U.S. patent application number 10/490559 was filed with the patent office on 2005-02-24 for liquid heating apparatus.
Invention is credited to Moulder, Steven.
Application Number | 20050041962 10/490559 |
Document ID | / |
Family ID | 9922514 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050041962 |
Kind Code |
A1 |
Moulder, Steven |
February 24, 2005 |
Liquid heating apparatus
Abstract
A method and apparatus for preventing build-up of deposits on
internal surfaces (6) of a water heater (1). A heat shock treatment
is periodically applied to the surfaces (6) resulting in
differential thermal expansion and/or contraction between the
internal surfaces (6) and deposits (7) adhering thereto that causes
the deposits (7) to crack and break away from the surfaces (6). The
heat shock treatment may include the step of alternatively heating
and cooling the internal surfaces (6) in any order and may be
repeated one or more times. The internal surfaces (6) may be low
friction surfaces to reduce adhesion between the surfaces (6) and
any deposits (7) that facilitates removal of the deposits (7)
during the heat shock treatment.
Inventors: |
Moulder, Steven; (Headless
Cross, GB) |
Correspondence
Address: |
PYLE & PIONTEK
221 N. LASELLE STREET
SUITE 850
CHICAGO
IL
60601
US
|
Family ID: |
9922514 |
Appl. No.: |
10/490559 |
Filed: |
October 25, 2004 |
PCT Filed: |
September 23, 2002 |
PCT NO: |
PCT/GB02/04321 |
Current U.S.
Class: |
392/466 |
Current CPC
Class: |
F24H 9/0042
20130101 |
Class at
Publication: |
392/466 |
International
Class: |
F24H 001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2001 |
GB |
0122856.8 |
Claims
1. A method of removing deposits from internal surfaces of water
heating apparatus by applying a heat shock treatment to the
internal surfaces.
2. A method according to claim 1 wherein the internal surfaces are
subject to thermal expansion and/or contraction during the heat
shock treatment.
3. A method according to claim 2 wherein the internal surfaces are
caused to expand by heating and/or contract by cooling whereby the
differential rate of expansion and/or contraction between the
surfaces and the deposits results in cracking of the deposits.
4. A method according to claim 3 wherein cooling the surfaces is
effected by flushing the apparatus with cold water.
5. A method according to claim 3 wherein heating the surfaces is
effected by heating water in the apparatus.
6. A method according to claim 3 wherein heating the surfaces is
effected by heating the surfaces directly.
7. A method according to claim 6 wherein the surfaces are directly
heated by resistance heater(s) surrounding or embedded in the
surfaces.
8. A method according to claim 3 wherein the surfaces are
alternately heated and cooled in any order.
9. A method according to claim 7 wherein one or both steps of
heating and cooling the surfaces is repeated.
10. A method according to claim 1 wherein deposits that break away
from the internal surfaces are collected and periodically
removed.
11. A method according to claim 1 wherein the internal surfaces are
low friction surfaces.
12. A method according to claim 1 wherein the internal surfaces are
subjected to a change in temperature during the heat shock
treatment producing forces that exceed the forces experienced
during normal operation of the apparatus.
13. A method of operating a water heater comprising the steps of
heating water in a tank to an elevated temperature, and
periodically applying a heat shock treatment to remove deposits
adhering to the internal surfaces by switching the water heater off
and flushing the tank with cold water to cause thermal contraction
of the internal surfaces, and switching the water heater on after
the cold flush to heat water in the tank.
14. A method according to claim 13 wherein the water heater is
operable to maintain the water at the elevated temperature in a
stand-by mode between heat shock treatments.
15. A method according to claim 14 wherein the water heater is
operable during the stand-by mode to provide a source of hot water
at a temperature higher than the elevated temperature.
16. Apparatus for heating water comprising a tank for holding water
to be heated and means for heating water in a tank, wherein the
tank has low adhesion internal surfaces by means of which deposits
adhering to the internal surfaces can be removed by applying a heat
shock treatment to the internal surfaces.
