US4474238A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for treatment of subsurface formations
Assignee: Phillips Petroleum Co
•
Filing: 1982-11-30
•
Granted: 1984-10-02
•
Expires: 2002-11-30
Abstract
Abstract A method of extracting bitumen from a subsurface tar sand bed wherein a shell of frozen earth is formed around the periphery of at least a portion of the tar sand bed, followed by recovering bitumen from such portion of the tar sand bed within the shell of frozen earth by suitable means such as, for example, solvent extraction. Also disclosed is apparatus for freezing the earth surrounding one of a plurality of boreholes drilled in the earth within earth freezing distance of each other around the periphery of such portion of the tar sand bed. The apparatus comprises concentric outer and inner conduits with the outer conduit having two strips of thermal insulation extending along substantially the full length of the exterior surface of the outer conduit, separated by two strips, preferably longitudinally finned, of relatively high thermal conductivity extending along substantially the full length of the exterior surface of the outer conduit so as to provide a predetermined freezing pattern about the axis of a borehole when refrigerant is circulated through the apparatus.
Inventors
- 👤 Cecil C. Gentry
- 👤 Henry E. Alquist
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 17:17
CPC Classifications
E; E21; E21B; E21B43/00; E21B43/30; E21B36/00; E21B36/003; E21B43/16
Claims Analysis
Total Claims: 51
Claim 1
Independent Claim
279 words
Apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis of said borehole, comprising: first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; second longitudinal tubular conduit means having a closed upper end and a open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively low thermal conductivity extending through an angle of about 120° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 2
Dependent Claim
279 words
Apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis of said borehole, comprising: first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; second longitudinal tubular conduit means having a closed upper end and a open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively low thermal conductivity extending through an angle of about 120° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 3
Dependent Claim
35 words
Apparatus in accordance with claim 1 wherein each longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 4
Dependent Claim
29 words
Apparatus in accordance with claim 2 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 5
Dependent Claim
42 words
Apparatus in accordance with claim 1 wherein each said longitudinally extending strip of relatively low thermal conductivity comprises a strip of non-metallic thermal insulation material and each said longitudinally extending strip of relatively high thermal conductivity comprises a strip of metallic material.
Claim 6
Dependent Claim
36 words
Apparatus in accordance with claim 4 wherein each said longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 7
Dependent Claim
29 words
Apparatus in accordance with claim 5 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 8
Dependent Claim
22 words
Apparatus in accordance with claim 1 wherein each said longitudinally extending strip of relatively low thermal conductivity comprises a strip of polyethylene.
Claim 9
Dependent Claim
37 words
Apparatus in accordance with claim 1 wherein each of said two longitudinally extending strips of relatively high thermal conductivity extend through an angle of about 60° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 10
Dependent Claim
279 words
Apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis of said borehole, comprising: first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; second longitudinal tubular conduit means having a closed upper end and a open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively high thermal conductivity extending through an angle of about 60° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 11
Dependent Claim
279 words
Apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis of said borehole, comprising: first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; second longitudinal tubular conduit means having a closed upper end and a open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively high thermal conductivity extending through an angle of about 60° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 12
Dependent Claim
35 words
Apparatus in accordance with claim 9 wherein each longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 13
Dependent Claim
29 words
Apparatus in accordance with claim 10 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity
Claim 14
Dependent Claim
42 words
Apparatus in accordance with claim 9 wherein each said longitudinally extending strip of relatively low thermal conductivity comprises a strip of non-metallic thermal insulation material and each said longitudinally extending strip of relatively high thermal conductivity comprises a strip of metallic material
Claim 15
Dependent Claim
36 words
Apparatus in accordance with claim 12 wherein each said longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 16
Dependent Claim
29 words
Apparatus in accordance with claim 13 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 17
Dependent Claim
22 words
Apparatus in accordance with claim 9 wherein each said longitudinally extending strip of relatively low thermal conductivity comprises a strip of polyethylene.
