Abstract:
A geothermal heat exchange apparatus is disclosed that comprises a flexible assembly of a plurality of pipes twisted on a central conduit. The central conduit has a tubular structure. The plurality of pipes is twisted around the central conduit. The plurality of pipes is adapted to connect to an external environmental control system that supplies a heat exchange liquid for the transfer of heat through the plurality of pipes. The geothermal heat exchange apparatus is adapted for positioning in a hole in the earth for the exchange of heat.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and is a continuation in part of U.S. patent application Ser. No. 13/385,378 filed Feb. 16, 2012 that is a continuation-in-part of U.S. patent application Ser. No. 12/660,226 filed Feb. 23, 2010 and U.S. patent application Ser. No. 13/385,383 filed Feb. 16, 2012 that is a continuation-in-part of U.S. patent application Ser. No. 12/660,225 filed Feb. 23, 2010, the disclosures of which are incorporated by reference herein and made a part of this application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to the arrangement of pipes for geothermal heat exchange and in particular to arrangements of a plurality of pipes twisted onto a central conduit for geothermal heat exchange. 
         [0004]    2. Description of the Related Art 
         [0005]    Geothermal heat exchange structures are well known and include a broad array of configurations for the exchange of heat between an environmental conditioning device and the earth. An idealized example of an environmental conditioning system with a geothermal heat exchanger is shown in  FIG. 1 . The environmental conditioning systems defined herein include a geothermal heat exchanger that provide environmental conditioning for a structure  2  using an environmental conditioning apparatus such as a heat pump or other similar device  4  that is in fluid communication with a pipe  5  that contains a liquid for the transfer of heat. Pipe  5  is a geothermal heat exchanger positioned in a hole  6  in the ground  8 . Pipe  5  can be a single loop, a single pipe with multiple branches, a coaxial pipe and multiple pipes depending upon the desired construction of the geothermal heating system. 
         [0006]    Environmental conditioning apparatus or heat pumps  4  that use geothermal heat exchangers are commonly identified as heating and cooling systems. Geothermal heat pumps  4  are known for their superior performance in delivering energy conserving heating and/or cooling to homes, industrial buildings and residential and industrial complexes in many climates. As defined herein, environmental conditioning apparatus include heating, cooling and combined heating and cooling systems. See, for example, http://www.igshpa.okstate.edu/geothermal/geothermal.html; www.summitmechsystems.com/pages/3.1.html; www.renewableheating101.com/geothermal/loops; http://minnesotageothermalheatpumpassociation.com/geothermal/earth-loop-options/; and http://www.informedbuilding.com/Geothermal/Main16/Types-of-Geotherm. 
         [0007]    However, a barrier to the wide spread use of geothermal heat exchangers is the high cost of installation of pipe  5  ground loops that provide the essential heat transfer from the heat exchange liquid that is circulated through pipes  5  to the earth  8 . Also, the presently available ground-loop pipes  5  are limited in many instances in their ability to efficiently utilize vertical boreholes  6  and exchange heat with the earth. 
         [0008]    Different geothermal heat exchangers have attempted to overcome these efficiency limitations. The aforementioned websites discuss the various ground loop technologies. Examples of commonly used ground loop technologies include the following: horizontal ground loops, vertical ground loops, and slinky coil ground loops. The slinky coil ground loop is a variation of the horizontal ground loop and it too requires a substantial amount of horizontal land as do other horizontal ground loops. Vertical loops include multiple pipe vertical loops that use less horizontal land, but their structural configurations and relationship to the borehole still limit heat transfer. 
         [0009]    Ground loops are usually required to be at least partially grouted as part of their installation. Horizontal and/or multi-angled boreholes can also require grouting. While the thermal or heat transfer coefficients of grouts vary, it is preferred to grout the entire borehole of vertical installations. The goal is to preclude voids in the grout that reduce the efficiency of the heat transfer. The standard practice is to insert a grout pipe all the way to the bottom of the bore and fill the borehole from the bottom up. This process also displaces any water that has pooled at the bottom of the borehole. The grout pipe, however, takes up space in the borehole and can be difficult to insert into the borehole as it has a tendency to catch on irregularities in the surface of the wall of the borehole as well as the pipes. Further installations that only provide bottom to up grouting through a tremie are vulnerable to the creation of voids in and around the arranged pipes and clamps. 
