GB1099232A - Improvements relating to radiant tubular heating elements - Google Patents

Abstract

1,099,232. Radiant heating elements; burners. GAS COUNCIL. March 24, 1965 [March 6, 1964], No. 9476/64. Heading F4B and F4T. A radiant tubular heating element comprises a casing 32 extending into a furnace, a burner 10, heat exchanger 11 and gas off-take 12 being in mutual heat exchange relation, the burner 10 being formed by spaced concentric tubes 13, 14 defining fuel and restricted air passages respectively and the outer tube 14 and the rear of casing 32 forming the heat exchanger 11, A fuel nozzle 16 projects through an opening in a plate 23 into a short combustion chamber 17, forming with said opening an annular air nozzle 24. The tubes and casing are securely clamped at their respective rear ends to permit unobstructed axial expansion on heating. Hot combustion gases from chamber 17 recirculate in a closed loop through tube 33 before leaving via passage 46, pre-heating gas from inlet 15 and air from a manifold 20 in passages 13, 18 respectively, to annular flue off-take 12. An electric spark igniter 27 is situated in chamber 17 and a window 31 at the rear end of the fuel passage permits observation of the flame. In modifications, (Figs. 2 and 3) the casing 32 is wider and foreshortened at its rear-end, which does not protrude into the flue off-take 12. In Fig. 2, the heat exchanger 42, spaced from the case 32 by an annulus (52), forms a sleeve closely surrounding and spaced from the tube 14, the outer end of said sleeve being flared to form a convergent entry for the out-going flue gases into the passage 50. For high temperature operation the easing 32, (Fig. 3), is of ceramic material and carries a tube (56) surrounding a flue gas tube (53) and defining a restricted passage for diluting air from manifold (60), which air mixes with issuing hot gases and lowers their temperature. Suitable materials are 25 : 20 Cr/Ni steels, for tubes 14, 49 and 56 and stainless steel for the tube 13.