[esp-r] Re: Convection coefficients problem

[Michael Lucchi]

I have set manually a schedule of hc coefficients wich reflects the air
velocity in the zone: now the model runs correctly!
Thank you very much for the precious help.
Michael


2013/11/14 Jon Hand <jon at esru.strath.ac.uk>

>
> This shows the process of debug models.  An indication that Fisher
> correlation might
> be the cause.  This needs to be confirmed that conditions in the facade
> are suitable
> for this correlation (velocity might be high??) and it might be that there
> is another
> correlation that could be used.  There is also an option for the user to
> define hc
> coefficient manually - e.g. if you know the velocity is ~1.5m/s then set a
> schedule
> of hc coefficients that reflect that velocity within the zone hc defintion.
>
> Certainly a short timestep - perhaps 5 minutes down to 1 minute for the
> building &
> flow solution. Would be more appropriate for this model.
>
> -Jon Hand
> ________________________________________
> From: Michael Lucchi [michael.lucchi at gmail.com]
> Sent: 14 November 2013 09:34
> To: Jon Hand; esp-r at lists.strath.ac.uk
> Subject: Re: [esp-r] Convection coefficients problem
>
> Thank you Jon for the precious suggestions.
>
> The facade is connected with a HVAC system and it is a force ventilated
> facade. However, I also connected the three zone nodes corresponding to the
> ventilated facade with a flow network in order to simulate the behaviour of
> the facade when the plant turns off (in this period the mass flow between
> the three zones is due to only buoyance effects ). Generally, the
> simulation stops after few time-steps.  The only succeded simulation was
> set up with both  zones and plants time-steps of 30 minutes, but with wrong
> results.
> Turning off the Fisher correlation and using default correlation,  the
> model runs.
>
> Thank you for eventual helps.
>
>
> 2013/11/12 Jon Hand <jon at esru.strath.ac.uk<mailto:jon at esru.strath.ac.uk>>
>
> The first thing that caught my attention is [ventilated facade] and
> [forced ventilation].  What
> kind of ventilated facade is this - a rain-screen (in which case there
> would be low velocity
> flow).  Is the facade actually force ventilated or just ventilated by
> differences in temperature
> and thus one might describe it in via a flow network?
>
> mzsad is in the matrix solver.  There are a few folk who might be able to
> address that
> kind of issue.  It might be that the Fisher is causing this or perhaps
> not.  I would first
> explore the use of the [trace] facility in bps - it can write out lots of
> additional information
> about the heat transfer correlations.
>
> I would suggest that you turn off the Fisher in the 3 ventilated facade
> zones and see
> if the model runs.
>
> And also - what is happening at 93 time-steps. (Hour 10 on year day 189)?
>  Does
> the error happen if you run the assessment for a different day?
>
> -Jon
> ________________________________________
> From: esp-r-bounces at lists.strath.ac.uk<mailto:
> esp-r-bounces at lists.strath.ac.uk> [esp-r-bounces at lists.strath.ac.uk
> <mailto:esp-r-bounces at lists.strath.ac.uk>] on behalf of Michael Lucchi [
> michael.lucchi at gmail.com<mailto:michael.lucchi at gmail.com>]
> Sent: 12 November 2013 15:43
> To: esp-r at lists.strath.ac.uk<mailto:esp-r at lists.strath.ac.uk>
> Subject: [esp-r]  Convection coefficients problem
>
> Hello ESP-r users,
> I’m trying to model a ventilated façade characterized by a forced
> convection regime using Esp-r (version 12.0 for Windows 7) for my thesis.
> The model is composed by one single room, and the external facades are
> ventilated opaque walls. The ventilated façade is composed by three thermal
> zones, with the aim to obtain the vertical temperature distribution. In
> order to reach reasonable results, I tried to impose the Fisher and
> Pedersen correlation for mechanically driven flows both in the room and in
> the ventilated façades. However, when I run the simulation, a numerical
> error stops any module. The following text is the error displayed by the
> simulator:
> mzsad 1: numerical error after 93 time-steps.
> (Hour 10 on year day 189).
> e(iconst,n)    = -17999998.000000
> a1      = -18000000.0000
> I am still  a novice user of the software and any help is much appreciated.
> Kind regards.
> Michael Lucchi
>
>
>
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