A one-shell and multiple-of-two-tube-passes heat exchanger is to be designed. Wa
ID: 936764 • Letter: A
Question
A one-shell
and multiple-of-two-tube-passes heat exchanger is to be
designed. Water flows at a
rate of 60 kg/s and with velociyu 2.5 m/s in of 25 oD and
velocity m/s in tubes of 25 mm OD and
20 mm ID.
The thermal conductivity of tubes is 20 w/m.K. The inlet and outlet temperature of
the water are 120°C and 65°C. respectively. oil flows through the shell at a rate of 120 kgs and
its temperature increases
from 10°C. The
specific heat capacity of oil is 2.1 kj/kg.K. Assume the
shell-side heat transfer coefficient to be one-tenth of the tube side transfer coefficient. Heat exchanger fouling factors are negligible. Determine the heat transfer area
Explanation / Answer
q = -kA(dT/dx)
2.1 = - 20A((T2-(10+273))/(25-22))
2.1 = -20A((T2-283)/3)
-0.315= A(T2-283) (eqn 1)
T3= 120+273=393K
T4= 65+273=338K
T1= 283K
q = UoAo [(T3-T2)-(T4-T1)/ln{(T3-T2)/(T4-T1)}]
2.1= (2.1/10)A[(393-T2)-(55)/ln{(393-T2)/(55)}]
10=A(338-T2)/{ln(393-T2) - ln 55} (eq.2)
Using equation 1 and 2, solve T2 and A. A is the heat transfer area
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