cooling load calculation bug in Designbuilder Software

crb7 · Apr 26, 2024

Hi
I have modeled a 8-storey building in designbuilder software. there is a the problem in its cooling load report; The report indicates heat transfer in middle floors which are located between 2 conditioned spaces. I made the software to ignore thermal mass effect. Is it a bug in the software?
this is a screenshot of its report in summer season

HVAC-Novice · Apr 26, 2024

Did you contact their support?

Can you try to set both spaces to 24/7 operation to exclude any thermal mass delays? I assume both spaces have the same setpoints?

crb7 · Apr 26, 2024

Its not thermal mass effect and both set points are the same.
I guess surface convection cause this negative load but I dont get the physics behind its calculation .
This is the heat gain graph through floor for summer design day. The point is that, air temperature is less than surface temperature, so the surface convective heat gain must be positive!

HVAC-Novice · Apr 26, 2024

It looks like you are reducing air temperature (blue line) at 7:00 and raising it at 22:00?
Could the inside surface temperature be exterior wall warming up due to sunshine?

crb7 · Apr 26, 2024

No, because it is floor not a wall.

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cooling load calculation bug in Designbuilder Software

crb7

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crb7

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HVAC-Novice

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crb7

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