This paper deals with a boundary optimal control problem associated wi
th the stationary Navier-Stokes equations coupled with the heat equati
on. The most general type of boundary condition for the temperature is
considered. The existence of a solution of this problem and, for some
values of the viscosity coefficient, the uniqueness are proved. The c
ontrol problem consists in finding a temperature of the surrounding me
dium which leads to a desired configuration of the temperature of the
fluid. The existence of an optimal control is proved and necessary con
ditions of optimality are derived by introducing a family of regulariz
ed optimal problems.