
Forced Convection Heat Transfer: External Flows 239
10.5 FLOW ACROSS CYLINDERS
Another external ow that has many practical applications is the ow across a long
cylinder. Examples include heat transfer from hot wire anemometers used for velocity
measurement, circular or square pin ns, and tubes in a cross ow heat exchanger.
Let’s consider ow across a circular cylinder with diameter D, as shown in Figure
10.9, and assume that the free stream velocity is U
∞
. As uid particles approach the
cylinder, their velocities diminish. In fact, the uid particles that move normal to the
axis of the cylinder will come to complete rest in front of the ...