         [0010]    When multiple pipes  5  are closely arranged for geothermal heat exchange, it is known that spacing the pipes enhances the heat transfer by increasing the heat transfer surface area. Methods of keeping adjoining pipes separated include the use of headers, footers and clips, in various forms that position individual pipes  5  relative to one another, a tremie type pipe and/or the wall of the borehole. Some multiple pipe configurations include secondary branches that define loops. These branched structures join branches using extended rigid connectors that are known as headers and footers that divide and/or connect pipes  5  in fixed spaced separation relative to one another. Headers and footers, however, take up an excessive amount of horizontal and/or in particular vertical space in the earth which undesirably increases time and cost for installation. 
         [0011]    Clips and springs and even headers and footers, keep the pipes separated and oriented advantageously where the pipe is close to objects. Problems arise, however, because the Clips are typically installed every 10-20 feet and between the clips the pipes are not controlled and can maneuver themselves into undesirable positions away from the borehole wall. Clips have some advantages in potentially fixing the position of pipes  5  relative to one another, a tremie pipe or the borehole in proximity to the clip, but clips require manual positioning prior to installation and take up valuable space within the borehole. The taking of excessive space in the borehole can undesirably reduce the quantity and/or size of pipes  5  in the borehole and complicate the use of a tremie pipe and/or grouting due the position of the clips extending transverse to the alignment of the borehole. Headers, footers and clips also limit the flexibility of arranging pipes  5  in that the ability to add or remove one or more pipes can be burdensome and require the changing of headers and/or footers as well as the type of clip installed on pipes  5 . 
         [0012]    It is also known that geothermal heat exchange applications using straight and/or rigid pipes have multiple limitations that include transportation and manual labor required to connect and then install the one or more straight pipes  5 . Coaxial pipes are typically straight pipes with thicker walls that structurally support and maintain the relative position of the inner walls of the pipe that separate the inflow and outflow. The thickness of walls of coaxial pipes undesirably decreases the heat exchange properties of those pipes. Further straight pipes  5  require the creation of turbulent flow in order to achieved preferred rates of heat transfer or exchange. This requires the insertion of mechanical interruptions in the interior of pipe  5  such as undulations and/or vanes that deflect and/or interrupt the flow in pipe  5  to create turbulent flow in pipe  5  with elevated Reynolds numbers and enhanced heat transfer. The creation of turbulent flow is commonly created through high flow rates of the heat exchanging fluid within pipe  5  and can result in undesirable increased power consumption of the overall system. 
         [0013]    Heretofore there has not been a high efficiency compact and flexible arrangement of a plurality of pipes for geothermal heat exchange. The geothermal heat exchange apparatus includes a twisted, approximately parallel and spaced arrangement of individual pipes of a plurality of pipes around a central conduit. The geothermal heat exchange apparatus is flexible and can be compactly coiled for storage and transportation as a complete assembly and then readily installed in a borehole. The twist of the plurality of pipes controls the position of each pipe of the plurality of pipes ensuring contact with the center conduit and establishing each pipe of the plurality of pipes in an approximately fixed spaced relation relative to the other pipes of the plurality of pipes. 
       SUMMARY OF THE INVENTION 
       [0014]    The present disclosure is a novel structure of a geothermal heat exchange apparatus that facilitates the ease of storage, transportation, installation and thermal transfer efficiency. Specifically, the geothermal heat exchange apparatus includes the twisting of a plurality of pipes onto a central conduit in a compact minimum diameter form that can be readily uncoiled and inserted into a borehole. It is understood that while it is preferred in general to minimize the diameter of the borehole, there are applications in which the minimum diameter borehole is not necessarily the most desired or preferred approach for heat exchange. It is understood that it can be desirable to drill the borehole to a desired diameter vice the minimum diameter for the installation of the compact geothermal heat exchange apparatus. The structure of the geothermal heat exchange apparatus makes more efficient use of the borehole space by placing more pipe into the borehole in a compact spaced arrangement for heat transfer. The unique structural arrangement of the geothermal heat exchange apparatus creates additional surface area for heat transfer surface through flexible thin walled pipes in a small diameter borehole. The twisted plurality of pipes is wrapped in helical arrangement that is in contact with the center conduit such that the interface between the plurality of pipes and the central conduit bind the plurality of pipes in position on the central conduit. This structural arrangement also provides support for retaining the relative position of each pipe during installation in a relatively tight borehole. The flexible nature of the conduit and the plurality of pipes in a twisted arrangement is easily coiled and transported in a roll to a job site. 
