Basic equations of continuum mechanics reflect deep symmetry properties of Euclidean space and medium, which moves in it. As a corollary, these equations admit a wide Lie group that allows us to apply group-theoretical methods for continuum motion study. In this paper, both gravitational heat convection and thermocapillary convection equations are considered from the group-theoretical point of view. It turned out that classical Ostroumov and Birikh's solutions have a group nature. We present a number of new solutions, which describe a non-isothermal viscous liquid motion in channels, tubes and layers under action of gravity, centrifugal and thermocapillary forces.