Abstract: An heating drum for use in a radiant heater having a burner for the combustion of fuel, which comprises an axially corrugated barrel made of steel material and forming therein a generally cylindrical inner chamber and a plurality of annular chambers communicated with the cylindrical inner chamber and alternating with concave exterior spaces over the length thereof. The cylindrical inner chamber is defined by furrow-defining walls while each of said annular chambers is defined by a ridge-defining wall and opposedly inclined first and second annular side walls on respective sides of the associated ridge-defining wall. The barrel has one end closed and the other end adapted to seat over the burner and also has first circumferential rows of combustion gas outlet perforations, the combustion gas outlet perforations of each row being defined in at least one of the first and second annular side walls for each annular chamber.