Note: Descriptions are shown in the official language in which they were submitted.
1236C~B8
This invention relates to apparatus for the recovery of waste
energy, particularly to a device, such as a dishwashing machine,
wherein hot water, as for a rinse cycle, is supplied directly from
a hot water heater, while waste water, such as at a lower tempera-
ture, is normally available, as from the wash cycle.
Background of the Invention
The utilization of waste heat to preheat water supplied to a
dishwasher is known, but has not been accomplished in the most
effective manner. Thus, U.S. patent 3,789,860 discloses a dish-
washer, the normal operation of which produces steam passing into
a room in which the dishwasher is installed. Instead, the steam
i8 collected in a hood and passed through a heat exchanger to
preheat incoming water which, along with the condensate from the
steam, is supplied to a pre-rinse stage of the dishwasher.
~owever, the hot water supplied for rinsing by a hot water heater,
or similar source, is not affected, so that none of the recovered
energy is utilized to reduce the fuel consumed by the hot water
heater. U.S. patent 3,946,802 discloses a method of and apparatus
for recovery of heat involving a supply pipe for supplying cold
water to a water heater and a waste pipe which is supplied with
waste water from different consumption points, including dishing
machines, washing machines, bath tubs, kitchen sewage and the
like. Such waste water is directed to a collecting receptacle
from which the waste water is either bypassed to a second
receptacle or supplied to a concurrent flow heat exchanger in
which the heat is inefficiently utilized, since the hot-test waste
water first transfers heat to the coldest incoming water.
Temperature responsive elements control the bypass flow, so that
if the waste water in the receptacle is at a lower temperature
than the incoming water reaching the concurrent heat exchanger,
the waste water will be bypassed to a second receptacle. There is
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i236~88
a probability that this system will delay unduly in responding to
a new supply of waste water, since the collecting receptacle has a
central overflow and considerable waste water could be bypassed
before the temperature sensor responds. The waste water bypassed
to the second receptacle is, in turn, bypassed to the sewer or
directed to a second concurrent flow heat exchanger, with the same
loss of efficiency and probability of undue delay in response to
incoming waste water.
Summary of the Invention
The apparatus of the invention, for conserving energy for a
device using a heated liquid from a liquid heater and producing
waste liquid at a lower temperature than the heated liquid, may
include a holding tank for collecting and releasing the waste
liquid, an elongated outlet adjacent the holding tank and into
which waste liquid from the holding tank may overflow, an upright
baffle separating the holding tank from the outlet, whereby waste
liquid from the holding tank may overflow into the outlet, a
generally horizontal screen disposed above the normal liquid level
in the holding tank through which waste liquid normally flows but
adapted to cause waste liquid to overflow into the outlet to carry
material into the outlet which retards flow through the screen,
equipment including a conduit for transferring waste liquid from
the holding tank to a heat exchanger to preheat incoming liquid
for use in the device after heating in the liquid heater, equip-
ment including a conduit for transferring the preheated liquid to
the liquid heater for heating the preheated liquid to a
temperature sufficient for use in the device and equipment
including a conduit for transferring waste liquid from the heat
exchanger to the outlet. Or, the holding tank may have a capacity
generally equal to the amount of waste water from a wash cycle and
the apparatus includes equipment for transferring waste water from
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~Z36088
the holding tank to the heat exchanger, equipment for transferring
the preheated water to a hot water heater and for transferring
waste water from the heat exchange to an outlet, as well as
equipment for controlling the transfer of waste water to the heat
exchanger at a time corresponding to the flow of heated water to
the dishwasher and responsive to the level of waste water in the
holding tank when it reaches a predetermined level. Or the
apparatus may include a housing enclosing a heat exchanger and a
holding tank, an inlet for a pump extending to a lower portion of
the holding tank, an upright baffle separating the holding tank
from an outlet, with the heat exchanger having upright coils and
one or more first conduits connecting the pump with the upper ends
of the waste liquid coils, one or more second conduits for trans-
ferring waste liquid from the lower end of the waste liquid coils
to the outlet area, one or more third conduits for supplying the
lower ends of feed liquid coils with cool liquid, one or more
fourth conduits for transferring preheated feed liquid to a heater
and equipment for starting the pump at a time corresponding to the
flow of heated liquid to the device.
