Note: Descriptions are shown in the official language in which they were submitted.
CA 02550281 2006-06-12
Descripiirin
BACKGROUND OF TBE INVENTION
1. Field of the Invention
The instant invention relates to a method for increasing heat energy recovered
by the apparatus
disclosed in U.S. Patent No. 4,619,311 hereinatter called the GFXTM Patent;
the heart of which is a
Gravity Film heat eXchanger (GFX).
Many coil & tube GFX units like those illustrated in FIGS. 1& 2 have been sold
by various Licensees
of the GFXTM Patent who have manufactured them using trade-secret coiling
techniques and tools.
Other types of heat exchangers can also be used with the instant invention,
which also anticipates
multi-drain installations, does not require wastewater storage or other
complex accessories, and can be
used to increase energy savings of eacisting GFX uistallations.
2. Description of the Prior Art
The prior art is exemplified by many examples of heat reclaimation systenis,
most of which are
expensive, complicated, may require convective chambers, means to store
wastewater or separate
solids and require periodic cleaning and maintenance in order to avoid fouling
andlor degradation of
heat recovery efficiency; examples of which are shown in U.S. Patent Nos.
6,722,421, 5,791,401,
5,740,857, or 4,821,793, and Foreign Patent Nos. 3011111, 3244600, 2165932,
57142488, for
example.
A notable exception is the apparatus of U.S. Patent No. 4,619,311, which, as
illustrated in FIG. 3
below, saves little energy in households where shower and small sink usage is
low. According to FIG.
4, such usage represents 43% + 15% = 58% of the domestic hot water consumption
in typical
American homes.
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G.,FX-STARTm Performam*
AM l~~i~
c~6o cFx so-" cFx
50 .
G -STA TM 1) 1 . tYloillis . lw
4ft .
~ .
?30 ~
OkAh"
42%
10 G rr[ ~' . .
0 20 40 60 80 100
Ratio of hot.-shower/faucet use to total hot water ("/=)
FIG. 3 Energy saviags of a GF'X-STAR'rm DHR-system FIG. 4 From Heat
Reroveryfrom Wactewater Using Gravity-
compared to conventional GFX spstem oovered by U.S. Filnr Hed Exclianger, U.S.
Departmetrt of Energy (DOE) by
Patent #4,619,311. the Oak Ridge Nationai Laboraiory, DOF/EE-0247, May
*AssaYnes approximately 80% of a water heater's 2001.
heat reaches a Model G3-60 or S4-60 GFX. (From: htt :i! xtecli o1o e
qu
SUMMARY OF THE IliVENTION
In the present invention, the disadvantages of prior art and limitations of
the GFXrm Patent are
overcome by making a simple, cost-effective modification to a conventional
GFX'rm system that not
only can enhance heat recovery efficiency for its substantial infringing-use -
from near 50% to about
59%, it can significantly improve energy savings in homes that use little to
no hot water for showers
and sinks --- from nil to about 50%, according to FIG. 3, while preserving
GFX's self-cleaning, non-
fouling, maintenance-free operation.
This improved performance is accomplished by simply adding a pump and check-or
solenoid-valve to
the patented GFXTM system as illustrated in FIG. 1 so as to cause GFX's coil
flow rate to substantially
exceed its drain flow rate, something that is not possible in a conventional
GFXTm system.
For example a Model G3-60 GFX is rated @ 60% DHR-efl"iciency for equal coil &
drain flow rates of
2.25 GPM, but if a pump is instalied to double its coil-flow rate, its DHR
efficiency increases from
60 /a to about 77% if 2.25 GPM continues to flow down its drain tube. The G3-
60's coil pressure drop
wiil increase from 8 to about 32 PSI, so a pump offering sufficient head must
be chosen. Similarly, a
GFX-STARTm system can double an S4-60's coil flow rate to boost its DHR-
efficiency increases from
62% to about 73% with 2.25 GPM flowing down its drain tube. The S4-60's coil
pressure drop will
increase to about 5 PSI, so a much snialier pump could be used than that
required to force 4.5 GPM
through a G3-60's coil. Clearly, coil pressure drop and pump power
requirements will limit the
maximum practical ratio of coil- to waste-water flow rate. In addition to
pressure drop, avoiding
erosion corrosion in a GFX's coil will set a maximum flow rate for a G3-60 of
about 4-5 CrPM,
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according to the Copper Tube Handbook of the Copper Development Association.
