Due to recombination and dissociation processes an essential increase (in several times) of the heat transfer coefficient is observed with convective instability and flow intensification. The model of the chemical equilibrium is applied, all numerical values of the constants refer to a stoichiometric hydrogen-oxygen mixture.

The convection in Boussinesq approximation is considered in a horizontal layer at heating from below. It is shown that resulting equation system can be received from corresponding systems changing Rayleigh number Ra on CRa, where non-dimensional heat expansion coefficient C = C(T) is determined by recombination and dissociation processes at chosen the absolute temperature T.

It is shown that the control of the convection intensity at fixed Ra and Pr mainly possible by choice the corresponding temperature T and therefore by changing of the multiplier C. The local maximum of C connected with maximum convection intensity exists and at small and large temperature the convection intensity decreases to its minimum value.