Note: Descriptions are shown in the official language in which they were submitted.
HORIZONTAL DRAINPIPE HEAT EXCHANGER
DESCRIPTION
FIELD OF THE INVENTION
The present invention is in the field of energy savings by use of a big bore,
straight-
through drainpipe heat exchangers for drainwater (which may contain large
solids) and fresh
water to be tempered. They flow separately through the exchanger to exchange
heat thereby pre-
tempering the water before final tempering in a heater or chiller.
BACKGROUND OF THE INVENTION
Using hygienic hot water as an example, heating the cold supply water requires
vast
amounts of money (in USA+Canada $77 billion/year) and energy (-1.7 million
MW/year), and
releases equivalent amounts of pollution, city smog, and causes climate change
and habitat
destruction. Virtually all of the used hot water is simply drained away
wasting its valuable heat
energy and directly adding to global warming.
The instant invention is a low cost horizontal drainpipe heat exchanger that
requires no
power, no maintenance, is non-blocking, and can pre-heat (or pre-cool) fresh
cold water supply
without danger of cross-contamination.
SUMMARY OF THE INVENTION
The instant heat exchanger has a plastic tubular housing with inlet and outlet
orifices for
water. Inside, a smaller and longer composite drainpipe for drainwater extends
from each end.
The annular space between has a sealed conduit for the potable water to flow
and be tempered.
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The drainpipe is a composite of plastic and copper. A long segment plastic
tube with gap
has recesses along the gap. A concave copper first strip bridges the gap and
is sealed into the
recesses. A copper second strip nests against the first strip. A stretched 0-
ring in the annular
space contacts the exposed perimeter margin of the strip and co-contacts the
housing thereby
defining an open upper arcuate space and a smaller enclosed lower arcuate
space including inlet
and outlet. The gasket also off-sets the drainpipe upwards.
An arcuate plastic compression shoe is forced into the narrower upper space to
urge the
drainpipe downwards compressing the gasket and sealing the resulting conduit.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a cross sectional end view of the outer housing with composite
drainpipe
inside and annular space between;
Figure Is shows the same view as Fig I but with the missing elements added
including,
second metal strip, compression shoe, conduit, water orifice, gasket,
turbulator, flow distributor,
recess seal and vias;
Figure 2 is an end view of the drainpipe element with separated components to
show in
more detail the upper outer portion wall with longitudinal recesses, lower
concave metal strips
with inner one in recesses and outer strip having bendable tabs to restrain
the gasket after
assembly;
Figure 3 how the concave metal strips can be formed from a single wider piece
of folded
in half lengthwise. and how it can be impacted to produce a localized dents
and dimples to create
turbulent flows in both the drain water and the conduit water;
Figure 4 is a partial section side view showing the details of a manifold at
an end of the
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housing and how the drainpipe extends outwardly for plumbing to;
Figure 5 shows a partial sectional side view and how the heat exchanger
connects into a
drainage system;
Figure 6 is a section end view of the composite drainpipe and an end view of
the shorter
housing, compression show and gasket, and how the gasket contacts the
perimeter margins of the
strip and the end margin of the housing.;
Figure 7 shows a tool that has a chamfered end to pre-compress the gasket so
as to ease
entry of the compression shoe into the narrow upper annular space. The tool is
pushed through
and out the opposite by the shoe;
Figure 8 shows how the end of the housing can be notched to hold gasket
accurately
during assembly. After the shoe is installed, the loop ends are disengaged and
forced into place
between the housing inner wall and the drainpipe with the help of a lubricant;
Figure 9 shows a perspective of the cradle-shaped elongated or stretched
gasket, in this
case an 0-ring, when in its final location below between drainpipe and
housing;
Figure 10 a perspective of mesh-type turbulators inserted in the conduit
between flow
distributors to generate turbulent flow through the conduit for faster heat
exchange;
Figure 11 is a perspective view of a flow distributor for the conduit having
an crescent
shape that spreads out flow from a single central inlet into a sheet-like flow
across and along the
copper strip for faster heat exchange with the drainwater.
DETAILED DESCRIPTION
Referring to the drawings, although shown horizontal, in use such a drainpipe
heat
exchanger would be properly angled. Any two liquids can be used in exchanger
200 however for
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simplicity the terms drainwater and potable water are used herein.
Fig 1 shows the two main components, the non-slit, continuous wall, tubular
plastic
housing 1 encircling a smaller, longer composite drainpipe 100.
The housing 1 has aligned inlet and outlet orifices 31 for the water supply to
be tempered.
The inner surface of the housing has margins at each end and paths between
margins, one on
each side of the orifices.
In Fig 1 drainpipe 100 has an upper portion 12 and lower portion 7. Upper
portion is a
segment a plastic tube with gap that has recesses 6b along each side. Lower
portion is a concave
metal strip 7 nested in the recesses to which it is sealed and flush.
Additional components shown in Fig la are: lower metal strip 7 (copper) that
bridges the
gap and is sealed flush into recesses 6b and has a perimeter margin, a second
strip 3 which nests
against first strip 7 and has a perimeter margin, one-piece compressible
gasket 5 shown
contacting margin of second strip 3, orifices 31, fitting 23, compression shoe
12 , turbulator 52,
and flow distributor 55. First strip 7 has vent flat 50 and second strip 7 has
vent groove 51.
Second strip 3 provides double-wall protection from cross-contamination.
