GB1578663A

GB1578663A - Boiler unit

Info

Publication number: GB1578663A
Application number: GB449277A
Authority: GB
Original assignee: Stelrad Group Ltd
Current assignee: Stelrad Group Ltd
Priority date: 1978-01-24
Filing date: 1978-01-24
Publication date: 1980-11-05

Description

(54) BOILER UNIT (71) We, STELRAD GROUP LIMI TED, a British Company of Newtown Road, Henley-on-Thames, Oxfordshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a boiler unit and particularly, but not exclusively, to a gas fired boiler unit for heating water for use in a central heating system.

According to the present invention there is provided a boiler unit comprising an array of parallel horizontal conduits for conducting a liquid to be heated, said array defining and enclosing a combustion zone, a first series of chambers at one end of said conduits and in communication with said conduits, a second series of chambers at the other end of said conduits and in communication with said conduits, an inlet for liquid in communication with one chamber of said first series of chambers and an outlet for liquid in communication with another chamber of said first series of chambers, said first and second series of chambers being arranged such that liquid from said inlet makes a plurality of passes from the first series of chambers to said second series of chambers along said conduits before flowing out of said outlet, and a burner disposed within the combustion zone defined and enclosed by the array of conduits, said first and second series of chambers each being formed by two longitudinally spaced plates which are spaced apart by longitudinally extending ribs which separate the respective chambers, means being provided for securing the two plates relative to each other in a detachable manner.

Preferably the conduits are arranged in an annular array.

Preferably the burner comprises a gas burner and a fan is provided for supplying the burner with a gas/air mixture.

The conduits are preferably tubes provided with an extended heat exchange surface or surfaces and such surface or surfaces may comprise a helical fin or a plurality of fins.

The array of conduits may be enclosed within a member provided with a plurality of longitudinally extending slots.

A boiler unit as defined above may form a module for use in the boiler which forms the subject of our copending United Kingdom Patent Application No. 33535/76 (Serial No.

1,556,813).

An embodiment of the present invention will now be described by way of an example, with reference to the accompanying drawings, in which: Figure 1 is an end view of the boiler unit, Figure 2 is a longitudinal section taken along the line 11-Il of Figure 1, Figure 3 is a transverse section taken along the line Ill-Ill of Figure 2, Figure 4 is a transverse section taken along the line IV-IV of Figure 2, and Figure 5 is a longitudinal section taken along the line V-V of Figure 1.

The boiler unit comprises an annular array of horizontal heat exchange tubes 10 defining and enclosing a combustion zone and each tube 10 is provided with a helical fin or a plurality of fins 11 forming an extended heat exchange surface. The tubes 10 extend between a plate 12 and a plate 13 in which the respective ends of the tubes 10 are fixed by expansion or brazing or welding. Connected to the plate 12 by bolts (not shown) is a plate 14 and connected to the plate 13 by bolts (not shown) is a plate 15. Formed between the plates 12 and 14 is a series of chambers 16 consisting of chambers 16a, 16b, 16c, 16d, 16e and 16f and formed between the plates 13 and 15 is a series of chambers 17 consisting of chambers 1 7a, 1 7b, 1 7c and 17d.The chambers 1 6a to 1 6e are defined by axially extending ribs 12a and 14a which are axially aligned and in abutment with each other. The chambers 1 7a to 1 7d are defined by axially extending ribs 13a and 15a which are axially aligned and in abutment with each other.

Connected to the plate 14 is an inlet pipe 18 which is in communication with the chamber 16a and connected to the plate 14 is an outlet pipe 19 which is in communication with the chamber 16d. Water from the inlet pipe 18 will enter chamber 16a and will flow along the four tubes 10 which are in communication with the chamber 1 6a to the chamber 17a. Some of the water in chamber 17a will flow through two tubes 10 to the chamber 1 6b and the remainder will flow through two further tubes 10 to the chamber 16f. The water in the chamber 1 6b will flow through two tubes 10 into chamber 17b and the water in chamber 16f will flow through two tubes 10 into chamber 17d.The water in the chambers 17b and 17d will flow through two further tubes 10 into respective chambers 16c and 16e and the water in the chambers 1 6c and 1 6e will flow through two further tubes 10 into chamber 17c. The water in chamber 1 7c will flow through four tubes 10 to chamber 1 6d and then flow through the outlet pipe 19. The water in flowing from the inlet pipe 18 to the outlet pipe 19 will therefore make six passes through tubes 10.