The apparatus includes a device, such as a dishwasher, using
heated water from a hot water
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123601~
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heater, a countercurrent heat exchanger for preheating
the feed water to the hot water heater, a separate
tank for collecting waste water discharged from the
device and a pump for supplying the waste water to the
heat exchanger at essentially the same time that the
device requires hot water from the heater, as for
rinsing. Thus, the incoming cold feed water is
preheated at the time it is needed by the hot water
heater. A dishwasher is ideally adapted for this
usage, although the flow of collected waste water
through the heat exchanger may be timed to coincide
with hot water requirements of the device, or even
another device operated in conjunction therewith in
the case of devices other than a dishwasher. For a
dishwasher, used waste water may be collected in a
holding tank which is provided with a removable tray
and a fixed screen for straining unwanted food or the
like from the waste water. When the waste water is
sufficiently electrically conductive, the holding tank
may be provided with a series of electrodes, which
turn the motor off when a low level of waste water in
the holding tank is reached, turn the pump on when a
higher level of waste water in the holding tank is
reached, and actuate an alarm, such as a light,
buzzer, bell, etc., when an unduly high level of waste
water in the tank is reached. The holding tank may
instead be provided with a mechanical level sensor,
such as a pivoted float mounted on a stem which
actuates a switch for turning the pump motor on and
off.
The heat exchanger is preferably of the type
produced in accordance with Canadian patent No.
1,163,792 issued March 30, 1984. As disclosed
therein, each multiple tube row is wound outside the
preceding row and the tubes for the respective fluid
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~Z36088
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alternate, so that a tube carrying one fluid and
passing in one direction with respect to the
preferably hollow axis of the coil is interspaced in
its own row with tubes carrying the other fluid in the
opposite direction, as well as essentially alternating
with tubes in the rows inside and outside of the
aforesaid row. In addition, a heat conductive mastic
is compressed between the tubes as they are formed
into the spiral, generally circular rows.
The heat exchanger may be mounted at a position
adjacent to or remote from the dishwasher, such as
adjacent the hot water heater, The holding tank may
be constructed so as to be beneath the dishwasher, or
the holding tank and heat exchanger may be
incorporated as a single unit, which may conveniently
be mounted adjacent the dishwasher, such as beneath
the dish table.
The Drawings
The foregoing features, as well as additional
features, will become apparent from the following
description taken in conjunction with the accompanying
drawings, in which:
Fig. 1 is a diagram including a dishwasher, a
heat exchanger and a hot water heater to which the
principles of this invention have been applied.
Fig. 2 is a vertical section taken along line 2-2
of Fig. 1 through a holding tank mounted beneath the
dishwasher.
Fig. 3 is a condensed vertical section on an
enlarged scale, taken along line 3-3 of Fig. 2.
Fig. 4 is an enlarged perspective view of a
removable screen tray, normally positioned in the
upper portion of the holding tank.
Fig. 5 is an enlarged perspective view of a fixed
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12360~8
screen tray in the holding tank.
Fig. 6 is a side elevation of a heat exchanger and holding
tank unit.
Fig. 7 is a rear elevation of the unit of Fig. 6.
Fig. 8 is a vertical section, on a larger scale and taken
along line 8-8 of Fig. 6.
Fig. 9 is a horizontal section taken along line 9-9 of Fig.
8.
Fig. 10 is a front elevation, on the same scale of Fig. 8, of
the front wall of the holding tank, which wall is normally covered
by the front plate of a removable slide which carries a screen for
the tank.
Fig. 11 is a diagrammatic illustration of a pump control and
alarm circuit having electrodes installed in the holding tank.
Fig. 12 is a diagram of a system alternative of that of Fig.
1, which may include also a water cooled refrigerant compressor, a
grease extraction ventilator and waste food grinder.
Description of the Preferred Embodiment
As illustrated in Fig. 1 r waste energy in the waste
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form of heat is recovered from a dishwasher D for
circulation of the waste liquid from a washing or
other cycle through a countercurrent heat exchanger E,
rather than being discharged through a sewer drain.
