WASTE WATER HEAT RECOVERY SYSTEM

RECUPERATEUR DE CHALEUR DES EAUX DE VIDAGE

English Abstract

ABSTRACT OF THE DISCLOSURE
An improvement is provided in a system comprising (i) a source
of fresh hot water, (ii) a source of waste hot water fed from the fresh hot
water, and (iii) a drain for discharging the waste hot water. The improve-
ment comprises a hot water heat recovery system interposed between the
source of waste hot water and the drain, comprising: (a) a water/water heat
exchanger; (b) conduit means automatically controllably continuously and
selectively passing the waste hot water to the heat exchanger before the
waste hot water passes to the drain; (c) conduit means automatically con-
trollably continuously selectively passing the cool fresh water to the heat
exchanger to be preheated and pipe means connecting to said heat exchanger
to said shource of fresh hot water and for continuously withdrawing the
preheated water from the heat exchanger, and contuit means automatically
controllably, continuously and selectively simultaneously passing the waste
hot water to the heat exchanger in heat exchange contact only with the cool
fresh water; and (d) temperature control means associated with the conduit
means to shunt the waste hot water from the heat exchanger to the drain and
simultaneously to shunt the flow of cool fresh water from the heat exchan-
ger when the water temperature drops below a selected value. By these
means, the waste heat in hot water is recovered and is used to preheat in-
coming cool water before it proceeds to the hot water heater and the waste
hot water does not enter the heat exchanger unless it is hot enough. Thus
plugging of the heat exchanger by sedimentation and precipitation of solids
out of cooler water is minimized.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a system comprising (i) a source of fresh hot water,
(ii) a source of waste hot water, and (iii) a drain for discharging said
waste hot water, a hot water heat recovery system interposed between said
source of waste hot water and said drain comprising:
(a) a water/water heat exchanger;
(b) conduit means automatically controllably continuously and
selectively passing said waste hot water to said heat
exchanger before said waste hot water passes to said
drain;
(c) conduit means automatically controllably continuously
selectively passing said cool fresh water to said heat
exchanger to be preheated and pipe means connecting to
said heat exchanger to said source of fresh hot water
and for continuously withdrawing said preheated water
from said heat exchanger, and conduit means automatical-
ly controllably, continuously and selectively simultane-
ously passing said waste hot water to said heat exchanger
in heat exchange contact only with said cool fresh water;
and (d) temperature control means associated with said conduit
means to shunt said waste hot water from said heat ex-
changer to said drain and simultaneously to shunt the
flow of cool fresh water from said heat exchanger when
the water temperature drops below a selected value.

2. The system of claim 1 wherein said source of waste hot water
is an automatic dishwasher and wherein said heat exchanger is a separate
and distinct unit from said dishwasher.
3. The system of claim 1 wherein said source of waste hot water
is an automatic clothes washer and wherein said heat exchanger is a separ-
ate and distinct unit from said clothes washer.
4. The system of claims 1, 2 or 3 wherein said source of fresh
hot water is a hot water heater, and wherein said heat exchanger is a
separate and distinct unit from said hot water heater.
5. The system of claims 1, 2 or 3 wherein said heat exchanger
is intimately associated with said automatic dishwasher, or automatic
clothes washer or hot water heater.
6. The system of claims 1, 2 or 3 wherein said source of fresh
hot water is a hot water heater, and wherein said heat exchanger is a
separate and distinct unit from said hot water heater and wherein said
heat exchanger is intimately associated with said automatic dishwasher, or
automatic clothes washer or hot water heater.
7. The system of claims 1, 2 or 3 wherein all said conduit mean
are wrapped with heat insulating material to minimize heat loss therefrom.
8. The system of claims 1, 2 or 3 wherein said temperature con-
trol means is adjusted to operate when the temperature of said waste hot
water falls below 90°F.

