Heat exchangers often utilize concentric tubes, with a hot fluid flowing through

Question

Heat exchangers often utilize concentric tubes, with a hot fluid flowing through the inner tube and a coolant (which itself will heat up) in the annnulus: i.e., the space
surrrounding the inner tube (see fig. 2.22)

Create an Excel worskeet to determine the outer pipe diameter that will support the same volumetric flow as the inner pipe, assuming the fluid velocities will be the same
in the annulus and the inner pipe. Hint: Since the mean fluid velocities are the same, the cross-sectiona flow area of the annulus must be the same as the cross-sectional flow
area of the inner pipe:
i.e., A2=A1. Hence,
Pie/4(d2-2t2)^2 -pie/4(d1)^2= pie/4(d1-2t1)^2
or D2= 2t2+square root(d1^2+(d1-2t1)^2))
where
d2= the outside diameter of the outer pipe, in
d1=the outside diameter of the inner pipe, in
t2= the thickness of the outer pipe, in
t1= the thickness of the inner pipe, in

Determine the outer pipe diameter for a pipe whose thickness is 0.25 inch, if the inner pipe has an outside diameter of 3 inches and a thickness of 1/8 inch.

Explanation / Answer

enter inner thick ness in cell B6 outer thick ness in cell C6 outside diameter of the inner pipe in cell D6 Then formula Bar enter the formula as 2*C6+SQRT(D6^2+(D6-2*B6)^2) Now from the excel work sheet outside diameter of the outer pipe is 3.66227766 t1        t2    d1   d2 0.125 0.25 3    4.569705149 I hope this helps you....................

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