The value must be scalar or a matrix issue using range to create values for plotting

Its hard up to impossible to debug a picture.

If ever possible always attach the worksheet itself.

In your case the reason for the error seems to be that you did not consider the difference between a range and a vector.

A range is just kind of an implicit loop, its NOT a collection of various values!

Her one way to define m.air as vector, not as range (assuming that ORIGIN is at its default value 0)

Note that the "i" is a vector/matrix index, not a literal index as "air".

Ranges should only be used for three reasons:

• To index the elements of a vector/matrix (as in the example above)
• To form a for-loop in a program
• To make the abscissa in a plot

Remark: Up to version Prime 9 we could convert easily a range into a vector using an undocumented trick. PTC promised to provide a "legal" way to do so in Prime 11.

Here in the forum you will find user-defined functions which turn a range into a vector and also function which create a vector with a sequence of values by providing the first, second and last value (similar to the range definition).

Some additional comments:

As Th2 would be a vector as well, chances are that you have to vectorize the function call to F_CrossFlowHX...

When displaying the result of the difference of two temperates given in °C, you should not use °C but rather Delta°C (equivalent to Kelvin).