IE85128B1 - Water heaters - Google Patents
Water heaters Download PDFInfo
- Publication number
- IE85128B1 IE85128B1 IE2004/0483A IE20040483A IE85128B1 IE 85128 B1 IE85128 B1 IE 85128B1 IE 2004/0483 A IE2004/0483 A IE 2004/0483A IE 20040483 A IE20040483 A IE 20040483A IE 85128 B1 IE85128 B1 IE 85128B1
- Authority
- IE
- Ireland
- Prior art keywords
- water
- flow
- heater tank
- heater
- inlet
- Prior art date
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 393
- 229910001285 shape-memory alloy Inorganic materials 0.000 claims description 36
- 238000010438 heat treatment Methods 0.000 claims description 34
- 230000004044 response Effects 0.000 claims description 29
- 230000000051 modifying Effects 0.000 claims description 8
- 230000001419 dependent Effects 0.000 claims description 7
- 230000000694 effects Effects 0.000 claims description 7
- 239000008236 heating water Substances 0.000 claims description 6
- 229910000990 Ni alloy Inorganic materials 0.000 claims description 3
- 229910001069 Ti alloy Inorganic materials 0.000 claims description 3
- 230000001276 controlling effect Effects 0.000 claims description 3
- 238000005485 electric heating Methods 0.000 claims description 2
- 230000005611 electricity Effects 0.000 claims description 2
- 210000000188 Diaphragm Anatomy 0.000 description 13
- 239000007921 spray Substances 0.000 description 7
- 230000004048 modification Effects 0.000 description 6
- 238000006011 modification reaction Methods 0.000 description 6
- 230000001105 regulatory Effects 0.000 description 5
- 238000004140 cleaning Methods 0.000 description 2
- 230000000875 corresponding Effects 0.000 description 2
- 235000013305 food Nutrition 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 235000015450 Tilia cordata Nutrition 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000008233 hard water Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000000717 retained Effects 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H9/00—Details
- F24H9/20—Arrangement or mounting of control or safety devices
- F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
- F24H9/2014—Arrangement or mounting of control or safety devices for water heaters using electrical energy supply
- F24H9/2028—Continuous-flow heaters
Abstract
ABSTRACT An instantaneous water heater has a heater tank (1) and a water inlet control Valve (2) with two water inlets (5), (6) connected to an incoming water supply and a water outlet (7) connected to a water inlet (3) of the heater tank (1). The inlet (5) has a flow regulator (8) to provide a minimum flow rate at the outlet (7), and the other inlet (6) communicates with the outlet (7) Via a pressure balanced Valve (1 1). Water flow to the inlet (5) by—passes the pressure balanced Valve (11) and the pressure balanced valve (11) is responsive to the outlet water temperature from the tank (1) to supplement water flow to the tank (1) to maintain a selected outlet water temperature.
Description
Water Heaters
This invention relates to water heaters and in particular instantaneous
water heaters of the kind in which water is heated as it flows through a
heater tank to provide a source of hot water on demand. Instantaneous
water heaters are widely used to provide hot water in a variety of
installations such as showers and hand washers.
Typically. the heater tank is provided with one or more electrical heating
elements over which the water flows and the temperature of the water
emitted from the heater tank is user controlled by varying the rate of flow
of water through the heater tank. For a given flow rate and power input,
the temperature of the water is raised by a fixed amount and the output
water temperature can be affected by variations in water pressure. mains
voltage and inlet water temperature.
Water pressure variations, which affect the rate of flow and hence
temperature are usually compensated for by a flow regulating valve. A
common type of flow regulating valve employs an O-ring operable in
response to the water pressure to adjust the size of flow passages to
control the flow rate. More sophisticated systems make use of an output
water temperature sensor with electronic feedback and control to adjust
the flow regulating valve to control the flow rate.
Mains voltage variations, which affect the power input and hence
temperature, and inlet water temperature variations, which affect the
outlet water temperature, are less easily catered for and are typically only
provided in the more sophisticated systems employing electronic feedback
and control which adds to the cost.
E85130
Attempts have been made to provide thermostatic control of the
temperature of the output water without electronic feedback and control
by mixing a fixed flow of hot water from the heater tank with a separate
flow of cold water via a mixing valve actuated by a wax element
responsive to the output water temperature to adjust the mixing valve to
maintain the selected output water temperature substantially constant.
The problem with this non electronic type of thermostatically controlled
instantaneous electric water heater is that the fixed flow of hot water from
the heater tank has to be fixed low enough to allow the water heater to
give sufficiently hot water when the inlet water temperature is very cold
during the winter months. Conversely, during the summer months when
the inlet water temperature is much higher, the fixed flow of water from
the heater tank is very hot and this has the undesired effect of depositing
more lime scale on the heater elements than would occur in a normal
water heater.
Another problem with this type of water heater is that it also has the
effect of producing scalding shots of hot water when the control knob of
the output mixer valve is rapidly operated. for example to increase _the
output water temperature from 259C to 409C.
The present invention has been made from a consideration of the
foregoing problems and disadvantages of existing instantaneous water
heaters.
Thus it is an object of the present invention to provide an instantaneous
water heater capable of compensating for variations in one or more of the
water pressure, power input and inlet water temperature in a reliable
manner.
According to a first aspect of the present invention, there is provided an
instantaneous water heater comprising a water heater tank, means for
heating water flowing through the heater tank, first means for supplying
cold water to the heater tank with a constant flow rate, and second means
for supplying cold water to the heater tank with a variable flow rate. the
first means providing a substantially fixed flow and the second means
providing a variable flow additional to the fixed flow of the first means in
response to the outlet water temperature from the heater tank, wherein the
variable flow is added to the heater tank separately from the fixed flow
for modulating the flow of cold water flowing through the heater tank for
heating by the heating means.
