Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
SYSTEM FOR RECOVEP~ING HEAT FROM A FI~ST
_ _ _ . _ _
LIQUID AND IJS ING IT TO HEAT A SECOND LIQUID
BACKGROUND OF THE INVENTION
~ t the present time it is not common practice
to recover the heat that is pxesent in domestic waste hot
water. Hot water from bath tubs, showers and sinks
simply is sewered resulting in a great deal of
recoverable energy literally "going down the drain". In
accordance wi-th this invention, there is provided a
system for the recovery of this energy. While the system
will be hereinafter described as one in which heat is
recovered ~rom waste water in a house and used to heat
water for domestic operations, it is to be understood
that this is exemplary only. The liquid containing heat
to be recovered may be other than water and may be
derived from other than a domestic operation. For
example, it may be industrial liquid waste. Likewise,
the liquid to be heated may be other than water and may
be for other than domestic use. However, the system
hereinafter described was conceived for use in a domestic
environment for recovering heat from waste water and
using the same to heat water, and the invention thus will
be so described~
SUMMARY OF THE INVENTION
Various aspec-ts of this invention are as
follows:
2~ ~ ~
A system for recovering heat from a first
liquid and using the heat recovered to heat a second
liquid comprising: a first storage tank for said first
liquid, said first tank having a top, a bottom and side
walls, an overflow weir located within said first tank
adjacent said top thereof, a first outlet from said first
tank for said first liquid, said first outlet being
located nearer said top than said bottom of said first
tank but below the level of said overflow weix, a riser
channel connecting said first outlet and a part of said
first tank adjacent said bottom thereof in liquid-flow
relationship to permit relatively cold first liquid at
the bottom of said first tank to be displaced and to
discharge from said first tank via said first outlet upon
introduction of frech first lîquid intc said first tank,
means for introducing said first liquid into said first
tank via a first inlet at a location above said botto~ of
said first tank but below the level of said first liquid
established in said first tank b~7 said first outlet, a
second outlet from said first tank for said first liquid
and a second inlet i.nto said first tank for said first
liquid, said seccnd outlet being clGser to said top than
to said bottom of said first tank and said second inlet
being closer to said bottom than said top of said first
tank; a second storage tank for said second liquid, said
second tank having a top, a bottom and side walls, means
including a first inlet for introducing said second
liquid to be heated into said second tank adjacent said
bottom thereof, ~lectrical heating means for heating said
second liquid located in the upper part of said second
tank, a first outlet from said second tank for said
second liquid, and a second inlet into ~aid second tank
1 g. ~
for said second liquid, said second inlet being located
below said electrical heating means and above said first
outlet, sa.id first outlet being located between said
second inlet and said bottom of said second tank, a
second outlet from said second tank for said second
liquid, said second outlet being located above said
electrical heating means, and means for assisting the
thermal stratificaticn of said second liquid in said
second tank, the last-mentioned means comprising a
separator located within said second tank below said
electrical heating means and above said second inlet of
said second tank, said separator inhibiting substantial
movement of said second liquid from below said separator
to above said separator but permitting a sufficient flow
of said second liquid from said second tank via said
second outlet of said second tank in response to demand;
and a heat pump including a condenser and an evaporator,
means for circulating said first liquid from said first
tank via said secolld outlet of said first tank in heat
exchange relationship with said evapora~or and back to
said first tank via said second inlet of said first tank,
whereby heat in said first liquid so circulated is given
up to a heat exchange fluid in said evaporator, and means
for circulating said second liquid from said second tank
via said first outlet of said second tan~ in heat
exchange relationship with said condenser and back to
said second tank via said second inlet of said second
tank, whereby heat in said heat exchange fluid in said
condenser is given up to said second liquid.
3 ~ ~
4/5
A storage tank 'or liquid, said tank having a
top, a bottom and side walls, means including a first
inlet for introducing liquid to be heated into said tank
adjacent said bottom thereof, electrical heating means
for heating said liquid located in the upper part of said
tank, a first outlet from said tank for said liquid, a
second inlet into said tank for said liquid, said second
inlet being located below said electrical heating means
and above said first outlet, said first outlet being
located between said second inlet and said bottom of said
tank r a second outlet from said tank for said liquid,
said second outlet being located above said electrical
heating means, and means for assisting the thermal
- stratification of said liquid in said tank, the
last-mentioned means comprising a separator located
within said tank below said electrical heating means and
above said second inlet, said se~arator inhibitiny
substantial r.lcvemert or liquid frcm below said separator
to above said separator but permitting a sufficient flow
of liquid from said tank via said second outlet in
respcnse to demand.
