Determine the outlet temperature of oil for the same initial temperatures of the fluids if the flow arrangement is one shell pass and two tube passes, but with the same total area and average overall heat transfer coefficient as the unit in

Question

• Water cooling oil in a tube and shell heat exchanger

• Water flow rate ( m

w)= 1.25 kg/s

• Oil flow rate ( m

o)= 2.5 kg/s

• Oil specific heat (cpo) = 2093 J/(kg K)

• Water inlet temperature: (Tw,in) = 15°C

• Oil inlet temperature: To,in = 95°C

• Overall heat transfer coefficient (U) = 280 W/(m2 K)

• One shell and two tube passes

• Same surface area as Problem 10.23: A = 11.2 m2

FIND

• The oil outlet temperature (To,out)

SKETCH



PROPERTIES AND CONSTANTS

the specific heat of water (cpw) = 4187 W/(kg K)

Answer 1

From the solution to



The number of transfer units is



e ? 0.35 (for Ch/Cmin = 1.0) E = T o ,in T o ,in T o



COMMENTS

The outlet oil temperature is approximately the same as the previous problem because the effectiveness is not improved significantly by an additional pass for small values of NTU.