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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