[TRNSYS-users] Modelling a greenhouse thermal screen by using an internal window in Type 56

[knut.erik.enerstvedt at niva.no]

Hello TRNSYS users,

I am modelling a horizontal thermal screen in a greenhouse by using an 
internal (ADJACENT) window between to zones in Type 56, one below and one 
above the window (screen). The "window" is a virtual window with no 
glazing and no frame to let all the radiation through to the lower zone 
when the screen is open. I have defined an internal shading factor 
controlled by an input variable to model the effects when the screen is 
opened or closed. In the Window Type Manager, I wonder about the following 
settings:

Optional Properties of Shading Devices:

Additional Thermal resistance: Can I use this to set the thermal 
properties of the screen? Will it be effective only when the shading 
factor is greater than zero?
 Reflection Coefficient of Internal Device: How should I set this?

Convective Heat Transfer Coefficient of Window: Should I use 0 (direct 
contact) when the screen is open and 11 (inside value) when it is fully 
closed?

 I also have a question about coupling of air flow between the upper and 
lower zones. I use an equation based on the degree of screen opening, 
temperature difference and density difference to calculate air flowrate 
across the screen. The direction of flow depends on the level of 
temperature and/or density in the two zones. How can I ensure air balance 
between the adjacent zones? Can I take the absolute value of this air 
flowrate as air flow inputs into BOTH zones, that is the air flow from 
lower to upper zone equals the air flow from upper to lower zone?

All replies are higly appreciated.

Thanks,
Knut Erik
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