Using the equations of a non-isothermal thin layer of viscous fluid with an exponential dependence of the viscosity on temperature, a family of hydrodynamic models of a cooling lava flow over a conical surface in the presence of mass supply is constructed. These models correspond to asymptotically different rates of heat exchange with the ambient medium. The evolution of the free-surface shape and the temperature fields is investigated numerically for a stationary mass supply. Using the matched asymptotic expansions method, solutions valid both near and very far from the mass supply region are constructed. The solutions obtained are compared with known analytical solutions for isothermal flow.