U.S. patent application number 11/992079 was filed with the patent office on 2009-06-04 for water heater and a method of operating same.
Invention is credited to Patrick Pussell.
Application Number | 20090142720 11/992079 |
Document ID | / |
Family ID | 37864540 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090142720 |
Kind Code |
A1 |
Pussell; Patrick |
June 4, 2009 |
Water Heater and a Method of Operating Same
Abstract
A water heater (10) including a tank (12), a burner (26) and a
heated gas outlet duct (40). The tank (12) has a substantially
central flue (14) having an outlet (24) substantially adjacent the
top (20) of the tank (12). The tank (12) is adapted for mounting
with the flue (14) substantially vertically. The burner (26) is
located beneath the tank (12). The burner (26) has an air inlet
(32) and a pilot flame and is adapted to a burn a fuel to discharge
heated gases up through the flue (14). The heated gas outlet duct
(40) is of substantially unrestricted cross-section and has an
upper, first end (42) in gas communication with the flue outlet
(24) and a second, lower end (46) in gas communication with
atmosphere. When only the pilot flame is burning, the heated gas
outlet duct (40) is adapted to restrict the air drawn into the flue
(14) via the air inlet (32) to the minimum amount required to
maintain the pilot flame alight.
Inventors: |
Pussell; Patrick; (New South
Wales, AU) |
Correspondence
Address: |
Patent Group;C/O Dla Piper US
203 N Lasalle St Suite 1900
Chicago
IL
60601
US
|
Family ID: |
37864540 |
Appl. No.: |
11/992079 |
Filed: |
August 1, 2006 |
PCT Filed: |
August 1, 2006 |
PCT NO: |
PCT/AU2006/001085 |
371 Date: |
February 6, 2009 |
Current U.S.
Class: |
432/29 ;
122/19.2 |
Current CPC
Class: |
F24H 1/205 20130101;
F23L 11/00 20130101 |
Class at
Publication: |
432/29 ;
122/19.2 |
International
Class: |
F24H 9/20 20060101
F24H009/20; F24H 9/02 20060101 F24H009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 2005 |
AU |
2005905137 |
Claims
1. A water heater including: a tank with a substantially central
flue having an outlet substantially adjacent the top of the tank,
the tank being adapted for mounting with the flue substantially
vertical; a burner located beneath the tank, the burner having an
air inlet and a pilot flame and being adapted to a burn a fuel to
discharge heated gases up through the flue; and a heated gas outlet
duct of substantially unrestricted cross-section having an upper,
first end in gas communication with the flue outlet and a second,
lower end in gas communication with atmosphere, wherein, when only
the pilot flame is burning, the heated gas outlet duct is adapted
to restrict the air drawn into the flue via the air inlet to the
minimum amount required to maintain the pilot flame alight.
2. The water heater as claimed in claim 2, wherein the length of
the duct is approximately 20% to 30% of the length of the flue.
3. The water heater as claimed in claim 1, wherein the length of
the duct is approximately 25% of the length of the flue.
4. The water heater as claimed in claim 1, wherein the duct and the
flue are cylindrical.
5. The water heater as claimed in claim 4, wherein the duct and
flue have approximately equal diameters.
6. A water heater including: a tank with a substantially central
flue having an outlet substantially adjacent the top of the tank,
the tank being adapted for mounting with the flue substantially
vertical; a burner located beneath the tank, the burner having an
air inlet and an electronically controlled ignitor and being
adapted to a burn a fuel to discharge heated gases up through the
flue; and a heated gas outlet duct of substantially unrestricted
cross-section having an upper, first end in gas communication with
the flue outlet and a second, lower end in gas communication with
atmosphere, wherein, the duct has approximately the same cross
sectional area of the flue and is approximately 25% of the length
of the flue.
7. The water heater claimed in claim 6, wherein the duct and the
flue are cylindrical.
8. A method of maintaining a pilot flame alight in a water heater
having a tank with: a bottom; a top; and a substantially central
flue, the method including the steps of: directing the heated gases
from the pilot flame from the tank bottom to the tank top via the
flue; and directing the heated gases from the tank top to
atmosphere via a generally downwardly directed duct of
substantially unrestricted cross-section, the duct being adapted to
restrict the gas flow drawn into the flue to only the minimum
amount required to maintain the pilot flame alight.
9. A method of operating a water heater in idle mode, the water
heater having a tank with: a bottom; a top; a burner with a pilot
flame; and a substantially central flue, the method including the
steps of: directing the heated gases from the pilot flame from the
tank bottom to the tank top via the flue; and directing the heated
gases from the tank top to atmosphere via a generally downwardly
directed duct of substantially unrestricted cross-section, the duct
being adapted to restrict the gas flow drawn into the flue to only
the minimum amount required to maintain the pilot flame alight.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a water heater and a method
of operating same.