The limit on an S4-
60 will be about 8-10 GPM
The use of a GFX, or any other heat exchanger, as taught herein is inventive
because it discloses a
cost-effective means to significantly improve the heat recovery of said
conventional GFXTm system,
with or without equal flow in its GFX, as well as a means for recovering heat
lost to the sewer
whenever hot drain water is flowing down its drain tube and no cold water
would normally be flowing
in its coil.
DESCRIPTION OF THE DRAWING
FIG. I of the drawing shows a system whereby cold feed water is preheated in a
heat exchanger and is
then further heated and stored in a conventional hot water heater. The same
heat exchanger is used via
pipe 27 to reduce the quantity of hot water required in preparing a tepid
water mixtur.e for direct use as
in showering, for example.
FIG. 2 of the drawing shows obvious variations of the basic GFX STARTM system
illustrated in FIG.
1.
DESCRIPTION OF TH'E PREFERRED EMBODIlVIENT SHOWN IN FIG. 1
The prior art includes many techniques for the recovery of heat energy
contained in wastewater. As
disclosed, for example, in U.S. Pat. Nos. 6,722,421; 5,791,441; 5,740,857;
4,821,793; 4,619,311;
4,304,292; 4,300,247; 4,321,798; 4,150,787; 4,352,391; 4,372,372, and Foreign
Patent Nos. 3,011,111;
3,244,600; 2,165,932; 57,142,488; for example, water used for showering and
discharged through
drain Iines can be placed into a heat exchange relationship with colder feed
water 17 in order to preheat
either water heater feed water 18 and/or cold water 27 prior to mixing with
hot water 34 to provide
tepid water for direct use 36. (See also A.A. Field, Heating/Piping/Air
Conditioning, Volume 48, No.
3, pp. 87-91, "Solar Energy: Part II, The Continent," March 1976.)
Said heat exchange relationship conserves energy by lowering the temperature
of said wastewater by
transferring heat energy to said feed water, or said cold water, or both,
thereby reducing primaty hot
water heater input energy requirements and the quantity of hot water used in
showering, for example.
Maximum wastewater cooling, hence maximum energy savings, will occur when the
volume of the
coolant is made to exceed the volume of wastewater by as much as practical.
The present invention is directed at instaliations whereby tepid water is
produced by mixing hot and
cold water in a nnixing valve 34, for example, wherein a conventional GFX
system cannot recycle
much of the heat wasted in a typical American household; about 48% from
dishwashers, clothes
washers and baths according to FIG. 4, for example.
Referring to FIG. 1 of the drawing, cold feed water enters the system through
cold water pipe 16 which
is connected to heat exchanger 30 at inlet 17 and exits heat exchanger 30 as
preheated feed water at
outlet 19 which is communicated to hot water heater 20 by pipe 18 where said
preheated feed water is
fiurther heated and stored for domestic hot water requirements. Wastewater
pipe 10 is provided to take
the wastewater from bathtubs, sinks, showers, hot industrial equipments and
etc., and communicate
same to the sewer.
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The inventive feature illustrated in FIGS. 1 and 2 is the addition of means to
prevent back-flow 74,
such as a check- or solenoid-valve, for example, in series with a pump 72 to
circulate potable water
through a substantially vertically oriented heat exchanger 30, that is
inserted directly into a common
drain conduit 10. Exchanger 30 pre-heats a volume of feed water 18 and cold
water 27 as determined
by pump 72 capacity and back pressure and incoming cold water 16 line
pressure.
