Question 14.5: Assuming that the five-row configuration in the previous exa......
Assuming that the five-row configuration in the previous example is not satisfactory, reconsider the circuiting and use one pass per row and a six-row coil. The coil will then have 10 tubes per row.
The height H of the coil is
H = 10 \chi _{a} = 10(1.25) = 12.5 in.
The width will then be
W = \frac{2.22}{12.5/144} = 25.6 in.
and
L_{w} = 2(6) (25.6/12) = 25.6 ft
Assuming that the friction factor is unchanged,
l_{fw} = 0.023 \frac{(25.6) (4)^{2}}{(0.483/12) 64.4} + 2 (5) \frac{(4)^{2}}{64.4} = 6.2 ft of head
The geometry of the six-row coil is more reasonable; however, the coil is about 20 percent overdesigned. This value of the lost head does not include the losses in the inlet and outlet headers. Header losses may be substantial, depending on the design and fabrication, and may be equal to the losses in the tubes and return bends.