Re: [TRNSYS-users] About Active Layer of TRNBuild

[David Bradley <bradley@tess-inc.com>]

At 23:03 11/26/2006, Aquila wrote:
> 1. Definition
>
> 1)      inlet
> temperature : is this the initial temp. of water after heating or the
> initial temp. before heating?

the inlet temperature is simply the temperature of water that is entering
the floor. 

> 2)
>       gain : is this means the
> basic heat gain for floor heating by the boiler or an additional heat
> gain except the boiler?

I am not sure where the gain is applied to the fluid.

> 2. about ¡®min.
> inlet mass flowrate¡¯
>
> 1)      What¡¯s
> the meaning and purpose of determining ¡®min. desired inlet mass
> flowrate¡¯ ?  And why the unit of it needs square meter(m2) ? 

the active layer is developed using a series of correlations that derive
in part from experimental results. The correlations are only valid within
certain ranges of floor thickness, tube diameter to spacing ratio, and
flow rate. It is okay if the fluid does not flow through the floor at all
(flow rate = 0) but if there is flow, then the flow must be above a
certain specific flow rate kg/h.m2. The area refers to the area of the
floor through which fluid is flowing. Information about the mathematics
of the active layer model can be found in section 6.3.2.4 of the
documentation set (manual 06-Multizone Building modeling with Type56 and
TRNBuild).

> 2)
>       How the ¡®min. allowed inlet
> mass flowrate¡¯ will be decided?

I believe that the minimum flow rate is simply 13 kg/h.m2.

> 3. about
> ¡®autosegmentation¡¯
>
> 1)      What¡¯s
> the exact relationship between ¡®min. desired inlet mass flowrate¡¯ and
> the number of segmentation ?

if you want to use a smaller flow rate than is allowed for your actual
floor area, you need to break up the floor into a series of smaller
segments. To do so, enter the lowest flow rate that you want to be able
to use and click the autosegment button. The floor should be broken up
into its component parts automatically.

> 2)
>       If the value of ¡®min.
> desired inlet mass flowrate¡¯ is larger than ¡®min. allowed inlet mass
> flowrate¡¯, the simulation don¡¯t work with the following error
> message.  Do I have to use autosegmentation always when I use the
> active layer?
>
> ¡® Specific fluid mass flow of active layer in surface 1 below minimum
> value of 32.76 kg/m2h Please, increase the minimum mass flow rate
> or ?se the autosegmentation feature of TRNBuild for subdividing the
> surface.¡¯

the error message means that your fluid mass flow rate is smaller than
the minumum allowable fluid mass flow rate. For a time there was a bug in
calculating the minimum and you would sometimes get the error even though
the actual flow rate was high enough. Make sure that you are using the
latest version (TRNSYS 16.1).

Kind regards,
 David

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Thermal Energy System Specialists (TESS), LLC
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