17. Apparatus according to claim 16 wherein the tank is made of
metal provided with low adhesion internal surfaces by a lining of a
material to which deposits adhere less strongly than the metal of
the tank.
18. Apparatus according to claim 17 wherein the lining is inert to
water and capable of withstanding temperature changes occurring
during operation of the water heater without degrading to any
appreciable extent.
19. Apparatus according to claim 18 wherein lining material is
polytetrafluoreothylene (PTFE).
20. Apparatus according to claim 18 wherein the lining is
pre-formed for insertion in the tank.
21. Apparatus according to claim 18 wherein the internal surfaces
of the tank are coated with material to form the lining.
22. Apparatus according to claim 16 wherein the tank has a base
wall and side walls upstanding from the base wall of which at least
the side walls have low adhesion internal surfaces.
23. Apparatus according to claim 22 wherein the side walls are
inclined relative to the base wall at an angle of less than
90.degree. so as to converge in a direction away from the base
wall.
24. Apparatus according to claim 16 wherein the heating means is
positioned internally or externally of the tank.
25. Apparatus according to claim 24 wherein the heating means
comprises at least one electrical heating element positioned within
the tank.
26. Apparatus according to claim 25 wherein the or each electrical
heating element located within the tank is positioned in the upper
half of the tank.
27. Apparatus according to claim 16 wherein the tank is adapted to
enable deposits that have broken away from the internal surfaces to
be removed.
28. Apparatus according to claim 27 wherein the tank is provided
with a removable sump at the bottom that can be detached for
disposal of deposits collected therein and the sump re-attached for
continued use of the water heater.
29. Apparatus according to claim 27 wherein the tank is provided
with an openable drain at the bottom through which deposits
settling on the bottom of the tank can be flushed.
30. Apparatus according to claim 16 wherein the tank has an inlet
for connection to a water supply and an outlet from which water can
be discharged from the tank.
31. Apparatus according to claim 30 wherein the inlet and/or outlet
have low adhesion internal surfaces.
32. A water purifier comprising apparatus according to claim
16.
33. A beverage dispenser including apparatus according to claim
16.
34. A beverage dispenser according to claim 33 wherein the heating
means is operable to maintain the water at an elevated temperature
in a stand-by mode of operation.
35. A method according to claim 7 wherein the surfaces are
alternately heated and cooled in any order.
36. A method according to claim 8 wherein one or both steps of
heating and cooling the surfaces is repeated.
37. A method according to claim 36 wherein deposits that break away
from the internal surfaces are collected and periodically
removed.
38. A method according to claim 10 wherein the internal surfaces
are low friction surfaces.
39. A method according to claim 11 wherein the internal surfaces
are subjected to a change in temperature during the heat shock
treatment producing forces that exceed the forces experienced
during normal operation of the apparatus.
40. Apparatus according to claim 19 wherein the lining is
pre-formed for insertion in the tank.
41. Apparatus according to claim 19 wherein the internal surfaces
of the tank are coated with material to form the lining.
42. Apparatus according to claim 21 wherein the tank has a base
wall and side walls upstanding from the base wall of which at least
the side walls have low adhesion internal surfaces.
43. Apparatus according to claim 23 wherein the heating means is
positioned internally or externally of the tank.
44. Apparatus according to claim 26 wherein the tank is adapted to
enable deposits that have broken away from the internal surfaces to
be removed.
45. Apparatus according to claim 29 wherein the tank has an inlet
for connection to a water supply and an outlet from which water can
be discharged from the tank.
46. A water purifier comprising apparatus according to claim
31.
47. A beverage dispenser including apparatus according to claim
31.
48. A beverage dispenser according to claim 31 wherein the heating
means is operable to maintain the water at an elevated temperature
in a stand-by mode of operation.
Description
[0001] This invention relates to liquid heating apparatus. The
invention is especially concerned with a method for removing
deposits that form during operation of liquid heating apparatus and
to liquid heating apparatus in which the removal of such deposits
is facilitated. The invention has particular, but not exclusive,
application to water heaters, boilers and similar apparatus.