By this invention. the first means inputs cold water with a constant flow
rate to the heater tank and the second means inputs additional cold water
with a variable flow rate to the heater tank separately to adjust the total
flow of cold water supplied to the heater tank to control the outlet water
temperature.
In one arrangement, the first means is a cold water by-pass that provides
a fixed flow of cold water and the second means is an inlet control valve
that is adjustable in response to the outlet water temperature to provide a
variable additional flow of cold water in accordance with user selection of
a desired outlet water temperature.
Preferably, the inlet control valve controls the additional flow of cold
water into the heater tank by sensing the output temperature via an
actuator which directly acts on the valve to control the additional input
flow.
In this way. the inlet control valve controls its own input flow dependent
on the output temperature from the heater tank. As a result, the
temperature within the heater tank remains predominantly the same as the
user selected output temperature no matter what the temperature of the
input water may be.
Preferably, the actuator comprises a memory alloy having elastic
properties responsive to the outlet water temperature and the flow control
valve is operable in response to an applied force by the actuator to control
the additional input flow. More especially, the memory alloy actuator
preferably has a modulus that changes with temperature, and more
preferably has a modulus that increases with increase in temperature, to
vary an actuating force applied to the flow control valve. Suitable
memory alloys include nickel/titanium alloys.
In one embodiment, the flow control valve is biased towards a closed
position by a biasing element that is opposed by the actuating force
applied by the memory alloy actuator. In this way, the control valve
adopts an equilibrium position where the biasing element and opposing
memory alloy actuator coil are compressed by an amount according to the
stiffness of the biasing element and the memory alloy actuator. The
stiffness of the memory alloy actuator is a function of its modulus which
varies with temperature such that the equilibrium position of the flow
control valve changes in response to the outlet water temperature to vary
the additional input flow of cold water to the heater tank.
The memory alloy actuator may be in the form of a helical coil capable of
changing length as the stiffness (modulus) changes in response to the
outlet water temperature to adjust the position of the control valve. In
this way, the memory alloy actuator responds rapidly with the result that
hot shots associated with wax element type actuators when the water
temperature is adjusted or when the heater is re-started shortly after being
shut down may be significantly reduced if not eliminated.
The reaction time of the memory alloy actuator may be further enhanced
when it is used in conjunction with ‘a relatively low capacity heater tank.
For example, instantaneous electric water heaters used for ablutionary
showers typically have a heater tank capacity of about 250ccs and the
present invention using a memory alloy actuator to control the inlet
control valve can be employed with heater tanks having a capacity as low
as 20ccs.
We have found that a heater tank with a low capacity of the order of
20ccs can reach a selected water temperature within 1 second of turning
the unit on. This compares with 20 seconds for a typical instantaneous
water heater employing a larger capacity heater tank without the inlet
control valve of the present invention.
This is of particular benefit in a variety of applications where
instantaneous water heaters are used to provide a source of hot water on
demand. For instance, the present invention enables instantaneous
electric water heaters for showering and hand washing to give an
immediate supply of hot water to the user without waiting for hot water to
feed through.
It has been noted with electric showers that users will often switch the
shower on without getting under the spray so as to avoid being subjected
to an initial spray of cold water. This can result in the user leaving the
shower for some time to reach a stable condition before getting under the
spray which is wasteful of water and energy.
It has also been noted with electric hand washers that users will not wait
for hot water to feed through but use the initial cold stream for washing
and then turn the unit off which may not provide adequate cleaning. This
can be a particular problem where the hand washers are deployed in food
preparation areas where regular hand cleaning is required for health and
safety reasons to avoid contamination of food.
Preferably, the cold water by-pass is connected to an inlet at one end of
the heater tank, typically the lower end, and the hot water outlet is
provided at the opposite end or communicates with the opposite end of the
heater tank.
In one embodiment, the cold water inlet control valve is connected to
another inlet separate from the inlet for the cold water by-pass. The inlet
for the cold water inlet control valve may be spaced from the inlet for the
cold water bypass in the direction of flow of cold water through the
heater tank.
In this way, the heat input to the heater tank has a reduced effect on the
additional flow of cold water from the cold water inlet control valve. As
a result, the effect of the additional flow of cold water on the temperature
of the hot water flowing out of the heater tank is enhanced and response
times may be reduced leading to improved temperature control and
stability of the operating conditions. More specifically, the additional
flow of cold water added to the heater tank from the inlet control valve
combines with the flow of water from the cold water by-pass and provides
a negative feed back effect that not only reduces further increase in water
temperature but may lead to a reduction in water temperature.
The inlet for the cold water inlet control valve may be located at any
position between the inlet for the cold water by-pass and the outlet for hot
water from the heater tank. Preferably, the inlet for the cold water
control valve is positioned closer to the hot water outlet than the cold
water by-pass inlet and may be arranged substantially at the outlet.
In a preferred arrangement, a plurality of separate inlets may be provided
for adding cold water from the cold water inlet control valve at several
locations axially and or circumferentially spaced apart. In this way, the
additional flow of cold water may be controlled to optimise mixing and
control of the outlet water temperature.
Advantageously, the cold water by-pass includes a flow regulator for
maintaining a fixed or constant flow rate of cold water by-passing the
inlet control valve for supply to the heater tank. As a result, the
additional flow of cold water from the inlet control valve modulates the
flow of cold water flowing through the heater tank.
