GB2119078A

GB2119078A - Improvements in or relating to gas fired heat exchangers

Info

Publication number: GB2119078A
Application number: GB08211811A
Authority: GB
Inventors: Colin Barrie Roe
Original assignee: WELLMAN SELAS Ltd
Current assignee: WELLMAN SELAS Ltd
Priority date: 1982-04-23
Filing date: 1982-04-23
Publication date: 1983-11-09
Also published as: GB2119078B

Abstract

A gas fired heat exchanger, comprising a burner head (1) in which gas and air are mixed, a combustion chamber (2) in which said mixture of gas and air is burned, heat transfer means (9) whereby heat from the combustion of said gas and air mixture is transferred from said gas fired heat exchanger, and means (12) for venting from said gas fired heat exchanger the exhaust gases produced by the combustion of said gas and air mixture. The burner head (1) comprises a chamber (6) through which air to be mixed with said gas passes, which chamber (6) is located adjacent a further chamber (10) through which exhaust gases pass from said heat transfer means (9) to said venting means (12). The two chambers are separated from each other by heat conducting means (11), so that the air in said chamber (6) is heated by the residual heat contained in the exhaust gases in said further chamber (10). <IMAGE>

Description

SPECIFICATION Improvements in or relating to gas fired heat exchangers The present invention relates to a gas fired heat exchanger for use, for example, in vat and tank heating installations.

Conventional gas fired heat exchangers for use in vat and tank heating installations comprise a burner head in which gas and air are mixed, a combustion chamber in which the gas and air mixture is burned, a single immersion tube shaped to run ariound the interior of the vat and connected to the end of the combustion chamber to transfer heat to the product contained within the vat, and a flue assembly connected to the end of the immersion tube through which the products of combustion are vented.

In gas fired heat exchangers of the aforementioned type the degree of efficiency of the heat exchanger is largely determined by the immersion tube length to diameter ratio (LID). With such heat exchangers a maximum efficiency of about 80% can be achieved, but the UD ratio must be of the order of 140:1. Such high ratios are not always possible however, due to restrictions of tank size and other factors which bring down the practically achievable UD ratio.

A further factor which affects the efficiency of such heat exchangers in the temperature of the gas/air mixture as it enters the burner head. For optimum efficiency the temperature of the gas/air mixture should be high and constant.

It is an object of the present invention to provide a gas fired heat exchanger in which the above mentioned problems are obviated or mitigated to provide a more efficient heat exchanger.

According to the present invention there is provided a gas fired heat exchanger, comprising a burner head in which gas and air are mixed, a combustion chamber in which said mixture of gas and air is burned, heat transfer means whereby heat from the combustion of said gas and air mixture is transferred from said gas fired heat exchanger, and means for venting from said gas fired heat exchanger the exhaust gases produced by the combustion of said gas and air mixture, characterised in that the burner head comprises a chamber through which air to be mixed with said gas passes, which chamber is located adjacent a further chamber through which exhaust gases pass from said heat transfer means to said venting means, the two chambers being separated by heat conducting means so that the air in said chamber is heated by the residual heat contained in the exhaust gases in said further chamber.

Preferably the burner head comprises means for mixing gas with air for combustion, which means is contained within the chamber through which air passes to be mixed with said gas.

The chamber through which exhaust gases pass may encircle the chamber through which air passes.

Alternatively the chamber through which exhaust gases pass may be located within the chamber through which air passes.

Preferably the said chambers are annular in shape.

Preferably the heat transfer means comprises a plurality of tubes connected at one end to the end of the combustion chamber and at the other end to the chamber through which exhaust gases pass.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a gas fired heat exchanger embodying the present invention, in which the burner head and combustion chamber have been partly cut away; Figure 2 is an end view of the heat exchanger of Figure 1; and Figure 3 is a side view of a further gas fired heat exchanger embodying the present invention in which the burner head and combustion chamber have been partly cut away.

Referring to Figures 1 and 2 the gas fired heat exchanger embodying the present invention comprises a burner head 1, in which gas and air are mixed for combustion in a combustion chamber 2.

Gas is supplied to the burner head 1 through a female gas inlet connection 3 and a pipe 4, and air is supplied to the burner head 1 through a male air inlet connection 5, which is connected to an annular chamber 6 surrounding the pipe 4. Air from the chamber 6 is entrained in the gas passing through the pipe 4 through holes (not shown) in the pipe 4 and the resulting gas/air mixture is output into the combustion chamber 2 through a burner nozzle 7.

As previously stated hereinabove, combustion of the gas/air mixture takes place in the combustion chamber 2. Since the end of the combustion chamber 2 is closed by a cap 8 the products of combustion, in the form of exhaust gases and heat, pass from the combustion chamber 2 into a plurality of tubes 9 secured around the end of the combustion chamber 2. As the exhaust gases pass through the tubes 9, the tubes 9 are heated, and heat transfer takes place between the tubes 9 and the surrounding environment. The other end of each tube 9 is connected to an annular exhaust gas chamber 10 into which the exhaust gases enter from the tubes 9.

The exhaust gas chamber 10, being annular encircles the annular chamber 6 into which air for combustion is input. As a result the exhaust gases entering the annular chamber 10, which are still hot, heat the annular ring 11, dividing the chambers 6 and 10, and the air inlet 5, which heats the air within the chamber 6 and the inlet 5. The effect of heating the air within the chamber 6 and inlet 5 is to greatly increase the efficiency at which combustion takes place within the combustion chamber 2. Finally the exhaust gases, from which most of the heat of combustion has been stripped in the tubes 9 and the chamber 10 are vented through an exhaust gas pipe 12.

