| 摘要 |
A hot water boiler, particularly for central heating systems, has a double-walled structure containing water passages and bounding a combustion chamber, and a multi-walled structure outside the double-walled structure providing passages for the combustion gases and the incoming air for combustion. In order to increase thermal efficiency, while providing an economic and simple design, the double-wall structure is a pair of opposed hollow metal castings which bound not only the combustion chamber but also a combustion gas passage leading upwardly from that chamber and having in it projections integrally formed on the castings. Outside the castings are walls providing, in sequence, downward and upward passages for combustion gas and a downward passage for combustion air.
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