The additional flow of cold water from the inlet control valve may be
split and a small proportion directed within the vicinity of the temperature
responsive actuator in order to provide negative feedback. In this way,
response times may be further enhanced.
Preferably, the inlet control valve is a pressure balanced valve having a
valve member axially movable relative to a valve seat to open and close a
transfer port in response to axially opposed forces applied to the valve
member by the biasing element and by the temperature responsive
actuator. In this way. operation of the inlet control valve is independent
of any variations in the pressure of the cold water supply.
The biasing element may be a return spring. The spring biasing may be
adjustable, for example by a user operable control such as a knob or
lever, to vary the actuator force required to overcome the biasing and
open the cold water inlet control valve. In this way, the output
temperature of the hot water from the heater tank may be adjusted
according to user selection.
Alternatively, the biasing element may be a temperature responsive
actuator exposed to the cold water inlet temperature. This actuator may
be a memory alloy actuator similar to the memory alloy actuator
responsive to the outlet water temperature. In this way, the actuator
responsive to the cold water inlet temperature adjusts the force required
to open the cold water inlet control valve in response to changes in
temperature of the incoming cold water supply.
In one embodiment, the temperature responsive actuator is arranged
externally of the heater tank. In another embodiment, the temperature
responsive actuator is arranged internally of the heater tank.
The power input to the heater tank may be provided by any suitable
energy source for example electricity, gas or oil. Preferably, the heater
tank is provided with one or more electrical heating elements.
The heating elements may be printed circuit heating elements applied to a
surface of the heater tank over which the water flows. Alternatively, the
heating elements may be resistance heating elements positioned within the
heater tank over which the water flows.
The power input may be fixed or adjustable. For example, a user
operable control may be provided for user selection of the power input.
In this way, for a selected outlet water temperature, the flow rate may be
altered by adjusting the power input. In this way, for application to
showers, the spray force may be altered.
According to a second aspect of the invention, there is provided an
instantaneous water heater comprising a water heater tank, first means for
supplying the heater tank with a substantially fixed minimum flow of cold
water, and second means for supplying the heater tank with a variable
flow of cold water in addition to the fixed minimum flow, the heater tank
being provided with means for heating water flowing therethrough and
outputting water having a temperature according to user selection,
wherein variable flow is input to the heater tank separately from the fixed
minimum flow and the second means is operable in response to the
temperature of the water output from the heater tank to adjust the flow of
water through the heater tank for heating by the heating means to achieve
the selected temperature of the water output from the heater tank.
According to a third aspect of the present invention, there is provided a
method of controlling the outlet water temperature from an instantaneous
water heater comprising providing a heater tank with means for heating
water flowing therethrough, providing a cold water inlet control valve
responsive to the outlet water temperature from the heater tank for
supplying cold water to the heater tank with a variable flow rate, and
providing a cold water input to the heater tank by-passing the inlet control
valve for supplying cold water to the heater tank with a constant flow rate
separately from the variable flow rate, wherein, in use, the cold water
input provides a fixed flow of cold water to the heater tank and the cold
water inlet control valve provides a separate variable flow of cold water
to the heater tank additional to the fixed flow for modulating the flow of
cold water flowing through the heater tank for heating by the heating
means in response to the outlet water temperature.
The invention will now be described in more detail. by way of example
only, with reference to the accompanying drawings wherein:
Figure 1 shows an instantaneous electric water heater not according to the
invention with parts of an inlet control valve being shown in section;
Figure 2 is a section through the water inlet control valve shown in
Figure 1;
Figure 3 shows an instantaneous electric water heater according to a first
embodiment of the invention;
Figure 4 shows an instantaneous electric water heater according to a
second embodiment of the invention with parts of the heater tank and inlet
control valve being shown in section; and
Figure 5 shows a detail of the inlet control valve of Figure 4 to an
enlarged scale;
With reference to Figures 1 and 2 of the accompanying drawings. there is
shown an instantaneous electric water heater including a heater tank l and
a water inlet control valve 2. The water heater may be employed in an
ablutionary installation to provide a source of hot water for a shower or
hand washer. .
The tank 1 has a cold water inlet 3 at the bottom and a hot water outlet 4
at the top. In this embodiment, the tank 1 is of rectangular shape with
printed circuit heating elements (not shown) on one or both side walls of
the tank 1. The side walls are closely spaced to provide a thin, slim-line
construction of tank 1 having a volume of approximately 20ccs.
The water inlet control valve 2 has a pair of cold water inlets 5, 6 and a
cold water outlet 7. The inlets 5. 6 are connected to an incoming cold
water supply, for example mains cold water, via an onloff valve (not
shown) operable by the user. The outlet 7 is connected to the inlet 3 to
the heater tank 1.
One of the inlets 5 is provided with a flow regulator 8 operable to provide
a minimum fixed flow rate at the outlet 7. The flow regulator 8 may be
of any suitable type and in this embodiment comprises an O-ring 9
surrounding a central core 10 provided with a series of longitudinal
grooves (not shown) in the outer surface that define with the O-ring 9
flow passages. The 0-ring 9 is deformable in response to changes in the
water pressure to vary the cross-sectional area of the flow passages to
maintain the minimum fixed flow rate.
The other inlet 6 communicates with the outlet 7 via a pressure balanced
valve 11 responsive to the outlet water temperature from the heater
tank 1. The valve 11 comprises a poppet valve member 12 biased at one
end by a return spring 13 to a closed position in which a sealing element
14 carried by a valve head 15 engages an annular valve seat 16 closing a
transfer port 17 to isolate the inlet 6 from the outlet 7.
