WATER SPRAY SOURCE

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enviadmin
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Re: WATER SPRAY SOURCE

Postby enviadmin » Thu Aug 29, 2019 7:00 am

If you know the emission at the nozzle it should be easy to convert it into gramms per second and the thing should work.
I am not sure what you mean with the cell size... The emission rate of a point source is not related to a volume
best
Michael

claudia
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Re: WATER SPRAY SOURCE

Postby claudia » Fri Sep 06, 2019 1:23 pm

In the envimet version I have (v4.4.3 Summer19 licensed version), I checked the units of measurement of the output data. I opened the "pollutants" folder in LEONARDO and the data on water spray ("concentration" and "source") are all expressed in µg (micrograms) and not in grams. I carried out the simulation in both units: the flow rate per µg / s crashes the system providing temperatures below zero, while the flow rate in g / s implies a paltry temperature reduction compared to the one I have obtained experimentally, considering that the program well approximates the temperatures in an undisturbed environment. The unit of measurement to be used for the flow rate in the case of the version I use, what could it be, the mg / s (milligram / second) as read in an article by Bruse in 2007 concerning the simulation of fine dust? Am I doing something wrong? Please give me some explanations. I thank you in advance for your ever-present availability and courtesy.
Claudia

claudia
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Re: WATER SPRAY SOURCE

Postby claudia » Fri Sep 06, 2019 6:55 pm

Sorry Michael, in the above example you previously had a system with a flow rate of about 4L / H (about 1.1g / s) for each nozzle. This model is similar to mine, as each nozzle delivers 1g / s time (each nozzle sprays 3.75L / H) which, if I remember correctly, is precisely the value that I have to enter in the emission rate of the DB since the hourly rates are always constant . It is possible that in mild weather conditions without the presence of clouds, by operating the 24 nozzles at the same time, positioned very close to each other, in the area below I only get a max reduction of 0.05 ° C with 24g / s total hourly flow rate The nozzles are positioned at a height of 2.80 meters and I can obtain values ​​that can be approached to the experimental ones by setting a value of 24g / s instead of 1g / s. I write this because, experimentally, the maximum reduction in temperature in the area below the water sprays exceeds 1 ° C and this is in contrast to what was obtained with envimet. I would like to understand where I actually make mistakes in order to be able to do a thorough job. Is the overall flow rate too low to achieve satisfactory temperature reduction results? Or is there something wrong with the unit of measure? I believe I have complied with all the relevant references, but my doubts are equal to my questions and I trust in your answers.
Thank you.

Tim
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Re: WATER SPRAY SOURCE

Postby Tim » Fri Sep 06, 2019 7:28 pm

Hi Claudia,

I quite lost you both in the discussion about the units, nozzles, flow rates and the respective references.
What I can say is that a temperature difference of 0.05 K is pretty low for the default water spray values of the DB. If I use them, I find differences of several Kelvin (1-5) at pedestrian level near the nozzles. I magine it should be more than 0.05 K even if you only have 1 g/s instead of 5 g/s as emission rate.
Might be that something else is a problem there!

Best regards,
Tim

claudia
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Re: WATER SPRAY SOURCE

Postby claudia » Fri Sep 06, 2019 8:22 pm

Thanks for the reply Tim. Can I ask you a favour? In the previous answers you asked me for the work files, but I didn't send them to you anymore because I thought I had solved my doubts. Now, as I continue to encounter problems, can I humbly ask you to send you my work files so that I can understand with you where I am wrong to use water sprays or possibly to verify that the project is consistent with what is indicated in envimet? If possible I ask you politely because I am curious to know where I'm wrong and to always learn new things. It's possible?
I thank you in advance.
Claudia

Tim
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Re: WATER SPRAY SOURCE

Postby Tim » Sat Sep 07, 2019 10:11 am

Hi Claudia,

Yes of course. You can zip and attach them.