Claim 18
Independent Claim
143 words
A method of recovering bitumen from a subsurface tar sand bed comprising: drilling a plurality of downwardly extending boreholes spaced within earth freezing distance of each other about the periphery of at least a portion of said tar sand bed; circulating refrigerant in said boreholes in such a manner as to freeze the earth surrounding said boreholes in a predetermined pattern about the axis of each of said boreholes, said pattern extending substantially farther radially outwardly along a first line through the axis of each borehole toward the next adjacent borehole through the axis of each borehole and substantially normal to said first line, thereby forming a shell of frozen earth around said periphery of at least a portion of said tar sand bed; and recovering bitumen from at least a portion of said tar sand bed within said shell of frozen earth.
Claim 19
Independent Claim
143 words
A method of recovering bitumen from a subsurface tar sand bed comprising: drilling a plurality of downwardly extending boreholes spaced within earth freezing distance of each other about the periphery of at least a portion of said tar sand bed; circulating refrigerant in said boreholes in such a manner as to freeze the earth surrounding said boreholes in a predetermined pattern about the axis of each of said boreholes, said pattern extending substantially farther radially outwardly along a first line through the axis of each borehole toward the next adjacent borehole through the axis of each borehole and substantially normal to said first line, thereby forming a shell of frozen earth around said periphery of at least a portion of said tar sand bed; and recovering bitumen from at least a portion of said tar sand bed within said shell of frozen earth.
Claim 20
Dependent Claim
252 words
A method in accordance with claim 16 wherein the refrigerant circulated in said boreholes is circulated through apparatus in each said borehole, said apparatus comprising: first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed in said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means having two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof and further having two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 21
Dependent Claim
35 words
A method in accordance with claim 7 wherein each longitudinally extending strip of relatively high thermal conductivity faces a corresponding longitudinally extending strip of relatively high thermal conductivity of the apparatus in an adjacent borehole.
Claim 22
Dependent Claim
37 words
A method in accordance with claim 18 wherein each said longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 23
Dependent Claim
30 words
A method in accordance with claim 19 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 24
Dependent Claim
37 words
A method in accordance with claim 17 wherein each of said two longitudinally extending strips of relatively low thermal conductivity extends through an angle of 120° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 25
Dependent Claim
38 words
A method in accordance with claim 21 wherein each of said two longitudinally extending strips of relatively high thermal conductivity extends through an angle of about 60° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 26
Dependent Claim
38 words
A method in accordance with claim 20 wherein each of said two longitudinally extending strips of relatively high thermal conductivity extends through an angle of about 60° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 27
Dependent Claim
27 words
A method in accordance with claim 17 wherein water is present in at least one of said boreholes during the step of circulating refrigerant in said boreholes.
Claim 28
Independent Claim
316 words
A method of recovering bitumen from a subsurface tar sand bed comprising: forming a plurality of generally downwardly extending boreholes in the earth with said boreholes spaced within earth freezing distance one from the other about the periphery of at least a portion of said tar sand bed; circulating refrigerant through apparatus in each of said boreholes to freeze the earth surrounding each of said boreholes and intermediate adjacent pairs of said boreholes to thereby form a shell of frozen earth around said periphery of at least a portion of said tar sand bed, said apparatus comprising: first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed the lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means having at least one strip of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further having at least one strip of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means; and recovering bitumen from said at least a portion of said tar sand bed within said shell of frozen earth.
Claim 29
Independent Claim
316 words
A method of recovering bitumen from a subsurface tar sand bed comprising: forming a plurality of generally downwardly extending boreholes in the earth with said boreholes spaced within earth freezing distance one from the other about the periphery of at least a portion of said tar sand bed; circulating refrigerant through apparatus in each of said boreholes to freeze the earth surrounding each of said boreholes and intermediate adjacent pairs of said boreholes to thereby form a shell of frozen earth around said periphery of at least a portion of said tar sand bed, said apparatus comprising: first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed the lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means having at least one strip of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further having at least one strip of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means; and recovering bitumen from said at least a portion of said tar sand bed within said shell of frozen earth.
Claim 30
Dependent Claim
35 words
A method in accordance with claim 25 wherein each longitudinally extending strip of relatively high thermal conductivity faces a corresponding longitudinally extending strip of relatively high thermal conductivity of the apparatus in an adjacent borehole.
