[TRNSYS-users] How to change minimum allowed value for TYPE 560?

[Jeff Thornton]

By definition the heat transfer coefficient must always be greater than or equal to zero.  Otherwise you’ll move heat from colder surfaces to warmer surfaces:  

Qloss = UA*(T-Tenv)

If T is greater than the environment temperature then heat will be transferred away from your surface and T will get cooler.  If T is cooler than the environment temperature then heat transfer from the surface will be negative and your surface will get warmer.  The model takes into account the direction of heat transfer based on the temperatures.

Jeff

Sent from my iPhone

> On Jun 4, 2021, at 5:11 AM, Janus Rathke via TRNSYS-users <trnsys-users at lists.onebuilding.org> wrote:
> 
> 
> Hi everybody 
> 
> I am using an equation to calculate the convective heat transfer coefficient, which i used as the input "Top Heat transfer coefficient" for TYPE 560 solar collector. 
> The model works fine, but TRNSYS gives an error every time the loss coefficient becomes negative. This will happen when the surface temperature is below ambient temperature and convective heat transfer direction will be reversed. 
> 
> I get the error "The top loss heat coefficient must be greater than 0". I have tried to remove this restriction, in the source code for Type 560, but the error still emerges. 
> 
> Does anybody know a way to change the allowed minimum values? 
> <image.png>
> 
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