[0002] For convenience, the invention will be described hereinafter
with reference to apparatus for heating water but it will be
understood that the invention is not limited thereto and has
application generally to apparatus for heating liquids where
removal of deposits formed during operation of the apparatus is
desirable.
[0003] Accordingly, as used herein the term "water" is intended to
include any liquid from which deposits may be formed when heated
and is to be construed accordingly.
[0004] A common problem, especially in water heaters, is the
accumulation of deposits on the internal walls, in particular, but
not exclusively, calcium carbonate deposits. This occurs
particularly where the calcium carbonate content of the water is
high.
[0005] In water heaters, the build-up of such deposits can cause
problems by affecting the heating cycle and may eventually result
in premature failure of heating elements by collecting around the
heating element and causing the element to overheat and/or burn
out.
[0006] The present invention has been made from a consideration of
the foregoing problems and disadvantages of the existing water
heaters.
[0007] Thus, it is an object of the present invention to provide a
method of removing at least some of the deposits that form during
operation of water beaters and to water heaters in which removal of
such deposits is facilitated.
[0008] According to a first aspect of the invention, there is
provided a method for removing deposits from internal surfaces of
water heating apparatus by applying a heat shock treatment to the
internal surfaces.
[0009] By the invented method, deposits formed on internal surfaces
of the water heater are subjected to a heat shock treatment that
promotes cracking of the deposits and reduces the adhesion of the
deposits to the internal surfaces.
[0010] More particularly, the internal surfaces are subject to
thermal contraction and/or expansion during the heat shock
treatment. In this way, the differential rate of expansion and/or
contraction between the surfaces and the deposits results in
cracking of the deposits which break away from the surfaces and
fall to the bottom of the apparatus. For example, the internal
surfaces may be caused to expand by beating and/or contract by
cooling
[0011] Cooling the surfaces may be effected by flushing the
apparatus with cold water. Heating the surfaces may be effected by
heating water in the apparatus and/or by heating the surfaces
directly e.g. by resistance heater(s) surrounding or embedded in
the surfaces.
[0012] The steps of flushing with cold water and heating the water
may be carried out in any order. Preferably, the flushing with cold
water follows a cycle in which the water has been heated. In this
way, the thermal contraction caused by rapid flushing with cold
water is enhanced promoting cracking of the deposits and increasing
further the effectiveness of the heat shock treatment.
[0013] In a typical application, the apparatus may be operable to
provide and maintain a supply of hot water. In this case, the
apparatus is rapidly cooled down by flushing with cold water
producing thermal contraction of the internal surfaces causing the
deposits to crack and begin to break off from the internal
surfaces. The apparatus may then be rapidly heated up by heating
the water and/or the internal surfaces producing thermal expansion
of the internal surfaces causing the deposits to crack and break
away even further from the internal surfaces.
[0014] In this way, the thermal contraction and expansion of the
apparatus produced by the heat shock treatment produces forces
acting on the deposits adhered to the internal surfaces that are
more extreme than the deposits would otherwise be subjected to
under normal operating conditions of the apparatus. As a result,
the beat shock treatment enhances cracking and breaking away of the
deposits from the internal surfaces. Flushing with cold water
and/or expansion of water trapped in the deposits during reheating
may assist in breaking away any deposits that have been loosened by
cracking and are no longer tightly adhered to the internal
surfaces.
[0015] The method may include repeating one or both steps of
heating and cooling more than once. For example, we may repeat the
step of flushing the tank with cold water after the step of heating
the water in the tank.
[0016] This may further assist removal of deposits that have been
cracked and may allow the deposits to be flushed from the tank.
[0017] In a preferred arrangement, the method further includes the
step of providing a low adhesion surface on the internal surfaces
of the apparatus. In this way, breaking away of deposits that have
cracked is enhanced promoting removal of the deposits from the
internal surfaces and increasing the effectiveness of the heat
shock treatment still further. As used herein "a low adhesion
surface" is a surface to which deposits from the water adhere less
strongly than to a surface formed of stainless steel.