In the heat exchanger E, incoming cold water for the
hot water heater H is preheated, with the then cooled
waste dishwasher being suitable for discharge through
the drain. The dishwasher D may be of a dual type
having a dishwashing section and a rinsing section
separated by depending flexible strips and through
which the dishes stacked on racks may be moved. The
racks are movable along conventional supporting rods
and are first moved into the dishwashing section for
washing, and then into the rinse section for rinsing.
lS These sections are conventional and the parts thereof
are therefore not shown, but are behind upper panels
10, 11 and 12. The center panel 11 may be lifted for
access to the central portion of the dishwashing space
by means of a handle 13, while an entrance door 14 and
an exit door 15 may be raised, as indicated by the
dotted lines, to permit racks for dishes to be moved
into the washing section and removed from the rinsing
section, respectively. The dishwasher may be
supported by legs 16.
The dishwasher illustrated is of a type in which
the hot rinse water received from a suitable source of
supply, such as a hot water heater, is discharged onto
the dishes as through arcuate rotating arms having
discharge holes or nozzles and normally located both
above and below the dishes, as for one minute, then
collected in a tank, such as tank 17 located behind a
panel 18. When rinsing is completed and the rinse
water has been collected in tank 17, a detergent is
added to the still hot but somewhat cooled water in
the tank, and this detergent water is pumped through
.,
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1236088
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similar rotating sprays for discharge onto the dishes
in the washing section, from both above and below, and
also recirculated by the pump from the tank through
the sprays for an appropriate period of time, such as
5 one minute. When washing is completed, the used wash
water is drained through an outlet pipe 19, as for ten
seconds, controlled by a solenoid valve 20. After a
predetermined period of time, sufficient to enable the
waste wash water in tank 17 to be drained, the
solenoid valve 20 is automatically closed and the
rinsing operation begun. Thus, the hot rinse water
will collect again in tank 17, while after the
detergent is added, the washing process may be
repeated. While this system saves the heat remaining
in the rinse water for use in washing, there is still
a considerable temperature differential between the
waste dishwater and the normal temperature of the cold
water fed to the hot water heater, even when the so-
called low temperature washing cycles are utilized.
Thus, the dishwasher D may be such a low temperature
washer in which a special detergent is utilized
permitting the wash water to be at 130F or 54C or
above and the rinse water to be at 140 P or 60 F or
above, compared with the usual requirement of 140 F to
25 150F or 60C to 66C for the wash water and 180F or
82C or above for the rinse water. Nevertheless, the
method and apparatus of this invention recovers a very
worthwhile portion of the energy normally lost, i.e.
contained in the waste wash water.
In accordance with this invention, instead of
being thrown away, the waste dishwater is drained
through outlet 19 into a holding tank T which has a
capacity equal to the collection tank 17, so that the
wash water may be passed through the heat exchanger E
during the rinse period, i.e. when cold feed water is
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flowing to the hot water heater H, since hot water is
discharged from the heater during the rinsing period.
Of course, there may be other demands on the hot water
heater, but in a restaurant, for instance, the
dishwasher is the primary equipment user of the hot
water, the hot water used for washing pans and for
washing dishes being at times as much as 90% of the
hot water produced by the hot water heater. The
method of this invention is applicable to dishwashers
in which the used rinse water, as well as used
dishwasher, would otherwise be discharged down a
drain. In such an instance, both the used rinse water
and the used dishwater may be collected in a holding
tank corresponding to tank T. As the waste water
passes through outlet 19 into holding tank T, which
outlet is connected to the top wall 21 of the tank, it
first encounters a rectangular screening tray 22, the
bottom of which is provided with a series of holes 23,
the size of which is exaggerated in Fig. 4 for
purposes of illustration, but which prevent, as far as
possible, the further flow of material which has been
removed from the dishes in the washing operation.
Tray 22 is removable through an opening 24 in the
front wall 25 of the holding tank and, as a safeguard,
a fixed screen 26 having similar holes 23 is mounted
in the holding tank beneath the removable tray 22.
The holding tank may be suspended from the underside
of the dishwasher, as by straps 27 engaging rods 28 of
Fig. 2. The sides of tray 22 are provided with
lateral flanges 30 which are received, as in Fig. 3,
by Z-shaped guides 31 attached to the underside of top
21 of the holding tank, while the front of tray 22 is
provided with a handle 32. The fixed tray 26 may be
provided with upstanding sides for attachment, as by
welding, to the inside of the side walls 33 of the
~236088
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tarlk T, a corresponding upstanding rear wall for
attachment to the rear wall 34 of the tank, and a
depending front flange 35 for attachment to the front
wall 25 of the tank. A sump 36 collects the waste
wash water for discharge through an outlet pipe 37
which connects with the sump above the bottom thereof,
so that no water will flow to a pump 38 below a
predetermined height, such as indicated by the dotted
line 39 of Fig. 3, to cause any material which may
pass through holes 23 in tray 22 or screen 26 to
collect in the bottom of the sump, for periodic
removal. The sump is box shaped and the warmed or
somewhat hot waste water is discharged by the pump 38,
during the time that hot rinse water is being supplied
to the dishwasher, through a transfer pipe 40 which is
connected to the discharge outlet of pump 38 and leads
to the waste water inlet of heat exchanger E. An
overflow pipe 41, leading to a drain, relieves excess
waste water from the holding tank T.
