We study the heat generation by an electric current in a quantum dot (QD) molecular coupled to a single-model phonon bath in the Coulomb blockade regime.It is found that when the system is driven out of equilibrium by the thermal bias applied across the two terminals of the structure,the heat flowing between the QD and the phonon bath can be very small for one direction of the thermal bias,while it becomes quite large when the corresponding direction of the thermal bias is reversed.The device thus operates as a heat rectifier or heat diode.Moreover,the heat generation can be suppressed to negative values by the thermal bias.We emphasize that the above-mentioned two effects are beyond the reach of the usual electric bias.