U.S. patent application number 14/511438 was filed with the patent office on 2016-04-14 for packaged helical heat exchanger.
The applicant listed for this patent is Richard Curtis Bourne. Invention is credited to Richard Curtis Bourne.
Application Number | 20160102922 14/511438 |
Document ID | / |
Family ID | 55655211 |
Filed Date | 2016-04-14 |
United States Patent
Application |
20160102922 |
Kind Code |
A1 |
Bourne; Richard Curtis |
April 14, 2016 |
Packaged Helical Heat Exchanger
Abstract
This invention provides an economical helical polymeric heat
exchanger that packages tightly for handling and then is quickly
assembled to its full length prior to placement in either the
ground or water.
Inventors: |
Bourne; Richard Curtis;
(Davis, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bourne; Richard Curtis |
Davis |
CA |
US |
|
|
Family ID: |
55655211 |
Appl. No.: |
14/511438 |
Filed: |
October 10, 2014 |
Current U.S.
Class: |
165/156 |
Current CPC
Class: |
Y02E 10/125 20130101;
F28D 1/022 20130101; F24T 10/15 20180501; F28D 1/0472 20130101;
F28F 9/013 20130101; F28F 21/062 20130101; Y02E 10/10 20130101 |
International
Class: |
F28F 1/00 20060101
F28F001/00 |
Claims
1. A helical liquid-to-ground or liquid-to-water heat exchanger of
continuous tubing with at least two flexible straps that securely
hold the tubing, establish a maximum helical pitch, and allow
compact packaging before installation, with at least two linear
compression members that secure to the strips just prior to
installation, where the compression members cause the heat
exchanger to be installed in its extended position.
2. Claim 1 where the compression members secure to clips along the
straps.
3. Claim 1 where the compression members insert through openings in
clips along the straps.
4. Claim 2 where the compression members are retained with
fasteners to the clips at both ends of the helix.
Description
BACKGROUND ART
[0001] This invention relates generally to heat exchangers that are
used for heating and cooling of buildings or of hot or chilled
water for buildings or industrial purposes, and in particular to
heat exchangers that are used to extract or discharge heat from and
to the ground or large bodies of water, either stable (lakes or
oceans) or moving (streams or rivers). Such heat exchangers are
typically used in conjunction with closed-loop heat pumps that are
able to transfer heat from a colder source to a warmer sink.
[0002] In the prior art, typical installations in the ground use a
6'' to 8'' diameter, 100-to-200 foot deep bore with a polymeric
U-tube (typically of high-density polyethylene, HDPE) grouted in
place to maximize heat transfer. These installations are relatively
expensive and have the performance liability of allowing a
relatively short heat transfer path from the downward supply tube
to the upward return tube. Thus, in heat extraction mode, for
example, warmer water returning from the bottom is being re-cooled
by water flowing downward a few inches away. A better thermal
solution for in-ground applications is a vertical, spiral heat
exchanger with a straight supply or return near the center of the
spiral. Excavation per foot of heat exchanger is typically much
lower for spirals, using augur equipment well-developed for power
pole excavation. These relatively shallow bores do not puncture
impervious soil layers below 30.degree. deep, thus limiting the
dangers of surface contaminants penetrating downward into water
supply layers.
[0003] Spiral ground exchangers were pioneered in the US beginning
in the 1990's, typically with installations of spirals 18'' to 36''
in diameter and 20' to 35' deep. The first of these used HDPE
pre-wired to cylindrical reinforcing steel cages formed from either
reinforcing bars or wire mesh. Beginning in 1997, this inventor
developed a "suspender" design that allowed compact packaging of
the heat exchanger and elimination of the steel cage. This work was
carried out with support from the California Energy Commission, as
fully and publicly reported in 1999. No patent application was
filed, and subsequently European patent EP1992886A2 was issued in
2008 covering precisely the concept demonstrated in the two
California projects summarized in the 1999 reports that apparently
were not discovered in connection with the European patent.
