U.S. patent number 3,828,845 [Application Number 05/346,622] was granted by the patent office on 1974-08-13 for permafrost structural support with internal heat pipe means.
This patent grant is currently assigned to McDonnell Douglas Corporation. Invention is credited to Elmer D. Waters.
United States Patent |
3,828,845 |
Waters |
August 13, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
PERMAFROST STRUCTURAL SUPPORT WITH INTERNAL HEAT PIPE MEANS
Abstract
Structural support assembly for use in arctic and subarctic
(permafrost) areas or in any areas where the upper ground layer is
subject to a severe annual freeze-thaw cycle, including the
cooperative combination of a support structure and a heat pipe
element installed in generally frozen soil. The heat pipe is of a
suitably complementary configuration and/or disposition with
respect to the support structure to provide appropriate
stabilization of the surrounding frozen soil. In one embodiment,
the heat pipe element is disposed externally of the support
structure and, in another embodiment, it is disposed internally of
such structure. The external embodiment further includes one
version employing a linear (straight) heat pipe element and another
version employing an angular (helical) element. The internal
embodiment further includes one version wherein a heat pipe is
integrally combined with a support structure and another version
wherein a heat pipe is cooperatively installed inside a support
structure.
Inventors: |
Waters; Elmer D. (Richland,
WA) |
Assignee: |
McDonnell Douglas Corporation
(Santa Monica, CA)
|
Family
ID: |
26870462 |
Appl.
No.: |
05/346,622 |
Filed: |
March 30, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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174687 |
Aug 25, 1971 |
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Current U.S.
Class: |
165/45;
165/104.21; 165/185; 165/104.26 |
Current CPC
Class: |
E02D
3/115 (20130101); F24T 10/30 (20180501); F28D
15/0233 (20130101); E02D 27/35 (20130101); F24T
10/40 (20180501); Y02E 10/10 (20130101); F28F
2200/005 (20130101) |
Current International
Class: |
E02D
3/115 (20060101); E02D 27/35 (20060101); E02D
3/00 (20060101); E02D 27/32 (20060101); F28D
15/02 (20060101); F28d 015/00 () |
Field of
Search: |
;165/45,105,106,104,76 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Davis, Jr.; Albert W.
Attorney, Agent or Firm: Jeu; D. N. Jason; Walter J. Royer;
Donald L.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This is a continuation-in-part of U.S. Pat. application Ser. No.
174,687 filed Aug. 25, 1971.
Claims
I claim:
1. For use in ground areas subject to an annual freeze-thaw cycle,
a structural support assembly comprising:
a support structure for installation in generally frozen soil, said
support structure being made of a good heat conducting material,
and including an accommodation space therein;
a heat pipe element of a configuration and disposition
complementary to said support structure, said heat pipe element
including a relatively small amount of working fluid therein, the
lower portion of said heat pipe element being installed in said
accommodation space, the upper portion of said heat pipe element
being adapted to be coupled to heat exchanger means, and the lower
portion of said support structure being installed in said frozen
soil; and
a good heat transfer medium provided in said accommodation space
whereby heat from said frozen soil adjacent to said lower portion
of said support structure is transferred by said heat transfer
medium to said lower portion of said heat pipe element and
transported by vaporization of part of said working fluid to said
upper portion thereof and diposed of by condensation of said
vaporized working fluid in said heat exchanger means to stabilize
said frozen soil adjacent to said lower portion of said support
structure throughout the year.
2. The invention as defined in claim 1 wherein said support
structure includes a hollow metallic pile having an internal
chamber space for accommodating said lower portion of said heat
pipe element.
3. The invention as defined in claim 1 wherein said lower portion
of said heat pipe element includes a generally cylindrical tube and
at least one longitudinal fin extending laterally therefrom.
4. The invention as defined in claim 3 wherein said generally
cylindrical tube has a largely circular cross section and said
longitudinal fin extends radially therefrom.
5. The invention as defined in claim 3 wherein said heat pipe
element includes flow means installed in said lower portion of said
heat pipe element for directing and distributing working fluid
condensate return flow therein.
6. The invention as defined in claim 1 wherein said lower portion
of said support structure is closed at its lower end and said heat
transfer medium includes a good heat transfer liquid.
7. The invention as defined in claim 1 wherein said lower portion
of said support structure is open at its lower end and said heat
transfer medium includes a slurry of soil and water.
8. The invention as defined in claim 2 wherein said lower portion
of said heat pipe element includes a generally cylindrical tube and
at least one longitudinal fin extending laterally therefrom.
9. The invention as defined in claim 8 wherein said hollow metallic
pile is closed at its lower end and said heat transfer medium
includes a good heat transfer liquid.
10. The invention as defined in claim 8 wherein said hollow
metallic pile is open at its lower end and said heat transfer
medium includes a slurry of soil and water.