After passage through countercurrent heat
exchanger E, the waste water may be discharged to a
drain through a heat exchanger waste outlet 42. Also,
during the time that cold makeup water is required by
the hot water heater H, cold water flows, as indicated
by the arrow, through a pipe 43, to the lower end of
the heat exchanger and, after preheating by heat
exchange, is discharged through an outlet pipe 44
which leads to the normal cold water inlet at the
lower end of the hot water heater. Although heat may
be supplied to the hot water heater by any type of
fuel, including fuel oil or coal, it is illustrated as
being supplied with heat through gas from a gas supply
pipe 45 having a control valve 46 therein, and leading
to a gas burner 47 adjacent the lower end of the hot
water heater. The products of combustion are
lZ3G~)88
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discharged upwardly through a flue 48, while the hot
water, when called for, is discharged through an
outlet pipe 49. Of course, hot water from outlet pipe
49 will be supplied to other equipment, such as
lavatories, sinks and the like, in addition to the
dishwasher, although the heat from the washington
operation of the dishwasher is made available for
preheating incoming cold water for the hot water
heater during the time that the primary withdrawal is
taking place, i.e. for rinsing. nevertheless, even
when no waste dishwater is being supplied to the heat
exchanger E, there will still be some residual heat
from the dishwasher remaining in the heat exchanger,
in the event that other equipment requires hot water
from the hot water heater, and there is necessarily an
inflow of cold water. By this invention, not only may
the fuel required by the hot water heater be reduced,
but a saving in equipment may be made, since a smaller
capacity heater may be utilized when the amount of
B.T.U. required for heating the necessary hot water is
reduced.
An alternative construction in which the holding
tank and heat exchanger are combined in one unit,
conveniently placable adjacent the dishwasher, such as
beneath the dish table thereof, is illustrated in
Figs. 6-10. This construction includes a housing H
which, as in Fig. 7, may be placed beneath a dish
table 51 of a conventional dishwasher. The upper
portion of housing H encloses a coil assembly A,
preferably constructed in accordance with Canadian
patent No. 1,163,793, as indicated previously. The
yeneral shape of the coil assembly A is indicated
diagrammatically in Fig. 8, being essentially a
modified octagon. $he smaller, lower portion of the
housing H encloses a holding tank T', as also shown in
1236088
Fig. 8. The upper portion of the housing H, as in
Figs. 6 and 7, includes a front wall 52, side walls 53
and 54 and a rear wall 55, with a top 56 adapted to
close the upper end of the housing and a partition 57
separating the upper portion from the lower portion of
the housing H. The tank T' is enclosed by a front
wall 58, shown in Figs. 9 and 10, and side walls 59,
60 and a rear wall 61, shown in Figs. 6-9. The lower
portion of tank T' is closed by a bottom wall 62 from
which depends a rectangularly constructed sump 63
having an outlet 64, as well as a depending
cylindrical cup 65, the purpose of which will be
described later. The housing H may be supported by
legs 66 of a height to space the lower edge of sump 63
appropriately above the floor or surface on which the
unit rests.
