Patent ID: 8161759
Filing Date: 2012-04-24
Classification: F24T,F25B,F28D,F28F,Y02B,Y02E

Abstract:
1. A method of transferring heat energy between a heat exchanging subsystem installed above the surface of the Earth, and material beneath the surface of the Earth, said method comprising the steps: (a) installing said heat exchanging subsystem above the surface of the Earth, wherein said heat exchanging subsystem has a first heat exchanger for supporting the flow of a heat conducting stream through said first heat exchanger, and a second heat exchanger for supporting the flow of an aqueous-based heat transfer fluid through said second heat exchanger, wherein said first heat exchanger and said second heat exchanger are arranged in a heat transfer relationship with each other; (b) installing one or more coaxial-flow heat exchanging structures in the material beneath the surface of said Earth, wherein each said coaxial-flow heat exchanging structure includes: a proximal end and a distal end; an input port, provided at the proximal end, and an output port, provided at the proximal end; an inner tube section being substantially straight and having an outer wall surface extending between said proximal and distal ends, and said inner tube section supporting an inner flow channel having a substantially uniform inner diameter along its length between said proximal and distal ends; a thermally conductive outer tube section, disposed coaxially around said inner tube section, and having an inner wall surface extending between said proximal and distal ends, and a cap portion at said distal end sealing off said thermally conductive outer tube section from fluid leaks at said distal end; wherein an outer flow channel of annulus geometry is formed between the outer wall surface of said inner tube section and the inner wall surface of said thermally conductive outer tube section; wherein multiple helically-arranged fins are disposed along a substantial portion of the length of said outer flow channel of annulus geometry so as to form multiple helically-extending outer flow channels having cross-sectional dimensions and disposed between said inner tube section and said thermally conductive outer tube section; (c) arranging said input and output ports of each said coaxial-flow heat exchanging structure in fluid communication with said second heat exchanger so that said second heat exchanger is in fluid communication with said inner flow channel and said helically-extending outer flow channels of each said coaxial-flow heat exchanging structure; (d) filling said second heat exchanger and said inner flow channel and said helically-extending outer flow channels of each said coaxial-flow heat exchanging structure, with a predetermined volume of aqueous-based heat transfer fluid; (e) circulating said predetermined volume of aqueous-based heat transfer fluid so that said aqueous-based heat transfer fluid flows out of said second heat exchanger and into said input port at a first temperature, and then flows down along said inner flow channel in a substantially laminar manner, and then around said cap portion, and then flows along said helically-extending outer flow channels and out of said output port and back into said second heat exchanger at a second temperature, in a closed-loop fashion, sealed off from the material beneath the surface of said Earth; and (f) said cross-sectional dimensions of said helically-extending outer flow channels producing turbulence in the aqueous-based heat transfer fluid flowing along said helically-extending outer flow channels and having vortex characteristics that disturb the formation of boundary layers along the inner surface of said thermally conductive outer tube section and increase the transfer of heat energy between said aqueous-based heat transfer fluid flowing along said helically-extending outer flow channels and the inner surface of said thermally conductive outer tube section, so as to increase the rate of heat energy transfer between said aqueous-based heat transfer fluid and material beneath the surface of said Earth along the length of said helically-extending outer flow channels; during which the heat transfer process occurring between said aqueous-based heat transfer fluid and the material beneath the surface of said Earth is carried out without a change in state of said aqueous-based heat transfer fluid flowing within and along said inner flow channel and said helically-extending outer flow channels of each said coaxial-flow heat exchanging structure.