[0004] Work on the California ground helix was tabled for business
reasons in 2000. Development work was resumed in 2012 on the
improved version of the helix described here. The improved design
does not rely on gravity to extend the helix into its final,
working position, and also allows the heat exchanger to be used in
bodies of water where a non-vertical helix working position is
advantageous. These helical heat exchangers are typically polymeric
but may also be made of soft copper to contain a refrigerant
instead of an aqueous liquid.
SUMMARY OF INVENTION
Technical Problem
[0005] Vertical-helix ground exchangers are a cost-effective
alternative to deep bores for geothermal heat pump applications,
and "suspender" helix designs facilitate compact handling before
the exchangers arrive at the jobsite. But the suspender designs
require both a support rig to hold them in suspended position for
deployment and backfill, and strong, supportive attachments between
the rig and the suspenders. This need can be structurally
challenging, since in its suspended position the helix may not
reach the bottom of the hole. In this case the entire weight of the
heat exchanger and the (often considerable) backfill soil or sand
that clings to it must be carried by the exchanger and its support
rig. Also, the support rig interferes with the backfill operation,
and may require installers to lean into a very deep hole to connect
and disconnect the helix to/from the suspension rig. Finally, the
suspender helix design does not facilitate installation in water
where a horizontal position is more stable and better protected
from damage.
Solution to Problem
[0006] The solution provided by this invention is to add
two-to-four inexpensive vertical supports that intermittently
connect to the circumference of the helix and extend it to full
length. This solution provides enough rigidity that a helix 20'
long (tall) can be easily tilted and slid into a deep augured hole.
No support rig is required. The assembled helix then rests on the
bottom of the hole, so that backfill material is not continuously
trying to pull the helix further down. Delivery to the jobsite
includes one or more tightly packed helical heat exchangers, and
linear compressive members, (typically inexpensive rigid PVC pipe)
that quickly secure to the flexible strips that determine the final
coil spacing of the helix. These compressive members provide
sufficient rigidity for placing the fully-extended helix either
into a bored hole (typically with the axis of the helix vertical),
or into a body of water (typically with the axis of the helix
horizontal).
Advantageous Effects of Invention
[0007] This invention provides an improved, more versatile
geothermal heat exchanger that can be installed more quickly and
can better survive installation hazards for ground burial
applications, compared to previously-used "suspender" helix
designs. The invention also facilitates installation in bodies of
water in non-vertical positions where gravity alone would not hold
the helix in a fully-extended position. It eliminates the need for
placing and removing a holding jig during onsite deployment of the
helix, and minimizes the likelihood of damage during placement in
the ground, by assuring that the helix is supported at the bottom
of the augured hole.
BRIEF DESCRIPTION OF DRAWINGS
[0008] The following description of a principal embodiment of the
invention refers to four drawings:
[0009] FIG. 1 is a cut cross sectional view of the assembled helix
in a vertical-axis orientation.
[0010] FIG. 2 is a cut top view of the helix of FIG. 1 showing both
top and middle segments of the helix.
[0011] FIG. 3 is a close-up view taken from FIG. 1, showing key
features at a middle segment of the helix.
[0012] FIG. 4 is a close-up view taken from FIG. 1, showing key
features at the top and bottom of the helix.
[0013] FIG. 1 shows a wound helix 1 held in its final configuration
by flexible straps 2, holding clips 3 and 4, and compression
members 7. The helix 1 performs as a closed loop heat exchanger
with liquid entering through inlet tube 5 to enter helix 1 at one
end (typically the bottom for vertical in-ground applications).
Liquid flows upward through helix 1 to emerge through exit 6.
Contact with the ground or water causes the liquid to be heated or
cooled as it passes through the helix. (In water applications the
helix will most often be posited with its axis approximately
horizontal, so the assembly rests on the bottom of either a
stationary or flowing body of water.) Horizontal ground
applications are also possible.
