GB1285749A - Water heaters - Google Patents

Abstract

1285749 Water heaters SULZER BROS Ltd '17 Dec 1969 [6 Oct 1969] 61507/69 Heading F4A A water heater has at least one swirl-type muffle burner 6 arranged at the entry of a cooled flue gas duct 4 containing a heating surface 10, 15. The flue gas duct is of square cross-section and is formed from finned cooling tubes 3 welded together and connected to headers 1, 2. A wall 5 is welded into header 1 and the ceramically lined muffles of four burners 6 extend through it. Each burner is fed with fuel gas and/or oil and air through pipes 40 and 41 and at least two coaxial annular ducts impart a swirl to the air entering the muffle so that combustion requires a minimum of air and gives a high flue gas temperature. The sections 10 and 15 of the heating surface are composed of several pipe coils, disposed across the flue, joined to headers 11, 12 and 13, 14 respectively. Water flows through section 10 first, then through section 15 and finally through the cooling pipes 3. The total flow of the heater is heated in cooling pipes 3, only part flowing through sections 10 and 15. In this way the temperature outside the heating surfaces never falls below the dewpoint of the flue gases. To further ensure this some of the water leaving the heater through pipes 32 to be circulated to a heating system which is pressurized is diverted through a shunt 33 to the return line 20 so that the return water is warmed slightly. A thermostat 50 controls a valve 24 so that a rise in temperature at header 12 causes more water to flow through section 10 and a similar system between valve 30 and header 14 may be provided. In modifications one burner only may be provided and also the heating surface may be divided into three sections rather than two.