| 摘要 |
PROBLEM TO BE SOLVED: To eliminate some disadvantages that a structure of the prior art water tube boiler becomes complicated and its manufacturing cost becomes expensive due to a drum structure of its main body. SOLUTION: This water tube boiler has a simple structure and its manufacturing cost becomes less-expensive by employing a rectangular header with its sectional surface being turned by 45 deg. in place of upper and lower drums. Since a ratio of contact heat transfer surface is reduced less than that of the prior art boiler, an amount of evaporation per unit heat transfer area can be increased and this is manufactured with a unit price per amount of evaporation being less expensive. Both ends of the header are of a blind-plate structure to enable an inspection of the water contact surface to be carried out and no trouble is generated at its maintenance and inspection work. In addition, both economizer and an air pre-heater are arranged at an auxiliary heat transfer surface to attain a sufficient improvement of thermal efficiency.
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