A pipe 68, as in Figs. 6 and 7, extends from the
sump outlet 64 to a pump 69, which is mounted on the
rear of the housing and is driven by an electric motor
70. From the pump 69, an outlet hose 71 leads to a
waste liquid inlet for the heat exchanger coil
assembly A, at the upper end of hose 71. The sump 63
is also provided with a float connection 72, as in
Fig. 7, to which a conventional float 73 of Fig. 8 is
pivotally connected, in order to turn the pump on
whenever the level of waste water in tank T' reaches a
desired higher level and to turn the pump off whenever
the level of waste water reaches a lower level, such
as down to a point within the sump, the prevent the
sump outlet 64 from being uncovered and the pump
thereby possibly lose its prime. A waste water hose
74 of Fig. 6 leading from the waste water discharge
connection of the dishwasher connects with a waste
water inlet 75 in rear wall 61 of the housing H, shown
in Fig. 8, for discharging the waste water into the
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1~36~88
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tank T', while a waste water hose 76 of Figs. 6 and 7
leads from an outlet 77 at a lower point of the tank
T', as in Figs. 7 and 8. As will be evident, the
heated waste water flows through one set of the dual
alternating tubes of the heat exchanger, from the top
to the bottom of the coils, while the incoming cold
water to be preheated flows from the bottom to the top
of the alternate tubes of the coils, from a lower
inlet 78 to an upper outlet 79, as in Figs. 6 and 7.
An electrical control box 80 having conventional
outlet connections, as shown, may be mounted on the
upper, rear wall 55 of the housing H.
The front wall 58 which encloses tank T', as in
Fig. 10, is provided with a generally rectangular
opening 82 having a lower portion 83 of lesser width
which provides ledges 84 to accommodate a slide which
includes a screen 85 having holes of an appropriate
diameter, as indicated in Fig. 9, to permit the waste
water to flow through but to catch any food refuse or
material of a larger size. A cover 86, to which
screen 85 is attached, is in turn removably attached
to the front wall by a latch 87 at each side. The
slide is, of course, removable by unhooking the
latches 87 and removing the front cover and the screen
with it, then replacing the cover and screen, after
the screen has been cleaned off. The screen 85 may be
provided with an upstanding front flange 88, by which
the screen may be removably attached to the cover in a
conventional manner, as by a series of studs and nuts.
The cover 86 is also provided with a rectangularly
arranged gasket 89 which seals the cover against the
front wall 58, around opening 82, as in Fig. 9, and
may be formed of any suitable compressible gasket
material to provide the desired seal.
As the screen is inserted, the opposite lower
1;236088
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edges thereof are slid along the ledges 84 of opening
82 of Fig. 10, and thence at one side along the top
flange of an angular guide 90 of Fig. 8 and at the
opposite side along the top of an apron 91 having
S depending flanges 92, one of which may be attached to
the side walls 60 and the other of which laterally
engages a flange 93 depending from the underside of
screen 85. A corresponding flange 94, depending form
the underside of screen 85 and spaced from the
opposite edge, is adapted to engage the side flange of
guide angle 90 which extends between and is attached
to the front wall 5~ and the rear wall 61 of tank T',
as in Fig. 9. A baffle 95 beneath the outer, lower
edge of guide angle 90 extends alongside the cup 65
lS and permits overflow of excess waste liquid from the
area beneath screen 85 to flow into an outlet area 96
adjacent wall 59, and in Fig. 9, and thence flow
through outlet 77 of Fig. 8 and through hose or pipe
76 to the sewer, or to another piece of equipment, as
described later.
From a tubular waste outlet connector 97 adjacent
the lower end of the coil assembly A, a pipe 98
extends downwardly and into the cup 65, so as to be
immersed in the water in the cup and thereby prevent
the pump 69 from losing its prime and also holding the
waste water within the coils above until additional
waste water is pushed through by the pump. By holding
such wa~te water in the coils, any fresh water passing
to the hot water heater, such as due to the
requirement of some fixture other than the dishwasher,
will tend to be preheated and additional heat to be
extracted from the water. ~he prime of the pump is
also maintained by the sump 63. A tubular connector
99 is also adjacent the lower end of coil assembly A,
but receives incoming feed water.
