Re: [TRNSYS-users] trnflow-inside airspeed

[Mariëlle Nuchelmans <M.Nuchelmans@chri.nl>]

Hi Matthias,

Unfortunately I can't download your research. But the correlation you proposed is for natural convection and not forced convection? 

I always use the following correlation for natural convection:

Hc = 1.45 * ((Tsi-Tair)/H)power0.25  [W/m2K]  H is height window.

And I want to use the following correlation for forced convection:

If v < 5 m/s : hc = 5.8 + 4 * v     [W/m2K]
If v < 5 m/s : hc = 7.14 * v^0.78    [W.m2K]

Met vriendelijke groet,

Mariëlle Nuchelmans
________________________________

Denk aan het milieu en print deze email alleen als het noodzakelijk is.
-----Oorspronkelijk bericht-----
Van: Matthias Haase [mailto:mathaase@gmail.com] 
Verzonden: maandag 15 februari 2010 22:38
Aan: Mariëlle Nuchelmans
CC: trnsys-users@cae.wisc.edu
Onderwerp: Re: [TRNSYS-users] trnflow-inside airspeed

Hi Mariëlle,

I am not sure if your approach will give you satisfying results since
airflow near surface should be less than Bernoulli-average (as you
proposed). A different approach uses correlation between hc and
temperature regimes.

'For internal vertical surfaces, the convective heat transfer
coefficient due to the difference between the surface temperature and
the temperature of the air adjacent to the surface was chosen for
natural ventilated cavities to

hc = K1 x (Tsi - Tair)powerK2

with
K1, K2 correlation factors.'
Several sources give you a variation of answers (f.e. Recknagel or
Glueck). I used K1=1.5 and K2=0.25 for natural ventilation mode in my
research which you might find helpful and which can be downloaded
here:
http://sunzi.lib.hku.hk/hkuto/record/B41896993

Best regards
Matthias Haase
BSc, Dipl-Ing, MSc, Ass. Prof
Norwegian University of Science and Technology
Trondheim, Norway


On Tue, Feb 9, 2010 at 12:46 PM, Mariëlle Nuchelmans
<M.Nuchelmans@chri.nl> wrote:
> hello,
>
> I'm modelling a natural ventilated double facade with trnflow. To determine
> the convective heattransfer coefficient on the inside, I need the
> windvelocity inside. The only thing I can think of is to take the mass flow
> between two airlinks and to divide it by the area (of the opening). Is this
> the way to determine it? Or does anyone know a better way?
>
> With kind regards,
> Marielle
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