The flow characteristics and the heat transfer rate on a surface by interaction of a pair of vortices were studied experimentally. The test facility consisted of a boundary-layer wind tunnel with a vortex introduced into the flow by half-delta wings protruding from the surface. In order to control the strength of the longitudinal vortices, the angles of attack of the vortex generators were varied from - 20 degree to - 45 degree, but spacings between the vortex generators were fixed to 4 cm. The 3-dimensional mean velocity measurements were made using a five-hole pressure probe. Heat transfer measurements were made using the thermochromatic liquid to provide the local distribution of the heat transfer coefficient. Unlike common flow down, common flow up vortices moved toward the centerline as they developed and interacted strongly with each other but not with the boundary layer. Spanwise profiles of Stanton number were similar for ${eta}=-20^{circ};and;-35^{circ}$, but not similar for ${eta}=-45^{circ}$. The case of ${eta}=-20^{circ};and;-35^{circ}$ showed the two peak Stanton number, but the case of ${eta}=-45^{circ}$ showed the only one peak Stanton number.