Geothermal heat exchange unit

• US 5,816,314 A
• Filed: 01/29/1996
• Issued: 10/06/1998
• Est. Priority Date: 09/19/1995
• Status: Expired due to Fees

• Current Assignee: Geothermal Heat Pumps, Inc.
• Original Assignee: Geothermal Heat Pumps, Inc.
• Inventors: Bickford, William C., Womack, Jack L., Hawk, John E., Wiggs, B. Ryland
• Primary Examiner(s): Leo, Leonard R.
• Application Number:
  US08/593,361
• Time in Patent Office: 981 Days
• Field of Search: 165/45, 165/134.1, 165/163, 62/260
• US Class Current: 165/45
• CPC Class Codes: F24T 10/15 using bent tubes; using tubes assembled with connectors or with return headers
• CPC Class Codes: F28F 2270/00 Thermal insulation; Thermal decoupling
• CPC Class Codes: Y02E 10/10 Geothermal energy

Abstract

An improved geothermal heat exchange unit, which can be placed in ground and/or water, has a rigid hollow core about which is formed a helical winding of thermally conductive tube. The return section of the tube extends vertically along a central axis of the core, separated from the inner wall of the core by thermal insulating material. The heat exchange unit is optionally encased in a solid thermally conductive casing and may have a small diameter oil return tube from the lowermost portion of the unit to the suction intake port of a gas compressor. An optional high pressure water hose is attached for installation assistance in wet sand or wet soils.

Claims

1. A geothermal heat exchange unit comprising:

a. a substantially cylindrical core having a rigid wall defining a central axis;

b. a heat transfer fluid tube having a supply section helically formed around the wall of the core, and a return section connected to a distal end of the supply section;

c. the return section of the tube disposed along the central axis of a sleeve, the return section separated from the wall of the core by a thermal insulating material; and

d. the core and heat transfer fluid tube enclosed in a rigid casing, the casing having a thermally conductive outer wall filled with a thermally conductive fill material.

2. The geothermal heat exchange unit of claim 1 wherein the supply section and return section of the heat transfer fluid tube each have an entering portion of the tube which is external to the casing and wherein the supply section further comprises a plurality of parallel fluid conducting tubes having a common inlet and outlet tube.

3. The geothermal heat exchange unit of claim 2 wherein a combined interior area of the fluid conducting tubes is greater than an interior area of the larger of the entering portions of the return section and the supply section.

4. The geothermal heat exchange unit of claim 1 wherein the heat exchange unit is positioned in a sub-surface hole having a diameter larger than the heat exchange unit to define an initial void space between the casing and an inner margin of the hole, with the void space filled with a thermally conductive fill.

6. The geothermal heat exchange unit of claim 1 further comprising means to cathodically protect the heat transfer fluid tube from adverse acidic or basic interaction with soil surrounding the tube.

7. The geothermal heat exchange unit of claim 6, the cathodic protection means including one or more sacrificial anodes placed in the soil at a distance from the tube, the distance being in a range of substantially ten to twenty feet, the sacrificial anodes electrically connected to the tube by an electrically insulated wire.

8. The geothermal heat exchange unit of claim 6, the cathodic protection means comprising a source of electrical power connected to the tube and to one or more conductive rods placed in the soil at a distance from the tube, the distance being in a range of substantially ten to twenty feet, whereby a DC current flow is maintained between the rods and the tube, the rods acting as an anode and the tube acting as a cathode.

9. The geothermal heat exchange unit of claim 1 further comprising a compressor oil return tube connected to a lowermost portion of the heat transfer fluid tube, the compressor oil return tube adapted for receiving compressor oil which has separated from heat transfer fluid in the heat transfer tube and for delivering the compressor oil back to a compressor.

5. The geothermal heat exchange unit of 1 wherein the return section of the heat exchange fluid tube is made of a material having a low thermal conductivity.