Crease or
groove 51 along strip 3 vents any leak to the ambient for visual detection. A
vent can also be a
flat 50 draw-filed or milled on strip 7. Additional vents 11 are naturally
created in the void where
the gasket cannot conform to the inherently sharp corners.
Vias 65 (Fig la) can be used to inject a solvent cement after assembly to bond
the
concentric plastic elements together.
Inlet and outlet 23,31 for for the water are located at opposite ends of
housing 1. They
can be single centred fittings 23a (Fig la) or multiple orifices 31 with
associated manifold 20
(Figs 4,5) which can be rotated to have fitting 23 on top (Fig 4) to lower
installation height and
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to add protection from breakage.
When one-piece elongated gasket 5 is inserted, unequal upper and lower arcuate
spaces
are created. Gasket 5.contacts the perimeter margin of second strip 3 and
complementary
margins and paths on interior of housing 1. Gasket 5 also encloses the inlet
and outlet thereby
defining an arcuate conduit 12a for the water.
A arcuate compression shoe 12, a plastic tube segment, has a wall thickness
equal to the
target compressed thickness of gasket 5. Shoe 12 is forcibly inserted into the
thinner upper
annular space 12a which urges drainpipe 100 down against gasket 5 compressing
it against the
margins and paths thereby sealing conduit 12a.
Fig 4 shows exchanger 200 lengthwise in cross-section. Manifold 20 has 0-rings
22 in
grooves 25 on either side of water flow path 21. Fitting 23 communicates with
flow path 21.
Orifices 31 are shown at a severe angle to direct water 30 against gasket 5
ensuring heat transfer
from the endmost portion and reduce erosion of strip 3. Manifold 20 is shown
to have a flange 24
at the end to restrain gasket 5. Second fluid 30 is shown by linear arrows to
be flowing through
conduit 12a.
In Figs 1,11 flow distributor 55 (only one shown) prevents a direct, narrow
linear flow
between inlet and outlet by providing more flow restriction at the centre
where inlet pressure at
inlet 23 is highest, and proportionally diminishing restriction towards the
extremities where
water pressure is lowest thereby providing a wide, even, curtain-like flow
along strip 3 or 7 for
faster heat transfer.
Fig 3 shows a lower concave metal strip 40 formed from a wider copper strip
folded in
half lengthwise as shown at fold 40a to replace separate strips 3,7. With
folded strip 40 there is
no unwanted relative movement between strips 3,7 during handling and assembly.
Further, this
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design lends itself to the impact-punching of pits 60 (only one shown) which
raises dimples 60a
without interfering with the all-important thermal contact conductance. The
pits and dimples
create turbulence in both the drainwater and the fresh water which improves
heat exchange. Also
with folded strip 40, vents can be co-formed with wire inserts while forming
and removed after.
Both nested strips 3,7 and folded strip 40 are held in intimate contact by the
water
pressure in the conduit.
In Fig 5 the connections to the instant drainpipe heat exchanger 200 are shown
at both
ends where a common drainpipe B carries drainwater A through coupling C with
insertion stop
ridge C'. Fluid fittings 23 are shown at different radial positions which can
be useful for
plumbing to the second fluid supply.
In Fig 6 housing I, shoe 12, safety layer 3, and gasket 5 are all shown in end
view while
the composite drainpipe 100 is shown in cross-section indicating it extends
beyond housing 1 to
provide a stub for pluming connection.
Insertion tool 102 with chamfered end 101 shown in Fig 7 can be used to wedge
apart
upper arcuate space. A second such tool 102 may be used at the other end to
keep the drainpipe
evenly positioned. Tool(s) 101 are pushed through and out by permanent shoe
12.
Fig 8 shows how notches 5a in the housing rim may be used to hold gasket 5 in
place
during insertion of drainpipe 100 after which the loop ends are released from
the notches 5a and
pushed into position between the housing I and strip 3. A food-safe lubricant
such as K-Y jelly
can be used. Strips 3,7 can have its tabbed ends Sc bent up (two shown in Fig
2) after assembly
to prevent end loops of gasket 5 from being displaced from internal water
pressure.
Fig 9 shows a perspective of how elongated 0-ring gasket 5 becomes cradle-
shaped when
in place and can be pre-formed to that shape.
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Figs 1,10 show turbulator 52 used to generate turbulent flow in the conduit,
especially if
the conduit has considerable depth, that is, has a thick gasket 5. Fig 10
shows turbulator 52 as
sheets of mesh. Punched tabs (not shown) can also be used. Fig 10 also shows
how the turbulator
is in sections to be inserted from one end between spaced flow distributors
before the second end
loop of gasket 5 is pressed into position finally sealing conduit 12a.
In certain plumbing installations it may be that using multiple heat
exchangers 200 is
preferable. For example several shorter standardized units can be joined end-
to-end. Several may
operate in parallel where a portion of the drainwater flows through each
branch. Or several may
be arranged in a zig-zag fashion (with elbows between) and installed against a
vertical wall in
place of a vertical heat exchanger thereby offering more heat transfer surface
area at lower cost
due to elimination of an expensive vertical copper drainpipe.
If necessary a common water pressure regulator (not shown) can be used to
control
pressure in conduit 12a.
Although the invention has been shown and described it should be understood by
those
skilled in the art that various changes in form and detail may be made without
departing from the
spirit and the scope of the claimed invention.
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