         [0015]    An arrangement of flexible pipes for geothermal heat exchange is described that comprises a central conduit and a plurality of pipes. The central conduit has a tubular structure that includes a first end portion and an opposed second end portion. The central conduit defines an aperture in the first end portion that is aligned with the longitudinal axis of the central conduit and extends the first end portion and the second end portion. 
         [0016]    Each pipe of the plurality of pipes has a first end portion and an opposed second end portion. Each pipe has a tubular structure that preferably has a circular cross-section perpendicular to the longitudinal axis. The plurality of pipes is twisted around the central conduit in an approximately parallel arrangement and in an approximately fixed spaced separation that defines a gap between adjacent pipes. Each pipe of the plurality of pipes is positioned in direct contact with the central conduit. The second end portion of each pipe of the plurality of pipes is connected by a joint. The geothermal heat exchange apparatus is flexible and coilable into a roll. The first end portion of each pipe of the plurality of pipes is adapted to connect to an external environmental control system for the transfer of a liquid that is a heat exchange medium through the plurality of pipes. The plurality of pipes provides an extended arcuate pathway for the exchange of heat through the plurality of pipes and between the liquid and the earth. The external environmental control system at least includes heating and/or cooling. 
         [0017]    Each pipe of the plurality of pipes is connected to one U-bend. The U-bend preferably connects the pipes of the plurality of pipes in the twisted approximately parallel arrangement. The first end portion of a first set of pipes connects to a first manifold that receives inflow to the first set of pipes and a second set of pipes connects to a second manifold that receives outflow from the second set of pipes. The first set of pipes and the second set of pipes comprise the plurality of pipes. The manifold is adapted to connect to the external environmental control system. 
         [0018]    The joint receives and redirects the flow from a first set of pipes of the plurality of pipes to at least one outflow pipe. The first set of pipes and the at least one outflow pipe comprise the plurality of pipes. The joint can be a manifold that defines a reservoir. The manifold receives the flow from a first set of pipes of the plurality of pipes and directs the flow into the reservoir and redirects the flow from the reservoir into a second end portion of at least one outflow pipe. The first set of pipes and the at least one outflow pipe comprise the plurality of pipes of the geothermal heat exchange apparatus. 
         [0019]    The geothermal heat exchange apparatus can further include bands transverse to a longitudinal axis of the multipipe arrangement. The center pipe is a through pipe that defines a first aperture that extends between the first end portion and the second end portion. The diameter of each pipe of the plurality of pipes in the twisted arrangement can vary. In one preferred embodiment, the plurality of pipes includes at least one pair of pipes. The second end portion of each pipe of the at least one pair of pipes connects to a U-bend type joint. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a perspective view of an idealized prior art environmental control system that uses a single conduit for geothermal heat exchange; 
           [0021]      FIG. 2  is a perspective view of the geothermal heat exchange apparatus of the present disclosure; 
           [0022]      FIG. 3  is a partial cut-away perspective view of the geothermal heat exchange apparatus of  FIG. 2 ; 
           [0023]      FIG. 4  is a cross-section taken along lines  4 - 4  of the geothermal heat exchange apparatus of  FIG. 3 ; 
           [0024]      FIG. 5  is a perspective view of the geothermal heat exchange apparatus of  FIG. 2  coiled into a roll; 
           [0025]      FIG. 6  is a side perspective view of the geothermal heat exchange apparatus of  FIG. 2  positioned in a borehole in the earth, a source of grout connected to the geothermal heat exchange apparatus; 
           [0026]      FIG. 7  is a side perspective view of the geothermal heat exchange apparatus of  FIG. 6  positioned and grouted in the borehole; and 
           [0027]      FIG. 8  is a cross-sectional taken along lines  8 - 8  of  FIG. 7  showing the grout filling the borehole, around the plurality of pipes and the center conduit. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Referring initially to  FIG. 2 , a geothermal heat exchange apparatus  10  includes a center conduit  12  and a plurality of pipes  14 . The plurality of pipes  14  is positioned in a twisted arrangement on center conduit  12 . Geothermal heat exchange apparatus  10  defines a first longitudinal axis-X aligned with a centerline of central conduit  12 . 