~236Q~
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The dual coils of the coil assembly A are wound
about a hollow center 101, while the lower and upper
ends of one series of tubes 102 extend into the
tubular connectors 97 and 103, respectively, being
secured and sealed therein, as by soldering or
brazing. Connector 103 is in turn connected with
incoming waste water hose 71. The lower ends of the
other series of tubes 104 similarly extend within and
are secured and sealed within tubular connector 99, in
turn connected to feed water inlet 78, while the upper
ends of tubes 104 are inserted within and sealed to a
tubular connector 105 which, in turn, is connected to
feed water outlet 79. The general shape of the coil
assembly A is cylindrical, with a flat top and bottom
at the ends of hollow center 101. The remainder oE
the top is gcnerally conical, due to the winding Oe
the alternating pairs of tubes 102 and 10~, while the
remainder of the lower end of the assembly is also
conical, but at a sharper angle due to the lesser
number of turns of the outer coils, in order to
provide coils of as equal length as possible and
therefore equalize the resistance to flow there
through. Thus, both the inside coils and the outside
coils, as well as those in between, should convey
approximately the same amount of waste water or feed
water, respectively. At the lower end of the hollow
center 101 of the coil assembly is a drain hole 106
which permits liquid from any leaking tube, which will
tend to seek a path through the mastic, to drain into
the tank T', rather than contaminating any incoming
feed water. The outer surface of the coil assembly
may be covered by a layer of insulation 110, such as
fiberglass, to reduce radiation and conduc-tion heat
losses. The insulation 110 at the top may extend out
to the upper connectors 103 and 105 but may be spaced
~236088
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from the lower connectors 97 and 99. The insulated
coil assembly may be encased in a layer of foam
insulation 111, such as polyurethane foam, which has
two purposes. The first is, of course, to act as
insulation, and the second is to retain the coil
assembly in position within the housing H, to prevent
breakage of any of the coil tubes during shipping or
installation,
One advantage of the outlet area 96 is that it
tends to render the screen ~35 self-cleaning, since the
waste inlet 75 is at the opposite side of the tank
from the outlet area and if the screen becomes
clogged, the waste water will flow across the screen
to the outlet or discharge area and tend to carry with
it the material which clogs the screen. A similar
result occurs in the event that there is a malfunction
of the float 73 of the pump 69, so that the waste
water is not removed from the tank on one cycle and
the level of the water in the tank rises over the top
of the baffle 95. In such an event, water which
continues to pass through the screen will tend to
overflow the baffle, but for complete discharge of the
waste water, this overflow would be insufficient, so
that the excess will flow across the screen and into
thé discharge area 96, tending to carry with it any
material collected on the screen. Such material,
along with the waste water, will be discharged through
the waste water outlet 77. Thus, the discharge area
96 eliminates the necessity for a special device for
sounding an alarm, as described later in connection
with the tank T of Fig. 1.
Direct control of the motor 69 by a conventional
switch associated with the float 73, as described, is
pa~ticularly adaptable for use with a dishwasher whose
rinse cycle beings concurrently with or shortly after
~2361:~88
the discharge of the waste water from the wash cycle.
However, when the discharge of waste water is not
closely correlated with the rinse cycle, the switch
control actuated for the float 73 may be placed in
series with a switch controlled by the timer of the
dishwasher, so that when the rinse cycle is started,
the waste water will be pumped through the heat
exchanger and thereby preheat the incoming fresh
- water, normally cool or cold, which replaces the hot
water withdrawn for the rinse cycle. Also, when the
rinse water, as well as the used dishwater, is
discharged as waste water, the dishwater and the rinse
water may be saved for countercurrent heat exchange
with the incoming fresh water on the next rinse cycle
and the pump motor controlled by a switch which, in
turn, is controlled by the timer or other appropriate
control mechanism of the dishwasher.
The pump control and alarm circuit of Fig. 1l is
adapted to control the operation of pump 38 of Figs. l
and 2 through a low level electrode 115 and a high
level electrode 116. This circuit also includes a
safety electrode 117 which is disposed above the
normal water level 118 in the tank T. The electrodes
115, 116 and 117 each extend through the rear wall 34
of the tank T, at the positions indicated in Fig. 3.
Each electrode may pass through a compression fitting
ll9 installed in the wall of the tank T, which not
only insulates the electrode, but also prevents
leakage of waste water around it. ~riefly, the pump
38 is turned on if the water reaches the level of
electrode 116 and is turned off when it reaches the
level of electrode 115. In the event that the level
of waste water in the tank T becomes unduly high,
indicating that the pump is not functioning or some
other problem exists, the waste water will cover the
1;i~36088
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alarm electrode 117 and actuate an alarm, such as a
light L or a bell, buzzer or any other type of
suitable signaling deviceO
Power is supplied to the circuit through
electrical leads 120 and 121, such as 110 volts, to a
transformer 122 which reduces the voltages to 20 to 40
volts. From one side of the transformer 122, a lead
123 extends to a relay R, with a ground wire l24 being
attached to the tank. On the opposite side of
transformer 122, a lead 125 extends t the high level
electrode 116, while a branch lead 126, having
normally open holding contacts 127 therein, extends to
low level electrode 115. The motor 128, for pump 38
of Figs. I and 2, is supplied with electricity, as at
110 volts, through a pair of leads 129 and 130, with
contacts 131 interposed in lead 130. Assuming that
the holding tank T has been essentially empty but
begins to fill at the end of a wash cycle, when the
level of water reaches the high level electrode 116,
the circuit through relay R will be closed through
lead 125 and ground wire 124. The relay will then
close both normally open contacts 127 and 131, so that
pump motor 128 will be started and the relay circuit
will remain closed as long as low level electrode 115
is immersed. Thus, as long as the level of waste
water in the tank remains above electrode 116 or below
electrode 115, the motor 128 will remain running.
