CA2188321A1

CA2188321A1 - gas water heater

Info

Publication number: CA2188321A1
Application number: CA 2188321
Authority: CA
Inventors: Leonard Roy Hansen
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-10-16
Filing date: 1996-10-16
Publication date: 1997-04-17
Also published as: AU7024196A; NZ280255A

Abstract

A gas fuelled water heater for small scale (4-6kw) supply has an upright, tubular water jacket with a multi-jet gas burner at the lower end and a finned multi-tube preheater at the upper end. The incoming water is preheated before it enters the jacket. Heat exchange is promoted by water tubes which criss cross the diameter of the jacket. These are staggered radially by 10-35 degrees in order to slow the passage of the flue gases without creating back pressure.
A thermostat controls gas supply from a bottled or reticulated supply. As the heater is connected in circuit with a domestic hot water tank it can supplement or replace electric water heating. The heater needs no electric current and can operate in areas without gas or electric reticulation.

Description

. -GAS WATER HEATER

FIELD OF THE INVENTION
This invention concerns heating apparatus and in particularheaters for the supply of hot water in a building.
BACKGROUND
A variety of hot water cylinders are already known including those which rely on electrical elements for the heating source as well as hot water supplies operable from a wet back on a stove or a fuel burning fire. Many of these hot water systems are unsuitable in places such as holiday homes which may not have a permanent power supply and there may be no wish nor need to use a wet back stove or heater just to supply a permanent hot water system.

Furthermore electrically powered hot water systems may be subject to power failure and are usually subject to control by power supply authorities managing peak loads by interrupting the ripple control which are part of most electrical systems. This invention aims at the provision of a heating apparatus which uses a source of energy other than electricity either alone or in conjunction with conventional heating apparatus or which overcomes a disadvantage of the existing arrangements or at least provides the public with a useful choice.

SUMMARY OF THE Ihv~NllON
This invention provides a gas fuelled water heater

2~8832l comprising a burner and a heat exchanger with a water inlet and a water outlet wherein the heat exchanger at least partially defines a flue and multiple water passages extend into the flue transversely to the flue gas flow, the passages being disposed to scatter the flue gases and promote heat transfer.

The heat exchanger may present a spiral upward path to the flue gases generated by the burner.

The heat exchanger may alternatively have a spiral baffle directing flue gases onto water-containing parts of the exchanger.

Particularly the exchanger may have two or more coaxial cylinder collectors separated by a spiral insert.

Alternatively the heat exchanger has flow passages for water extending transversly to the flow path of the flue gases. The exchanger may be formed as an annular jacket and tubes may criss-cross the lumen of the annular jacket.
The spiral conformation may be provided by displacing one tube from the next by 10-35 degrees. As the aim of the design is to function without an external electricity supply the heater cannot rely on an electric pump for circulation or heat exchange. If the flue gases escape before an economically uæeful proportion of heat has been captured the heater will not reach the necessary 21 ~8321 performance.

In using the term "scattering" I should explain that I have found that a compromise exists between too rapid an escape and impeding the gases by back pressure. I prefer to stagger the pathway of the gases by partly obstructing the flue with water pipes forming part of the exchanger, causing the gases to flow around the pipes thereby slowing the escape without actually impeding the gases. This design feature can be optimised by trials .

The heat exchanger preferably defines a flue and a preheater is may be located at the flue discharge in order to extract the heat remaining in the flue gases and donate it to the water entering the heat exchanger. The preheater may be a finned tubular connector of similar area to the flue discharge.

DESCRIPTION OF THE DRAWINGS
One embodiment of the invention is now described with reference to the accompanying drawings in which Fig 1 is a diagrammatic side elevation of the heater.

Fig 2 is a plan of the main heat exchanger.

Fig 3 is a diagrammatic side elevation of a domestic hot water cylinder fitted with a heater.

DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to figure 1 and 2, the main heat exchanger 2 is a cylindrical copper jacket having an outer wall 4 and an inner wall 6, both 300 mm long. The inner wall 2 defines the flue 8, 80 mm in diameter. The inner wall is pierced to allow the connection of a vertical series of horizontal copper tubes 10, 15 mm in diameter to cross the flue diametrically. In this way water in the jacket is exposed to the flue gases which rise in a spiral pathway because successive tubes are rotated by 15 degrees. This slows the rise of the gases and gives sufficient time for heat exchange. Heated water leaves through exit pipe 12, at 75 degrees C.