         [0029]    Center conduit or conduit  12  has a flexible tubular structure that includes a first end portion  16  and an opposed second end portion  18 . The tubular wall of conduit  12  defines an aperture  20  that is a through hole that extends between first end portion  16  and second end portion  18 . Aperture  20  has a first inside diameter. In one preferred embodiment, the corrugated center conduit  12  dimensions include an inside diameter of approximately 1.9 inches, outside diameter of approximately 2.375 inches and a wall thickness of approximately 1/16 th  or 0.0625 inches. It is understood that the size of the inside diameter can vary depending upon the intended geothermal heat exchange application. 
         [0030]    As shown in  FIGS. 2 and 3 , geothermal heat exchange apparatus  10  has an approximately tubular overall structure defined by through hole  20  of the center conduit  12  and the twisting arrangement of the plurality of pipes  14  around central conduit  12 . Plurality of pipes  14  has a flexible tubular structure that includes a first end portion  22  and an opposed second end portion  24 . Each pipe  15  of the plurality of pipes  14  is a conduit that defines an aperture  26  that is a through hole that extends between the first end portion  22  and the second end portion  24 . Aperture  26  of each pipe  15  of the plurality of pipes  14  is shown as having a relatively small diameter relative to center conduit  12 , but the size of each pipe  15  and the corresponding aperture  26  of each pipe  15  of the plurality of pipes  14  can vary depending upon the intended application. In one preferred embodiment, individual pipes  15  of the plurality pipes  14  are standard % or 0.75 inch inside diameter of pipes  15  with a wall thickness of approximately 0.078 inch. The size of each pipe  15  of the plurality of pipes  14  is varied to accommodate the liquid flow and/or cooling demand for a given application. 
         [0031]    As shown in  FIG. 2 , the first end portions  22  of the inflow pipes  14 A of the plurality of pipes  14  connect to at least one manifold  28 . In one preferred embodiment, first end portions  22  of inflow pipes  14 A of first manifold  28  connect to a first manifold  28  and the first end portions  22  of the outflow pipes  14 B of the plurality of pipes  14  connect to a second manifold  28 . It is understood that the number of manifolds  28  can vary depending upon the intended geothermal heat exchange application. Geothermal heat exchange apparatus  10  can optionally include one or more manifolds that are connected in the field either before or after installation in the borehole. Alternatively, manifolds  28  can be connected the plurality of pipes in a controlled setting during the assembly of geothermal heat exchange apparatus  10 . 
         [0032]    Each pipe  15  of the plurality of pipes  14  is twisted onto and preferably around the central conduit or conduit  12  in a parallel, spaced and twisted arrangement. Twisted onto as defined herein includes directly positioning the plurality of pipes  14  in direct contact with central conduit  12  in an arcuate arrangement. In the preferred embodiment the plurality of pipes  14  is positioned in an approximately parallel spaced helical arrangement around the central conduit  12 . Each pipe  15  of the plurality of pipes  14  is approximately in direct contact with central conduit  12 . Each pipe  15  of the plurality of pipes  14  is positioned in approximately fixed spaced separation on center conduit  12  relative to the adjacent pipe  15  of the plurality of pipes  14 . 
