GB2105834A

GB2105834A - Heating feedwater

Info

Publication number: GB2105834A
Application number: GB08111488A
Authority: GB
Inventors: Bruce Robert Mace
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-04-13
Filing date: 1981-04-13
Publication date: 1983-03-30
Also published as: GB2105834B

Abstract

For reducing fuel consumption in a hot water boiler, a section of flue just above the boiler is replaced bye heat exchanger unit comprising a gas-tight casing (10) through which a water pipe (20, 22) winds in a tortuous or helical path from inlet (18) to an outlet (24), through which inlet and outlet said pipe is connected in the return water feed to the boiler. <IMAGE>

Description

SPECIFICATION Heat exchanger for hot-water boiler This invention relates to a heat exchanger unit for reducing fuel consumption in a hot-water boiler, and more generally to a method of reducing fuel consumption at such a boiler.

Hot water boilers, often gas or oil burning boilers, are in common use both in industrial and domestic installations. Except in so far as heat radiated by a hot flue may assist in heating the surrounding interior atmosphere, nearly all heat contained in the waste gases is commonly lost to the outside when the waste gases exit from the flue into the exterior atmosphere.

It is an object of this invention to provide a method of and a device for reducing fuel consumption in a hot water boiler.

According to one aspect of the invention, there is provided a method of reducing fuel consumption in a hot water boiler, according to which a section of flue adjacent the boiler is replaced by a heat exchanger unit comprising a casing adapted to fit in place of the removed section of flue to contain and provide for passage of the flue gases and a continuous length of pipe passing back and forth transversely through and across the casing in a tortuous path or as a descending helix extending between a top inlet and a bottom outlet at which inlet and outlet and pipe is connected into the water return feed to the boiler. Preferably, the heat exchanger unit is installed in place of the first section of flue immediately above the boiler, which section is known to be a hot spot of wasted heat.

According to another aspect of the invention, there is provided a heat exchanger unit for reducing fuel consumption in a hot water boiler, comprising a casing having top and bottom openings and adapted to fit in place of a removed section of flue to contain and provide for passage of the flue gases, and a continuous length of pipe entering the casing at or adjacent the top thereof, passing back and forth through and across the casing in a descending tortuous path or as a descending helix and emerging from the casing at or adjacent the bottom thereof, said pipe being carried by the casing and being sealed in gas-tight manner to all openings in the casing through which said pipe enters or emerges.

A practical embodiment of heat exchanger unit and method of use thereof in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which Figure lisa front elevational view of the unit.

Figure2 is a side elevational view thereof; and Figure 3 is a view of the unit from above.

The heat exchanger unit shown in the drawings comprises a c sing 10, of uniform square crosssection from top to bottom, as is clear from Figure 3.

The casing 10 has top and bottom circular openings defined by stub pipes 12, 14, of which the top opening is visible in Figure 3.

Typically, the casing 10, made of mild steel, may be about 20 cm across for domestic installation, with the top and bottom stub pipes 12, 14 dimensioned to fit in gas-tight manner to the cut-off ends of a flue from which a section has been removed, such flue commonly being of about 16 cm diameter. The removed section of flue is preferably a section substantially immediately above the boiler. Again, in a typical domestic situation, the casing 10 may be about 40 cm top to bottom (excluding stub pipes 12, 14, about 4 cm long), to replace a removed flue section of generally corresponding length.

Entering the casing 10 at a top inlet 18 is a 2 cm diameter stainless steel pipe which, as will be clear from the drawings, traverses back and forth through and across the casing by means of parallel straight portions 20 connected by respective uniform bends 22 all of equal radii, these bends 22 being just outside the casing. The pipe emerges from the casing 10 at a bottom outlet 24 on the same side of the casing as the inlet 18. Such an arrangement is convenient for the connection of the pipe, at its inlet and outlet, into the return water feed to the boiler, this return feed often being a straight down pipe spaced to the side of the flue. A section of the return water feed will usually be removed to faciliate introduction of the heat exchanger pipe.

