AW: [TRNSYS-users] Adiabatic boundary wall in TYPE56

Matthias Rudolph rudolph at
Wed Dec 8 07:48:04 PST 2004

Dear Xavier,
you are right with the explanation of boundary identical.
However for boundary walls you can define a very small convective heat transfer condition > 0.001 W/m²K. For alpha < 0.001 you will receive direct contact (almost equivalent to > 999 W/m²K). We kept this for backwards compatibility.
So if you want to create a wall with mass towards the zone and the adiabatic condition on the back (not in the middle of the wall as in boundary identical mode), you might use following approaches
1. choose a low alpha e.g. 0.002 on the back of the boundary identical wall
2. define the wall adjacent to a ficitve zone with alpha_back = 999. In this fictive zone define a resistance only wall with alpha_front = 999 and boundary identical to the back.

	-----Ursprüngliche Nachricht-----
	Von: trnsys-users-admin at [mailto:trnsys-users-admin at] Im Auftrag von Xavier García Casals
	Gesendet: Donnerstag, 2. Dezember 2004 19:12
	An: trnsys-users at; David Bradley
	Betreff: Re: [TRNSYS-users] Adiabatic boundary wall in TYPE56
	With the 'identical' option, from what I understood from the manual, what you do is to impose the condition that the convective fluid in the back of the surface has the same temperature as the 'star temperature' from the front of the surface. In this way you create an adiabatic plane INSIDE the wall, but not on the back surface (there are non nule heat flows at both sides of the wall). What I was wondering is whether you can impose an adiabatic condition straight on the BACK surface of the wall.

		----- Original Message ----- 
		From: David Bradley <mailto:bradley at>  
		To: Xavier García Casals <mailto:xavi at>  ; trnsys-users at 
		Sent: Thursday, December 02, 2004 5:26 PM
		Subject: Re: [TRNSYS-users] Adiabatic boundary wall in TYPE56

		Dear Xavier,
		  With a BOUNDARY wall, you have the option of defining the temperature on the other side of the wall as "userdefined" (either an input, a constant value, or a schedule) or as "identical." To define an adiabatic wall, simply set the boundary temperature to "identical"
		Kind regards,
		At 10:14 AM 12/2/2004, Xavier García Casals wrote:

			Is there a direct way to specify an adiabatic boundary wall in TYPE56?. From what I could find in the documentation, only boundary walls with a boundary temperature may be deffined. In principle setting a very small wall convection coefficient (HBACK) would fisically lead to an adiabatic condition, but from the manual it seems it leads to the oposite (wall temperature equal to boudary temperature). Two aproximations I can think of are to specify the identical condition, in which case an adiabatic plane would apear WITHIN the wall, or specifying a layer with a very high resistence at the outer side of the wall. But is there not a way to specify the boundary adiabatic condition straight?

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