[0018] Advantageously, the method includes the step of collecting
deposits that have broken away from the internal surfaces and
periodically removing the deposits. For example, the deposits may
collect at the bottom of a tank in which the water is heated and
the tank is adapted to allow removal of the deposits. Thus, the
tank may be provided with an openable drain in the bottom through
which the deposits can be flushed at intervals. Alternatively, the
bottom of the tank may be in the form of a detachable sump that can
be disconnected at intervals to dispose of deposits collected
therein.
[0019] According to a second aspect of the invention, there is
provided apparatus for heating water comprising a tank for holding
water to be heated and means for heating water in the tank, wherein
the tank has low adhesion internal surfaces.
[0020] By providing the invented water beater of the present
invention with low adhesion internal surfaces, deposits adhere less
strongly to the internal surfaces and are more easily broken away
from the internal surfaces. For example, the deposits may crack and
break away from the internal surfaces when subjected to a heat
shock treatment by the method according to the first aspect of the
invention. In this way, removal of deposits from the internal
surfaces is facilitated.
[0021] The tank may be made of metal, for example stainless steel
or aluminium, provided with low adhesion internal surfaces by a
lining of a material to which deposits adhere less strongly than
the metal of the tank. The lining may be applied to all the
internal surfaces of the tank or to selected regions where it is
desired to facilitate removal of deposits formed during operation
of the water heater.
[0022] The lining material is preferably inert to water and capable
of withstanding temperature changes occurring during operation of
the water heater without degrading to any appreciable extent. A
suitable lining material is polytetrafluoroethylene (PTPE) but it
will be understood that other materials may be employed to suit any
particular application.
[0023] The lining may be pre-formed for insertion in the tank. More
preferably, however, the internal surfaces of the tank are coated
with PTFE or other suitable material to form the lining. Any
suitable method may be employed to coat the internal surfaces, for
example spraying or dipping. The lining is preferably of
substantially uniform thickness, for example from a few microns up
to about 2 mm and the coating may be applied in one or more layers
to provide the desired thickness of lining. If the lining is not
applied to all the internal surfaces, areas where it is desired not
to form the lining may be masked or otherwise treated to prevent
adhesion of the lining material.
[0024] The lining provides the tank with relatively smooth, low
adhesion internal surfaces that facilitates removal of deposits
formed during operation of the water heater by the above-described
heat shock treatment. Thus, the thermal contraction and expansion
of the tank produced by alternately flushing the tank with cold
water and then heating the water in the lank generates forces that
cause the deposits to crack and break away from the lining more
readily than from the material forming the surfaces of the tank
covered by the lining.
[0025] In an alternative arrangement, the tank may be made from a
material providing low adhesion of deposits formed on internal
surfaces of the tank. For example, the tank may be made of a
plastics material such as polyethylene by any suitable method, eg
moulding. In this arrangement, a lining of low adhesion material is
not required but the material chosen should produce sufficient
expansion and contraction of the tank under the conditions of the
heat shock treatment to cause cracking of the deposits.
[0026] Preferably, the tank has a base wall and side walls
upstanding from the base wall of which at least the side walls have
low adhesion internal surfaces. In this way, deposits that crack
and break away from the side walls during the heat shock treatment
fall to the bottom of the tank where they collect. The side walls
may extend normal to the base wall and can be of circular
cross-section, for example the tank may be of cylindrical shape.
More preferably, however, the side walls are inclined relative to
the base wall at an angle of less than 90.degree. so as to converge
in a direction away from the base wall. The side walls may have an
inclination >70.degree.<90.degree. relative to the base wall.
The inclination of the sidewalls may assist break away of the
deposits from the side walls during the heat shock treatment under
the force of gravity.
