GB2340594A

GB2340594A - Heating and destratifying apparatus

Info

Publication number: GB2340594A
Application number: GB9817210A
Authority: GB
Inventors: John Andrew Thomason
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-08-08
Filing date: 1998-08-08
Publication date: 2000-02-23
Anticipated expiration: 2018-08-08
Also published as: GB2340594B; GB9817210D0

Abstract

A heating and destratifying apparatus comprising a heater (10) provided with a flue (11) having a riser (18). The riser (18) comprises a tube surrounded by a tubular Jacket (19) defining an air inlet duct for the heater (10). A body in the form of a tubular duct (20) is disposed within the riser (18) to increase the velocity of the flue gases and hence the heat transfer rate between the flue gases and the air flowing to the heater through the inlet duct. The tubular duct (20) may also be arranged to convey air to the heater. The body may be disposed coaxially within the riser (18) with closed tapered ends.

Description

1 2340594 IMPROVEMENTS IN OR RELATING TO HEATING AND DESTRATIFYING

APPARATUS The present invention relates to flue assemblies for 5 heating and destratifying apparatus.

Such apparatus is disclosed in GB 2296316A (Thomason) which flues comprise a riser to connect an exhaust outlet of a heater with an exhaust discharge outlet which is usually arranged to discharge the exhaust gases to atmosphere, and a jacket surrounding the riser to permit a counter current of air to be drawn into the heating apparatus via a passage between the jacket and the riser to absorb heat from the riser as it flows towards the heating apparatus.

is It has been noted that only a proportion of the heat from the flue gases in the riser is usually transferred to the counter current of air in the surrounding jacket. This is due, in part, to the fact that only a proportion of the flue gases in the riser come into contact with walls of the riser.

Another object of the present invention, therefore, is to increase the efficiency with which heat is transferred from the flue gases to the air to be drawn into the heater.

According to the present invention there is provided heating and destratifying apparatus comprising a heater with a flue connected thereto, a riser portion of the flue 2 extending in thermal contact with air in an air inlet duct connecting an elevated air inlet opening with an air inlet to the heater wherein there is disposed in the riser a body arranged to conduct the flow of flue gases in the riser 5 between the body and a wall of the riser.

The presence of the body serves to increase exposure of the flue gases in the riser to a wall of the riser and hence enable an increase in heat f low f rom the f lue gases to the 10 air drawn through the air inlet duct.

Preferably the air inlet duct is formed by a jacket surrounding the riser, permitting air to be drawn into the heater via a passage between the jacket and riser.

Preferably, the body serves to reduce the crosssectional area of the riser through which the flue gases are conducted, compared to other regions of the flue, so that the velocity of the flue gases is increased when flowing 20 past the body for example doubled.

The rate of heat transfer from the flue gases to the walls of the riser increases with flue gas velocity.

Preferably the body is disposed in the riser to conduct the flow of flue gases in a region generally annular in cross-section.

3 The body is preferably a duct, through which air may also be drawn into an inlet of the heater. The duct could, for example comprise a tube and may be connected to an elevated air inlet opening.

It is most preferred that where the body is a duct, this is in addition to a duct formed by a jacket surrounding the riser. This arrangement significantly increases the available heat transfer area between the flue gases and air drawn into the heater through the inlet. The combination of increased flue gas velocity and greater heat transfer area can double or even treble the total heat transferred compared to a conventional arrangement where the riser is only a single pipe.

Where the body is a duct it may be extended to draw in fresh air, so that the air recirculated by the heating and destratifying apparatus will contain a proportion of fresh air.

The surfaces of the riser and/or body may be corrugated or finned to increase the rate of heat transfer.

The heating and destratifying apparatus preferably comprises a forced draught fuel-burning heater, a housing in which a combustion chamber of the heater is disposed, and an impeller within the housing to draw air from an inlet of the housing and propel it past the combustion chamber and a heat exchanger to an outlet of the housing.

4 The apparatus is preferably installed in a single space.

In order that the invention may be more clearly understood embodiments thereof will now be described, by way of example, with reference to the accompanying drawings in which:- Figure 1 shows a cross-sectional view of a first embodiment of heating and destratifying apparatus according to the invention, in diagrammatic form; Figure 2 shows a cross-sectional view of a second embodiment of heating and destratifying apparatus according to the invention, in diagrammatic form; Figure 3 shows a cross-sectional view of a third embodiment of heating and destratifying apparatus according to the invention, in diagrammatic form; and Figure 4 shows a cross-sectional view of a fourth embodiment of heating and destratifying apparatus according to the invention, in diagrammatic form; and Figure 4 shows a cross-sectional view of a fifth embodiment of heating and destratifying apparatus according to the invention, in diagrammatic form.

Referring to Figure 1 the apparatus comprises a heater unit 10 which is connected to a flue assembly generally 11 and installed in a building 12. The heater unit 10 has a fuel fired burner 13 and is substantially as described in GB 2296316A to which reference should be made.

In this embodiment the burner 13 products of combustion or exhaust flows through an exhaust outlet 17 into a riser 18.