Cold incoming water then enters by pipe 14. A preheater 16 has a pair of manifolds 18, 20, and these are connected by upper tubes 22, middle tubes 24 and lower tubes 26 which are braced by fins 28. The preheater is located in the path of the flue gases and extracts what heat remains. The preheated water enters the base of the main heat exchanger 2.

A 60 mm diameter gas burner 30 has multi-jets 32 supplied by a gas pipe 34 controlled by a thermostat 36. An LPG
bottle 38 (see Fig 3) supplies gas to the standard thermostat. A temperature probe 40 supplies an intermit-tent signal to the thermostat in known manner. A

thermocouple generates 250mv and supplies the thermostat 36through lead 42. As long as the pilot 44 stays alight the thermostat keeps the main gas supply to the burner flowing.
If the pilot light ceases the voltage drop closes the gas supply. Relighting of the pilot requires a manual sequence.

The pilot 44 plays on the site of the incoming preheated water. The probe 40 measures the water temperature about half way up the exchanger.

The burner 30 is located beneath the flue space allowing incoming air to mix with the flue gas.

In Fig 3 a domestic hot water cylinder 46 has a cold inlet 48 and a hot water outlet 50. The cylinder 46 is in a linen cupboard 52 and the heater is mounted on a wall in the laundry 54 below. The pipe connections are as shown.

I have found the advantages of the above embodiment to be 1. Efficient heat exchange coupled with ease of manufacture.

2. The heater works with a variety of gas fuels including reticulated gas.

0 3 No moving parts and no pump.

Claims

CLAIMS:

1. A gas-fuelled water heater comprising a burner and a heat exchanger with a water jacket having a water inlet and a water outlet wherein the heat exchanger presents a spiral upward path to the flue gases generated by the burner.

2. A gas fuelled water heater wherein the heat exchanger has a spiral baffle directing flue gases onto water-containing parts of the exchanger.

3. A gas fuelled water heater as claimed in Claim 2 wherein the exchanger has two or more coaxial cylindrical collectors separated by a spiral insert.

4. A gas fuelled heater as claimed in Claim 1 wherein the heat exchanger has flow passages for water extending transversely to the flow path of the flue gases.

5. A gas fuelled heater as claimed in Claim 4 wherein the heater exchanger is an annular jacket and diametrical tubes cross the lumen of the annular jacket.

6. A gas fuelled heater as claimed in Claim 5 wherein the tubes are mutually spaced by a distance of the same order as the diameter of the tube.

7. A gas fuelled heater as claimed in Claim 6 wherein the angular tube displacement from one to the next adjacent tube is 10-35 degrees.

8 A gas fuelled heater as claimed in claim 7 wherein the tube displacement is 10-20 degrees.

9. A gas fuelled heater as claimed in Claim 1 wherein the heat exchanger at least partially defines a flue and a preheater is located at the flue discharge in order to extract the heat remaining in the flue gases and donate the heat to the water entering the heat exchanger.

A gas fuelled heater as claimed in Claim 9 wherein the preheater is a finned tubular connector of similar area to the flue discharge.

11. A gas fuelled heater as claimed in Claim 10 wherein the preheater has two or more layers of tubes.

12 A gas fuelled heater comprising a burner and a heat exchanger with a water jacket having a water inlet and a water outlet wherein the heat exchanger at least partially defines a flue and multiple water passages extend into the flue transversely to the flue gas flow, the passages being disposed to scatter the flue gases and promote heat transfer.

13. A gas fuelled heater as claimed in claim 12 claims wherein a thermostat is located adjacent the heat exchanger with a temperature sensor extending from the thermostat.

14. A gas fuelled heater as claimed in claim 12 the burner has a pilot and the pilot heat is applied to the water inlet.

15. A gas fuelled heater as claimed in Claim 13 wherein the thermostat controls the gas supply to both the burner and the pilot and the voltage to reignite the pilot.