| 摘要 |
The width of at least one felt out of a plurality of felts (22 to 24) is formed of ceramic fibers superposed between two wire nets (26, 27) for a heater is made to be narrower than the width w of the wire nets for heater (26, 27), and the width of other felts (22, 24) is made to be the same as the width w of the wire nets (26, 27) for the heater. A superposed body (28) of the wire nets (26, 27) for a heater and the felts (22 to 24) is bent lengthwise to form a tube (21) having a petal shape in section, and a metal frame (31) is connected to both ends of the tube (21).
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