Apparatus for capturing heat from a stove

Abstract

Apparatus for capturing heat from a stove to enable it to be transferred to a central heating system is disclosed. The apparatus comprises an air-water heat exchanger, the heat exchanger having an air side and a water side and being operative to transfer heat between air on the air side and water flowing in channels in the water side. The apparatus includes an air duct through which air heated by a stove can pass by convection to contact the air side of the heat exchanger and control means operable to control the amount of air flowing to the heat exchanger. The control means may include a fan that can be operated to direct the flow of air to the heat exchanger.

1 . Apparatus for capturing heat from a stove, the apparatus comprising an air-water heat exchanger, the heat exchanger having an air side and a water side and being operative to transfer heat between air on the air side and water flowing in channels in the water side, the apparatus including an air duct through which air heated by a stove can pass and control means operable to control the flow of air within the apparatus; wherein in a first mode, the control means allows air to flow from the air duct to a space surrounding the stove at least partly by natural convection and in a second mode, the control means induces air to flow from the air duct to the air side of the heat exchanger, such that air within the duct flows in opposite directions in the first and second modes. 
     
     
         2 . Apparatus according to  claim 1  in which, in the first mode, air flows generally upward within the air duct. 
     
     
         3 . Apparatus according to  claim 1  or  claim 2  in which the control means includes a fan that is operable to induce a flow of air in the apparatus during operation in the second mode. 
     
     
         4 . Apparatus according to  claim 3  in which the fan is operable to draw air from a space surrounding the stove into the air duct for heating by the stove and then to the heat exchanger. 
     
     
         5 . Apparatus according to  claim 3  or  claim 4  in which, when the fan is not operating, air can be drawn from a space surrounding the stove for heating by the stove, and subsequently returned to the space surrounding the stove by natural convection. 
     
     
         6 . Apparatus according to any one of  claims 3  to  5  in which the state of the control means is primarily determined by whether or not the fan is running. 
     
     
         7 . Apparatus according to any preceding claim that further includes a bypass means that allows air to flow through the duct to receive air transferred from the stove without passing through the heat exchanger in the first mode. 
     
     
         8 . Apparatus according to  claim 7  in which the bypass means includes a closable opening to surrounding air in the duct between the stove and the heat exchanger. 
     
     
         9 . Apparatus according to any preceding claim in which the air duct includes a plate, a first portion of the air duct being defined as a chamber that is formed between the plate and a heating surface of a stove. 
     
     
         10 . Apparatus according to any preceding claim in which the air duct has a second portion that connects the lower part of the first portion of the air duct to the air side of the heat exchanger. 
     
     
         11 . Apparatus according to any preceding claim in which the air duct causes air to flow over one or more external heating surfaces of a stove. 
     
     
         12 . Apparatus according to  claim 11  in which the external heating surfaces include heat transfer fins. 
     
     
         13 . Apparatus according to any preceding claim in which the heat exchanger includes a fin-and-tube heat exchanger element. 
     
     
         14 . Apparatus according to any preceding claim that further includes an outer cover that creates a second air duct between itself and the cover. 
     
     
         15 . Apparatus according to  claim 14  in which air can be caused to flow in the second air duct by natural convection to reduce an outer casing temperature of the apparatus. 
     
     
         16 . Apparatus according to any preceding claim in which the control means is fail-safe such that it diverts air from the heat exchanger in the event of there being insufficient flow of water within its water side. 
     
     
         17 . A stove that incorporates apparatus for capturing heat from a stove according to any preceding claim. 
     
     
         18 . A stove according to  claim 17  in which the apparatus for capturing heat can capture heat from outer surfaces of the stove. 
     
     
         19 . A stove according to  claim 18  in which the apparatus for capturing heat can capture heat from one or more of a side surface, a rear surface or a top surface of the stove. 
     
     
         20 . A heating installation that includes a stove according to any one of  claims 16  to  19  and a central heating system that includes a pumped water circulation circuit that operates to transport heat from a boiler to one or more radiators, the water side of the heat exchanger being connected to the circulation circuit such that water from the circulation circuit is caused to flow through the heat exchanger while the pump of the circulation circuit is operational. 
     
     
         21 . A heating system according to  claim 20  in which the control means operates to minimise the flow of heated air from the stove to the heat exchanger when the pump of the circulation system is not operational. 
     
     
         22 . A heating system according to  claim 20  or  claim 21  in which the water side of the heat exchanger is connected between a flow and a return pipe of the central heating system in parallel with radiators of the central heating system. 
     
     
         23 . A heating system according to  claim 22  further including a water pump connected in series with the heat exchanger. 
     
     
         24 . A heating system according to  claim 23  further including a non-return valve connected in series with the heat exchanger. 
     
     
         25 . A heating system according to  claim 20  or  claim 21  in which the water side of the heat exchanger is connected within a return pipe of the central heating system such that water returning to the boiler passes through the heat exchanger.