[0002] The invention has been primarily developed for use in a
natural draft water heater that has a gas burner at the base of the
water tank and a flue which passes through the water tank for
heating water in the tank.
BACKGROUND OF THE INVENTION
[0003] Natural draft water heaters are well known and are used
extensively in domestic water heating and other applications. The
energy efficiency of such water heaters is considered to be an
important consideration by many purchasers and owners of such water
heaters.
[0004] The Australian Gas Association (AGA) conducts performance
testing for water heaters and generates a Star (Trade Mark) rating
indicating the heater's overall energy efficiency (e.g. 5 Star).
The higher the Star rating, the higher the overall energy
efficiency. The Star rating is, generally speaking, a combination
of: Efficiency; and Maintenance. Efficiency is a measure of the
energy transfer from fuel to heated water (i.e. heat exchanging
efficiency). Maintenance is a measure of retaining stored energy in
the water (i.e. insulation effectiveness).
[0005] Natural draft water heaters operate in two modes: a
`heating` mode when the main burner is operating (i.e. alight); and
an `idle` mode when the main burner is not operating. In water
heaters that have a constantly operating pilot flame, only the
burner's pilot flame is alight in idle mode. In water heaters that
have an electronically controlled gas valve that re-ignites the
main burner electronically, there is no pilot flame alight in idle
mode.
[0006] Further, a water heater with a pilot flame and an open flue
(i.e. a flue vented directly to atmosphere without restriction)
will, in idle mode, transfer approximately 60% of the pilot flame's
energy to the water and lose approximately 40% through the flue.
Attempts to minimise this energy loss include placing a damper
(i.e. a flow control valve) downstream of the flue which is
controlled to block the flue opening to atmosphere when in idle
mode.
[0007] However, disadvantages of this approach are that the damper
adds to the cost and complexity of the water heater and can also
create a safety hazard if it jams in the closed position when the
heater is in the heating mode.
OBJECT OF THE INVENTION
[0008] It is an object of the present invention to provide a
mechanically simple, relatively low cost water heater able to
achieve a 5 Star AGA energy rating.
SUMMARY OF THE INVENTION
[0009] Accordingly, in a first aspect, the present invention
provides a water heater including: [0010] a tank with a
substantially central flue having an outlet substantially adjacent
the top of the tank, the tank being adapted for mounting with the
flue substantially vertical; [0011] a burner located beneath the
tank, the burner having an air inlet and a pilot flame and being
adapted to a burn a fuel to discharge heated gases up through the
flue; and [0012] a heated gas outlet duct of substantially
unrestricted cross-section having an upper, first end in gas
communication with the flue outlet and a second, lower end in gas
communication with atmosphere, [0013] wherein, when only the pilot
flame is burning, the heated gas outlet duct is adapted to restrict
the air drawn into the flue via the air inlet to the minimum amount
required to maintain the pilot flame alight.
[0014] The length of the duct is preferably approximately 20% to
30%, most preferably 25%, of the length of the flue. The duct and
the flue are preferably cylindrical and have approximately equal
diameters.
[0015] In a second aspect, the present invention provides a water
heater including: [0016] a tank with a substantially central flue
having an outlet substantially adjacent the top of the tank, the
tank being adapted for mounting with the flue substantially
vertical; [0017] a burner located beneath the tank, the burner
having an air inlet and an electronically controlled ignitor and
being adapted to a burn a fuel to discharge heated gases up through
the flue; and [0018] a heated gas outlet duct of substantially
unrestricted cross-section having an upper, first end in gas
communication with the flue outlet and a second, lower end in gas
communication with atmosphere, [0019] wherein, the duct has
approximately the same cross sectional area of the flue and is
approximately 25% of the length of the flue.
[0020] The duct and the flue are preferably cylindrical.
[0021] In a third aspect, the present invention provides method of
maintaining a pilot flame alight in a water heater having a tank
with: a bottom; a top; and a substantially central flue, the method
including the steps of: [0022] directing the heated gases from the
pilot flame from the tank bottom to the tank top via the flue; and
[0023] directing the heated gases from the tank top to atmosphere
via a generally downwardly directed duct of substantially
unrestricted cross-section, the duct being adapted to restrict the
gas flow drawn into the flue to only the minimum amount required to
maintain the pilot flame alight.