The water inlet control valve 2 also has a hot water inlet 18 connected to
the hot water outlet 4 from the heater tank I and a hot water outlet 19.
The hot water outlet 19 may be connected to an outlet fitting of a shower
or hand washer. For example, the outlet l9 may be connected to a
shower handset (not shown) via a flexible hose (not shown).
The other end of the poppet valve member 12 is operatively connected to
an actuator 20 positioned in a chamber 21 between the hot water inlet 18
and hot water outlet 19. The actuator 20 comprises a helical coil 22 of
memory alloy having elastic properties responsive to the temperature of
the output hot water from the heater tank 1 to adjust the force applied by
the coil 22 to the poppet valve member 12 that opposes the biasing of the
return spring 13. In this embodiment, the coil 22 is a nickel/titanium
alloy having a modulus (stiffness) that increases with temperature to vary
the force applied to the poppet valve member 12 opposing the biasing of
the return spring 13.
The return spring 13 acts between the poppet valve member 12 and a
spring seat 23. A setting member 24 threadably engages the spring seat
23 and is rotatable via a user operable control such as a temperature
control knob or lever (not shown) to axially adjust the position of the
spring seat 23 to set the actuating force required to overcome the biasing
of the return spring 13 to move the poppet valve member 12 to open the
transfer port 17.
The actuating force applied to the poppet valve member 12 is dependent
on change in stiffness (modulus) of the actuator 20 which in turn is
dependent on the temperature of the output hot water from the heater tank
1. In this way, the user can adjust the outlet water temperature at which
the transfer port 17 is opened.
In use, when the water heater is switched on, the control valve 2 is closed
and cold water is initially introduced in to the heater tank 1 via the flow
regulator 8 which ensures a minimum fixed flow rate that by-passes the
inlet control valve 2.
A device (not shown) is provided to detect the presence of water either
prior to or after energy has been applied via the heating elements to the
water flowing through the heater tank 1. Devices that assume the
presence of water prior to the energy being applied normally take the
form of a diaphragm pressure or flow switch but could also be an
electronic flow detector. A device that detects that no water is present
after the application of energy could take the form of a heat sensitive
switch, typically a bimetal switch that senses the temperature of the
heating elements.
When the temperature of the hot water from the heater tank 1 exceeds that
set by the user via the setting member 24. the force applied to the poppet
valve member 12 by change in stiffness (modulus) of the actuator 20
overcomes the biasing of the return spring 13 and moves the poppet valve
member 12 to open the transfer port 17 allowing cold water to flow from
the inlet 6 to the outlet 7 to supplement the flow of cold water from the
flow regulator 8.
In this way, the flow of cold water through the tank 2 is increased to
maintain the selected temperature of the outlet water from the heater
tank 1. The water heater may include a user operable control to allow the
user to select different power settings to vary the flow rate and thus the
spray force for any selected temperature of the outlet water from the
heater tank 1.
The inlet control valve 2 has a high-pressure diaphragm 25 and a low-
pressure diaphragm 26 which balance the forces of pressurised water
across the valve 2 and the transfer port 17 so that no matter what pressure
is applied, the resultant forces are substantially zero. In this way, the
forces generated by the actuator 20 and the return spring 13 are the only
forces that control the operation of valve 2.
More particularly, the diaphragms 25, 26 are sized so as to be the same
effective diameter as the poppet valve sealing element 14 and valve seat
l6. There are three pressure levels to be balanced. The First, and
highest, is the mains inlet water pressure that acts on the diaphragm 25 to
open the control valve 2 and on the poppet valve member 12 to close the
control valve 2. As the diameters are equivalent, the inlet water pressure
forces are balanced and there is no resultant force acting on the valve
mechanism. The next highest pressure region is the inlet water pressure
to the heater tank 1. This acts on the poppet valve member 12 to open
the control valve 2 and on the diaphragm 26 to close the control valve 2.
Again the effective diameters are the same so there is no resultant force
due to the inlet water pressure to the heater tank 1 influencing the
position of the poppet valve member 12. The third pressure region is the
outlet water pressure from the heater tank I which is also the inlet water
pressure to a shower spray or similar. The outlet pressure which acts on
the memory alloy actuator side of diaphragm 26 and tends to open the
poppet valve member 12 may be substantially balanced by connecting
chamber 27 containing the return spring 13 and acting on diaphragm 25
tending to close poppet valve member 12 to atmosphere via inlet 28. In
this way, the hydraulic pressures tending to influence the position of the
poppet valve member 12 can be substantially balanced.
In some cases, however, the shower spray can become partially blocked,
for example due to limescale deposits, particularly where there is hard
water, and this could give rise to a significant outlet pressure acting on
the diaphragm 26 tending to open the poppet valve member 12.
Accordingly, in a modification (not shown). the outlet waterway from the
heater tank 1 may be connected to the chamber 27 to balance any change
in the outlet pressure acting on diaphragm 26.
If the temperature of the outlet water from the heater tank 1 increases or
decreases due to changes in inlet water temperature or voltage or any
other reason, then the actuator 20 senses the change and adjusts the
opening of the control valve 2 in order that the system is brought to a new
equilibrium condition at predominantly the same user set temperature.
In this way, the outlet water temperature is thermostatically controlled by
modulating the flow of cold water through the control valve 2 in addition
to the minimum fixed flow of cold water that bypasses the control
valve 2.
