Abstract: A heating system for a building comprises a boiler and radiators to which hot water is supplied from the boiler, in which at least some of the return water flow from the radiators, typically at 6° C., circulates through a first heat exchanger to cool the exhausting products of combustion, means is provided to direct a small part of the return water flow through at least one heat exchanger which gives up heat to the building and/or to the boiler heating the water for heating he building, to cool the diverted water to well below the dew point, and means is provided to supply the cooled water to a second heat exchanger through which the already cooled exhaust products of combustion have to pass after leaving the first heat exchanger, to achieve full condensation of the water vapour content of the products of combustion form the boiler.

Abstract: A method of heating a building in which a boiler provides hot water for circulating through radiators in the building and a condensing heat exchanger recovers heat from the boiler flue gases. Air entering the building is heated by an additional heat exchanger through which water flows which has been heated by the condensing heat exchanger. Cold air supplied to the combustion chamber is also employed to cool the flue gases. The condensing heat exchanger comprises a first exchanger in which the hot flue gases are cooled to a temperature above the dew point and a second in which the previously cooled flue gases are cooled to below the dew point. The second exchanger includes a primary water circuit which cools water in a secondary circuit, in which water is in contact with the flue gases and the secondary circuit water passes through a heat exchanger in an air inlet to the building. Some of the water returning from the radiators is cooled before supply to the primary circuit.

Abstract: A heating system for a building comprises a boiler and radiators to which hot water is supplied from the boiler, in which at least some of the return water flow from the radiators, typically at 6° C., circulates through a first heat exchanger to cool the exhausting products of combustion, means is provided to direct a small part of the return water flow through at least one heat exchanger which gives up heat to the building and/or to the boiler heating the water for heating he building, to cool the diverted water to well below the dew point, and means is provided to supply the cooled water to a second heat exchanger through which the already cooled exhaust products of combustion have to pass after leaving the first heat exchanger, to achieve full condensation of the water vapour content of the products of combustion form the boiler.

Abstract: Solar energy converters convert solar radiation into usable heat energy by means of a reflector which collects and focuses the solar radiation onto an absorber provided with an internal chamber through which a heat exchange fluid may be passed. As the absorber is heated by radiation focussed thereon the heat may be extracted into the fluid. To minimize the volume of the internal chamber and thus increase the efficiency and sensitivity of the heat transfer, the absorber is formed with curved walls to define an internal chamber having a crescent-shaped cross-section.