A solution with a boiling point of 82°C boils on the outside of a 2.5 cm tube with a No. 14 BWG gauge wall. On the inside of the tube flows saturated steam at 40 kPa(abs). The convection heat transfer coefficients are 8.5 kW/(m2 K) on the steam side and 6.2 kW/(m2 K) on the exterior surface. Calculate the increase in the rate of heat transfer if a copper tube is used instead of a steel tube
GIVEN
• Tube with saturated steam on the inside and solution boiling at 82°C outside
• Tube specification: 1 in. No. 14 BWG gauge wall
• Saturated steam in the pipe is at 40 kPa(abs)
• Convective heat transfer coefficients
? Steam side ( ci h ) : 8.5 kW/(m2 K)
? Exterior surface ( co h ) : 6.2 kW/(m2 K)
FIND
• The increase in the rate of heat transfer for a copper over a steel tube
ASSUMPTIONS
• The system is in steady state
• Constant thermal conductivities
SKETCH
The thermal circuit for the tube is shown below
The individual resistances are
The rate of heat transfer is
For the copper tube
For the steel tube
The increase in the rate of heat transfer per unit length with the copper tube is
You might also like to view...
A sprinter runs 100.0 m. If he travels at constant acceleration of 1.95 for the first 6.00 s and then at constant velocity for the remaining time, what was his average velocity?
A. 8.8 m/s B. 10.2 m/s C. 9.9 m/s D. 9.8 m/s
A galvanometer can be converted to an ammeter by the addition of a
A) small resistance in parallel. B) large resistance in parallel. C) small resistance in series. D) large resistance in series.
Parallel light rays from a distant object strike the surface of a concave mirror. After reflecting from the mirror's surface, the rays will converge at
a. the mirror's focal point b. a point beyond the mirror's focal point c. a point nearer than the mirror's focal point d. none of the above
Series/Parallel Circuits: A 4.0-? resistor is connected with a 12-? resistor and this combination is connected across an ideal dc power supply with V = 6.0 V, as shown in the figure. When a total current I flows from the power supply, what is the current through the 12-? resistor?
A. 1.5 A B. 2.0 A C. 2.5 A D. 3.0 A E. 0.50 A