Water is to be heated from 55 to 105 Fat the rate of 275,000 gal/hr in a single-
ID: 2074374 • Letter: W
Question
Water is to be heated from 55 to 105 Fat the rate of 275,000 gal/hr in a single-pass shell-and-tube heat exchanger consisting one 1-in schedule 40 steel pipe. The surface coefficient on the stem side is estimated to be 9,000 Btu/hr-ft^2-F. A pump is available that can deliver the desired quantity of water , provided that the pressure drop through the pipes do not exceed 1 psi. Water is supplied at 100 psi. The pump is to be used to make up the pressure drop. Saturated steam is supplied at 30 psi to the shell. (a) Calculate the number of tubes i parallel and the length of each tube required to fulfill the requirement. (b) Present the information in TEMA form. (c) How much steam is condensed on the shell side?
Explanation / Answer
Given that ,
m = 275000 gal/hr
surface coefficient = 9000 btu /hr ft2 F
T1 = 55 F T2 = 105 F
P = 100 psi
No.of tubes in parallel and their length = ?
N = UA / Cmin
Cmin = mc
c = specific entropy of the fluid = 5.59 KJ/ kg k
m = 275000 gal /hr = 275000/ 9.11X 3600 = 8.38 Kg /s
Cmin = 8.38 X 5.59 = 46.84
N = UA / Cmin = 9000 / 46.84 X 3600 X 5.61 = 9.15 X 10-4
n = N-0.22
=( 9.15 X 10-9 )-0.22
= 22
The length of the each tube is =?
n = 178.7 ft2 / Sa
Sa = 178.7 / 22
= 8.12
3.14 X L X 3/12 = 8.12
L = 10.33 ft
c) Steam condensed = ?
Q = m c ( t2 - t1 )
= 8.38 X 1.005 X ( 40.55 - 12.78)
= 233.7
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