Heat exchange – Geographical
Reexamination Certificate
2002-04-22
2004-09-14
Leo, Leonard (Department: 3753)
Heat exchange
Geographical
C062S260000
Reexamination Certificate
active
06789608
ABSTRACT:
APPLICATION FOR UNITED STATES LETTERS PATENT
Be it known that I, B. Ryland Wiggs, 425 Sims Lane, Franklin, Tenn. 37069, have invented a new and useful “Thermally Exposed, Centrally Insulated Geothermal Heat Exchange Unit”.
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark office patent file or records, but otherwise reserves all copyright rights whatsoever.
BACKGROUND OF THE INVENTION
The present invention relates to an improved in-ground/in-water heat exchange means for use in use in association with any heating/cooling system and/or any geothermal thermal energy generation system utilizing in-ground and/or in-water heat exchange elements as a primary or supplemental source of heat transfer.
Ground source/water source heat exchange systems typically utilize fluid-filled closed loops of tubing buried in the ground, or submerged in a body of water, so as to either absorb heat from, or to reject heat into, the naturally occurring geothermal mass and/or water surrounding the buried or submerged tubing. Water-source heating/cooling systems typically circulate water, or water with anti-freeze, in plastic underground geothermal tubing so as to transfer heat to or from the ground, with a second heat exchange step utilizing a refrigerant to transfer heat to or from the water, and with a third heat exchange step utilizing an electric fan to transfer heat to or from the refrigerant to heat or cool interior air space. Direct expansion ground source heat exchange systems typically circulate a refrigerant fluid, such as R-22, in copper underground geothermal tubing to transfer heat to or from the ground, and only require a second heat exchange step to transfer heat to or from the interior air space by means of an electric fan.
While most in-ground/in-water heat exchange designs are feasible, various improvements have been developed intended to enhance overall system operational efficiencies. Several such design improvements are taught in U.S. Pat. No. 5,623,986 to Wiggs, and in U.S. Pat. No. 5,816,314 to Wiggs, et al., the disclosures of which are incorporated herein by reference. These designs basically teach the utilization of a spiraled fluid supply line subjected to naturally surrounding geothermal temperatures, with a fully insulated fluid return line.
Other predecessor vertically oriented geothermal heat exchange designs are disclosed by U.S. Pat. No. 5,461,876 to Dressler, and by U.S. Pat. No. 4,741,388 to Kuriowa. Dressler's “876” patent teaches the utilization of an in-ground spiraled fluid supply line, but neglects to insulate the fluid return line, thereby subjecting the heat gained or lost by the exiting circulating fluid to a “short-circuiting” effect as the return line comes in close contact with the warmest or coldest portion of the entering fluid supply line. Kuriowa's preceding “388” patent is virtually identical to Dressler's subsequent claim, but better, because Kuriowa insulates a portion of the return line, via surrounding it with insulation, thereby helping to reduce the “short-circuiting” effect. Dressler's “876” patent also discloses the alternative use of a pair of concentric tubes, with one tube being within the core of the other, with the inner tube surrounded by insulation or a vacuum. While this multiple concentric tube design reduces the “short-circuiting” effect, it is practically difficult to build and could be functionally cost-prohibitive.
The disadvantage encountered with insulating the heat transfer return line, by means of fully surrounding a portion of same with insulation as per Kuriowa, or by means of a fully insulated concentric tube within a tube as per Dressler, or by means of a fully insulated return line as per Wiggs' predecessor designs, is that the fully insulated portion of the return line is not exposed to naturally occurring geothermal temperatures, and is therefore a costly necessary underground/underwater system component which is not capable of being utilized for geothermal heat transfer purposes. While the utilization of such fully insulated costly components is an improvement over prior totally un-insulated geothermal heat transfer line designs subject to a “short-circuiting” of the maximum heat gain/loss potential, a design which insulates the supply line from the return line and still permits both lines to retain natural geothermal heat exchange exposure would be preferable.
SUMMARY OF THE INVENTION
It is an object of the present invention to further enhance and improve the efficiency and installation cost functionality of predecessor geothermal heat exchange designs. This is accomplished by means of insulating the underground and/or underwater heat transfer fluid supply line, or lines, from the fluid return line, or lines, while still providing for natural geothermal heat exchange exposure along the entire length of both the supply line, or lines, and the return line, or lines.
To accomplish this objective, in a vertically oriented borehole for example, insulation, which is non-corrosive to fluid supply and return line tubing, is inserted between the supply line, or lines, and the return line, or lines, across the entire central diameter of the hole, with the supply line, or lines, on one side of the centrally located insulation, and the return line, or lines, on the other side. The borehole may be an open hole drilled into the ground, or may be a hole drilled into the ground within which a heat conductive casing, such as a metal water-well casing, is placed along the exterior perimeter of the hole, directly adjacent to, and in thermal contact with, the ground. Each respective side of the centrally located insulation, containing the respective supply and return lines, would then be filled with a non-corrosive, heat conductive, fill material, such as a thermal grout
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mixture. As a result, during system operation, the supply and the return lines will each transfer heat to or from their respective surrounding non-corrosive, heat conductive, fill material, with both the respective supply and return lines and their respective surrounding non-corrosive, heat conductive, fill material separated from each other by insulation. In turn, each respective combination of heat exchange line and its surrounding non-corrosive, heat conductive, fill material will transfer heat to or from the adjacent sub-surface ground and/or water. If the insulation width at the exterior edge of the borehole does not exceed one-third of the borehole's diameter, each respective combination of heat exchange line and its surrounding non-corrosive, heat conductive, fill material will be exposed to about 140 degrees of earth and/or water, for geothermal heat exchange purposes, for the entire depth and/or length of the borehole, absent any material “short circuiting” effect. The earth on the opposite sides of the centrally insulated borehole will be relatively unaffected by the heat transfer on the other side so long as the central insulation, separating the supply and return lines, extends for the greater distance, as measured from one side of the borehole to the other, of at least three times, and preferably four times, the diameter of the largest geothermal fluid transfer line, and at least three times, and preferably four times, the combined diameter of the largest multiple fluid transfer lines on either respective side of the central insulation. The width of separating insulation will generally be restricted by the borehole width, consequently, the borehole should be drilled at a diameter of sufficient width to accommodate at least this minimum insulation distance.
An additional advantage of surrounding the copper refrigerant supply and return lines with a non-corrosive, thermally conductive, fill material, such as a thermal grout
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mixture, is that it eliminates the necessity for cathodic protection of t
Leo Leonard
Patterson Mark J.
Waddey & Patterson
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