!****
> >
> > p.s., In one of his publications, Mirza Shah says that a pool cover drops
> > evaporation essentially to zero. I suspect that depends on the quality of
> > the pool cover, but I agree with the idea.****
> >
> > p.p.s., It is interesting also that none of the references cited by your
> > article are for any of Mr. Shah's work.****
> >
> > ** **
> >
> > ** **
> >
> > *James V Dirkes II, PE, BEMP, LEED AP**
> > **www.buildingperformanceteam.com*
> > *
> > *
> > *Energy Analysis, Commissioning & Training Services**
> > *1631 Acacia Drive, Grand Rapids, MI 49504 USA
> > 616 450 8653****
> >
> > ** **
> >
> > *From:* EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:
> > EnergyPlus_Support@xxxxxxxxxxxxxxx] *On Behalf Of *Chien Si Harriman
> > *Sent:* Saturday, July 13, 2013 7:11 PM
> > *To:* EnergyPlus_Support@xxxxxxxxxxxxxxx
> > *Subject:* Re: [EnergyPlus_Support] Re: Pools in E+****
> >
> > ** **
> >
> > ****
> >
> > Hi Jim-****
> >
> > ** **
> >
> > Thanks for this spreadsheet. It spurred some real interest on my part. I
> > wondered what you thought of this study, and how you view it in relation to
> > Shah's work?****
> >
> > ** **
> >
> > http://www.rlmartin.com/rspec/whatis/studies_outdoor_inactive.htm****
> >
> > ** **
> >
> > And what to do about pool covers?****
> >
> > ** **
> >
> > Just thinking of this really for the first time.****
> >
> > ** **
> >
> > On Sun, Jul 7, 2013 at 3:34 AM, Rui ruiigreja@... wrote:****
> >
> > ****
> >
> >
> >
> > Dear James,
> >
> > I'm also interested in the calculation of evaporation from swimming pools,
> > and have read a few of Shah's papers.
> > I'm still new in this forum ... is that spreadsheet you created available
> > here in the forum?
> > Thanks,
> >
> > Rui****
> >
> >
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Jim Dirkes jim@ wrote:
> > >
> > > Dear Forum,
> > > A couple of weeks ago, upon responding to a post by Maxime, I attached a
> > spreadsheet that was intended to help calculate pool evaporation. I have
> > since cleaned it up quite a bit, updated the formulae to the most recent
> > versions by Mirza Shah, and checked it fairly thoroughly. My great thanks
> > go to Mr. Shah, who graciously and patiently offered guidance and input
> > about his formulae.
> > > This spreadsheet:
> > > ****
> >
> > > * Incorporates AHRAE-based psychrometric custom functions that you may
> > find helpful for other purposes. They calculate both in SI and IP units.
> > Thanks to Eric Kozubal of NREL for the original functions! (Eric, I found
> > some small errors and have corrected them.)
> > >
> > > * Calculates evaporation for two pools (e.g., a swimming pool and a spa
> > pool)****
> >
> >
> > >
> > > o Occupied and unoccupied evaporation is shown for the indoor pools
> > >
> > > o Occupied and unoccupied evaporation is shown for outdoor pools based
> > on TMY data. The result is a column of fractions which represent the
> > percentage of evaporation compared to the maximum value. These can be used
> > in a Schedule:File object. The biggest issue NOT addressed by the outdoor
> > calculations is the impact of wind; I don't yet know how to do that, or
> > even if it is a big factor.
> > > ****
> >
> > > * Assumes that you will use IP units, but can easily be adapted to SI.
> > (I have not had time or inclination yet to do so. :))****
> >
> >
> > >
> > > I hope that this is helpful for all of my energy modeling colleagues! If
> > you find any mistakes or add features, please consider sharing them with
> > the forum! I'm sure it's not perfect, so you should carefully review
> > results. I have, however, done a lot of checking and believe it is accurate.
> > >
> > >
> > > James V Dirkes II, PE, BEMP, LEED AP****
> >
> > > www.buildingperformanceteam.com
> > ****
> >
> >
> > > Energy Analysis, Commissioning & Training Services
> > > 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> > > 616 450 8653
> > >
> > > From: Jim Dirkes
> > > Sent: Monday, June 24, 2013 9:52 PM
> > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > > Subject: RE: [EnergyPlus_Support] Pools in E+
> > >
> > > Dear Maxime,****
> >
> > > I hesitate to send this because it is not organized very well ... but
> > it's that or send nothing at all. Please be patient!****
> >
> >
> > >
> > > 1. "Indoor Pool Calc" is a spreadsheet which uses the "Shah Method" for
> > calculating pool evaporation. I include it for reference only.
> > >
> > > 2. "TMY-based Hourly Schedule Data" combines TMY data (Talahassee,
> > Florida in this case) with the Shah method calculations to derive
> > evaporation at each hour. This sheet includes psychrometric calculations as
> > custom Excel functions. Frankly, I do not remember all of my assumptions,
> > and would need to review the equations carefully in order to explain
> > better. (I do not have the time to do so, at this moment, however. Sorry!)
> > >
> > > a. You can import TMY data for your site fairly easily by copying it
> > from the .epw (TMY weather) file.
> > >
> > > b. The spreadsheet primarily uses IP units of measure. If you are using
> > SI units, you may need to make some conversions.
> > >
> > > 3. For my project, I created two 8760 row .csv files from the
> > spreadsheet which are called by EnergyPlus Schedule:File objects. One was
> > used for the winter months when the pool water is heated. The other was
> > used for summer months when the pool is not heated. They are used to
> > provide the "Use Flow Rate Fraction Schedule" for WaterHeater:Mixed object.
> > >
> > > 4. I hope that is enough to get you started! If something is unclear
> > after studying the information, please send a private message and I'll do
> > my best to answer.
> > >
> > >
> > >
> > >
> > > James V Dirkes II, PE, BEMP, LEED AP****
> >
> > > www.buildingperformanceteam.com
> > ****
> >
> >
> > > Energy Analysis, Commissioning & Training Services
> > > 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> > > 616 450 8653
> > > ****
> >
> > > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:
> > EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of max4706****
> >
> >
> > > Sent: Monday, June 24, 2013 10:19 AM****
> >
> > > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > EnergyPlus_Support@xxxxxxxxxxxxxxx****
> >
> >
> > > Subject: [EnergyPlus_Support] Pools in E+
> > >
> > >
> > >
> > > Hello everybody,
> > >
> > > I am looking for some clues about modeling an outside swimming pool with
> > E+. I don't know where to start actually. I created a zone, underground,
> > with a large horizontal window which will allow me to simulate all the
> > gains from solar radiation...
> > > I am trying to change the characteristics of the air (fluid) inside this
> > zone, but I didn't manage to find where, or if it is possible.
> > >
> > > Is someone already done such a thing before ? Are there any feedback on
> > this ?
> > >
> > > Thanks to all of you.
> > >****
> >
> > ** **
> >
> > ****
> >
> >
> >
>

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