11. For use in ground areas subject to an annual freeze-thaw cycle,
a structural support assembly comprising:
a support structure for installation in generally frozen soil, said
support structure including a pole-like member made of a heat
conducting material and having an accommodation space in at least
the lower portion thereof;
a heat pipe element including a tubular container having a charge
of working fluid therein and a heat exchanger coupled to the upper
portion of said container, said working fluid normally existing as
a small quantity of liquid in said container with saturated vapor
filling the remainder thereof, said heat pipe element being of a
configuration and disposition complementary to said support
structure, said outer surface of said heat pipe element having an
extended heat transfer surface throughout substantially the full
length of the lower portion of said tubular container, the lower
portions of said container and said pole-like member being normally
installed in said frozen soil with said lower portion of said
container being indirectly installed in said frozen soil within
said accommodation space and said lower portion of said pole-like
member being directly installed in said frozen soil, and said lower
portion of said container being disposed at least adjacent and
generally parallel to a surface in said accommodation space of said
lower portion of said pole-like member in heat transfer
relationship therewith; and a heat transfer medium provided in said
accommodation space whereby heat from said frozen soil adjacent to
said lower portion of said support structure is effectively
transferred by said heat transfer medium to said lower portion of
said tubular container and transported by vaporization of part of
said working fluid to said upper portion thereof and disposed of by
condensation of said vaporized working fluid in said upper portion
of said container coupled to said heat exchanger to stabilize said
frozen soil adjacent to said lower portion of said support
structure throughout the year.
12. The invention as defined in claim 11 wherein said lower portion
of said container comprises a generally cylindrical tube and at
least one longitudinal fin extending laterally therefrom.
Description
BACKGROUND OF THE INVENTION
My invention relates generally to support structures and, more
particularly, to a novel and useful structural support assembly for
use in permafrost areas or in any areas having active ground layers
subject to a severe annual freeze-thaw cycle.
Permafrost is material which is largely frozen permanently. It is
usually a mixture of soil, rock and ice although it can be anything
from solid rock to muddy ice. In the arctic regions, permafrost may
extend from a few feet to hundreds of feet below the surface. The
permafrost is separated from the surface by an upper layer (the
tundra) and its surface vegetation. The upper layer or tundra
serves as insulation to limit permafrost thaw in the summer but is
subject to a seasonal freeze-thaw cycle. The permafrost thaw in the
summer, however, can create an unstable condition for structures
constructed in permafrost areas. This is, of course, more so in
wet, ice-rich, permafrost areas than in dry, stable, permafrost
areas of well drained soil or rock.
There are severe problems associated with support and stabilization
of structures in the arctic regions where permafrost is prevalent.
Alaskan railroads, for example, require the expenditure of
thousands of dollars each year to repair soil slippages and track
roughness resulting from the annual freeze-thaw cycle and
disturbances of the ground cover by the intrusion of man and his
machines. When the tundra is broken or removed, the permafrost
loses its insulation and begins to melt and erode. Thus, tracks
left by a tractor or caterpillar train can become a deep ditch and
alter the surface drainage pattern over a wide area.
In cities and regions which overlay permafrost areas, a gravel
insulating technique is generally used in construction over such
areas. A raised gravel pad, for example, is ordinarily employed to
provide a suitable support or work area on permafrost. Foundation
structures embedded in permafrost are also commonly surrounded
completely by a layer of insulating gravel. In areas of ice-rich
permafrost and/or during a strong summer thaw, however, even the
use of a relatively thick insulating gravel layer is inadequate to
prevent some subsidence and possibly accompanying damage of the
supported structure or apparatus. On the other hand, instead of
subsiding, support posts or poles for arctic overhead
communications and power lines have presented a particular problem
with "pole jacking" wherein the annual seasonal uplift due to frost
heave can actually lift the poles and their anchors completely out
of the ground. The pole jacking problem has plagued all of the
utility companies throughout vast areas of the subarctic regions,
and is presently considered to have no reasonable economic
solution.
The U.S. Pat. No. 8,217,791 of Erwin L. Long on Means for
Maintaining Permafrost Foundations patented Nov. 16, 1965 discloses
and claims a thermo-valve foundation system including a closed
tubular container partially filled with a low boiling point liquid,
either propane or carbon dioxide, and a layer of gravel completely
surrounding its lower portion. The thermo-valve tubular container
operates during periods of subfreezing temperatures to absorb heat
from the adjoining permafrost, to freeze the adjacent unfrozen soil
and increase its strength of adhesion to the foundation. The
container itself serves as a foundation piling or support pole
which is used with a gravel layer completely surrounding its lower
portion. It is, however, not only costly but frequently impractical
and infeasible to provide a sufficiently large and thick insulating
gravel layer entirely around and below the lower portion of each
pole to stabilize it. Moreover, the metallic tubular container of
the thermo-valve system is obviously limited by practical
considerations in height or length and location whereas a wooden
utility pole of any substantial height or length can be
economically used in any location.
SUMMARY OF THE INVENTION
Briefly, and in general terms, my invention is preferably
accomplished by providing a structural support assembly for use in
arctic, subarctic and similar regions, including a cooperative
combination of a support structure and a heat pipe element, which
can be directly and easily installed in generally frozen soil to
provide a stable support for various apparatus and structures. The
heat pipe element is of a suitably complementary configuration
and/or disposition with respect to the support structure to provide
appropriate stabilization of the surrounding frozen soil.