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BRIEF DESCRIPTION OF THE DRAWI~GS
.. . ... _ _
This invention will become more apparent from
the following detailed description, taken in conjunction
with the appended drawing, which i5 a schematic
representation of a complete waste water recovery and
utilization system constituting an aspect of this
invention.
DETAILED DESCRIPTION OF THE INVENTION INCLUDING
THE PR~FERRED EMBODIMENT
Referring to the drawing, the system is
composed of a waste water holding tank 10, a heat pump
11, a hot water tank 12 and various controls including
controls l3.
Tank 10, which should be well thermally
insulated (thermal insulation not shown) and
appropriately constructed to resist corrosion, has a top
14, a kottom 15 and side walls 16. The tank is generally
cylindrical in cross-section, but adjacent top 14 side
walls 16 slope inwardly, as seen at 17, for a purpose
that will be outlined in greater detail hereafter.
An outlet 18 is located in bottom 15 of tank
10, it being noted that bottom 15 is of conical
configuration sloping towards outlet 18 so that all of
the water in tank 10 can be drained therefrom via outlet
18. A valve 19 for opening and closing outlet 18 is
provided.
Within tank 10 is an overflow weir 20. It is
located ad~acent top 14 and, in an emergency, functions
to permit excess water in tank 10 to overflow from the
tank and to discharge to waste via a waste pipe 21.
9 ~ ~
There is a second outlet 22 for water in tank
lO. It is located nearer top l~ than bottom 15 but helow
the level of overflow weir 20 and is connected in
liquid-flow relationshlp with the lower part of tank 10
via a riser channel 23. In this manner relatively cold
water fron~ the lower part of tank lO can be displaced by
waste water entering the tank. The displaced water
overflows from outlet 22 and discharges into waste pipe
21. It will be seen than the level of outlet 22
determines the level 24 of water in tank 10. Riser
channel 23 preferably is thermally insulated from waste
water in tank 10 by thermal insulation 25. This also may
be accomplished by making riser channel 23 a separate
, pipe that is kept well away from side wall 16 of tank lO.
15Waste water is introduced into tank 10 from a
pipe 26 via an inlet 27. Inlet 27 preferably is located
at a point about /3 of the depth of tank lO. It must be
noted, in this connection, that the waste water
introduced into tank lO is not always hot. For example,
if cold water were being run in a sink, the waste water
going into tank 10 would be cold. Therefore the location
of inlet 27 relative to thermal stratification within
tank 10 must take this into consideration.
An outlet 28 and an inlet 29 for waste water
r~ 25 from tank 10 that is recirculated are provided in side
wall 16, the former being closer to the top of tank lO
(where the water is hotter) and the latter being closer
to the bo~tom of tank lO (where the water is colder).
A rinsing device 30, which may be like the
30 rotating arm of a dishwasher or a tubular ring provided
with spaced apart openings therearound through which
water can spray, is provided for rinsing the interior
surface of tank lO. It is arranged so as to direct its
spray against inwardly sloping section 17 and weir 20,
35 these components being at substantially the same level,
namely the level 24 of water in tank 10. Because of
this, scum and solid waste material accumulate thereon,
and the inward slope of section 17 and weir 20 assists in
J
the removal of such scum by the rinsing action and under
the influence of gravity.
Hot water tank 12 also is cylindrical in
cross-section, should be thermally well insulated and
should be constructed to be corrosion resistant. It has a
top 30, bottom 31 and side walls 32. Water to be heated
is introduced, e.g., from city mains, from a pipe 33 via
an inlet 34 located adjacent bottom 31 (the coldest water
always should be introduced into the lowest point of a
hot water tank).
A conventional electrical resistance heater 35
is located in the upper part of tank 12 along with a
thermostat 35a that controls the supply of power to
heater 35.