[0024] In a fourth aspect, the present invention provides a method
of operating a water heater in idle mode, the water heater having a
tank with: a bottom; a top; a burner with a pilot flame; and a
substantially central flue, the method including the steps of:
[0025] directing the heated gases from the pilot flame from the
tank bottom to the tank top via the flue; and [0026] directing the
heated gases from the tank top to atmosphere via a generally
downwardly directed duct of substantially unrestricted
cross-section, the duct being adapted to restrict the gas flow
drawn into the flue to only the minimum amount required to maintain
the pilot flame alight.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Preferred embodiments of the present invention will now be
described, by way of examples only, with reference to the
accompanying drawing wherein:
[0028] FIG. 1 is a cross-sectional schematic side view of an
embodiment of a water heater according to a first embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Referring to FIG. 1, there is shown a natural draft water
heater 10 according to a first embodiment of the invention. The
water heater 10 includes a cylindrical steel water tank 12 with a
central flue 14. The flue 14 has a length L1 and a spiral baffle 16
therein. The tank has an outwardly concave (domed) bottom 18 and an
outwardly concave (domed) top 20. The flue 14 has an inlet 22
adjacent the tank bottom 18 and an outlet 24 slightly above the
tank top 20. In use, the tank 12 is almost completely filled with
water.
[0030] It will be well understood by those skilled in the art that
cold water is introduced from mains water supply via a cold water
inlet (not shown) near the tank bottom 16 of the tank 12 and hot
water is drawn off for use via a hot water outlet (not shown) near
the top 20 of the tank 12.
[0031] A burner 26 is located beneath the tank bottom 18. As is
well understood by persons skilled in the art, the burner 28 has a
pilot flame (not shown) and is adapted to burn fuel, preferably
natural gas, and discharge heated gases up through the flue 14 for
heat transfer to the water in the tank 12. The exterior of the tank
12 is surrounded by insulation 28. The tank 12 and the insulation
28 are contained within an outer casing 30, which includes an air
inlet 32. The air inlet 32 is in gas communication with the burner
26 via passage 34. The burner 28 also has an associated gas control
system 36.
[0032] The water heater 10 also includes a heated gas outlet duct
40 having a first upper end 42 connected to the outlet 22 of the
flue by an insulated U-shaped connector 44 and a lower second end
46 open to atmosphere. The duct 40 has a length L2 and has a
substantially open or unrestricted cylindrical cross-section (i.e.
free of valves or dampers and the like). The duct 40 is adapted to
provide a resistance to the gas flow therethrough such that when
the water heater is in idle mode (i.e. only the pilot flame is
burning) the gas passing through the duct 40 is subjected to a
balancing resistance, which limits the air drawn into the flue 14
to only the minimum that is required to achieve combustion and
maintain the pilot flame alight. Generally speaking, as a result,
the energy that would ordinarily be lost, in idle mode, through an
unrestricted outlet is minimised and the Star rating of the water
heater is improved, particularly the Maintenance-based component of
the Star rating.
[0033] The resistance of the duct 40 is primarily adjusted by
varying its diameter and length. The diameter of the duct 40 is
approximately equal to that of the flue 16 to avoid choking the gas
flow through the flue/duct. In the embodiment shown, the duct
length L2 is approximately 25% of the flue length L2. Further, it
will be appreciated by those persons skilled in the art that other
factors can influence the resistance provided by the duct 40
including material and internal surface finish.
[0034] Generally speaking, the relative length of the duct 40 is
determined by the following iterative process. Firstly, the gas
supply for the pilot flame is established as the minimum amount
possible to meet environmental (e.g. wind) and legislative
requirements. Secondly, the water heat 10 is tested, without the
duct 40 attached, and the restriction of the baffle 16 adjusted to
meet emission requirements and maximise the Efficiency-based Star
rating component. The duct 40 is then attached. As discussed above,
this improves the Maintenance-based Star rating component. However,
it also generally lead to a reduction in the Efficiency-based Star
rating component. The baffle 16 is then adjusted, by making it less
restrictive, to increase the Efficiency-based component until an
acceptable level of emissions is reached. The length of the duct 40
is then adjusted to seek improvements in the Maintenance-based
component. This process continues in an iterative manner until the
overall Star rating is maximised.
[0035] The water heater 10 provides improved efficiency as the duct
40 increases the transfer of heat from the pilot flame to the water
when the heater 10 is in idle mode by reducing heat loss from the
flue 14 to atmosphere. This improves the Maintenance-based Star
rating component. More particularly, it is estimated that water
heaters similar to that described with reference to the water
heater 10 will, in idle mode, transfer approximately 80% of the
pilot flame energy to the water and only lose approximately 20%
through the flue. Further, such water heaters do not exhibit a loss
in their Efficiency-based Star rating component sufficient to
compromise their Star rating overall. Moreover, this is achieved in
a relatively mechanically simple arrangement that is not
susceptible to blocking or other mechanical failure.
[0036] A water heater (not shown) according to a second embodiment
of the invention is similar to the heater 10 except it has an
electronically controlled gas valve that re-ignites the main burner
electronically. This heater has no pilot flame alight in idle mode.
The duct 40 also improves the Star rating of this heater as it
provide a resistance to, and thus slows, the flow of the heated air
(ie. air heated by transfer from the surrounding water) leaving the
flue.
[0037] Although the invention has been described with reference to
the preferred embodiments, it will be appreciated by those skilled
in the art that the invention may be embodied in many other
forms.
* * * * *