Best regards,
Tim

claudia
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Re: WATER SPRAY SOURCE

Postby claudia » Sat Sep 07, 2019 2:06 pm

Hi Tim, I send you the project files. The .INX file contains the 24 nozzles that work simultaneously with the same hourly flow rate, which I remember is equal to 3.75 liters / hour for each nozzle. The capacities are issued continuously between 9.00 am and 6.00 pm, except for the fact that half of the flow is delivered in the first hour. Thank you in advance for your full availability.
Claudia
Attachments
file zippati Roma.rar
(154.54 KiB) Downloaded 3 times

Tim
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Re: WATER SPRAY SOURCE

Postby Tim » Mon Sep 09, 2019 7:36 am

Hi Claudia,

In general, the model looks OK. I would recommend to use Splitting and then a coarser resolution Z. You are then able to start stretching above building height. I'd also try to make the model area larger at all sides in order to have more open space at the borders.

What may cause your issues with the spray is that I did not find the water spray source 0000WS that you used in the model in the uploaded database. When the database entry is not found, the water spray cannot be simulated. I'd recommend to use a projectdatabase so that you find all the used materials etc. in the edb file of the specific folder.

Best regards,
Tim

claudia
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Joined: Tue Jun 11, 2019 2:56 pm

Re: WATER SPRAY SOURCE

Postby claudia » Mon Sep 09, 2019 10:14 am

Hi Tim, I saw the .edb file and I realized that it was out of date so you couldn't see the water sprays. To update it I thought that just the "save database" was enough, but it is not. So that I can send you the correct file, to update the database I have to click on "Reload database"? For you this last question will be trivial, but I would not like to lose the work done so far.

Tim
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Re: WATER SPRAY SOURCE

Postby Tim » Mon Sep 09, 2019 10:59 am

Hi,

I don't think you need to reload it again. I would just click on Save User DB as... and save it then.
However, you can also go into the folder of the project and copy the projectdabase.edb if you use that one. Otherwise, you need to copy the userdatabase.edb in the ENVI-met program folder and then in the folder sys.userdata. In both cases, you do not need to export the database.

Best regards,
Tim

claudia
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Joined: Tue Jun 11, 2019 2:56 pm

Re: WATER SPRAY SOURCE

Postby claudia » Mon Sep 09, 2019 11:50 am

Thanks again Tim, especially for your patience. I found the correct .edb file with all the data including and sending it to you.
Attachments
Roma.rar
(43.3 KiB) Downloaded 3 times

Tim
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Re: WATER SPRAY SOURCE

Postby Tim » Wed Sep 11, 2019 8:03 am

Hi Claudia,

I ran several test simulations and found that two factors limit your water spray effect:
1. The specialID of 2 only releasing the spray at the height of the nozzle and not over the whole height of a fountain such as the default water spray fountain in the DB. I would say that is correct according to your description.
2. The amount of water spray released: Only certain hours during midday and only values around 1 g/s instead of our default values of 5 g/s. I'd also say that is correct.

I found air temperature reductions of 0.2 K during midday for your simulation. If I took a higher emission rate (of 5 g/s), I found around 0.9 K air temp reduction. Changing from a nozzle to a fountain greatly enlarged the effect.

The simulation thus seems fine to me.

Best regards,
Tim

claudia
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Joined: Tue Jun 11, 2019 2:56 pm

Re: WATER SPRAY SOURCE

Postby claudia » Wed Sep 11, 2019 8:41 am

Thank you very much Tim, you confirmed all my doubts.
From these results, I find that the operation of water sprays is not able to satisfy my experimental data obtained on site, reducing the temperature by very few degrees compared to the real case in which the temperature dropped by about 1-2 ° C. What do you advise me to do since ws don't work for such low flow rates? I'm going to the water fountain? I regret the fact that I purchased the license solely to use water sprays ...
Claudia

Tim
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Joined: Mon May 15, 2017 3:46 pm

Re: WATER SPRAY SOURCE

Postby Tim » Wed Sep 11, 2019 9:33 am

Hi Claudia,

I am sorry to hear that but would definitely not see it like that.
It works for all kinds of flow rates but is a parametrized approach which can thus not include all shapes and characteristics of the real world. Several assumptions (e.g. droplet size) are made which can be different in reality.

Furthermore, I would not rely on the measurements in general. It is not easy to measure the effect of water spray on the air temperature, especially not how large it might be.

Best regards,
Tim


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