This study presents visual observation of enlarged fin-and-tube heat exchangers with and without the presence of vortex generators. Three samples of fin-and-tube heat exchanger having inline arrangements are examined, including one plain fin and two wave-type vortex generators. For plain fin geometry at Re = 500, the horseshoe vortex generated by the tube row is not so pronounced, and a very large secondary flow circulation is seen between the first and second row. This flow re-circulation phenomenon is almost disappeared with the presence of proposed vortex generators. The presence of vortex generators significantly increase the vortrical motions of the horseshoe vortices hitting on the tubes. A much better mixing characteristics is seen by introducing the vortex generators. The frictional penalty of the proposed vortex generators are about 25-55% higher than that of the plain fin geometry. The penalty of pressure drops of the proposed vortex generators relative to plain fin geometry is relatively insensitive to change of Reynolds number.