In the lower part of tank 12 there are provided
an outlet 36 and an inlet 37, the latter being located
below heater 35, and above outlet 36 and preferably about
one-half way along the depth of the lower part of tank
12, the former being located adjacent bottom 31. A
thermostat 39 also is provided.
~ n outlet 40 for hot water frcm tank 10 is
provided in top 30 above heater 35.
A sacrificial corrosion anode 60 is provided,
as is conventional, to reduce corrosive attack on the
c- 25 tank welds or any other exposed metal surfaces.
~ An important feature o~ tank 12 is the
provision of a separator 61 that- assists in the thermal
stratification of the water in tank 12. Separator 61,
which may be a circular plate that spring fits into
30 glazed over lugs 62 on the inner wall of tank 12, is
located below heater 35 and well above inlet 37.
Separator 61 divides tank 12 into an upper resistance
heater section and a lower preheater section and prevents
bulk circulation between the two sections. However, it
35 is provided with a small opening 63 suf~icient to permit
water to flow from the lower section to the upper section
and out of tank 12 via outlet 40 in response to demand.
Heat pump 11 is essentially conventional in
nature and includes a compressor 41, condenser 42 and
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g
evaporator 43. Refrigerant vapour from compressor 41
flows past a manual-reset high pressure circuit breaker
44 into condenser 42. Condensed refrlgerant exits
condenser 42 and flows through a liquid line filter-drier
45 and a thermostatic controi valve 46. Now at reduced
pressure, the refrigerant traverses evaporator 43 and the
refrigerant vapour from evaporator 43 is returned to
compressor 41 via an optional low pressure cut-out 47.
A dual head magnetically driven purnp employing
one head 48 to circulate waste water from tank 10 over
evaporator 43 in heat exchange relationship therewith and
the other head 49 to circulate water f`rom tank 12 to be
heated over condenser 42 in heat exchange relationship
therewith is provided. With this arrangement the w~ter
'~ 15 in each pump head is isolated from the motor by magnetic
coupling, and hence the waters are ,isolated and cannot
contaminate each other.
Optionally, the condensing refrigerant in
condenser 42 may be isolated from the water being heated
by a double-walled con~enser optional]y 'having an
indicator dye between the double walls. The indicator
dye would colour the hot water in the event of a rupture
in the dye/water interface indicating possible
contamination of the hot water by the refrigerant.
( 25 In operation, waste water flows into tank 10
-'` via pipe 26 and inlet 27 displasing cold water from the
bottom of tank 10 via riser channel 23, outlet 22 and
waste pipe 21. In the event that channel 23 should
become plugged or should be unable to accommodate the
30 volume of water being displaced by waste, water coming
into tank 10, overflow over weir 20 will occur, but
operation in this mode is not desirable, of course, since
the hottest water in tank 10 will be at the top of the
tank.
Water from tank 10, if sufficiently warm, is
circulated by pump 48 and gives up heat to the
refrigerant in evaporator 43, the warmest water from the
top of tank 10 being used for this purpose. The
resulting cold water is returned to tank 10 via lower
lo ~ ~29l7
inlet 29, which is below inlet 27. The extracted heat
from this water is transferred in condenser 42 to water
from tank 12 being circulated by pump 49. In this manner
the water in the lower (preheater) section of tank 12 is
heated to a temperature that is determined by the setting
of thermostat 39. This thermostat usually will be set to
the same temperature, e.g., 130F, as that of thermostat
35a. When the desired temperature is reached, thermostat
39 inhibits operation of heat pump 11.
Turning now to the controls, a timing device 70
controls the opening and closing of valve 19 by operation
of a valve actuator 71 and holds valve 19 open until the
entire contents of tank 10 have drained followed by an
f automated spray rinse controlled by a controller 72.
15 Valve 19 is closed by timing device 70 and actuator 71
after the rinse water has drained away. As previously
noted, the hot water rinse removes surface rim and bottom
deposits from the interior of tank 10 prevent their
accumulation.
A level sensor 73 inhibits operation of heat
pump 11 if tank 10 is not full, while a th~rmostatic
control 74 shuts off heat pump 11 if the surface waste
water is too cool for worthwhile heat recovery.
While preferred embodiments of the invention
have been disclosed herein, those skilled in the art will
appreciate that changes and modifications may be made
therein without departing from the spirit and scope of
this invention as defined in the appended claims.