Where the support structure is of the form of a wooden utility
pole, for example, the heat pipe element can be of either a linear
(straight) configuration or an angular (helical) one positioned
adjacent to the surface of the lower embedded portion of the pole.
Both straight and helical elements extend at least over the
embedded length of their respective poles and protrude a
predetermined distance linearly above the ground for heat exchange
purposes. The heat pipe element broadly includes an elongated
tubular container having a filling or charge of a suitable working
fluid, and a heat exchanger (radiator) suitably coupled or
integrally incorporated with the protruding upper portion of the
tubular container. Means for attaching the lower embedded portion
of the tubular container to the surface of the pole can be utilized
where desired or required.
Each of the straight and helical heat pipe elements can be
fabricated in a two-part assembly wherein the upper radiator
section, located above the ground, can be readily separated and
detached from the lower embedded section. In this instance, the
upper and lower heat pipe sections are secured together in an
overlapping joint. Heat transfer between the two parts is
facilitated by, for example, a thermal paste used between the
contiguous faces of the joined parts. While the heat removal rate
with the two-part assembly is about 12 percent less than with a
one-part assembly, the two-part assembly permits easy replacement
of a radiator that may be damaged by large animals (migrating
caribou, bears, etc.) or by vandalism.
Where a wooden pole or piling cannot be used or is not desired,
advantage can be taken of an integrally combined metallic support
structure and heat pipe element assembly. This structural support
assembly includes a closed, elongated, tubular container having a
filling or charge of a suitable working fluid, a helical wall fin
protruding radially inwards from the internal surface of the
tubular container, and a heat exchanger (radiator) suitably coupled
or integrally incorporated with the upper portion of the tubular
container. The lower portion of the tubular container is installed
directly in permafrost to a depth such that the upper radiator
portion is positioned above the ground with its upper end located
at a desired height to provide support for associated apparatus or
structure.
Where the support structure is a hollow metallic pile, the lower
portion of a heat pipe element can be generally installed linearly
(or angularly) inside of the pile which is then filled with a good
heat transfer medium. A filler liquid such as kerosene can be used
to fill the pile if it is closed or sealed at its lower end or
bottom and is not leaky. If, however, the pile is leaky or is open
at the bottom, a suitable slurry of soil and water or sand and
water can be used to fill the pile. The heat pipe element installed
in the hollow metallic pile is an elongated tubular container
including a relatively small quantity of a suitable working fluid
therein. A heat exchanger (radiator) is suitably coupled to the
upper portion of the tubular container extending normally above and
outside of the pile. The lower portion of the tubular container has
at least one longitudinal, heat transferring, fin or flange affixed
thereto and extending laterally or radially therefrom. Preferably,
two such fins are diametrically affixed to the lower portion of the
tubular container to provide an axially symmetrical member which
can be easily bent (perpendicularly to the plane of the fins) as
required. Flow or wick means can be included under certain
conditions in the lower portion of the tubular container for
generally directing and distributing fluid condensate flow
therein.
BRIEF DESCRIPTION OF THE DRAWINGS
My invention will be more fully understood, and other features and
advantages thereof will become apparent, from the following
description of certain exemplary embodiments of the invention. The
description is to be taken in conjunction with the accompanying
drawings, in which:
FIG. 1 is a front elevational view, shown partially in section and
in simplified form, of a test installation of different poles
including control poles and those constructed according to this
invention;
FIG. 2 is a front elevational view, shown partially in section and
in fragments, of a linear (straight) heat pipe element that is
normally attached to a wooden utility pole to stabilize the
surrounding permafrost in which it is installed;
FIG. 3 is a fragmentary sectional view of a lower part of the
linear heat pipe element as taken along the line 3--3 indicated in
FIG. 2;
FIG. 4 is a side elevational view of a central part of the linear
heat pipe element as taken along the line 4--4 indicated in FIG.
2;
FIG. 5 is a cross sectional view of an upper part of the linear
heat pipe element as taken along the line 5--5 indicated in FIG.
2;
FIG. 6 is a front elevational view, fragmentarily shown, of an
angular (helical) heat pipe element that is normally attached to a
wooden utility pole to stabilize the surrounding permafrost in
which it is installed;
FIG. 7 is a side elevational view of a central part of the angular
heat pipe element as taken along the line 7--7 indicated in FIG.
6;
FIG. 8 is a cross sectional view of the central part of the angular
heat pipe element as taken along the line 8--8 indicated in FIG.
