[TRNSYS-users] Hconv and convective heat transfer coefficient

[hotline]

Dear Wirich,

there is no blanket response to this issue. Could you please provide us your simulation project to hotline at transsolar.com<mailto:hotline at transsolar.com>, so we can reproduce your problem.
To rule out a user error, please make sure which Longwave radiation mode you are using.

  *   In the standard model (starnet model) the REQV combines radiation and CHTC
  *   In detailed mode the user defined emissivities of surface are handeld.

Regards,
Christoph

Von: TRNSYS-users [mailto:trnsys-users-bounces at lists.onebuilding.org] Im Auftrag von adnan rasheed via TRNSYS-users
Gesendet: Donnerstag, 1. März 2018 03:33
An: TRNSYS users mailing list at OneBuilding.org <trnsys-users at lists.onebuilding.org>
Cc: adnan rasheed <adnan.upm.spain at gmail.com>
Betreff: Re: [TRNSYS-users] Hconv and convective heat transfer coefficient

Dear  Wirich FREPPEL,

Recently i did some work related to  internal and external convective heat transfer coefficient and its effect on  temperature  and Overall heat transfer coefficient you can read the model calibration section of the following paper "Development of a model to calculate the overall heat transfer coefficient of greenhouse covers" . Hope this will help you.if you have any question you are most welcome.

here is the link of the paper

http://revistas.inia.es/index.php/sjar/article/view/10777/3790


Adnan Rasheed

On Wed, Feb 28, 2018 at 11:21 PM, Wirich FREPPEL via TRNSYS-users <trnsys-users at lists.onebuilding.org<mailto:trnsys-users at lists.onebuilding.org>> wrote:
Hi everyone,

I ran 3 different simulations with TRNSYS, in which the only parameter I changed was the convective heat transfer coefficient CHTC (as seen in picture 1). It seems that nothing really differ from a simulation to another, though I tried with h=1, then h=100 (see picture 6 which shows the airnode temperature). Then, in order to identify the problem, I set as output the HCONV (type 108) and the resistance between the surface and the starnode Req (type 86).

Two observations :

1) HCONV does not correspond to the CHTC I set in TRNBUILD (even by dividing it by the surface area)

2) Req is very close to 0. I guess that's why I observe no real difference between each simulation.

So I've got a few questions:

1) What am I actually observing with HCONV?

2) Why is Req close to 0 ?  And what does it mean? (I assume that when Req=0, there is no heat transfer by convection between the surface and the airnode)

Thanks in advance for the clarification

--
Wirich FREPPEL
Ingenieur Doctorant en Recherche & Developpement
Centre R&D de Noirot - Groupe Muller
8 rue Louis Ampere, 02030 Laon
+33 (0)3 23 27 31 99


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