The riser 18 comprises a tube disposed generally coaxially within a tubular jacket 19. Disposed generally coaxially within the riser 18 is a tubular duct 20. Both the tubular jacket 19 and duct 20 are connected with an inlet to the rear part 21 of the heater 10.

The upper end of the riser 18 is connected to a discharge outlet 24 by a connector 25 through which the tubular duct 20 extends to open in the space 26 within the building; and the jacket 19 terminates at an upper air inlet 22.

An impeller 27 in a lower part 21 of the unit 10 drives air through the heater 10 from the rear part 21 to an outlet 28 of the unit 10, and causes air to be sucked into the jacket 22 and inlet 23 of the duct 20 and to flow into said rear part 26.

6 In comparison to the flue assembly shown in GB 2296316A the effective heat exchange area between flue gases and air drawn into the heater is far greater. In addition, as the flue gases are conducted along the relatively narrow passageway 29 between the outside of duct 20 and the inside of the riser 16, this results in the gases flowing at an increased velocity, as compared to a conventional riser not including a duct. This dramatically increases the rate of heat absorption by the flow of air to the part 21.

Referring to Figure 2, in which similar reference numerals to those used in Figure 1 are used to label similar parts of the equipment, there is shown an alternative arrangement where the duct 20, disposed within the riser 18 extends out of the top of the riser 18. The inlet 23 to the duct is therefore positioned outside the building so that a proportion of fresh air may be drawn into the heater along with the recirculated air drawn through the jacket 19. This helps to ventilate the building, also the introduction of a proportion of fresh air can lead to a slight increase in air pressure in the building, thereby reducing draughts. Figure 3 shows another embodiment, again using the same reference numerals to identify similar components. In this 25 arrangement the duct 20 turns through 900 and extends through the riser 18 to pass through a wall of the building. Although this arrangement reduces the area available for heat transfer between flue gases in the riser 18 and air flowing in the duct 20, as the inlet 32 and outlet 24 are 7 spatially separated outside the building this reduces the risk that flue gases will be drawn into the building through the inlet 32.

Referring to Figure 4, in another embodiment, instead of a duct, the riser 18 has disposed coaxially within it a generally cylindrical body 30 with closed, tapered ends.

Any other suitable shape of body could be used however. The body 30 causes the flow of flue gases in the riser to be conducted into the region 31, between the body 30 and walls of the riser 18. The region 31 is generally annular in cross-section and of reduced area compared to the total cross-section of the riser 18 and the flue gas velocity is therefore increased in this region. This in turn increases the flow of heat from the flue gas to the air in the jacket 19. This embodiment offers a more economical, although ultimately less thermally efficient arrangement to those illustrated in Figures 1 to 3.

Figure 5 shows another embodiment, similar to that illustrated in Figure 1 except that duct 18 extends through the roof of the building enabling f resh air to be drawn in through inlet 23.

The above embodiments are described by way of example only, many variations are possible without departing from the invention. For example, any of the constructional variations, such as the use of spirally wound tubes, 8 mentioned in GR 2296316A may be applied to the present flu assembly.

Claims

1 A heating and destratifying apparatus comprising a heater with a flue connected thereto, the flue having a riser of which a portion extends in thermal contact with air in an air inlet duct connecting an elevated air inlet opening with an air inlet to the heater, wherein there is disposed in the riser a body arranged to conduct the flow of flue gases in the riser between the body and a wall of the riser.

2. An apparatus as claimed in Claim 1 wherein the air inlet duct is formed by a jacket surrounding the said portion of the riser, permitting air to be drawn into the heater via a passage between the jacket and riser.

3. An apparatus as claimed in Claim 1 or 2 wherein the body is arranged to reduce the cross-sectional area of the said portion of the riser through which the flue gases are conducted, compared to other regions of the flue, so that the velocity of the flue gases is increased when flowing past the body, for example doubled.

4. An apparatus as claimed in Claim 1, 2 or 3 wherein the body is disposed in the riser to conduct the flow of flue gases in a region generally annular in cross-section.

5. An apparatus as claimed in any one of the preceding claims wherein the body is a duct.

6. An apparatus as claimed in Claim 5 wherein the duct forming the body is arranged so that air may be drawn through it into the air inlet to the heater. 7. Apparatus as claimed in Claim 6 wherein the duct 5 forming the body comprises a tube connected to an elevated air inlet opening. B. An apparatus as claimed in Claim 7 wherein the tube is arranged to draw in air from outside the building in which the apparatus is installed.

9. An apparatus as claimed in any one of the preceding claims wherein the riser and/or the body have surfaces which are corrugated, finned or otherwise extended to increase the surface area and consequently the rate of heat transfer.

10. An apparatus as claimed in any one of the preceding claims which comprises a forced draught fuel-burning heater, a housing in which a combustion chamber of the heater is disposed, and an impeller within the housing to draw air from an inlet of the housing and propel it past the combustion chamber and a heat exchanger to an outlet of the housing.

11. An apparatus as claimed in any one of the preceding claims which is installed in a single space.

12. A heating and destratifying apparatus substantially as herein described with reference to Figure 1 or Figure 2 or Figure 3 or Figure 4 or Figure 5 of the accompanying drawings.