7;
FIG. 9 is a front elevational view, shown partially broken away, of
a structural support assembly wherein a heat pipe element is
constructed to serve simultaneously as the support structure;
FIG. 10 is a cross sectional view of a lower part of the support
assembly as taken along the line 10--10 indicated in FIG. 9;
FIG. 11 is a cross sectional view of an upper part of the support
assembly as taken along the line 11--11 indicated in FIG. 9;
FIG. 12 is a generally perspective view, shown partially in section
and in fragments, of a hollow metallic pile installed in permafrost
and having the lower portion of a heat pipe element positioned
internally of the pile which is filled with a good heat transfer
medium;
FIG. 13 is a cross sectional view of a lower part of the hollow
metallic pile and heat pipe element installation as taken along the
line 13--13 indicated in FIG. 12;
FIG. 14 is a cross sectional view similar to that of FIG. 13 and
showing a variation in cross sectional configuration of the heat
pipe element to provide a general shape for a double finned element
which is near optimum from a heat transfer surface and element
flexibility standpoint; and
FIG. 15 is another cross sectional view similar to those of FIGS.
13 and 14 and showing another variation in cross sectional
configuration of the heat pipe element to provide a general shape
which has a greatly increased heat transfer surface over that of a
central tubular element alone or with double fins but which,
however, cannot be bent as easily or to the extent of such
others.
DESCRIPTION OF THE PRESENT EMBODIMENTS
In the accompanying drawings and following description of certain
embodiments of my invention, some specific dimensions and types of
materials are disclosed. It is to be understood, of course, that
such dimensions and types of materials are given as examples only
and are not intended to limit the scope of this invention in any
manner.
FIG. 1 is a front elevational view, shown partially in section and
in simplified form, of a test installation of a group of different
poles including a regular power pole 20, a first control pole 22
set to simulate a typical utility pole installation, a second
control pole 24 set with a type AM-9 chemical grout solution added
to the backfill around the pole base, a utility pole 26 with a
linear heat pipe element S attached to its lower embedded portion,
and another utility pole 28 with an angular heat pipe element y
attached to its lower embedded portion. The purpose of the chemical
grout solution used in the backfill of the control pole 24 was to
prevent water migration to the soil-pole interface. For clarity of
illustration, the heat pipe elements S and y have been shown in
considerably simplified forms. The heat pipe poles 26 and 28 were
installed on either side of the first control pole 22.
The four poles 22, 24, 26 and 28 were installed to evaluate the
magnitude of pole jacking and the preventive effects of the heat
pipe elements S and y. The poles 22, 24, 26 and 28 were installed
at 30 feet spacings in order that the poles can function
independently but be comparable in movement. Thermocouples 30 and a
frost tube 32 were installed adjacent to each pole for data
comparison. A ground frost tube 34 was installed between the poles
22 and 26. A 24-inch auger unit was used to drill the installation
holes and, as each hole was drilled, the ground conditions were
observed and noted. In general, the test ground can be typified as
peaty organic silt to a depth of 2 feet and clay silt to a depth of
8 feet. The permafrost level was at a depth of approximately 6
feet.
Temperatures measured by the thermocouples 30 are suitably recorded
and plotted. The frost tubes 32 suspend or permit the lowering
therein of transparent containers of a (liquid) substance which
gradually changes from a green to red color as it changes from an
unfrozen to frozen condition. Thus, the frost tubes 32 provide or
permit the obtaining of visual indications of the (unfrozen or
frozen) conditions of the soil adjacent to the poles 22, 24, 26 and
28. The ground frost tube 34 was used to provide or permit the
obtaining of information on the extent of ground freezing between
the poles 22 and 26.
The heat pipe elements S and y are designed especially to cause
rapid freezing of the soil around a utility pole in a radial
direction along the full embedded pole portion so that the pole is
firmly anchored from the ground surface into the permafrost. Water
migration and frost heave due to progressive freezing and adhesion
to the pole from the ground surface downward are thus precluded.
Since soil expansion occurs in the radial direction, the vertical
forces acting on the pole are minimized. Of course, unfrozen soil
can accommodate the radial expansion, and there are no appreciable
detrimental forces acting to damage a heat pipe element in the
ground.
The primary measure of pole jacking is vertical movement throughout
the year. Test results showed that the existing power pole 20 and
its brace rose at a relatively rapid rate. Similarly, the plots for
the first and second control poles 22 and 24 also showed that both
moved upward at comparable rates. Of interest, the second control
pole 24 with chemical grout added to its backfill, rose at a
greater rate than any other pole. The pole 14 and stabilized soil
surrounding it were apparently being jacked as a single unit. The
poles 26 and 28 with their respective linear and angular heat pipe
elements S and y, however, did not establish any definite trend of
movement during the same period of time and the heat pipes
definitely developed a full jacket of frozen soil around their
poles from the ground surface to the permafrost. It appeared that
this jacket is strong enough to prevent any future upward
heave.
Also, the helical heat pipe element y definitely cooled the ground
more rapidly than the straight heat pipe element S and created a
larger frost jacket around its pole 28 but this additional freezing
(above that offered by the straight heat pipe element) did not
appear necessary to obtain an adequate frost anchor effective the
year round. One linear element S appears to be adequate to anchor
its pole 26 having a diameter of approximately 12 inches. For
substantially larger diameter poles, two or more linear elements
can be attached equiangularly spaced circumferentially about such
poles. Alternatively, a single angular element y can be used
instead on very large diameter poles.
