The heat transfer coefficient on the inside of a copper tube (1.9-cm-ID and 2.3-cm-OD) is 500 W/(m2 K) and 120 W/(m2 K) on the outside, but a deposit with a fouling factor of 0.009 (m2 K)/W (based on the tube outside diameter) has built up over time. Estimate the percent increase in the overall heat transfer coefficient if the deposit were removed.

GIVEN

• Heat transfer through a copper tube

• Heat transfer coefficients

? Inside h i= 500 W/(m2 K)

? Outside h o= 120 W/(m2 K)

• Tube diameters

? Inside (Di) = 1.9 cm = 0.019 m

? Outside (Do) = 2.3 cm = 0.023 m

• Fouling factor (Rd) = 0.009 (m2 K)/W

FIND

• Per cent increase in the overall heat transfer coefficient if the deposit were removed ASSUMPTIONS

• Constant thermal conductivity properties

• The copper is pure

SKETCH



PROPERTIES AND CONSTANTS

the thermal conductivity of copper (k) = 392 W/(m K) at 127°C


The overall heat transfer coefficient without fouling based on the outside tube area is given by



The overall heat transfer coefficient with fouling is

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