It is proposed to cool 64?C air as it flows, fully developed, in a 1 m length of 8 cm I.D. smooth, thin-walled tubing. The coolant is Freon 12 flowing, fully developed, in the opposite direction, in eight smooth 1 cm I.D. tubes equally spaced around the periphery of the large tube.
The Freon enters at -15?C and is fully developed over almost the entire length. The average speeds are 30 m/s for the air and 0.5 m/s for the Freon.
Determine the exiting air temperature, assuming that soldering provides perfect thermal contact between the entire surface of the small tubes and the surface of the large tube.
Criticize the heat exchanger design and propose some design improvement.