However, as soon as the level drops below the lower
electrode, the circuit through relay R will be broken,
the relay will be de-energized and each of contacts
127 and 131 will become open, thereby causing motor
128 to be stopped. Of course, as soon as the level
again reaches upper electrode 116, the pump motor 128
will again be started. Normally, a single emptying of
a dishwater washing tank, which will soon cause the
i:~3608~3
-18-
pump motor to be started, will be exhausted when the
waste water level falls past the lower electrode. A
branch lead 132 extends from lead 122 through light L
to alarm electrode 117, which will operate in the
S manner indicated previously.
In the alternative arrangement of Fig. 12, the
dishwasher D, holding tank T, heat exchanger E and hot
water heater H are utilized in essentially the same
manner as before, except that the cooled water from
heat exchanger E may flow, as through discharge pipe
42, to a cooled waste liquid collection tank 135, from
which it may be supplied to a second device, such as a
liquid cooled refrigerant compressor 136 and/or a
third device, such as a grease extraction ventilator
137 having water contact means, such as a water bath,
and/or a fourth device, such as a waste food grinder
138. The waste liquid, heated through cooling the
compressor 136, may be recirculated to the heat
exchanger, as through a pipe 139 which leads to a tee
140, which also receives heated waste liquid from
holding tank T, as described previously, through pipe
40. After flow through grease extraction ventilator
137, the waste liquid, which tends to be cooled in the
ventilator, may be recirculated to the waste liquid
collection tank 135, as from an outlet 141 through a
pipe 142, or the ventilator and the compressor may be
connected in series, as described below. Thus, cooled
waste water from tank 135 may be discharged through a
first outlet 143, as on the underside of tank 135, and
a pipe 144 to a pump 145 which supplies, through a
pipe 146 and a branch pipe 147, the water cooling
passages of the refrigerant compressor 136. Normally,
water cooled refrigerant compressors require
refrigeration equipment to cool water or an undue
volume of fresh, cooled water, since the water
~Z360~
discharged from the cooling passages of a water cooled
refrigerant compressor may reach temperatures on the
order of 100F to 130F, often depending on the time
of year. However, the supply of waste dishwater which
can pass through heat exchanger E is normally cooled
by heat exchange with the incoming cold water for the
hot water heater and is thus suitable for cooling a
water cooled refrigerant compressor. The presence of
detergent in the waste dishwater is of advantage in
maintaining the inside surfaces of the water cooling
passages of the refrigerant compressor in a clean
condition, so that no problem of this nature can be
expected in using waste water from this source. As
indicated previously, the then heated waste water from
the refrigerant compressor is conveyed by return line
139 to tee 140 for recirculation through the heat
exchanger and further cooling therein, then collection
in the cooled waste water tank 135.