In the above-described embodiment, the heater tank 1 has a relatively low
volume of approximately 20ccs. As a result. changes in the outlet water
temperature from the heater tank 1 can be compensated in a relatively
short period of time by combining the additional flow of cold water from
the control valve 2 with the fixed flow from the inlet 5 for input to the
inlet 3 at the bottom of the heater tank 1 so as to be hardly noticeable to
the user.
We have found that the heater tank 1 can reach a selected water
temperature within 1 second of turning the unit on and when changing the
selected temperature in use. Furthermore, the selected water temperature
is maintained substantially constant in response to changes in any one of
the water pressure, inlet water temperature and mains voltage.
Moreover, on shut-down, hot water is flushed from the heater tank 1 and
the residual heat of the heating elements dissipated. As a result, hot shots
in use of the water heater and when re-starting the water heater can be
reduced if not eliminated.
Referring now to Figure 3 of the drawings, there is shown an
instantaneous electric water heater according to a first embodiment of the
invention. This first embodiment is a modification of the water heater
shown in Figures 1 and 1 and like reference numerals in the series 100
are used to indicate corresponding parts.
In this embodiment of the invention, the heater tank 101 is of cylindrical
shape containing one or more electrical heating elements (not shown) and
has a larger volume of approximately 250ccs. The heating elements
extend from the upper end of the heater tank 101 to the lower end and
may be linear rods or coils.
The inlet 105 of cold water inlet control valve 102 is closed with a
blanking plug 130 and the incoming cold water supply to the inlet 106 is
provided with a cold water branch 131 by-passing the valve 102 and
connected to cold water inlet 103 at the bottom of the heater tank 101.
The inlet 103 is provided with a flow regulator (not shown) operable to
provide a minimum fixed flow rate to the inlet 103 of the heater tank 101.
The outlet 107 for the modulating flow of cold water from the control
valve 102 is connected to a separate cold water inlet 132 spaced above the
inlet 103 and closer to the hot water outlet 104.
With this arrangement, the portion of the heating elements extending
below the inlet 132 towards the bottom of the heater tank 101 is subjected
to a relatively low fixed flow of cold water whilst the portion extending
above the inlet 132 towards the top of the heater tank 101 is subjected to
the fixed flow of water from the inlet 103 at the bottom of the heater
tank 101 plus the additional flow from the inlet 132.
Injecting the additional flow of cold water fromithe control valve 102
closer to the outlet 104 from the heater tank 101 allows direct control of
the top heated portion of the relatively larger capacity heater so that a
faster response to changes in the outlet water temperature from the heater
tank 101 can be achieved without oscillation of the outlet water
temperature.
The volume of the top heated portion of the heater tank 101 can be
adjusted by altering the position of the inlet 132 to vary the thermal
inertia produced by the volume of heated water, which allows the system
to achieve inherent stability.
In a modification (not shown), the additional input flow of cold water to
the heater tank in Figures 1 and 3 may be split prior to adding to the
heater tank and a small proportion diverted directly into the chamber
containing the memory alloy actuator. This may assist in making the
system more stable.
The proportional split may be made by directing the regulated input flow
through a relatively small area aperture into the chamber containing the
memory alloy actuator and a relatively larger area aperture into the heater
tank. Since the pressure prior to these apertures is equal, the rates of
flow of water is proportional to their respective aperture areas. A
proportional split in the order of 6:1 — heater tank to memory alloy
actuator chamber - has been found to give good results.
Referring to Figures 4 and 5 of the drawings, there is shown a second
embodiment of an instantaneous water heater according to the present
invention. For convenience, like reference numerals in the series 200 are
used to indicate parts corresponding to the water heaters shown in
Figures 1 to 3. In this embodiment, the cold water inlet control
valve 202 is built-into the heater tank 201 with the coil 222 of memory
alloy located inside the heater tank 201 in the direction of flow of water
through the heater tank 201 to provide thermostatic control of the outlet
water temperature via change in modulus (stiffness) of the coil 222.
As shown, the upper end of the heater tank 201 is closed by a lid 233
provided with an electric heating element in the form of a helical coil 234
that extends from the upper end to the lower end of a heat exchange
chamber 235 within the heater tank 201. Cold water inlet 203 is arranged
at the lower end of the heat exchange chamber 235 for connection to a
cold water supply such as the incoming mains cold water supply and is
provided with a flow regulator (not shown) or similar device for inputting
cold water having a substantially constant flow rate to the heat exchange
chamber 235. More than one helical coil 234 may be provided to allow
user selection of different power inputs to the heater tank 201.
The heater tank 201 is provided with an internal outlet port (not shown) at
the upper end of the heat exchange chamber 235 above the helical heater
coil 234 that opens into a passageway (not shown) that extends axially to
the lower end of the heater tank 201 and terminates in outlet 204 for
delivery of heated water from the heater tank 201. The outlet 204 may
provide a supply of hot water to a shower or a hand washer or other
ablutionary fitting. In a modification (not shown) the outlet 204 may be
provided at the upper end of the heater tank 204 as in the previous
embodiments.
The inlet control valve 202 is mounted in a fluid tight manner in a
through hole at the lower end of the heater tank 201 and has a cold water
inlet 206 for connection to the cold water supply externally of the heater
tank 201. Both inlets 203, 206 are connected to the cold water supply via
a common inlet (not shown) and an on/off valve (not shown) such as a
solenoid valve for starting and stopping water flow through the heater.
