| 摘要 |
PURPOSE:To prevent a primary cooling medium from being fed eccentrically to a main cooling thermal conducting pipe by a method wherein a plurality of first thermal conducting pipes equally spaced apart in a peripheral direction toward the center part of a plenum barrel and a plurality of second thermal conducting pipes arranged between the first thermal conducting pipes at their specified positions are provided. CONSTITUTION:First thermal conducting pipes 28a of auxiliary cooling thermal conducting pipes are equally spaced apart toward the center of a plenum barrel 1, second thermal conducting pipes 28b are arranged in zig-zag form in such a way as a specified number of the thermal conducting pipes may be projected out of an outer circumference of the annular row between the first thermal conducting pipes 28a and displaced from the center part and thus the connection part with headers 21a and 21b is formed to face inwardly. With the above-described constitution, a spacing between the second thermal conducting pipes 28b faced to each of inlet windows 19 of the plenum barrel 1 is widened and the primary cooling medium is flowed between the second thermal conducting pipes 28b toward the center of the upper plenum 18. The flow along an inner circumference of the plenum barrel 1 is diminished by this flow, an eccentric flow rate between an area near an inlet window 19 and another area spaced apart from the inlet window is not generated, and then a uniform distribution of flow rate in the main cooling thermal conducting pipe 13 can be attained.
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