Pump 145 may also supply cooled water, as through
a branch pipe 148, to grease extraction ventilator 137
having water contact means, such as a water bath
against which hot gases, fumes, grease, etc. from
cooking equipment, usually mixed with air, are
directed, as in U.SO patent No. 3,841,062. Or, the
grease extraction ventilator may be provided with
other types of water contact means, such as water
sprays through which the hot gases, fumes, grease,
etc., again usually mixed with air, are directed or
pulled. The waste dishwater from a dishwasher is
particularly advantageous for use in a grease
extraction ventilator having water contact means,
since the detergent contained in the waste dishwater
tends to dissolve the grease and maintain the surfaces
within the ventilator in a clean condition. In water
spray ventilators, it is normally necessary to clean
~236088
-20-
the surfaces periodically~ as by special sprays of hot
water containing detergent, while water bath grease
extraction ventilators normally require either
periodic cleaning or the addition of detergent to the
water bath at regular intervals. A grease extraction
ventilator with water contact means is also
advantageous for use in conjunction with the cooled
waste water tank 135, since the flow of hot gases,
fumes, grease, etc., when mixed with air, has a
tendency to cool the water through evaporation, even
though the hot gases may not be cooled to a similar
extent. Thus, the waste dishwater supplied to water
contact ventilator 137 may instead be transferred
directly to the cooling compartment of refrigerant
15 compressor 136, as through a pipe 150, indicated by a
dotted line. As before, the waste water heated by
refrigerant compressor 136 may be recirculated through
the heat exchanger by pipe 139. However, for such a
connection, branch pipe 147 leading to compressor 136
20 may be omitted, as well as pipe 142 between outlet 141
and waste tank 135. When the waste water supplied to
compressor 136 is recirculated through heat exchanger
E, it, of course, is returned to tank 135, to which
the waste water from ventilator 137 may be returned.
Also, when the ventilator and compressor are placed in
series, as through pipe 150, all of the waste water so
circulated will be returned to tank 135. Thus, there
may tend to be an over accumulation of waste water in
tank 135, which may be relieved through an overflow
30 pipe 151.
Some of the excess of waste water may be used to
supply waste food grinder 138 through a second outlet
153, as also on the underside of cooled waste water
tank 135, through a pipe 154 to a pump 155, from which
35 a pipe 156 leads to the waste food grinder 138 having
~^ ~.,.
. .
i.236088
-21-
a discharge line 157 through which the ground food
waste and the waste water flow to a sewer or the like.
The cooled waste water is ideal for use in the food
grinder, since it not only lubricates the bearings
used in such equipment but also congeals grease and
reduces the possibility of it clogging a drain pipe,
as by deposition further downstream.
A cool water makeup line 158 may be utilized to
add cool water to tank 135, such as when the waste
food grinder requires more liquid than the dishwasher
can supply, or when there is normally no incoming feed
water for the hot water heater H, and thus no cooling
of the waste water, such as recirculated from the
compressor, passing through the heat exchanger E.
Thus, during periods when a restaurant, for instance,
is not in operation and no hot water is being used,
particularly by the dishwasher, but the refrigerant
compressors are still in operation due to heat leakage
from the refrigerator spaces, the makeup line 158 may
be used to maintain a sufficiently low temperature of
the waste water in cool waste tank 135. Thus, if
there is sufficient cool waste water in the tank to
cool the refrigerant compressors adequately during the
off periods of other equipment, particularly a
dishwasher, the makeup line will not be used. If
desired, a conventional temperature responsive element
159 may extend into the waste tank adjacent the outlet
143 to turn on line 158, by turning on a pump or valve
(not shown) in a conventional manner, to offset
heating of the water by the refrigerant compressor,
whenever the temperature of the waste water in the
tank rises to reach a predetermine degree.
The valve for makeup line 158 may also be
controlled by a low level electrode 160 and a higher
level electrode 161 when, as indicated above, the
123~;~)88
waste food grinder 138 requires more waste water than the
dishwasher supplies. Although it would be expected that
pre-rinsing dishes at the waste food grinder would take place
substantially contemporaneously with the washing of the dishes, it
may sometimes happen that dishes are pre-rinsed and stacked for a
period of time, such as 15 minutes, and pre-rinsing then
discontinued and the dishes washed for the next period of time,
such as lS minutes. The electrodes 160 and 161 may be connected
in a circuit, so that if the level of waste water in tank 135
falls below low level electrode 160, the pump or valve producing
flow through makeup line 158 will be turned on, but as soon as the
level of liquid reaches higher level electrode 161, the pump or
valve will be turned off. Electrodes 160 and 161 may be similar
to electrodes 115 and 116 of Fig. 10 and connected in a relay
circuit, but in a different but conventional manner, i.e.,
electrode 160 breaks a circuit to open the valve and electrode 161
closes the circuit to close the valve.
Although the application of the method and apparatus of this
invention to a dishwasher has been illustrated and described, it
will be understood that the method and apparatus may be utilized
in connection with other types of devices which produce waste
water having a sufficient heat content and require hot water from
a hot water heater, while embodiments other than those illustrated
and described may exist. It will further be understood that
various changes may be made in the apparatus for waste energy
recovery, without departing from the spirit and scope of this
invention.
P.,~
~ -22-