Claim 31
Dependent Claim
37 words
A method in accordance with claim 26 wherein each said longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 32
Dependent Claim
30 words
A method in accordance with claim 27 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 33
Dependent Claim
27 words
A method in accordance with claim 25 wherein water is present in at least one of said boreholes during the step of circulating refrigerant in said boreholes.
Claim 34
Independent Claim
326 words
A system for recovering bitumen from a subsurface tar sand bed comprising: a plurality of boreholes spaced within earth freezing distance one from the other about the periphery of at least of portion of said tar sand bed; apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis thereof positioned in each of said plurality of boreholes, said apparatus comprising; first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; said second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively low thermal conductivity extending through an angle of about 120° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 35
Independent Claim
326 words
A system for recovering bitumen from a subsurface tar sand bed comprising: a plurality of boreholes spaced within earth freezing distance one from the other about the periphery of at least of portion of said tar sand bed; apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis thereof positioned in each of said plurality of boreholes, said apparatus comprising; first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; said second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively low thermal conductivity extending through an angle of about 120° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 36
Dependent Claim
37 words
A system in accordance with claim 30 wherein each said longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 37
Dependent Claim
30 words
A system in accordance with claim 35 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 38
Dependent Claim
43 words
A system in accordance with claim 30 wherein each said longitudinally extending strip of relatively low thermal conductivity comprises a strip of non-metallic thermal insulation material and each said longitudinally extending strip of relatively high thermal conductivity comprises a strip of metallic material.
Claim 39
Dependent Claim
37 words
A system in accordance with claim 33 wherein each said longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 40
Dependent Claim
30 words
A system in accordance with claim 38 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 41
Dependent Claim
23 words
A system in accordance with claim 30 wherein each said longitudinally extending strip of relatively low thermal conductivity comprises a strip of polyethylene.
Claim 42
Dependent Claim
37 words
A system in accordance with claim 30 wherein water is present in at least one of said boreholes at least partially filling the annulus between said at least one of said boreholes and said apparatus positioned therein.
Claim 43
Dependent Claim
38 words
A system in accordance with claim 30 wherein each of said two longitudinally extending strips of relatively high thermal conductivity extends through an angle of about 60° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 44
Independent Claim
326 words
A system for recovering bitumen from a subsurface tar sand bed comprising: a plurality of boreholes spaced within earth freezing distance one from the other about the periphery of at least of portion of said tar sand bed; apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis thereof positioned in each of said plurality of boreholes, said apparatus comprising; first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; said second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively high thermal conductivity extending through an angle of about 60° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 45
Independent Claim
326 words
A system for recovering bitumen from a subsurface tar sand bed comprising: a plurality of boreholes spaced within earth freezing distance one from the other about the periphery of at least of portion of said tar sand bed; apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis thereof positioned in each of said plurality of boreholes, said apparatus comprising; first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means; said second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means; and the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively high thermal conductivity extending through an angle of about 60° about the longitudinal axis of said first longitudinal tubular conduit means.
Claim 46
Dependent Claim
37 words
A system in accordance with claim 39 wherein each said longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 47
Dependent Claim
30 words
A system in accordance with claim 40 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 48
Dependent Claim
43 words
A system in accordance with claim 39 wherein each said longitudinally extending strip of relatively low thermal conductivity comprises a strip of non-metallic thermal insulation material and each said longitudinally extending strip of relatively high thermal conductivity comprises a strip of metallic material.
Claim 49
Dependent Claim
37 words
A system in accordance with claim 42 wherein each said longitudinally extending strip of relatively high thermal conductivity comprises at least one fin extending radially outwardly from the longitudinal axis of said first longitudinal tubular conduit means.
Claim 50
Dependent Claim
30 words
A system in accordance with claim 43 wherein said at least one fin extends longitudinally along substantially the full length of said longitudinally extending strip of relatively high thermal conductivity.
Claim 51
Dependent Claim
23 words
A system in accordance with claim 39 wherein each said longitudinally extending strip of relatively low thermal conductivity comprises a strip of polyethylene.
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USPTO Annuity & Maintenance Windows
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| 7.5 Years (Year 8) | 1991-10-02 | 1992-04-02 | 1992-10-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-02 | 1996-04-02 | 1996-10-02 | $7700.00 | Window Closed / Lapsed |