FIG. 2 is a front elevational view, shown partially in section and
in fragments, of the linear heat pipe element S which is normally
attached to the wooden utility pole 26 (FIG. 1). The heat pipe
element S generally includes a lower embedded portion 36, a central
connecting tee portion 38, and an upper heat exchanger (radiator)
portion 40. The lower portion 36 is preferably fabricated largely
of a tubular (aluminum) extrusion 42 having a central bulbous tube
44 and side flanges or fins 46a and 46b. The lower portion 36 is,
for example, about 96 inches long and can be conveniently fastened
to the pole 26 by nails 42' and washers 44' located near the ends
of flanges 46a and 46b, and at spacings of approximately 12 inches
between the ends. The tube 44 has a circular inner diameter
nominally of 1/2 inch, and is suitably sealed and covered by a cap
48 at its lower end. With an aluminum extrusion 42, selection and
use of a suitable means of corrosion protection such as galvanic
protection, for example, the sacrificial washers 44', or surface
coating protection (organic film or chemical conversion film) is
normally required. A conventional wall screen (wire mesh) wick is
not used in the heat pipe element S although such means may be
preferably used in the lower embedded portion 36 when it is very
long (in one instance, 40 feet, for example).
FIG. 3 is a fragmentary sectional view of the lower end of the
lower portion 36 of the linear heat pipe element S as taken along
the line 3--3 indicated in FIG. 2. A standard pinch-off end plug 50
is welded to the lower end of the tube 44. The heat pipe element S
can be suitably loaded with a working fluid such as ammonia through
the end plug 50, and then closed by pinch-off and seal welding.
Approximately 48 grams of ammonia is used, for example, in this
illustrative embodiment. The end plug 50 is covered by cap 48 which
can be secured by epoxy cement to the lower end of the extrusion
42. Of course, any other suitable form of protective cover for the
pinch-off and weld can be used.
FIG. 4 is a side elevational view of the central connecting tee
portion 38 of the linear heat pipe element S as taken along the
line 4--4 indicated in FIG. 2. Referring to both FIGS. 2 and 4, it
can be seen that the upper end of the tube 44 of extrusion 42 is
joined to the lower end of the upper heat exchanger portion 40 by
the central portion 38. This central portion 38 includes a tee 52,
a lower tube 54, and left and right upper tubes 56 and 58. The ends
of the lower tube 54 extend approximately 1/2 inch into the upper
end of tube 44 and lower passageway of tee 52, respectively, and
are welded thereto. Similarly, the upper left and right tubes 56
and 58 connect the left and right passageways of the tee 52
respectively to the lower ends of adapter plugs 60 and 62 mounted
in left and right holes of a bottom support strap 64 as shown in
FIG. 2. The upper ends of the hollow adapter plugs 60 and 62 are
welded respectively to the lower tubular ends of passive radiators
66 and 68 of the upper heat exchanger portion 40. While two
radiators 66 and 68 have been shown, only one or more than two
radiators can be appropriately used.
FIG. 5 is a cross sectional view of the radiators 66 and 68 of the
upper portion 40, as taken along the line 5--5 indicated in FIG. 2.
Referring jointly to FIGS. 2 and 5, it can be seen that each of the
radiators 66 and 68 includes a central tubular body 70 and a
plurality of radial fins 72. The fins 72 are circumferentially
spaced equiangularly and protrude a slight distance (0.15 inch, for
example) radially into the tubular body 70 as indicated in FIG. 5.
Two of the fins 72 of each radiator 66 and 68 are welded at their
ends to channel members 74 which are, in turn, fastened to the
utility pole 26 (FIG. 1) by lag screws 76 and washers 78. The upper
end of the tubular body 70 of each of the radiators 66 and 68 is
closed by a solid end plug 80 and sealed by welding. The upper ends
of the plugs 80 of the radiators 66 and 68 are respectively mounted
in left and right holes of a top support strap 82 as shown in FIG.
2. The tubular body 70 is approximately 1 inch in diameter, and the
fins 72 are approximately 2 inches wide and 72 inches long, for
example. Obviously, other techniques of attaching the radiators to
the pole for support can be used, especially when only one radiator
is employed.
FIG. 6 is a front elevational view, fragmentarily shown, of the
angular (helical) heat pipe element y which is normally attached to
the wooden utility pole 28 (FIG. 1). The heat pipe element y
generally includes a lower embedded portion 84, a central
connecting joint and tee portion 86, and an upper heat exchanger
(radiator) portion 88. The lower portion 84 is fabricated largely
of a tubular (aluminum) extrusion 90 having a central bulbous tube
92 and side flanges or fins 94a and 94b. The tube 92 protrudes
radially inwards from the flanges 94a and 94b, and the inner
diameter of each coil is approximately 12.50 inches, to accommodate
a utility pole 12 inches in diameter. The lower portion 84 can be,
for example, about 72 to 96 inches long between the ends of the
coiled section, with six equally spaced coils or a nominal 12 to 16
inches lead per coil. The deeper that the pole 28 and its element y
are embedded in the ground, the less can be the number of coils
since a deeper embedded length tends to offset the lifting of the
pole.
