Heat Exchanger Design

Nothin,

This plate frame heat exchanger makes no sense... I assume that there is water on both sides and, as you state, the flow rate is the same for both sides

There is more heat being transferred from one side than is accepted by the other.

It depends on the area of each plate; half the area --> twice the number.

And then it depends on the fluid velocities and turbulence between the plates.

Usually this is done by vendor software.

Don't do it.

Will you build this yourself?

If not, give the vendor the temps and rates of flow.

If you will build this yourself, see first sentence.

There's free ware for this, if you can find it.

5....

You might be able to accomplish this if the space in which the heat exchanger remains reliably hot....preferably 45C or above. The key is to make sure however many plates you use that the cold water occupies the outer channels of the heat exchanger, that the exterior of the heat exchanger provides a large surface area, and that it is not well insulated.

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It won't necessarily be easy to pick up the additional heat for the larger ΔT requirement of the cold water, but it isn't necessarily impossible either.

The phrase for today is "deus ex machina"; that's a cute way to get the numbers to balance.

I've worked in an engine room wherein certain spaces regularly exceeded 110 F... which seemed to be fertile habitat for the related "diabolus ex machina".

LMTD method and Effectiveness & NTU method are few methods used to design heat exchanger. You can refer any heat transfer book and it is explained.

I readily saw the 6:5 imbalance, and even jokingly alluded to it. However, it could have been a mere typo. As far as sizing the HX, one could simply take the larger duty implied.

Invitation declined. Pick up the phone instead, and talk to a few plate heat exchanger manufacturers, who will have this information at their fingertips and will be in a good position to tender a quotation.