The pipe 18-24 is carried by the casing 10, and at all points of entry to and emergence therefrom, is sealed in gas-tight manner, as by brazing, welding or the like, to the openings in the casing through which said pipe passes.

In the arrangement illustrated, which is convenient for manufacture and affords efficient heat exchange in use, the straight pipe portions 20 define spaced pipe layers alternately consisting of four portions 20 and three portions 20 (see Figure 1). Such an arrangement, in the case illustrated, provides thirty two such straight portions 20 traversing across and through the casing 10 from one side to the other, with thirty one interconnecting bends 22. There is thereby provided a high density of pipe portions 20 for maximum heat exchange substantially without any reduction in the overall cross-sectional area available for passage of waste gases, when compared with the cross-sectional area of the flue in which the heat exchanger unit is fitted.Again, however, it should be mentioned that the illustrated arrangement is envisaged for domestic installations; a larger unit for industrial use could have a water pipe defining an analogous tortuous path through the casing, but possibly with a larger number of pipe layers and with a larger number of straight pipes portions in each layer.

It will be appreciated that the above-described arrangement may be modified in various ways within the scope of the invention, the more general aim of which is to provide a method of reducing fuel consumption in a hot water boiler. Thus, by diverting the water being returned to the boiler, e.g. from a remote hot water tank or remote hot water radiators, through the heat exchanger unit, the returning waters enters the boiler at a higher temperature than would otherwise be the case. This preheating allows the boiler to reach its operating temperature faster, thus shutting down sooner, and consequently providing a substantial saving in fuei.

The tortuous path of the pipe shown in the drawings may be replaced by a simple helix which may be of a constant diameter or of reducing radius to define a spiral.

Claims

1. A method of reducing fuel consumption in a hot water boiler, according to which a section of flue adjacent the boiler is replaced by a heat exchanger unit comprising a casing adapted to fit in place of the removed section of flue to contain and provide for passage of the flue gases and a continuous length of pipe passing back and forth transversely through and across the casing in a tortuous path or a descending helix extending between an inlet and an outlet at which inlet and outlet said pipe is connected into the water return feed to the boiler.

2. A heat exchanger unit for reducing fuel consumption in a hot water boiler, comprising a casing having top and bottom openings and adapted to fit in place of a removed section of flue to contain and provide for passage of the flue gases, and a continuous length of pipe entering the casing at or adjacent the top thereof, passing back and forth through and across the casing in a descending tortuous path or as a descending helix and emerging from the casing at or adjacent the bottom thereof, said pipe being carried by the casing and be-sealed in gas-tight manner to all openings in the casing through which said pipe enters or emerges.

3. A heat exchanger unit according to claim 2, wherein the pipe extends in straight portions across the interior of the casing between 180 degrees bends just outside the casing.

4. A heat exchanger unit according to claim 3, wherein said straight pipe portions lie in parallel relationship.

5. A heat exchanger unit according to claim 4, wherein said straight pipe portions define a plurality of spaced horizontal pipe layers descending the casing.

6. A heat exchanger unit according to claim 5, wherein said spaced horizontal pipe layers respectively comprise four straight pipe portions and three straight pipe portions, alternately.

7. A heat exchanger unit according to any of claims 1 to 6, wherein the pipe inlet and the pipe outlet are disposed to the same side of the casing.

8. A heat exchanger unit according to any of claims 1 to 7, wherein the casing has a square transverse cross-section, with circular top and bottom openings defined by stub pipes for fitting to the cut-off ends of a flue from which a section has been removed.

9. A heat exchanger unit according to claim 8 when appendantto claim 3, wherein the straight pipe portions are of equal lengths, with respective adjoining portions interconnected by respective uni formlycurved bends of equal radii.

10. A heat exchanger unit according to any of claims 1 to 9, having a casing of mild steel and a pipe of stainless steel.

11. A heat exchanger as claimed in any of claims 2 to 10 in which the pipe extends as a helix of reducing radius through the casing.

12. A method of reducing fuel consumption in a hot water boiler substantially as hereinbefore described.

13. A heat exchanger unit substantially as hereinbefore described with reference to the accompanying drawings.