[0027] The water may be heated in the tank by any suitable means
positioned internally or externally of the tank. Preferably, the
heating means comprises at least one electrical heating element
positioned within the tank. The or each electrical heating element
may be of any type conventionally employed in water heaters. The
power rating is preferably chosen to enable the water in the tank
to be heated in relatively short period of time, especially during
the beat shock treatment to enhance cracking of deposits caused by
the thermal expansion of the tank.
[0028] The tank may have a single heating element of appropriate
power rating for both normal operation and for the heat shock
treatment. Alternatively, we may provide two or more heating
elements allowing selection of different power ratings. For
example, at least one heating element may be employed for heating
the water during normal operation of the water heater with
additional heating element(s) being employed during the heat shock
treatment. In this way, the power rating can be increased to heat
the water more rapidly during the heat shock treatment to
accelerate the thermal expansion of the tank which may further
assist cracking of deposits on the side walls.
[0029] In a preferred arrangement, the or each electrical heating
element located within the tank is positioned in the upper half of
the tank. In this way, operation of the heating element(s) is not
affected by deposits that break away from the internal surfaces of
the tank during the heat shock treatment and fall to the bottom of
the tank. As a result, the heating efficiency is maintained and the
risk of the heating element(s) overheating or burning out as a
result of deposits over-growing or burying the heating element(s)
is considerably reduced. This may lead to the useful operating life
of the heating element being extended.
[0030] The tank may be adapted to enable deposits that have broken
away from the internal surfaces during the heat shock treatment and
collected at the bottom of the tank to be removed. In one
arrangement, the tank may be provided with a removable sump at the
bottom that can be detached for disposal of deposits collected
therein and the sump reattached for continued use of the water
heater. In another arrangement, an openable drain may be provided
at the bottom of the container through which deposits settling on
the bottom of the tank can be flushed. This arrangement has the
advantage that the deposits can be removed without disassembling
the water heater.
[0031] Preferably, the tank has an inlet for connection to a water
supply, eg mains water, and an outlet from which water can be
discharged from the tank. In a preferred arrangement, the inlet
and/or outlet have low adhesion internal surfaces whereby any
deposits formed therein can be removed by the heat shock
treatment.
[0032] According to a third aspect of the invention, there is
provided apparatus for heating water comprising a tank for holding
water to be heated, the tank having a base and sidewalls upstanding
from the base, at least one electrical heating element positioned
in the tank for heating the water, the or each heating element
being positioned in an upper half of the tank spaced from the base,
and the side why of the tank being inclined at an angle of less
than 90.degree. relative to the base so as to converge in a
direction leading away from the base.
[0033] According to a fourth aspect of the present invention, there
is provided apparatus for heating water comprising a tank for
holding water to be heated, the tank having a base and sidewalls
upstanding from the base, means for heating water in the tank, the
sidewalls having low adhesion internal surfaces for assisting
removal of deposits, and the base having means for removing
deposits collected therein.
[0034] The method and apparatus according to the various aspects of
the present invention may be employed in any installation where it
is required to heat water. For example, the invented water heater
may be used as a water purifier to provide a supply of pure water
for use in a beverage dispenser such as a coffee machine,
especially in areas where the natural water supply can be of poor
quality and/or purity. In such application, the water heater may be
operable to purify the incoming water and provide a source of
purified water for supply to a dispense outlet, eg a nozzle, for
mixing with a concentrate to produce a desired beverage when
required.
[0035] Deposits that build-up during operation of the water heater
may be removed by carrying out the heat shock treatment at regular
intervals and periodically removing deposits collected at the
bottom of the water heater. The beat shock treatment may be
effected automatically by a suitable control system or it may be
initiated manually. Similarly, removal of collected deposits may be
carried out automatically by opening a drain and flushing the
deposits from the tank or it may be done manually by detaching a
removable sump.
[0036] According to a fifth aspect of the invention, there is
provided in or for a beverage dispenser having a water heater for
providing a source of hot water for dispense of a beverage and for
maintaining the water at an elevated temperature in a stand-by mode
between beverage dispenses, a method of removing deposits from
internal surfaces of the water heater comprising the steps of
switching off heating means for heating the water, and flushing the
water heater with cold water.
