[TRNSYS-users] About Active Layer of TRNBuild

[David Bradley]

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
David BRADLEY                           2916 Marketplace Drive - Suite 104
Partner                                        Madison, WI 53719
Phone: (608) 274-2577 USA
Fax: (608) 278-1475
E-mail: bradley at tess-inc.com
Web Pages:  http://www.tess-inc.com     and      http://www.trnsys.com

"Providing software solutions for today's energy engineering projects"
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