The lower portion 84 can be conveniently fastened to the pole 28 by
nails 96 and washers 98 located near the ends of the coiled section
along the flanges 94a and 94b, and at spacings of approximately 12
inches along the longitudinal length thereof. The lower end of the
extrusion 90 of the lower portion 84 is sealed and capped in the
same manner as in the linear heat pipe element S. The tee 100 and
everthing above it, including the heat exchanger portion 88 and its
left and right radiators 102 and 104, can be identical to the tee
52 and heat exchanger portion 40 and its radiators 66 and 68 of the
linear heat pipe element S. The central portion 86 of the angular
heat pipe element y includes an overlapping joint 106 which is not
used in the central portion 38 of the linear heat pipe element S.
It is noted, however, that a similar overlapping joint 106a
(indicated in phantom lines in FIG. 4) can be readily incorporated
and used in the linear heat pipe element S, if desired or
required.
FIG. 7 is a side elevational view of the central portion 86 of the
angular heat pipe element y, as taken along the line 7--7 indicated
in FIG. 6. Referring to both FIGS. 6 and 7, it can be seen that the
angular heat pipe element y is essentially a two-part assembly of a
separate upper heat pipe section 108 and a separate lower heat pipe
section 110 which are thermally joined or connected together by the
overlapping joint 106. Thus, the upper heat pipe section can be
readily separated and detached from the lower heat pipe section, so
that it can be replaced when damaged without having to dig up the
entire pole 28 and replacing an entire heat pipe element because of
damage only to the upper radiator portion thereof. The heat removal
rate with the two-part assembly, as compared to a similar one-part
assembly, is about 12 percent less than the latter.
FIG. 8 is a cross sectional view of the central portion 86 of the
angular heat pipe element y, as taken along the line 8--8 indicated
in FIG. 7. Referring jointly to FIGS. 7 and 8, it can be seen that
the flanges 94a and 94b of each tubular extrusion 90 of the upper
and lower heat pipe sections 108 and 110 are fastened directly
together by bolts 112 spaced along the length of the overlapping
joint 106. A layer 114 of thermal paste (such as Dow Corning
DC-340) can be used between the contiguous faces of the joined
sections 108 and 110 to facilitate heat transfer between the
sections. The length of the overlapping joint is, for example,
approximately 2 feet. The lower end of the upper heat pipe section
108 and the upper end of the lower heat pipe section 110 are each
closed by a pinch-off end plug 116. Ground level can be at a few
inches or more below the end plug 116 of the upper heat pipe
section 108.
FIG. 9 is a front elevational view, shown partially broken away, of
a structural support assembly 118 wherein a heat pipe element is
integrally combined with and constructed to serve simultaneously as
a support structure. The assembly 118 includes a closed, elongated,
tubular container 120 having a charge of a suitable working fluid
(a small amount of liquid and remainder vapor) 122, a helical wall
fin 124 protruding radially inwards a short distance from the
internal surface of the tubular container, and a heat exchanger
(ambient air radiator) 126 suitably coupled or integrally
incorporated with the upper portion of the tubular container. The
assembly 118 further includes a structural attachment means 128
located normally above radiator 126 although it can in certain
applications be located on or below the radiator, and a layer 130
of thermal insulation applied in the annual freeze-thaw ground
region or layer 132 (largely the tundra) about the tubular
container 120.
FIG. 10 is a cross sectional view of a lower part of the support
assembly 118 as taken along the line 10--10 indicated in FIG. 9.
This lower part of the assembly 118 includes the lower portion of
the tubular container 120 with its helical wall fin 124, and is
embedded in permafrost 134. From FIGS. 9 and 10, it can be seen
that as the condensate runs down the container 120 wall, the
helical wall fin 124 ensures that the wall is wetted all the way
around and down. The fin 124 can be a narrow strip helical coil
insert, a small diameter spring wire insert or a fine helical screw
thread tapped in the tubular container wall, for example, each with
a suitable pitch (which can be variable along the container length)
between turns. Alternatively, a conventional wall screen (wire
mesh) wick can be provided on the circumferential wall surfaces of
the tubular container 120. It is noted that a helical wall fin or
wall screen wick is not used in the linear or angular heat pipe
elements S and y although such means can be used and may be
desirable under certain conditions.
FIG. 11 is a cross sectional view of an upper part of the support
assembly 118 as taken along the line 11--11 indicated in FIG. 9. It
can be seen that the heat exchanger 126 is a passive radiator
including a plurality of vertical fins 136 which extend radially
from the upper portion of the tubular container 120 and are
equiangularly spaced circumferentially thereabout. Heat transfer is
by way of the surfaces of the fins 136 to the ambient air. The
tubular container 120 contains a suitable working fluid 122 (such
as ammonia) which normally exists as a small quantity of liquid at
the bottom end of the container, with saturated vapor filling the
remainder thereof. This heat pipe device is highly effective, and
the heat transfer process is fully operational with temperature
drops of less than 1.degree. F in the working fluid 122.
