Method of manufacturing thermal insulation wall body

1. A method of manufacturing a cylindrical thermal insulation wall body having a holding unit of a heater element formed in an inner peripheral surface, the method comprising:

processing a plate-shaped thermal insulation member such that a plurality of groove portions are formed at a predetermined pitch, the plurality of groove portions extending from a first surface to a second surface opposite to the first surface;

processing the thermal insulation member such that an angle between either of the first surface and the second surface, and a third surface, on which the groove portions are formed and which is perpendicular to a depth direction of the groove portions, is 90+180/n degrees, wherein n is a natural number of three or larger; and

manufacturing the cylindrical thermal insulation wall body by bonding a plurality of sectional thermal insulation members, wherein the plurality of sectional thermal insulation members are bonded such that the groove portions of the adjacent sectional thermal insulation members are aligned with each other and to form the holding unit in the inner peripheral surface of the cylindrical thermal insulation wall body.

2. The method of claim 1 , wherein the bonding in the manufacturing the cylindrical thermal insulation wall body comprises one of processes including i) using an adhesive, ii) fixing adjacent sectional thermal insulation members with a pin-shaped member in an outer peripheral surface, a top surface or a bottom surface of the thermal insulation wall body, iii) forming a convex portion in one of the adjacent sectional thermal insulation members and a concave portion mating with the convex portion in the other one, and iv) covering an outer periphery of the thermal insulation wall body by a band member.

3. The method of claim 1 , wherein the manufacturing the cylindrical thermal insulation wall body comprises disposing a thermally shrinkable heat resistant member between bonding surfaces of the adjacent sectional thermal insulation members.

4. The method of claim 1 , wherein in the processing a plate-shaped thermal insulation member, the groove portions are formed to extend in a direction perpendicular to the first surface and the second surface.

5. The method of claim 1 , wherein in the processing a plate-shaped thermal insulation member, the groove portions are formed to extend at a predetermined angle with respect to a direction perpendicular to the first surface and the second surface.

6. The method of claim 1 , wherein before the manufacturing the cylindrical thermal insulation wall body, rounding process is performed on at least one of the inner peripheral surface and an outer peripheral surface of the thermal insulation wall body.