It will be appreciated that the number of passes can be varied by varying the number of tubes 10 and/or chambers 16, 17. It will be appreciated that the plates 12 and 14 and plates 13 and 15 can be easily separated so that the chambers 16, 17 and the tubes 10 can be easily cleaned.

The plate 12 is provided with a radially outwardly extending flange 20 which is fastened by bolts (not shown) to structure 21 forming an exhaust flue. Located within the zone bounded by the array of tubes 10 is a gas burner 22 in the form of a perforated cylinder closed at one end. A mixture of gas and air is conveyed to the burner 22 via a duct 23 from a fan 24. Gas is supplied to the inlet of the fan 24 via a pipe 25 and a gas control valve 26. Ignition of the gas/air mixture at the gas burner 22 is effected by a spark igniter 27 and the presence of a flame is detected by a flame ionization detector 28.

A control unit 29 controls the operation of the fan 24, the generation of the spark at the igniter 27, the opening of the gas control valve 26 and the operation of the flame detector 28.

The hot gases from the burner 22 flow radially outwards through the combustion zone and pass across the fins 11 of the tubes 10 into the exhaust flue structure 21. In order to ensure uniform radial outward flow through the tube surfaces and to aid the heat transfer from the hot gas to the tubes. 10, the array of tubes 10 is surrounded by a cylinder 30 provided with axial slots 31, each slot 31 being disposed on a radial line on which the axis of an associated tube 10 is disposed. The width of the slots 31 controls the pressure drop through the heating surface and hence overcomes the buoyancy of the hot gas, ensuring an even gas flow over the tubes 10.

By having the inlet 18 disposed diametrically opposite the outlet 19 thermal cracking of the plate 14 is avoided.

The boiler unit is very compact, has a low water content, has a fast response, does not have any tendency to promote nucleate boiling of the water, does not have any tendency for temperature overshoot and can be easily stripped down for cleaning of the water ways.

The tubes 10 are arranged circumferentially around the burner 22 and spaced at a sufficient radial distance from the burner 22 to allow complete combustion to take place without impingement of the flame on the fins 11 and so avoid substantial production of carbon monoxide even at fuel/air ratios close to stoichiometric.

It will be appreciated that the cylinder 30 may be dispensed with or replaced by a wire mesh.

The array of tubes 10 may be annular as shown or the array may be of any other suitable configuration such as rectangular. It will also be appreciated that the chambers 16, 17 can be formed by ribs provided on only one of the plates 12, 14 or 13, 15.

The boiler unit may form a boiler module for use in the boiler disclosed and claimed in our copending United Kingdom Patent Application No. 33535/76 (Serial No.

1,556,813).

WHAT WE CLAIM IS: 1. A boiler unit comprising an array of parallel horizontal conduits for conducting a liquid to be heated, said array defining and enclosing a combustion zone, a first series of chambers at one end of said conduits and in communication with said conduits, a second series of chambers at the other end of said conduits and in communication with said conduits, an inlet for liquid in communication with one chamber of said first series of chambers and an outlet for liquid in communication with another chamber of said first series of chambers, said first and second series of chambers being arranged such that liquid from said inlet makes a plurality of passes from the first series of chambers to said second series of chambers along said conduits before flowing out of said outlet, and a burner disposed within the combustion zone defined and enclosed by the array of conduits, said first and second series of chambers each being formed by two longitudinally spaced plates which are spaced apart by longitudinally extending ribs which separate the respective chambers, means being provided for securing the two plates relative to each other in a detachable manner.