Anytime that the (ambient air) radiator region of the tubular
container 120 becomes slightly (less than 1.degree. F) cooler than
the lower portion of the container, some saturated vapor will
condense in the radiator region, give up its latent heat and then
return by gravity down the wall of the container to its lower end.
The condensation of fluid 122 in the upper portion of the tubular
container 120 tends to decrease the pressure in the container,
causing more vapor to flow up it and causing some evaporation of
liquid in the lower embedded portion of the container. The latent
heat of evaporation is thus transported from the underground
(embedded) region to the exposed (radiator) region by this very
efficient refluxing process.
The process of evaporation is, of course, enhanced by the helical
wall fin 124 condensate spreader. The complete underground
(embedded) container portion acts to remove heat from the
surrounding permafrost, and the heat is removed first and most
rapidly from wherever the container temperature exceeds the ambient
air temperature. That is, heat is removed most rapidly from the
warmest part of the underground container portion and the device
does not depend upon the entire embedded region being warmer than
the ambient air before heat transportation begins.
The tubular container 120 is filled mostly with vapor and is,
therefore, very light in weight for ease of handling and
installation. Undesirable heat conduction downwards is nearly
insignificant during "warm" weather for the structural support
assembly 118 because the downward heat conduction (thermal
conductivity) in the vapor is very low and the available metal
cross section is small. The downward heat conduction is much
greater, for example, in a thermo-valve device. The support
assembly 118 (heat pipe element) can also function effeiciently in
nearly a horizontal position for stabilization or support of
structure on relatively steep grades whereas a thermo- valve device
is very inefficient or cannot function in such position or
orientation.
The structural support assembly 118 need be constructed only heavy
and sturdy enough to support the intended structure. Large
diameters and thick walls for the tubular container 120 are not
required for the necessary heat transfer function. The support
assembly 118 can be used to support pipe lines, railway trusses,
buildings, etc. in the arctic regions. Of course, the support
assembly 118 need not be confined to the configuration shown, and
can be suitably combined into an architectural design of a building
or other structure so as not to be apparent. A number of different
working fluids can be individually used efficiently in the support
assembly 118. Thus, the materials of construction of the tubular
container 120 can be readily selected to meet various soil
conditions because a variety of working fluids are available to
provide one which is compatible with any chosen tubular container
material.
FIG. 12 is a generally perspective view, shown partially in section
and in fragments, of a hollow metallic pile 138 installed in
permafrost 140 and having the lower portion 142 of a heat pipe
element 144 positioned internally of the pile which is filled with
a good heat transfer medium 146. Beam 148 is part of the structure
which is secured to and supported by a number of the piles 138
installed in permafrost 140 and having respective heat pipe
elements 144 positioned therein to stabilize the adjacent
permafrost surrounding the piles. The pile 138 is, for example, an
iron pipe 4 inches in (inside) diameter with a wall thickness of
approximately 1/4 inch. The lower portion 142 of the pile 138
illustratively extends 20 feet below ground surface 150. The pile
138, in this instance, is closed at the bottom by a welded plate
152.
The heat pipe element 144 includes a tubular container 154 having
lower, intermediate and upper sections 156, 158 and 160. The lower
container section 156 has, for example, a generally cylindrical
body 162 and two longitudinal, heat transferring and attachment (if
necessary), fins or flanges 164 extending laterally therefrom. The
lower container section 156 is the lower portion 142 of the heat
pipe element 144. The intermediate container section 158 can be a
connecting tubing 166 with an inside diameter approximately equal
to that of the cylindrical body 162 of the lower container section
156. The lower end of the tubing 166 is welded or otherwise
suitably joined to the upper end of the body 162. The lower end of
the cylindrical body 162 of the lower container section 156 is, of
course, plugged, sealed and covered by a cap (not shown) similar to
that in FIG. 3.
The upper container section 160 also has, for example, a
cylindrical body 168 and a plurality of thin lateral, heat
transferring, fins 170 affixed to and spaced longitudinally along
the cylindrical body as shown in FIG. 12. The fins 170 can be
illustratively made of aluminum sheets 8 inches square and 0.050
inch thick. The fins 170 can be spaced approximately 1/2 inch apart
and a sufficient number is used to form a stack about 4 feet long.
The right end of the cylindrical body 168 is suitably closed and
sealed, and the left end thereof is welded or otherwise suitably
joined to the upper end of the connecting tubing 166 which can have
an inside diameter approximately equal to that of the cylindrical
body 168 of the upper container section 160. The ends of the upper
container section 160 can be supported by straps 172 suitably
fastened to beam 148. The tubing 166 is appropriately bent to
connect with the upper container section 160 (which is thus the
upper radiator portion of the heat pipe element 144), and the lower
container section 156 through opening 174 provided in the pile 138.
The connecting tubing 166 can be secured to pile 138 by any
suitable means such as strap 176.