Where the gas fired heat exchanger described hereinabove is to be used in a vat ortank it can be inserted into the vat or tank through a hole in the side thereof and secured to the wall by bolts which are passed through holes 13 in the face-place 14.

Referring now to Figure 3 there is shown a further embodiment of a gas fired heat exchanger according to the present invention.

As in the previous embodiment of the invention described with reference to Figures 1 and 2, air and gas are mixed in a burner head 15, for combustion in combustion chamber 16. The exhaust gases from the combustion chamber 16 are then passed through a plurality of tubes 17 secured around the end thereof to an annular exhaust gas chamber 18 to heat air for combustion within the burner head 15. In this embodiment of the invention however, the annular air chamber is not encircled by the annular exhaust gas chamber, but rather the annular exhaust gas chamber 18 is located within the annular air chamber 19. In this embodiment of the invention therefor the exhaust gas chamber 17 is surrounded on three sides by air for combustion which means that the degree of heat transfer from the exhaust gases to the air is greater than in the previous embodiment.This results in even further improvements in the efficiency of combustion within the combustion chamber. A further advantage of this embodiment is that since no sides of the exhaust gas chamber 18 are formed by the casing of the burner head, the burner head can be touched without being burned.

It will be appreciated that the gas fired heat exchanger embodying the present invention may be provided with gas control train, isolating valves, air and gas control valves, spark ignition means and flame detection means amongst other things as appropriate.

In addition the gas fired heat exchanger embodying the present invention may be provided with an external casing around the combustion chamber and tubes to protect them from mechanical damage, for example, shock, or chemical damage, for example, corrosion.

CLAIMS (Filed on 22.4.83.) 1. A gas fired heat exchanger, comprising a burner head in which gas and air are mixed, a combustion chamber in which said mixture of gas and air is burned, heat transfer means whereby heat from the combustion of said gas and air mixture is transferred from said gas fired heat exchanger, and means for venting from said gas fired heat exchanger the exhaust gases produced by the combustion of said gas and air mixture, wherein the burner head comprises a chamber through which air to be mixed with said gas passes, which chamber is located adjacent a further chamber through which exhaust gases pass from said heat transfer means to said venting means, the two chambers being separated by heat conducting means so that the air in said chamber is heated by the residual heat contained in the exhaust gases in said further chamber.

2. A gas fired heat exchanger according to claim 1,wherein the burner head comprises means for mixing gas with air for combustion, which means is contained within the chamber through which air passes to be mixed with said gas.

3. A gas fired heat exchanger according to claim 1 or 2, wherein the chamber through which exhaust gases pass encircles the chamber through which air passes.

4. A gas fired heat exchanger according to claim 1 or 2 wherein the chamber through which exhaust gases pass is located within the chamber through which air passes.

5. A gas fired heat exchanger according to claim 3 or 4, wherein the said chambers are annular in shape and substantially coaxial with respect to each other.

6. A gas fired heat exchanger according to any preceding claim, wherein the heat transfer means comprises a pluralityoftubes connected at one end to the end of the combustion chamber and at the other end to the chamber through which exhaust gases pass.

7. A gas fired heat exchanger substantially as herein before described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. As in the previous embodiment of the invention described with reference to Figures 1 and 2, air and gas are mixed in a burner head 15, for combustion in combustion chamber 16. The exhaust gases from the combustion chamber 16 are then passed through a plurality of tubes 17 secured around the end thereof to an annular exhaust gas chamber 18 to heat air for combustion within the burner head 15. In this embodiment of the invention however, the annular air chamber is not encircled by the annular exhaust gas chamber, but rather the annular exhaust gas chamber 18 is located within the annular air chamber 19. In this embodiment of the invention therefor the exhaust gas chamber 17 is surrounded on three sides by air for combustion which means that the degree of heat transfer from the exhaust gases to the air is greater than in the previous embodiment.This results in even further improvements in the efficiency of combustion within the combustion chamber. A further advantage of this embodiment is that since no sides of the exhaust gas chamber 18 are formed by the casing of the burner head, the burner head can be touched without being burned. It will be appreciated that the gas fired heat exchanger embodying the present invention may be provided with gas control train, isolating valves, air and gas control valves, spark ignition means and flame detection means amongst other things as appropriate. In addition the gas fired heat exchanger embodying the present invention may be provided with an external casing around the combustion chamber and tubes to protect them from mechanical damage, for example, shock, or chemical damage, for example, corrosion. CLAIMS (Filed on 22.4.83.)

1. A gas fired heat exchanger, comprising a burner head in which gas and air are mixed, a combustion chamber in which said mixture of gas and air is burned, heat transfer means whereby heat from the combustion of said gas and air mixture is transferred from said gas fired heat exchanger, and means for venting from said gas fired heat exchanger the exhaust gases produced by the combustion of said gas and air mixture, wherein the burner head comprises a chamber through which air to be mixed with said gas passes, which chamber is located adjacent a further chamber through which exhaust gases pass from said heat transfer means to said venting means, the two chambers being separated by heat conducting means so that the air in said chamber is heated by the residual heat contained in the exhaust gases in said further chamber.