Solutions Manual - Chapter 5
Convective Heat and Mass Transfer, 4th Ed., Kays, Crawford, and Weigand                                                    rev 092004
5-1
Develop a momentum integral equation for steady flow without blowing or suction for use in the
entry region of a circular tube. Note that Eq. (5-4) is not applicable for this case because it has been
assumed that the boundary-layer thickness is small relative to the body radius R; in the present case
the boundary layer ultimately grows to the centerline of the tube.
Let r = R be the wall and r = y be the edge of the control volume where the velocity becomes the inviscid
core velocity of the developing flow. Typical terms would be
                       R
         Mx    2            u 2 rdr         and        My     (R   y)2        xv y   y   uy
                   R y
                                  R
        Normal stress = P               2 rdr
                                  R y
        Shear stress :                           s   2 R x;        y   2 (R     y) x
Now follow the procedure on pages 42-43,
                           1 d        R      2           ucore d       R                                        y ducore
                   s
                                            u rdr                            urdr             u   core
                                                                                                         y 1
                           R dx       R y                 R dx         R y                                     2 R dx