[0037] In use, the water heater maintains the water at an elevated
temperature and rapidly boiling the water when a beverage is to be
dispensed e.g. coffee. When the heating means is switched off and
the water heater flushed with cold water, the internal surfaces
contract causing deposits to crack and break away from the internal
surfaces. The cold flush may be effected periodically to prevent
build-up of deposits on the internal surfaces. Removal of the
deposits may be further enhanced by the expansion of the internal
surfaces when the heating means is switched on again to re-heat the
water. The cold flush way be repeated.
[0038] Features, benefits and advantages of the invention will be
apparent from the following description of exemplary embodiments
with reference to the accompanying drawings in which:
[0039] FIG. 1 is a diagrammatic representation of a water heater
according to a first embodiment of the invention after a period of
use;
[0040] FIG. 2 is a diagrammatic representation of the water heater
shown in FIG. 1 after the heat shock treatment;
[0041] FIG. 3 is a diagrammatic representation of a water heater
according to a second embodiment of the invention with inclined
side walls;
[0042] FIG. 4 is a diagrammatic representation of a water heater
according to a third embodiment of the invention with a removable
sump; and
[0043] FIG. 5 is a diagrammatic representation of a water heater
according to a fourth embodiment of the invention with a drain.
[0044] Referring first to FIG. 1 of the drawings, there is shown a
first embodiment of a water heater 1 according to the invention.
The water heater 1 has a tank 2 with a stainless steel body
comprising a base 3, sidewalls 4 upstanding from the base 3 and a
top 5. The tank 2 is cylindrical with the sidewalls 4 extending
normal to the base 3 and top 5.
[0045] Internal surfaces of the sidewalls 4 are provided with a
lining 6 of PTFE that adheres to the side walls 4 and forms a low
adhesion surface for deposits of calcium carbonate 7 produced
during operation of the water heater 1.
[0046] The tank 2 has an inlet (not shown) for connection to a
water supply and an outlet (not shown) for delivering water to be
used for any desired purpose. The tank 2 is provided with an
electrical heating element 9 in the upper half of the tank 2 spaced
from the base 3 and located below the water level for normal
operation indicated by reference numeral 8.
[0047] The heating element 9 is a conventional electrical
resistance heater typically having a power rating of 1-2 kilowatts
sufficient for heating the water in the tank. In this embodiment,
the heating element 9 is in the form of a flat, circular loop
connected to a power supply via a control system (not shown) for
switching the heating element 9 on and off. It will be understood,
however, that the heating element may be of any size or shape.
Additionally, more than one heating element may be provided to
allow the power input to the water heater to be varied by the use
of one or more heating elements in any desired combination
according to the required power input and/or heating cycle for any
application.
[0048] In use, incoming water from a supply is heated in the tank 2
by the heating element 9 to boil and purify the water for end use.
For example, the purified water may be transferred to a storage
reservoir (not use) to provide a supply of pure water for a
post-mix beverage dispenser where the water is mixed with a syrup
concentrate to produce a desired beverage. Water drawn off from the
tank 2 is replaced through the inlet and purified by heating in the
same manner.
[0049] During such operation of the water heater, deposits 7, eg.
calcium carbonate deposits, slowly build up on the lining 6 of the
side walls 4. As shown in FIG. 1, these deposits 7 eventually
bridge the gap between the lining 6 and the heating element 9 and,
if uncontrolled, would continue to grow over the heating element 9.
This can have an adverse affect on the heating cycle and may lead
to premature failure of the heating element 9 where the formation
of the deposits 7 causes the heating element 9 to overheat and burn
out.
[0050] In accordance with the present invention, a heat shock
treatment is carried out to remove the deposits 7 by switching off
the heating element 9 and flushing the tank 2 with cold water, and
then switching the heating element 4 back on and heating the water
in the tank 2.
