[TRNSYS-users] modelling differences of Type 56 between BOUNDARY=INTERNAL and BOUNDARY=IDENTICAL

[Marion Hiller <Hiller@Transsolar.com>]

Dear TRNSYS-Users,

 

In this news group a question concerning modelling differences of Type 56 between the following option of an opaque surface was posted:

1. BOUNDARY=INTERNAL
2. BOUNDARY=IDENTICAL

 

Both options yield to the exact same results

• if the surface construction type is defined symmetrically
  (symmetric layer composition, solar absorption front = solar absorption back, IR emissivity front = IR emissivity back, heat transfer coefficient front = heat transfer coefficient solar absorption back)
• if the a) is defined a single surface with double area and b) is defines as two surfaces with half the area:

 

                      WALL         =REFEND_TERRE_CRUE : SURF=  3 : AREA=         2 : INTERNAL

 

WALL         =REFEND_TERRE_CRUE : SURF=  5 : AREA=         1 : BOUNDARY=IDENTICAL

WALL         =REFEND_TERRE_CRUE : SURF=  6 : AREA=         1 : BOUNDARY=IDENTICAL

 

The reason for this is that Type56 splits the INTERNAL surface (a) into 2 equivalent surfaces with half the area.

 

We recommend to use the option “BOUNDARY=IDENTICAL” because

• the users enters directly what is modelled (no hidden rearrangement)
• it can be used  for 3D geometry

 

The option “BOUNDARY=IDENTICAL” is kept up to now for “historical reasons”.

It is under consideration to drop this option.

 

Marion

 

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Dipl.-Ing. Marion Hiller 
TRANSSOLAR Energietechnik GmbH 
Stuttgart - Munich - New York - Paris  

t: +49.711.67976.0   f: +49.711.67976.11

www.transsolar.com/   

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