FIG. 13 is a cross sectional view of a lower part of the hollow
metallic pile 138 and heat pipe element 144 installation as taken
along the line 13--13 indicated in FIG. 12. The pile 138 is filled
with a good heat transfer medium 146 which can be kerosene, for
example, when the pile is closed at the bottom by a welded plate
152 (FIG. 12). If the pile 138 is open at the bottom and is
installed in permafrost 140, the pile can be filled with a slurry
of soil and water or sand and water as a suitable heat transfer
medium 146. The lower container section 156 is, for example, an
aluminum extrusion of necessary length and having a cross sectional
configuration as illustrated. The lower container section 156 can
be similar to the extrusion 42 shown in FIG. 2.
The fins or flanges 164 of the lower container section 156 has an
overall width from tip to tip of 23/8 inches and a thickness of
1/16 inch, and the generally cylindrical body 162 has an inside
diameter of 1/2 inch and a wall thickness of basically 1/16 inch,
for example. A larger cylindrical body 162 containing more working
fluid would, of course, be required if the fins or flanges 162 were
deleted or not provided. Also, it may be noted that where the pile
138 is made of iron and the lower container section 156 is made of
aluminum, the use of a water in any combination for the heat
transfer medium 146 (as in a slurry of soil and water) can lead to
an unacceptable level of galvanic action between the aluminum and
iron materials unless suitable corrosion control techniques are
utilized. Kersosene, however, presented an acceptable solution as
the heat transfer medium 146 where an aluminum lower container
section 156 was used in an iron pile 138. The expansion of water on
freezing might, of course, further cause rupture of the pile 138 if
insufficient expansion space is not provided therein.
FIG. 14 is a cross sectional view similar to that of FIG. 13 but
showing a variation in cross sectional configuration for the lower
container section 156 of the heat pipe element 144 to provide a
general shape for a double finned element 178 installed in pile 180
and which is near optimum from a heat transfer surface and element
flexibility standpoint. It can be seen that the generally
cylindrical body 182 has been increased in inner diameter size and
the fins 184 taper radially outward an increased distance. Heat
transfer efficiency between the working fluid in the body 182 and
the inner wall 186 thereof is increased with the increase in inner
diameter size of the body, and heat transfer between the body 182
and the heat transfer medium 188 is made more efficient as the
outside surface area of the body and fins 184 is increased. Unless
the surface area of the element 178 (including body 182 and fins
184) is unusually small or of an unusual configuration, the change
in heat transfer is essentially proportional to the change in
surface area.
Heat transfer efficiency between the working fluid in the body 182
and the inner wall 186 thereof can be further increased by the use
of a suitable flow or wick means 190 installed in the body to
direct and distribute working fluid condensate return flow therein.
The flow means 190 can, for example, be a helically coiled, small
diameter, wire installed longitudinally in the body 182 to assume
the arrangement and position therein similarly as the helical wall
fin 124 of FIG. 9. While the double finned element 178
configuration has somewhat improved heat transfer efficiency over
that of the lower container section 156 configuration shown in FIG.
13, the latter configuration is fully adequate in virtually all
situations.
In addition, the broad flat surfaces provided by the fins or
flanges 164 tangentially joined at the body 162 are useful for
attaching the section 156 to flat or cylindrical surfaces. The
lower container section 156 can be easily inserted and installed in
the pile 138 or in a longitudinal pocket thereof. By helically
coiling the section 156 so that the broad flat surfaces of the fins
or flanges 164 lie on a cylindrical surface, the coiled section can
be readily slipped on and installed concentrically about
cylindrical core structure in an annular space, for example, which
is then filled with a suitable heat transfer medium.
FIG. 15 is another cross sectional view similar to those of FIGS.
13 and 14 and showing another variation in cross sectional
configuration for the lower container section 156 of the heat pipe
element 144 to provide a general shape for a multiple finned
element 192 installed in pile 194. The element 192 has, for
example, 8 longitudinal fins 196 affixed equiangularly to the
cylindrical body 198 and extending radially therefrom to provide a
greatly increased heat transfer surface. The cylindrical body 198
is larger in diameter than the generally cylindrical body 162 of
the configuration shown in FIG. 13 and, of course, has a larger
chamber therein.
The larger body 198 preferably includes a suitable flow or wick
means 200 installed in the body to direct and distribute working
fluid condensate return flow therein. Flow means 200 is impractical
and unnecessary in the body 198 having an inside diameter of about
1/2 inch or less but is practical and necessary where the inside
diameter is about 1 inch or greater. Where the inside diameter of
the body 198 is between 1/2 to 1 inch, the flow means 200 can be
either used or not used according to a weighing of the advantages
and disadvantages to be gained therefrom. The pile 194 contains, of
course, a suitable heat transfer medium 202.
While certain exemplary embodiments of this invention have been
described above and shown in the accompanying drawings, it is to be
understood that such embodiments are merely illustrative of, and
not restrictive on, the broad invention and that I do not desire to
be limited in my invention to the details of construction or
arrangements shown and described, for obvious modifications may
occur to persons skilled in the art.
* * * * *