[esp-r] Re: solar problem

Mon Oct 22 07:31:54 BST 2012

Dear Hua

O.K., just to be (almost) sure I understand your model:
- you have four walls, made of 100% glazing (TMC)
- the glazing is single pane
- apart from that, you have a roof and a floor.
- the floor is facing what on the other side?

How large is the space? Be aware, that "SW entering" and "SW (other fc)" will likely include diffuse radiation from all four wall surfaces, so tracking the exact numbers in such an example may be quite tedious.

Your write you get the "global irradiance" by the "other face" value when you " set all each glazing surface to be opaque ". I suppose you mean when you set the absorption to 0.99? Do you set all four walls to the same at the same time? To check the above (additional radiation entering and of course being reflected out again through the "other three walls"), have you tried having only one transparent wall?

Also, do get an idea of what is happening on the floor, maybe split this up into a set of surfaces, so you can see where the direct hits are and where only diffuse radiation is hitting the floor.

I am not quite sure what your goal is, though.

Best
Achim

Von: HUA SUO [mailto:surano1505 at hotmail.com]
Gesendet: Sonntag, 21. Oktober 2012 18:44
An: achim.geissler at intergga.ch
Betreff: RE: [esp-r] Re: solar problem

Dear Achim

Thanks for your quick reply and the comments.And sorry I did not specify clearly. Now I also have some comments below.Hope that you can have a look.

All The Best ,

Hua

________________________________
From: achim.geissler at intergga.ch
Date: Sun, 21 Oct 2012 18:12:00 +0200
To: surano1505 at hotmail.com
CC: esp-r at lists.strath.ac.uk
Subject: [esp-r] Re: solar problem

Dear Hua

I am not quite sure that I can follow your points below, but again some comments inline.

Best
Achim

On Oct 21, 2012, at 1:50 PM, HUA SUO <surano1505 at hotmail.com<mailto:surano1505 at hotmail.com>> wrote:

Dear Achim,
  Thanks for your great help.
  Could you also help me with the following questions?
1.why the output for each surface , "SW radiation(inside)" equals to "SW rad abs(other fc)", except that the information in the floor does not exit in "SW rad abs(other fc)" ?
Sorry, I don't know. I haven't looked at the "other face" thing in a while. Isn't "other face" the one facing outside of the zone under consideration? The value will depend on what boundary condition you defined. If you defined "similar" for internal walls, then "other face" will have the same values as "inside face".

The boundary conditoin is exterior for each surface, I do not have internal walls in the model.
2.I preset the absorbitivity 15% for the glazing in optical database, for each surface, should the "SW rad abs( other fc)"/global irradiance of this surface =15%?but it is only around 4%.The transmissivity is 10%.Why?
Careful with "global irradiance". What are you using, here? You should look at the radiation hitting the surface, not global (possibly horizontal?) radiation.

I got the "global irradiance" when I set all each glazing surface to be opaque, extracted from "SW rad incid(other fc)".It should be the correct one.
3.I tried to set the absorbability 99% for the grazing in optical database, for each surface, "SW rad abs( other fc)"/global irradiance of this surface=25%?
Strange values for a glazing. Typical values would be (double glazing unit) trans=60 - 70%, abs=8-15% refl=1-abs-trans

It is a test I did for understanding the output. When I set the absorbability 99%, I expected for each surface"SW rad abs( other fc)"/global irradiance of this surface=99%, but it turned out to be 25%...I also tried some other number , also disapponting result in the end.
4. Where I can get the absorbed solar energy by floor?
For any given surface, I find it easiest to add a small surface with an opaque material I called "sensor". This is totally black (absorption = 0.999). Thus, "solar absorbed" on this "sensor surface" is the amount that hits the surface (everything is absorbed).

In my case as the floor is in contact with the indoor air, is the output of "SW radiation(inside)"  for floor the total solar hitting on the it ?But how can I get from the result analysis the amount of the solar energy absorbed?

Regards,

Hua

________________________________
From: achim.geissler at intergga.ch<mailto:achim.geissler at intergga.ch>
Date: Sat, 20 Oct 2012 19:38:49 +0200
To: surano1505 at hotmail.com<mailto:surano1505 at hotmail.com>
CC: esp-r at lists.strath.ac.uk<mailto:esp-r at lists.strath.ac.uk>
Subject: [esp-r] Re: solar problem

Dear Suo Hua

see some comments / answers below, inline.

Best
Achim

On Oct 19, 2012, at 12:03 AM, HUA SUO <surano1505 at hotmail.com<mailto:surano1505 at hotmail.com>> wrote:

Hello, ESP-r experts.

I made a model that the all the façade is totally single grazing( material newly created by me) and the floor is opaque. After several test , I have some questions and hope that I can get help from you.
1. I found that if I change the properties in the material database for the single grazing, namely " the solar direct tran" ,  "solar reflec out", "solar reflect in", nothing changes for the simulation result. Only if I change properties in the optical database ,namely"direct trn" "reflct" "abs" that can affect the simulation result. Am I right?
Yes, the properties "trans" and "abs" ("refl") for transparent materials are taken from the optics database. The property "eps" (long wave emissivity), the geometry (i.e. the layer dimensions) and the thermal properties (thermal capacity and thermal conductivity) are taken from the materials database entry.
2. For the RES file, "solar entering the zone" is the summation of transmissivity (the parameter  in optical database) multiplies the global irradiance for each glazing surface. What is "solar absorbed in zone" ? I checked that it is not the summation of absorptivity (the parameter in optical database) multiplies the global irraiance for each glazing. It also can be noticed that " solar absorbed in zone" is less than "solar entering the zone" in all the test I did.
"solar absorbed" is that part of entering solar radiation that is not re-reflected directly back out of the zone.
3. When I try to get the solar energy that passes through the glazing and then absorbed by the floor , I extracted the information from " SW radiation(inside)" , it seems that this parameter is very large and obviously not equal to the absorptivity of the floor multiplies the global irradiance to the floor(how to get this parameter ?). And for the glazing "SW radiation(inside)" divided by the irradiance is not the absorptivity I gave .What is "SW radiation(inside)" means exactly?
Are you writing out the values "per m2"? SW (short wave) radiation inside should be closely correlated to radiation hitting the given surface and transmission of the transparent material (not absorption).

Regards,

Suo Hua

Ph.D Student in Tecnologia e Progetto per l'Ambiente Costruito/Technology and Design for Environment and Building

Il Dipartimento B.E.S.T.Dipartimento di Scienza e Tecnologie dell'Ambiente Costruito/ The Department of Building Environment Science & Technology

Politecnico Di Milano

Email:hua.suo at mail.polimi.it<mailto:Email%3Ahua.suo at mail.polimi.it>

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