[0051] Flushing the tank 2 with cold water causes the metal body of
the tank 2 to contract as it is rapidly cooled by the cold water.
Subsequent heating of the water causes the metal body of the tank 2
to expand as it is rapidly heated by the hot water. This rapid
thermal contraction and thermal expansion generates forces that
cause the deposits 7 on the lining 6 to crack. As a result of the
low adhesion of the deposits 7 to the lining 6, the deposits 7
readily break away from the lining 6 and fall to the bottom of the
tank 3 where they collect on the base 3 as indicated by reference
numeral 7' in FIG. 2. In a modification (not shown), the tank 2 may
be provided with heating means surrounding or embedded in the side
walls 4 for effecting heating to cause thermal expansion of the
tank 2 during the heat shock treatment. This may be employed in
addition to or in place of heating the water in the tank 2
following the cold flush.
[0052] Removal of deposits 7 in this way may be carried out at
predetermined intervals by initiating the heat shock treatment
either manually by the user or service engineer or automatically by
means of a suitable control system (not shown). The deposits 7'
collected at the bottom of the tank 3 do not have any significant
adverse affect on the heating cycle and, by locating the heating
element 9 in the upper half of the tank 2, the heating element 9 is
clear of the deposits 7'. As a result, the operating life of the
heating element 9 may be usefully extended.
[0053] More particularly, the low adhesion of the deposits 7 to the
lining 6 coupled with the heat shock treatment has been found to
result in the deposits 7 breaking away in relatively small pieces.
In this way, a large mass of deposits 7' can be collected before
operation of the heating element 9 is adversely affected by
build-up of the deposits 7' removed from the lining 6 by the heat
shock treatment.
[0054] As will now be appreciated, the heat shock treatment
produces rapid changes in temperature with the resulting thermal
contraction and expansion of the tank body producing forces that
exceed those generated during normal operation of the water heater.
Thus, thermal changes during the heat shock treatment occur more
rapidly and over a wider temperature range than during normal
operation of the water heater 1.
[0055] In particular, the addition of cold water to replace water
discharged from the tank 2 during normal operation does not produce
the same rapid cooling effected by flushing the tank 2 with cold
water and may not be followed immediately by rapid heating of the
water again. The extreme conditions created under the heat shock
treatment are believed to result in more extensive cracking of the
deposits 7 than would otherwise occur and, coupled with the low
adhesion of the deposits 7 to the lining 6, is thought to result in
the successful removal of the deposits 7.
[0056] Referring now to FIG. 3, a second embodiment of a water
heater according to the present invention is shown in which like
reference numerals in the series 100 are used to indicate parts
corresponding to the first embodiment.
[0057] The second embodiment differs from the first embodiment by
having side walls 104 of the tank 102 that are inclined at an angle
of about 75.degree. relative to the base 103 and converge in a
direction leading away from the base 103. As a result, the tank 102
is wider at the base 103 than the top 105.
[0058] The inclination of the side walls 104 is believed to assist
deposits 107 that have been cracked by the heat shock treatment to
the break off from the lining 106 under the force of gravity for
collection at the base 103 of the tank 102. In other respects, the
construction and operation of the water heater 101 is similar to
the first embodiment.
[0059] With reference now to FIG. 4 of the drawings, a third
embodiment of a water heater according to the present invention is
shown in which like reference numerals in the series 200 are used
to indicate parts corresponding to the first embodiment.
[0060] The third embodiment differs from the first embodiment by
having a detachable sump 210 at the base 203 of the tank 202. The
sump 210 is releasably secured by any suitable means providing a
fluid tight connection indicated generally by reference numeral
211. The sump 210 collects deposits 207' that have been removed
from the side walls 204 by the beat shock treatment and can be
detached at regular intervals to discard the deposits 207' and
re-attached to allow continued use of the water heater 201.
[0061] In this way, the useful operating life of the water heater
201 may be further extended by preventing buildup of a significant
mass of deposits 207 in the base 203 of the water heater 201
sufficient to interfere with the heating cycle and/or operation of
the beating element 209. As a result, the heating element 209 may
be located at a lower position within the tank 202. The
construction and operation of this embodiment is otherwise similar
to the first embodiment.
