Re: [TRNSYS-users] TRNSYS-users Digest, Vol 157, Issue 3

2018-01-05 21:15 GMT-03:00 <trnsys-users-request@lists.onebuilding.org>:

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Today's Topics:

1. Radiant barrier (Ilyas Ismaili)
2. Doubt on the codes of some TESS Unglazed collector models
(Javier Vega)
3. Re: Doubt on the codes of some TESS Unglazed collector models
(Jeff Thornton)
4. trnsys-greenhouse (azeddine fantasse)

---------- Mensaje reenviado ----------
From: Ilyas Ismaili <karaktus@gmail.com>
To: "TRNSYS users mailing list at OneBuilding.org" <trnsys-users@lists.onebuilding.org>, d.bradley@tess-inc.com
Cc:
Bcc:
Date: Fri, 5 Jan 2018 20:25:50 +0000
Subject: [TRNSYS-users] Radiant barrier
Dear TRNSYS users,
I'm trying to model a radiant barrier in the roof of a building, so I put a 10cm airgap into the external roof layers, and I set the back absorptance of the roof to 0.05 (since radiant barrier can achieve up to 95% heat reduction, correct me if this value is wrong).
Is this modelling correct, or there is another way to do it?
Regards,

‌

---------- Mensaje reenviado ----------
From: Javier Vega <jvega025@gmail.com>
To: trnsys-users@lists.onebuilding.org
Cc:
Bcc:
Date: Fri, 5 Jan 2018 17:45:34 -0300
Subject: [TRNSYS-users] Doubt on the codes of some TESS Unglazed collector models
Hi TRNSYS users,

I was just checking the codes of Type 553 and Type 1290 (Unglazed Solar Collector models) and something grabbed my attention. When both models do the Net Long Wave Radiation Balance, they do the following:

!Account for the long wave losses from the collector surface
T_ambient_K = T_ambient+273.15
T_sky_K = T_sky+273.15
Sigma = 3.6*5.67d-08 !Stefan Boltmann constant
Net_Longwave = Sigma*(T_ambient_K**4.-T_sky_K**4.)*Emissivity/Absorptance

That is a copy/paste of Type 553.

Why the Net Long Wave is defined with the Ambient Temperature and not with the Collector Average Temperature? It doesn't make sense to me. Is there something I'm uderstanding wrong?

Bests of wishes,

Javier Vega Benavente
Universidad de Concepción, Chile.

Libre de virus. www.avast.com

---------- Mensaje reenviado ----------
From: Jeff Thornton <thornton@tess-inc.com>
To: "TRNSYS users mailing list at OneBuilding.org" <trnsys-users@lists.onebuilding.org>
Cc:
Bcc:
Date: Fri, 05 Jan 2018 15:08:17 -0600
Subject: Re: [TRNSYS-users] Doubt on the codes of some TESS Unglazed collector models
Javier,

It's the net long wave radiation on the collector surface - not the long wave radiation from the collector surface to the sky. It's taken directly from the standards for modeling un-glazed solar collectors.

Jeff
---
Jeff Thornton
President - TESS LLC
22 N. Carroll Street, Madison WI USA 53703
Office: (608) 274-2577  Fax: (608) 278-1475
www.tess-inc.com
E-Mail: thornton@tess-inc.com
On 01/05/2018 2:45 pm, Javier Vega via TRNSYS-users wrote:
Hi TRNSYS users,

I was just checking the codes of Type 553 and Type 1290 (Unglazed Solar Collector models) and something grabbed my attention. When both models do the Net Long Wave Radiation Balance, they do the following:

!Account for the long wave losses from the collector surface

T_ambient_K = T_ambient+273.15

T_sky_K = T_sky+273.15

Sigma = 3.6*5.67d-08 !Stefan Boltmann constant

Net_Longwave = Sigma*(T_ambient_K**4.-T_sky_K**4.)*Emissivity/Absorptance

That is a copy/paste of Type 553.

Why the Net Long Wave is defined with the Ambient Temperature and not with the Collector Average Temperature? It doesn't make sense to me. Is there something I'm uderstanding wrong?

Bests of wishes,

Javier Vega Benavente

Universidad de Concepción, Chile.

Libre de virus. www.avast.com
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---------- Mensaje reenviado ----------
From: azeddine fantasse <azeddinefantasse@gmail.com>
To: trnsys-users@lists.onebuilding.org, d.bradley@tess-inc.com, thornton@tess-inc.com
Cc:
Bcc:
Date: Fri, 5 Jan 2018 21:26:17 +0000
Subject: [TRNSYS-users] trnsys-greenhouse
hello Ms bradley i want to ask you if i can find a type of greenhouse in trnsys?
if not i would like the mean for this.
thanxs
Cordialement

Azeddine FANTASSE
Doctorant en Sciences Physique et Ingenieurie
Faculté des Sciences Samlalia
Université Cadi Ayyad , Marrakech
Mail : azeddinefantasse@gmail.com
Tel : 06 35 74 41 33

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