2. Finally, consider a "cross" flow heat exchanger by changing again the flow direction. Find the minimum number of plates (including top and bottom plates) that will result in an amount

of exchanged heat equal to or greater than that of co-current (parallel) flow heat exchanger in Question 1, without changing the heat exchanger volume. Here, the effectiveness & of a cross flow heat exchanger (both fluids unmixed) can be calculated using Eq. (4) as: E= - 1 exp NTU 0.22 R [expR NTU °78). (4)