The inlet control valve 202 is biased to the closed position illustrated by
return spring 213 acting on valve member 212 via spring seat 223 and
diaphragm 225 to urge valve member 212 to engage valve seat 216 and
close transfer port 217. The transfer port 217 opens into an elongate
guide tube 236 arranged to extend towards the upper end of the heater
tank 201 within the heater coil 234.
The guide tube 236 slidably supports an actuator rod 237. The lower end
of the actuator rod 237 bears on the valve member 212. The upper end of
the actuator rod 237 projects from the guide tube 236 and supports the
temperature responsive actuator 220 for the inlet control valve 202 at the
upper end of the heater tank 201 adjacent to the outlet port.
The actuator 220 comprises helical coil 222 of memory alloy that is
guided axially in an open sleeve 239 at the upper end of the guide tube
236 and is retained at the free end by an inwardly turned flange 240. The
actuator rod 237 is axially movable to open the inlet control valve 202
against the biasing of the return spring 213 in response to change in
modulus (stiffness) of the memory alloy coil 222 when the outlet water
temperature sensed by the memory alloy coil 222 exceeds the selected
temperature.
In this embodiment, the actuator coil 222 is surrounded by the upper end
of the heater coil 223 and the heater tank 201 is provided with a flow
guide (not shown) at the upper end of the heater coil 223 that causes the
water to flow inwards over and through the actuator coil 222. In a
modification (not shown). the actuator coil 222 is supported above the
upper end of the heater coil 223 and the water is again guided over and
through the actuator coil 222 by a flow guide.
The actuator rod 237 is provided with an O-ring (not shown) in a groove
to provide a sliding seal between the actuator rod 237 and guide tube
.
substantially of X-shape in transverse cross-section to provide four
Between the lower end and the 0-ring, the actuator rod 237 is
elongate channels 241 (one only shown) extending lengthwise of the
actuator rod 237 along which water can flow when the inlet control valve
202 is open. It will be understood that the actuator rod may have any
suitable shape that permits water to flow to the holes in the guide tube
236.
The guide tube 236 is provided with a plurality of holes (not shown)
through which water in the channels 241 can flow out of the guide tube
236 into the stream of water flowing through the heat exchange chamber
235 at a plurality of positions spaced apart circumferentially and axially
of the guide tube 236 along the length of the heat exchange chamber 235.
The amount of water injected into the heat exchange chamber 235 is
controlled by movement of the valve member 212 to open the inlet control
valve 202 in response to the outlet water temperature sensed by the coil
of memory alloy.
The inlet control valve 202 is pressure balanced to substantially reduce or
eliminate the effects of water pressure on the movement of the valve
member 212 by the diaphragm 225 on the inlet side being sized to match
the effective diameter of the valve member 212 and by the O-ring on the
outlet side. In this way, operation of the valve 202 is controlled by the
opposing forces of the return spring 223 and actuator coil 222 of memory
alloy and is substantially unaffected by changes in the water pressure.
The force applied to the valve member 212 by the spring 213 to close the
inlet control valve 202 is adjustable via setting member 224 for user
selection of the outlet water temperature and the actuator 220 is operable
to open the inlet control valve 202 when the force applied to the valve
member 212 by the memory alloy coil 222 overcomes the set force of the
spring 213 to inject water into the heat exchange chamber 235 through the
holes in the guide tube 236.
With this arrangement, the injected water modulates the water flow over
substantially the whole length of the heater coil 223 and provides a rapid
response to correct any detected difference between the outlet water
temperature sensed by the actuator coil 222 and the selected outlet water
temperature. As a result, on start-up. the selected outlet water
temperature is achieved quickly and is maintained substantially constant
irrespective of changes in the pressure of the water supply or the inlet
water temperature or the voltage of the power supply to the heater coil
223.
may be enhanced.
In this way, thermostatic control of the outlet water temperature
The holes may be of the same size and uniformly spaced apart in an even
or regular pattern to distribute the added water uniformly along the length
of the heater coil 223. Alternatively, the size and/or spacing may be
chosen to provide any desired pattern of holes to vary the amount of
water added to the heat exchange chamber 235 along the length of the
heater coil 223, for example to increase the water input from the holes in
the direction of flow through the heat exchange chamber 235. In this
way. the arrangement of the holes may be chosen to optimise the response
and stability of the heater tank 201.
As will now be appreciated, the above-described water heaters employ a
cold water inlet control valve for controlling addition of cold water to the
heater tank in response to the temperature of the water output from the
heater tank. More specifically, a fixed flow of cold water is provided
that by-passes the control valve and the control valve is operable to adjust
the amount of cold water added to the fixed flow to maintain constant a
selected temperature of the outlet water.
It will be understood that the invention is not limited to the embodiments
above—described and that various improvements or modifications can be
made.
For example, the arrangement of two separate cold water inlets to the
heater tank in Figures 3 and 4 may be applied to the heater tank of
Figure 1. This may allow the capacity of the heater tank to be increased
whilst maintaining its stability and reaction time when using printed
circuit heating elements in place of traditional electrical resistance heaters
located within the heater tank.
The memory alloy actuator of the cold water inlet control valve could be
replaced with any other type of temperature responsive actuator having a
suitable response time.
The cold water inlet control valve could incorporate a secondary memory
alloy actuator on the input side of the valve which compensates for
changes in the temperature of the cold water supply by adjusting the force
required to open the valve by the actuator responsive to the outlet water
temperature in proportion to the temperature of the incoming cold water.
The pressure balanced valve could be of any other suitable type, for
example a pilot assisted diaphragm valve or a poppet valve fed from a
pressure regulator or a flow regulating core type valve.
