Hot gas generator for heating gas, comprising a housing which is cylindrical with respect to a longitudinal axis and has a. a heat supply opening to which a heat source designed as a burner can be connected for supplying heat along a heat propagation direction, b. a gas inflow opening for supplying gas, wherein a surface normal of the gas inflow opening is orientated perpendicular to the longitudinal axis, c. a gas discharge opening for discharging the heated gas, d. a gas flow direction orientated from the gas inflow opening to the gas discharge opening, which is orientated in the opposite direction to the heat propagation direction, e. a flow diverter unit for diverting the gas flow in the housing, wherein the housing comprises an outer housing and an inner housing which enclose a cavity, wherein the cavity is filled with an insulating layer of insulating material for thermal insulation, characterized in that - the flow diverter unit has an annular flow channel with respect to the longitudinal axis for a main stream of the supplied gas for generating a helical gas flow with respect to the longitudinal axis, which is guided around the open burner flame of the heat source, - the hot gas generator has a combustion chamber that tapers along the heat propagation direction, - the flow diverter unit has at least one flow diverter element for diverting at least a substream of the supplied gas, wherein the diverted partial flow is used for targeted cooling of the combustion chamber. a. a heat supply opening to which a heat source designed as a burner can be connected for supplying heat along a heat propagation direction, b. a gas inflow opening for supplying gas, wherein a surface normal of the gas inflow opening is orientated perpendicular to the longitudinal axis, c. a gas discharge opening for discharging the heated gas, d. a gas flow direction orientated from the gas inflow opening to the gas discharge opening, which is orientated in the opposite direction to the heat propagation direction, e. a flow diverter unit for diverting the gas flow in the housing, wherein the housing comprises an outer housing and an inner housing which enclose a cavity, wherein the cavity is filled with an insulating layer of insulating material for thermal insulation, characterized in that - the flow diverter unit has an annular flow channel with respect to the longitudinal axis for a main stream of the supplied gas for generating a helical gas flow with respect to the longitudinal axis, which is guided around the open burner flame of the heat source, - the hot gas generator has a combustion chamber that tapers along the heat propagation direction, - the flow diverter unit has at least one flow diverter element for diverting at least a substream of the supplied gas, wherein the diverted partial flow is used for targeted cooling of the combustion chamber. - the flow diverter unit has an annular flow channel with respect to the longitudinal axis for a main stream of the supplied gas for generating a helical gas flow with respect to the longitudinal axis, which is guided around the open burner flame of the heat source, - the hot gas generator has a combustion chamber that tapers along the heat propagation direction, - the flow diverter unit has at least one flow diverter element for diverting at least a substream of the supplied gas, wherein the diverted partial flow is used for targeted cooling of the combustion chamber.