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

[knut.erik.enerstvedt@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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