The separate inlet for the additional. cold water flow to the heater tank
from the water inlet control valve may comprise a single inlet as in the
embodiment of Figure 3 or multiple inlets as in the embodiment of
Figures 4 and 5.
Where multiple inlets are provided they may be spaced apart axially
and/or circumferentially to provide any desired flow pattern within the
heater tank to optimize mixing and control of the temperature of the
outflowin g water.
The inlet control valve may be built-into the heater tank as shown in
Figures 4 and 5 with the actuator coil located inside the heater tank or it
may be separate as shown in Figure 3 with the actuator coil arranged
externally of the heater tank.
Where the control valve is built into the heater tank as shown in Figures 4
and 5, it may be arranged to input water into the heater tank at a plurality
of positions as described or at a single position.
In the above-described embodiments. the water heaters are described
employing electrical heating elements to heat the water flowing through
the heater tank. It will be understood, however that this is not essential
and that other energy sources could be employed such as gas or oil.
As used herein the terms “cold water” and “hot water” are used for
convenience only and refer to the water supplied to the inlet(s) of the
heater tank (cold water) and water delivered from the outlet of the heater
tank (hot water) where the inlet water is colder than the outlet water.
The terms are relative and indicate the temperature difference of the
water and are not intended to indicate any particular temperatures.
Claims (49)
1. An instantaneous water heater comprising a water heater tank, means for heating water flowing through the heater tank, first means for supplying cold water to the heater tank with a constant flow rate. and second means for supplying cold water to the heater tank with a variable flow rate, the first means providing a substantially fixed flow and the second means providing a variable flow additional to the fixed flow of the first means in response to the outlet water temperature from the heater tank, wherein the variable flow is added to the heater tank separately from the fixed flow for modulating the flow of cold water flowing through the heater tank for heating by the heating means.
2. An instantaneous water heater according to claim 1 wherein. the second means comprises an inlet control valve operable in accordance with user selection of a desired outlet water temperature.
3. An instantaneous water heater according to claim 2 wherein, the inlet control valve controls the additional flow of cold water into the heater tank by sensing the output temperature via an actuator which directly acts on the valve to control the additional input flow.
4. An instantaneous water heater according to claim 3 wherein, the inlet control valve controls its own input flow dependent on the output temperature from the heater tank such that the temperature within the heater tank remains predominantly the same as the user selected output temperature no matter what the temperature of the input water may be.
5. An instantaneous water heater according to claim 3 or claim 4 wherein, the actuator comprises a memory alloy having elastic properties responsive to the outlet water temperature and the flow control 28 valve is operable in response to an applied force by the actuator to control the additional input flow.
6. An instantaneous water heater according to claim 5 wherein, the memory alloy actuator has a modulus that changes with temperature to vary an actuating force applied to the flow control valve.
7. An instantaneous water heater according to claim 6 wherein the memory alloy actuator has a modulus that increases with increase in temperature .
8. An instantaneous water heater according to any one of claims 5 to 7 wherein the memory alloy comprises nickel/titanium alloys.
9. An instantaneous water heater according to any one of claims 5 to 8 wherein, the inlet control valve is biased towards a closed position by a biasing element that is opposed by the actuating force applied by the memory alloy actuator.
10. An instantaneous water heater according to claim 9 wherein, the inlet control valve adopts an equilibrium position where the biasing element and opposing memory alloy actuator coil are compressed by an amount according to the stiffness of the biasing element and the memory alloy actuator.
ll. An instantaneous water heater according to claim 10 wherein the stiffness of the memory alloy actuator is a function of its modulus which varies with temperature such that the equilibrium position of the flow control valve changes in response to the outlet water temperature to vary the additional input flow of cold water to the heater tank.
12. An instantaneous water heater according to any one of claims 5 to ll wherein the memory alloy actuator is in the form of a helical coil capable of changing length as the stiffness (modulus) changes in response to the outlet water temperature to adjust the position of the control valve.
13. An instantaneous water heater according to any one of claims 3 to 12 wherein the temperature responsive actuator is located within the heater tank.
14. An instantaneous water heater according to any one of claims 3 to 12 wherein the temperature responsive actuator is located outside the heater tank.
15. An instantaneous water heater according to any one of the preceding claims wherein the heater tank has a low volume of the order of 20ccs.
16. An instantaneous water heater according to any one of the preceding claims wherein, an inlet for the fixed flow is provided at one end of the heater tank, and an outlet for hot water is provided at the opposite end or communicates with the opposite end of the heater tank.
17. An instantaneous water heater according to claim 16 wherein, the heater tank is provided with an inlet for the variable flow separate from the inlet for the fixed flow.
18. An instantaneous water heater according to claim 17 wherein the inlet for the variable flow is spaced from the inlet for the fixed flow in the direction of flow of cold water through the heater tank.
19. An instantaneous water heater according to claim 18 wherein the inlet for the variable flow can be located at any position between the inlet for the fixed flow and the outlet for hot water from the heater tank.
20. An instantaneous water heater according to claim 18 or claim 19 wherein, the inlet for the variable flow is positioned closer to the outlet for hot water than the inlet for the fixed flow.
21. An instantaneous water heater according to claim 20 wherein, the inlet for the variable flow is arranged substantially at the outlet for hot water.
22. An instantaneous water heater according to claim 16 wherein the heater tank is provided with a plurality of inlets for the variable flow separate from the inlet for the fixed flow.
23. An instantaneous water heater according to claim 22 wherein the plurality of inlets for the variable flow are provided at axially and/or circumferentially spaced apart locations.
