Combustion heater for caravans etc. - has heat exchanger with duct with increased cross-sectional area to increase heat transfer

摘要

The combustion heater can use either gaseous or vaporised liquid fuel. The combustion gases pass through a heat exchanger consisting of a vertical duct (3) which runs into a horizontal duct (4). The gas flow is then turned through 180 deg. in a duct (6) which directs it into a lower horizontal duct (8) before reaching the outlet (30) through an adjacent duct (9). The cross-sectional area of the lower horizontal duct is considerably greater than that of the other ducts so that the surface area of this duct is correspondingly increased. Also the greater cross-sectional area results in a lower gas velocity so that the time taken to pass through the duct is increased. These two factors increase the heat transfer from the combustion gases to the externally circulating air.