Abstract: The invention relates to a gas-heated or kerosene-heated boiler for warm water, hot water or for steam generation having a substantially horizontal cylindrical combustion chamber defined and surrounded by a flue tube (1) consisting of a plurality of annular ring tubes (b 2) that are arranged in succession for conveying a suitable heat carrier and are held together by means of annular distance strips (3). At least some of the annular ring tubes have different inner cross sections and/or are arranged in a manner of having different, unequal spacing distances one to the next. Thus, a substantially uniform main diameter of the flue tube (1) is maintained, and despite of this, the flow of heat carrier circulated is harmonized with the thermal load which is non-equally distributed along the axis of the combustion chamber, resulting in improved utilization of the heat energy radiation at substantially constant wall temperature along the flue tube (1).

Abstract: The invention relates to gas-, or oil-burning warm water, hot water or steam boilers, mainly for the supply of households, communal institutions, and industrial plants, the surfaces of which surrounding the furnace are formed as membrane walls having annular passageways connected by thin plates, the passageways receiving the heat carrying agent.The essence of the invention is that the flue-tube of the boiler is formed as a body of rotation with varying cross section conforming to the extent of heat radiation, and the flue-tube is surrounded by another convective heat exchanging flue-tube formed as a membrane wall conforming to the shape of the inner flue-tube, the convective heat exchanging flue-tube defining a flue passage with the inner flue-tube, the linings of the membrane wall of the annular passageways of the outer flue-tube being offset in relation to the passageways of the membrane wall of the inner flue-tube.

Abstract: A boiler for hot-water heating which is of rectangular cross section in vertical and horizontal planes and which comprises only two horizontal headers located on diagonally opposite sides of the fire chamber and connected by a first array of spaced apart parallel bent tubes forming the roof and one longitudinal side wall of the boiler chamber and with a second array of spaced apart bent tubes forming the other side wall and floor of the chamber. Additional tubes can be provided along the front and rear walls and slotted openings toward the rear of the boiler form passages traversed by the exhaust gas. The water return is connected to the lower header while the hot water supply pipe is connected to the upper header.