Description

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This invention relates to a heat dissipating system for recover-
ing heat from waste water.
Most heat dissipating systems are merely design~d for cooling
viscous liquids. For example, Canadian Patent No. 441,887 issued June 3,
1947 to Imperial Chemical Industries, provides such a system which
includes automatically operated by-pass valves in conjunction with auto-
matically controlled shutters or louvres arranged to control the flow of
the external cooling medium.
Canadian Patent No. 453,673 issued December 28, 1948 to Imperial
Chemical Industries, provides a cooling device in which the hot fluid to
be cooled can pass through all or some of interconnected cooling passages.
Canadian Patent No. 489,632 issued December 29, 1959 to The
Coleman Lamp & Stove Company Limited provides method and means for con-
trolling heat transfer in furnace casings in which heat reflective areas
are provided to avoid localization of high temperatures.
; Canadian Patent No. 689,184 issued June 23, 1964 to Sulzer
Frères provides a heat exchanger system and method in which the rates of
flow of heat exchanging fluid is dependent on the temperature of the heat
exchanging fluid leaving the heat exchanger.
Canadian Patent No. 737,807 issued July 5, 1966 to Vorcan Asso-
ciates provides a temperature control system having main heat exchange
lines and bypass heat exchange lines controlled in order to provide a
constant temperature supply fluid.
Canadian Patent No. 849,946 issued August 25, 1970 to A.B.
Svensk Flaktfabriken provides a method for recovering heat from an air-
water vapour mixture from a dissolved receiving melt which provides
generating steam from the melt and then using the steam in heat exchange
relation to condense the steam and simultaneously to heat the water in
the heat exchanger.
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Canadian Patent NO. 1,026,31~ issued February 14, 1978 to
Hayden Trans-Cooler Inc. provides a heat exchange valve system having pri-
mary and bypass valve functions.
Finally, Canadian Patent No. 1,078,823 issued June 3, 1980 to
T.A. Thoren provides a method for the utili~ation of the heat energy of
sewage by heating air with the waste heat from the sewage and then recover-
ing the heat in the hot air by an air/air heat exchanger.
Thus, while heat recovery systems have been proposed, none has
been devised to recover the sensible heat rom waste hot water and to re-
cycle and use that recovered heat to heat additional hot water.
Accordingly an object of a broad aspect of this invention is to
provide a system to recover the sensible heat from waste hot water and to
use such recovered heat to preheat cool water before such cool water is ?
passed to a hot water heater to be heated.
By a broad aspect of this invention, an improvement is provided
in a system comprising ~i) a source of fresh hot water, (ii) a source of
waste hot water fed from the fresh hot water, and (iii) a drain for dis-
charging the waste hot water, a hot water heat recovery system interposed
between the source of waste hot water and the drain comprising: (a) a
water/water heat exchanger; (b) conduit means automatically controllably
continuously and selectively passing the waste hot water to the heat ex-
changer before the waste hot water passes to the drain; (c) conduit means
automatically controllably continuously selectively passing the cool fresh
- water to the heat exchanger to be preheated and pipe means connecting to
the heat exchanger to the source of fresh hot water and for continuously
withdrawing the preheated water from the heat exchanger, and conduit means
~- automatically controllably, continuously and selectively simultaneously
passing the waste hot water to the heat exchanger in heat exchange contact
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only with the cool fresh water; and (d) temperature control means associa-
ted with the conduit means to shunt the waste hot water from the heat ex-
changer to the drain and simultaneously to shunt the flow of cool fresh
water from the heat exchanger when the water temperature drops below a
selected value.
By a variant thereof, the source of waste hot water is an
automatic dishwaster, and the heat exchanger is a separate and distinct
unit from the dishwasher
By another variant, the source of waste hot water is an auto-
matic clothes washer, and the heat exchanger is a separate and distinct
unit from the clothes washer.
By yet another variant, the source of fresh hot water is a hot
watér heater, and the heat exchanger is a separate and distinct unit from
the hot water heater.
By a variation thereof, the heat exchanger is intimately associ-
ated with the automatic dishwasher, or automatic clothes washer or hot wa-
ter heater.
By another variant, all the conduit means are wrapped with heat
insulating material to minimize heat loss therefrom.
. By yet a further variant, the temperature control means is ad-
justed to operate when the temperature of the waste hot water falls below
` 90F.
In the accompanying drawing, the single figure is a diagrammatic
representation of the system of an aspect of this invention.
In a conventional system, a source of hot water, i.e., a hot
water tank 11 is fed with cold water through water inlet 12 and, after
being heated in tank 11, emerges as hot water in line 13 and is fed to a
washer, i.e., an automatic washing machine or an automatic dishwasher 14.
.
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The waste hot water passes through outlet lines 15 and l5a to drain 16.
In the embodiment of this invention shown, cool water bypasses
hot water tank 11 in line 22 and enters a water/water heat exchanger 23 at
24. Waste hot water in line 15 enters heat exchanger 23 at 25. The
countercurrent separate water flows permit heat to pass from the waste hot
water to the fresh cool water. Thus, the fresh water outlet line 26 com-
prises preheated water and this merges with fresh cool water in line 12.10
Thus, the water entering hot water tank 11 is warm water, rather than cold
water. Similarly, waste water leaving via line l5a is warm water rather
than hot water, and so the water entering drain 16 is warm. All
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lines conduiting warm water, i.e., 13, 15, 25, 26 and 12 are wrapped
in heat insulation material to minimi~e heat loss.
A valve system 27 i5 provided which senses the temperature
of the water in line 15. If the temperature is sensed to be above a
certain value, i.e., about 90 F., water passes to heat exchanger 23,
If, however, the water temperature is below that level, the water passes
through bypass line 28 to drain 16.
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