WATER TUBE TYPE BOILER

PURPOSE:To improve the durability, reliability and heat exchanging efficiency of a boiler by a constitution wherein a plurality of water tubes are wound between upper and lower annular tube collecters and combustion gas is flowed into a cylindrical frame covering the water tubes. CONSTITUTION:A plurality of water tubes 3, which are wound spirally, are connected to the upper and lower annular tube collecters 1, 2. Respective water tubes 3 are connected to the inside of the cylindrical frame 4 provided with a surface, covering the space between respective water tubes 3 and meandering into circumferential direction with wavy form, to form a combustion chamber 5 and a heat exchanging chamber 6. The combustion gas passes through clearances G, G' between the cylindrical frame 4 and the water tubes 3 as well as baffles 8 provided in circular shapes concentric to the water tubes 3 as shown by the arrow sign A in the diagram while the heat thereof it exchanged with feed water rising through the insides of the water tubes 3. The water tubes 3 exchange the heat thereof with the combustion gas directly and the cylindrical frame 4 is connected to the water tubes 3 closely in such manners, therefore, heat transfer area and heat transfer efficiency may be increased and the efficiency of heat exchange between the combustion gas may be improved.