Re: [ASCEND] Doubt regarding fractional powers

[John P. <joh...@an...>]

Hi Vikram

I looked at your model and using the Diagnose feature, I found that the
solver is getting stuck on Block 2, which is a block containing only one
equation, namely "h * (D ^ 0.7) = (G ^ 0.7) * T". I clicked the green
square to highlight the relation in question, then clicked the [?] icon
next to that relation, and it shows the values of the variables in that
equation. I can see that the value of 'G' is negative, which means that
in attempting to solve that equation, you are attempting to take the 0.7
power of a negative number, which is not allowed.

I reloaded the model, then (right-click, properties) I set the lower
bound of both G and T to 0. After making this small change, the solver
converges without any problems.

I have written some further notes for you here:
http://ascend4.org/How_do_I_fix_my_model#Function_range_error

Cheers
JP

On 23/06/11 21:50, Vikram Kadam wrote:
> Hi again
>
> I am stuck with  *'function range error' *and* **'POW_D0' *errors
> while implementing Packed Bed Thermal Storage Tank model.
>
> *exp.a4l* contains a small code that ouputs similar errors.
> The strange part is on replacing line
> "D = T^2;" by 
> "T = D ^ 0.5"
> it works fine.
>
> Can you comment on this strange behavior ?
>
>
> regards,
> Vikram