Equation not referencing all values in vector

Question

I'm not that great a Mathcad and I apologize if some of my terminology is wrong but I'm having a problem. I'm trying to ultimately determine outlet temperatures in a set of parallel counterflow heat exchangers. At one point I have the worksheet solve for the minimum number of exchangers in parallel needed to satisfy a maximum pressure drop given a range of possible lengths. Everything seems to work fine but I noticed my temperatures were way off so looking back through the worksheet and starting the UA calculations, all the values are wrong. It appears as though the values aren't being pulled in the same order from all the vectors. If I reference the first value in each of the relevant vectors, I get the correct answer, but if I let Matchcad just run through and give the 10 answers, they are all wrong. It's as if its pulling random values. I've attached the worksheet for reference. Thanks for any help.

Werner_E · Accepted Answer

By solving the equation by hand i get around 1.3*10^5. If I change the equation to reference the 1st value of all the relevant variables, I get an answer of 1.285*10^4 which is what I expected. So it

I hope your manual calc gave you 10^4, not 10^5 !?

OK, as I expected - vectorization is needed.

h.ann and A.o are both vectors. In the formula for UA they are multiplied. Mathcad evaluates using the dot product (vector scalar product) but we need Mathcad to wade through the vectors element by element and the results being collected in a vector. This is what vectorization is intended for. You get this operator from the matrix palette or by typing Ctrl and the minus sign/hyphen. You may apply it on spec to all the calculation which utilize vectors.

I also attached two more simple ways to calculate the vector n.ex

Werner_E · Answer

Can you elaborate on which values are wrong and what values you expected.

You think the values n.1 ... are already wrong?

Maybe there is some vectorization necessary in parts of your calculation if they deal with vectors.

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