24. An instantaneous water heater according to any one of the preceding claims wherein the first means by-passes the second means for supplying cold water to the heater tank independently of the second means. 31
25. An instantaneous water heater according to any one of the preceding claims wherein, the first means includes a flow regulator for maintaining a substantially constant flow rate of cold water to the heater tank.
26. An instantaneous water heater according to claim 3 and any claim dependent on claim 3 wherein the additional flow of cold water from the inlet control valve is split prior to the heater tank and a small proportion added directly to a chamber containing the temperature responsive actuator .
27. An instantaneous water heater according to claim 3 and any claim dependent on claim 3 wherein, the inlet control valve is a pressure balanced valve.
28. An instantaneous water heater according to claim 27 as dependent on claim 9 wherein the pressure balanced valve has a valve member axially movable relative to a valve seat to open and close a transfer port in response to axially opposed forces applied to the valve member by the biasing element and by the temperature responsive actuator.
29. An instantaneous water heater according to claim 28 wherein the biasing element is a return spring.
30, An instantaneous water heater according to claim 29 wherein the spring biasing is adjustable.
31. An instantaneous water heater according to claim 30 wherein a user operable control is provided to vary the actuator force required to overcome the biasing and open the cold water inlet control valve such that the output temperature of the hot water from the heater tank may be adjusted according to user selection.
32. An instantaneous water heater according to claim 28 wherein, the biasing element is a temperature responsive actuator exposed to the cold water inlet temperature.
33. An instantaneous water heater according to claim 32 wherein the biasing element is a memory alloy actuator responsive to the cold water inlet temperature to adjust the force required to open the cold water inlet control valve in response to changes in temperature of the incoming cold water supply.
34. An instantaneous water heater according to any one of the preceding claims wherein the power input to the heater tank is provided by any one of electricity. gas or oil.
35. An instantaneous water heater according to claim 34 wherein. the heater tank is provided with one or more electrical heating elements.
36. An instantaneous water heater according to claim 35 wherein the or each heating element is a printed circuit heating element applied to a surface of the heater tank over which the water flows.
37. An instantaneous water heater according to claim 35 wherein the or each heating element is a resistance heating element positioned within the heater tank over which the water flows.
38. An instantaneous water heater according to any one of claims 34 to 37 wherein the power input is fixed or adjustable. 33
39. An instantaneous water heater according to claim 38 wherein a user operable control is provided for user selection of the power input.
40. An instantaneous water heater comprising a water heater tank. first means for supplying the heater tank with a substantially fixed minimum flow of cold water, and second means for supplying the heater tank with a variable flow of cold water in addition to the fixed minimum flow. the heater tank being provided with means for heating water flowing therethrough and outputting water having a temperature according to user selection, wherein variable flow is input to the heater tank separately from the fixed minimum flow and the second means is operable in response to the temperature of the water output from the heater tank to adjust the flow of water through the heater tank for heating by the heating means to achieve the selected temperature of the water output from the heater tank.
41. An instantaneous water heater according to claim 40 wherein the heater tank has an inlet for the fixed minimum flow and an outlet for the output water, and the second means is configured to provide the additional flow of water at a plurality of positions between the inlet and the outlet.
42. An instantaneous water heater according to claim 41 wherein the second means is arranged so that the additional flow of water is added to the fixed flow within the heater tank at a plurality of positions axially spaced apart between the inlet and the outlet.
43. A method of controlling the outlet water temperature from an instantaneous water heater comprising providing a heater tank with means for heating water flowing therethrough, providing a cold water inlet control valve responsive to the outlet water temperature from the heater tank for supplying cold water to the heater tank with a variable flow rate, and providing a cold water input to the heater tank by-passing the inlet control valve for supplying cold water to the heater tank with a constant flow rate separately from the variable flow rate, wherein, in use, the cold water input provides a fixed flow of cold water to the heater tank and the cold water inlet control valve provides a separate variable flow of cold water to the heater tank additional to the fixed flow for modulating the flow of cold water flowing through the heater tank for heating by the heating means in response to the outlet water temperature.
44. A method according to claim 43 wherein the cold water input from the inlet control valve is adjustable in accordance with user selection of any one of a range of outlet water temperatures.
45. A method according to claim 43 or claim 44 wherein the cold water from the inlet control valve is input to the heater tank at a position between an inlet to the heater tank for the fixed flow and an outlet for hot water from the heater tank.
46. A method according to claim 43 or claim 44 wherein the cold water from the inlet control valve is input to the heater tank’at a plurality of positions spaced apart between an inlet to the heater tank for the fixed flow and an outlet for hot water from the heater tank.
47. A method according to claim 46 wherein the heating means comprises one or more electric heating element extending between the inlet and the outlet and the plurality of positions for inputting cold water from the inlet control valve are spaced apart along the length of the one or more heating elements in the direction of flow through the heater tank.
48. A method according to any one of claims 45 to 47 wherein heat input to the heatertank has a reduced effect on the cold water input to the heater tank from the inlet control valve.
49. An instantaneous water heater substantially as hereinbefore described with reference to
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GBUNITEDKINGDOM17/07/20030316705.3 | |||
GBGB0316705.3A GB0316705D0 (en) | 2003-07-17 | 2003-07-17 | Water heaters |
Publications (2)
Publication Number | Publication Date |
---|---|
IE20040483A1 IE20040483A1 (en) | 2005-03-23 |
IE85128B1 true IE85128B1 (en) | 2009-02-18 |
Family
ID=
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