[0062] Referring now to FIG. 5 of the drawings, there is shown a
fourth embodiment of a water heater according to the present
invention in which like reference numerals in the series 300 are
used to indicate parts corresponding to the first embodiment.
[0063] In this embodiment, the tank 302 is provided with a drain
312 in the base 303 of the tank 302. The drain 312 is closed by a
valve during normal operation of the water heater 301. The valve
can be operated manually or automatically to open the drain 312
when it is desired to flush out of the tank 302 deposits 307'
broken off from the lining 306 during the heat shock treatment and
collected at the base 303 of the tank 302.
[0064] This arrangement enables the deposits 307' to be removed by
controlling operation of the valve 313 through the control system
to effect removal of the deposits 307' at regular intervals. This
may be beneficial in allowing longer intervals between servicing
the apparatus. The construction and operation of this embodiment is
otherwise similar to the first embodiment.
[0065] Although, the invention has been described with reference to
the exemplary embodiments it will be understood that the invention
is not limited thereto and that various modifications can be made
within the spirit and scope of the invention.
[0066] For example, the water heater may form part of a beverage
dispenser for hot beverages, eg tea or coffee, where the water
heater delivers hot water for the beverage to an outlet on demand.
Alternatively, the water heater may form part of a water
sterilisation apparatus where the water heater delivers purified
water to a storage reservoir.
[0067] The low adhesion surfaces may be provided on all the
internal surface of the tank or at least those internal surfaces
where deposits are formed. For example, the base and sidewalls of
the tank may be provided with low adhesion internal surfaces. The
inlet and/or outlet pipe connections may also be provided with low
adhesion surfaces.
[0068] Alternatively, the low adhesion surfaces may be provided in
selected areas or regions only of the tank. For example, the low
adhesion surfaces may be provided adjacent to the beating element
to allow removal of deposits that could otherwise overgrow the
heating element reducing its effectiveness and causing premature
failure of the heating element.
[0069] The low adhesion surfaces way be provided by a lining
applied to the internal surfaces of the tank body. Alternatively,
the tank body may be made of a material providing low adhesion
surfaces on the inside of the tank.
[0070] The tank may have a removable lid secured in a fluid tight
manner for access to the heating element and inspection of the
interior of the tank. This may allow manual flushing of the tank
during the heat shock treatment.
[0071] The water heater may be provided with an electrical heating
element internally or externally of the tank. Alternatively any
other suitable heating means may be employed, for example a gas
powered heater externally of the tank.
[0072] The heat shock treatment may involve carrying out the steps
of flushing with cold water and heating the water in the tank in
any order and/or repeating one or both steps more than once. For
example, we may rapidy heat the water after a quiet period followed
by flushing with cold water. In this way, the cold water flushing
may assist to break away deposits that have cracked and may remove
from the tank some or all of the deposits that have broken
away.
[0073] Although the heat shock treatment has been described in
combination with the provision of low adhesion surfaces in the
exemplary embodiments, the heat shock treatment may have
application generally to water heaters with or without low adhesion
surfaces where the thermal expansion and contraction generated by
the treatment are sufficient to cause the deposits to crack and
break away from the internal surfaces of the water heater.
[0074] It will be appreciated that the exemplary embodiments
described herein are intended to illustrate the range and
application of the invention and that features of the embodiments
may be employed separately or in combination with any other
features of the same or different embodiments to produce any
desired method and/or apparatus embodying the invention in any of
the aspects referred to herein.
[0075] Moreover, while the specific materials and/or configuration
of the apparatus and steps of the method described and illustrated
are believed to represent the best means currently known to the
applicant for carrying out the invention in each of its aspects, it
will be understood that the invention is not limited thereto and
other modifications and improvements will be apparent to those
skilled in the art and are deemed within the scope of the
invention.
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