For best heat recovery, said volume of feed water 18 and cold water 27 should
equal or exceed the
wastewater volume from drain 29 of tub 60 prior to mixing 50 with hot water 44
in valve 34, having
shower outlet 36 and bath outlet 52, for example.
Without a pump 72, the laws of thermodynamics make it impossible to cool the
wastewater more than
that attained by the apparatus of the GFX patern (4,619,311) which teaches the
significance of
preheating both feed water 18 and cold water 27 prior to mixing 27 so that
equal volumes of cold 17
and wastewater are flowing through the exchanger at the same rate.
For the example of FIG 3, if 1.125 GPM of cold water 50 were mixed with 1.125
GPM of hot water
44, 2.25 GPM would flow as wastewater 32 at a temperature equal to the average
of the premixed two
water temperatures. If said heat exchanger 30 is a selected to be a Model G3-
60 or S4-60 GFX, for
example, the most one can extract is about 60% of the wastewater's heat
energy. This is because, in
accordance with the laws of thermodynamics, the volume of the wastewater 32 is
equal to that of the
cold water 17 to which it is transferring heat. If the volume of cold water 17
entering said GFX 30 is
reduced its effectiveness will increase, but according to the laws of
thermodynamics, less energy will
be recovered because the volume of the wastewater 30 wiil exceed that of the
cold water 17 to which it
is transferring heat. In contrast, if the volume of cold water 17 entering
said GFX 30 is increasecl, its
effectiveness will also increase, and more energy will be recovered because
the volume of the
wastewater 32 will be less than that of the cold water 17 to which it is
transferring heat.
The present invention, however, teaches a method for causing optimal volumes
of wastewater 32 and
entering cold water 17 to exchange heat energy as determined by the parameters
of the pump 72 and
heat exchanger 30. Thus, as illustrated in FIG. 3, if a tub 60 were to dump 40
gallons of hot water
down the drain 29 at a rate of 2.25 GPM after losing about 20% of its input
heat, for example, said
conventional GFX system would recover negligible energy from the wastewater
32, whereas a G3-60
or S4-60 could recover close to half of said "input heat" if the pump 72 were
selected to circulate 40
galtons of cold water @ 2.25 GPM from the water heater 20 or storage tank 22.
A larger pump would save more energy by making the cold waterl7 flow rate
exceed the wastewater
32 flow rate because it generally costs far more to heat water than to pump it
absent excessive back
pressure.
The present invention also teaches how to increase the amount of heat
recovered by a conventional
GFX system by using the pump 72 to increase the cold water input 17 while a
shower is running, for
example, thereby causing the volume of cold water 17 entering a GFX 30 to
exceed the volume of
wastewater 32 simultaneously flowing down the drain 29.
This is the essence of the present invention; it teaches a simple cost
effective method that allows the
apparatus of said GFX patent (4,619,311) to recycle waste heat from
dishwashers, clothes washers and
baths, without having to add convective chambers or means to store wastewater
or separate solids as
illustrated in U.S. Patent Nos. 6 722 4 1; 5391,401; 5.740.857; 4,821,793 or
prior art.
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The present invention fiirther facilitates incxeased savings compared to prior
art m installations
wherein it is not practical to simuttaneously feed preheated water 18, 27 to a
water heater 20 and
shower 36, for example. This is often the case in a multistory building having
a central boiler 23
located far from showers and multiple drain 10 stacks as illustrated in FIG.
2(e).
In fact, many existing GFX insta.llations in hotels, college doms and other
multi-family buildings were
installed to preheat only cold water fed to the showers because it was not
practical to preheat water fed
to the central boiler. They can now be retrofit with a GFX-STARTm system to
enhance savings.
While the form of apparatus herein described constitutes a preferred
embodiment of the invention, it is
understood that the invention is not limited to this precise fonm of apparatus
and that changes may be
made therein without departang from the scope of this invention.
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