2. A boiler unit as claimed in claim 1, in which the conduits are arranged in an annular array.

3. A boiler unit as claimed in claim. 1 or claim 2, in which the conduits comprise tubes provided with an extended heat exchange surface or surfaces.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. pipe 18 will enter chamber 16a and will flow along the four tubes 10 which are in communication with the chamber 1 6a to the chamber 17a. Some of the water in chamber 17a will flow through two tubes 10 to the chamber 1 6b and the remainder will flow through two further tubes 10 to the chamber 16f. The water in the chamber 1 6b will flow through two tubes 10 into chamber 17b and the water in chamber 16f will flow through two tubes 10 into chamber 17d.The water in the chambers 17b and 17d will flow through two further tubes 10 into respective chambers 16c and 16e and the water in the chambers 1 6c and 1 6e will flow through two further tubes 10 into chamber 17c. The water in chamber 1 7c will flow through four tubes 10 to chamber 1 6d and then flow through the outlet pipe 19. The water in flowing from the inlet pipe 18 to the outlet pipe 19 will therefore make six passes through tubes 10. It will be appreciated that the number of passes can be varied by varying the number of tubes 10 and/or chambers 16, 17. It will be appreciated that the plates 12 and 14 and plates 13 and 15 can be easily separated so that the chambers 16, 17 and the tubes 10 can be easily cleaned. The plate 12 is provided with a radially outwardly extending flange 20 which is fastened by bolts (not shown) to structure 21 forming an exhaust flue. Located within the zone bounded by the array of tubes 10 is a gas burner 22 in the form of a perforated cylinder closed at one end. A mixture of gas and air is conveyed to the burner 22 via a duct 23 from a fan 24. Gas is supplied to the inlet of the fan 24 via a pipe 25 and a gas control valve 26. Ignition of the gas/air mixture at the gas burner 22 is effected by a spark igniter 27 and the presence of a flame is detected by a flame ionization detector 28. A control unit 29 controls the operation of the fan 24, the generation of the spark at the igniter 27, the opening of the gas control valve 26 and the operation of the flame detector 28. The hot gases from the burner 22 flow radially outwards through the combustion zone and pass across the fins 11 of the tubes 10 into the exhaust flue structure 21. In order to ensure uniform radial outward flow through the tube surfaces and to aid the heat transfer from the hot gas to the tubes. 10, the array of tubes 10 is surrounded by a cylinder 30 provided with axial slots 31, each slot 31 being disposed on a radial line on which the axis of an associated tube 10 is disposed. The width of the slots 31 controls the pressure drop through the heating surface and hence overcomes the buoyancy of the hot gas, ensuring an even gas flow over the tubes 10. By having the inlet 18 disposed diametrically opposite the outlet 19 thermal cracking of the plate 14 is avoided. The boiler unit is very compact, has a low water content, has a fast response, does not have any tendency to promote nucleate boiling of the water, does not have any tendency for temperature overshoot and can be easily stripped down for cleaning of the water ways. The tubes 10 are arranged circumferentially around the burner 22 and spaced at a sufficient radial distance from the burner 22 to allow complete combustion to take place without impingement of the flame on the fins 11 and so avoid substantial production of carbon monoxide even at fuel/air ratios close to stoichiometric. It will be appreciated that the cylinder 30 may be dispensed with or replaced by a wire mesh. The array of tubes 10 may be annular as shown or the array may be of any other suitable configuration such as rectangular. It will also be appreciated that the chambers 16, 17 can be formed by ribs provided on only one of the plates 12, 14 or 13, 15. The boiler unit may form a boiler module for use in the boiler disclosed and claimed in our copending United Kingdom Patent Application No. 33535/76 (Serial No. 1,556,813). WHAT WE CLAIM IS:

1. A boiler unit comprising an array of parallel horizontal conduits for conducting a liquid to be heated, said array defining and enclosing a combustion zone, a first series of chambers at one end of said conduits and in communication with said conduits, a second series of chambers at the other end of said conduits and in communication with said conduits, an inlet for liquid in communication with one chamber of said first series of chambers and an outlet for liquid in communication with another chamber of said first series of chambers, said first and second series of chambers being arranged such that liquid from said inlet makes a plurality of passes from the first series of chambers to said second series of chambers along said conduits before flowing out of said outlet, and a burner disposed within the combustion zone defined and enclosed by the array of conduits, said first and second series of chambers each being formed by two longitudinally spaced plates which are spaced apart by longitudinally extending ribs which separate the respective chambers, means being provided for securing the two plates relative to each other in a detachable manner.

4. A boiler unit as claimed in claim 3, in

which the extended heat exchange surface or surfaces comprise a helical fin or a plurality of fins.

5. A boiler unit as claimed in any preceding claim, in which the burner comprises a gas burner and a fan is provided for supplying the burner with a gas/air mixture.

6. A boiler unit as claimed in any preceding claim, in which the array of conduits is enclosed within a member provided with a plurality of longitudinally extending slots.

7. A boiler unit as claimed in any one of claims 1 to 5, in which the array of conduits is enclosed within a wire mesh member.

8. A boiler unit as claimed in any preceding claim, in which the two axially spaced plates are each provided with longitudinally extending ribs which are longitudinally aligned one with another and in abutment with each other, and which constitute said ribs which separate the chambers.

9. A boiler unit as claimed in claim 2 and any of claims 3 to 8 when dependent on claim 2, in which the inlet is disposed diametrically opposite the outlet.

10. A boiler unit substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.