[0014] For illustrative convenience these drawings show four sets
of straps 2, compression members 7, and clips 3 and 4 at 90 degree
spacing around the circumference of helix 1. Since each set adds
additional material and labor costs, the only rationale for more
than three sets is redundancy; one strap could fail during backfill
and the helix could still maintain fairly uniform coil spacing.
[0015] In a typical embodiment, helix 1 of continuous high density
polyethylene (HDPE) tubing has diameter of approximately 24'' and
the outside tubing diameter is 0.625'' or 0.75'', with total helix
length approximately 20', and helical coil spacing of about 6''.
These dimensions provide effective heat exchange performance with
modest pressure drop for the heat exchange liquid, which is
typically water or an anti-freeze/water solution.
[0016] As in prior designs, the helix 1 arrives at the jobsite with
the helical coils tightly packed to facilitate handling. Flexible
straps 2 allow the coil to be compressed for tight packing, with
clips 3 and 4 pre-secured intermittently at intersections of the
helix 1 and straps 2. Clips 3 have through holes that allow
compression members 7 to slide through, as further shown with
reference to FIG. 2 and FIG. 3. Clips 4 at both ends may be with or
without through holes, as further discussed with reference to FIG.
2 and FIG. 4.
[0017] FIG. 2 shows, in upper/right half and lower/left half,
respectively, how clips 3 and 4 respectively interact with helix 1,
strap 2, and compression member 7. Clips 3, located on middle coils
of helix 1, are spaced approximately every 6 coils. Clip 3 is a
short polymeric channel that can either be cut and drilled from an
extrusion, or injection-molded. At its inner edge it is secured,
preferably by adhesive, to strap 2 and to helix 1. In a preferred
embodiment, strap 2 wraps both ways around helix 1 as further
described with reference to FIG. 3. Compression member 7, typically
a 20' long nominal 1/2'' PVC pipe that is 0.84'' diameter, inserts
through holes 8 in clips 3. While clips 4 at the top and bottom of
helix 1 may be identical to clips 3, and fastened to compression
members 7 as further described with reference to FIG. 4, they may
also, as shown, be without holes so that compression members 7
dead-end against the middle surface of channel clip 4. Since helix
1 favors its compacted position when first extended, members 7 tend
to "stretch" the coil when they dead-end against closed clips
4.
[0018] FIG. 3 provides additional detail on the assembly at middle
coils that use clips 3. A preferred embodiment of strap 2 is shown
as a two-layer assembly surrounding helix tube 1. Both straps are
adhesive-coated tapes, and are deployed with adhesive face-to-face.
Each clip 3 has a middle segment 3a, a long leg 3b, and a short leg
3c. The outside of leg 3b adheres to strap 2a to help hold the
helix 1 in position, and strap 2b adheres to the inside of leg 3b
to further secure clip 3 to strap 2a. Compression member 7 inserts
through slightly over-sized hole 8 in middle segment 3a, and leg 3c
helps retain an orthogonal relationship between clip 3 and member
7. Above and below clip 3, strap 2a is continuous, and cover straps
2b extend over approximately five coils to either the next clip 3
or to a clip 4 at the top or bottom of the helix, as shown with
reference to FIG. 4.
[0019] FIG. 4 provides additional detail on the assembly at the end
coils, where end clips 4 are adhered to main strap 2a before helix
1 is wound. Each clip 4 has a middle segment 4a, a long leg b, and
a short leg 4c. The outside of leg 4b adheres to strap 2a such that
middle segment 4a is just outside the last coil of helix 1, and
strap 2b adheres to the inside of leg 4b to further secure clip 4
to strap 2a. Compression member 7 dead-ends against middle segment
4a, and leg 4c helps retain an orthogonal relationship between clip
4 and member 7. To prevent possible separation during handling and
placement, self-drilling screw 9 may be driven through leg 4c into
member 7. While FIG. 4 shows the top of a vertical-axis helix, it
should be clear that turned upside-down, it also represents the
bottom; or sideways, either end for a horizontal deployment in
either earth or water.
* * * * *