Abstract: A gas burner which consists of a cylindrical duct forming member closed at one end and open at the other end to receive a gas/air mixture under pressure. The member is perforated so that the gas/air mixture flows to the outside of the member where it is burned. The duct is provided with a cone-shaped plug for reducing the volume of the duct from the open end towards the closed end so that a constant velocity of gas/air mixture is maintained within the duct to obtain a uniform static pressure on the outside in the region where the gas/air mixture is burned.

Abstract: A heat exchanger system for preferably heating water in a space heating system, in which a plurality of heat exchanger units are connected in parallel between inflow and outflow conduits for the fluid to be heated, said heat exchanger units being housed in a common duct constituting a flue for gaseous products of combustion from said units.