         [0033]    The plurality of pipes  14  is a multipipe or multiple pipe twisted arrangement of the plurality of pipes  14  around center conduit  12 . Individual pipes  15  of the plurality of pipes  14  can vary in their respective inside diameters, the quantity of pipes  15  in the plurality of pipes  14  and the arrangement of pipes  15  on center conduit  12  depending upon the intended application of geothermal heat exchange apparatus  10 . For example, in one preferred embodiment, there are a total of eight (8) pipes  15  in a twisted arrangement around the conduit  12 . The second end portion  24  of each pipe  15  of the plurality of pipes  14  connects to a joint  30  to define four (4) pairs of pipes  15  with each pair of pipes  15  connected by one joint  30 . In this one preferred embodiment, joint  30  is a U-bend that receives the downwardly directed inflow from a first pipe  15  of a first set of pipes  14 A and redirects the flow upwardly into a second pipe  15  of a second set of pipes  14 B connected to manifold  28  in this one example. 
         [0034]    Other arrangements the plurality of pipes  14  and joint  30  include, for example, three (3) pairs of pipes  15  with each pair of pipes  15  connected by one joint  30 . Additional arrangements include joint  30  having a manifold type structure that connects to the second end portions of the first set of pipes  14 A and to the second end portion of the second set of pipes  14 B that includes at least one pipe  15 . Thus, joint  30  can for example receive the flow input from first set of pipes  14 A that is four (4) pipes  15  and redirect that flow into the second set of pipes  14 B that is the same or a different quantity of pipes  15  than first set of pipes  14 A. As another example, in one preferred embodiment, joint  30  receives the input flow of four (4) pipes  15  with an inside diameter of approximately 0.8 inches that is the first set of pipes  14 A and redirects and realigns that flow in to joint  30  to the second set of pipes  14 B that is a single pipe  15  with an inside diameter of approximately 1.6 inches. Similarly, the first set of pipes  14 A of the plurality of pipes  14  for inflow can be a single pipe  15  and the second set of pipes  14 B for outflow can be multiple pipes  15 . 
         [0035]    Center conduit  12  preferably has a length that is less than that of the plurality of pipes  14  in order to accommodate the central positioning of one or more joints  30  within the compact diameter of geothermal heat exchange apparatus  10 . In one preferred embodiment, the plurality of pipes  14  and/or one or more joints  30  extend past conduit  12 . Center conduit  12  can be any shape of tubular conduit, but preferably has a circular cross-section perpendicular to the longitudinal axis. In addition, conduit  12  can have a structure that facilitates flexing and reduces the minimum bend radius for applications such as, for example, coiling into a roll. These structures of the tubular wall of conduit  12  can include, but are not limited to undulations in any form to include corrugations  36  that retain the approximately continuous inside diameter during flexing. 
         [0036]    Plurality of pipes  14  is preferably positioned on central conduit  12  in a twisted arrangement. In addition, each pipe  15  of the plurality of pipes  14  is positioned in an approximately fixed spaced separation with other pipes  15  in the plurality of pipes  14 . A space or gap  32  is defined by the fixed spaced separation between each pipe  15  of the plurality of pipes  14 . 
         [0037]    Geothermal heat exchange apparatus  10  can further include one or more bands  34  around the twisted plurality of pipes  14  on center conduit  12 . Bands  34  can optionally assist in fixing the spacing between each pipe  15  of the plurality of pipes  14 . Bands  34  are preferably tape, but can be any type of structural band that assists in the retention of the spaced separation between each pipe  15  of the plurality of pipes  14 . In the preferred embodiment, bands  34  are positioned approximately every four feet along the length of the plurality of pipes  14 , but it is understood that this can vary with the size of each pipe  15  and size of the plurality of pipes  14  overall. 
         [0038]    Center conduit  12  can have a solid tubular wall, but the tubular wall of conduit  12  preferably defines a plurality of apertures  38 . The shape of apertures  38  is shown as being circular, but it is understood that apertures  38  can have any shape and/or directional alignment suitable for the flow of grout from conduit  12  through apertures  38 . 
         [0039]    As shown in  FIG. 4 , the plurality of pipes  14  is in direct contact with central conduit in this one preferred embodiment. Each pipe  15  of plurality of pipes  14  is separated by gap or space  32  defined between adjacent pipes  15  of the plurality of pipes  14 . The plurality of pipes  14  is twisted such that it is tight bound to center conduit  12 . Band  34  can optionally augment the retention of the plurality of pipes  14  in fixed spaced separation. 
         [0040]    Referring now to  FIG. 5 , the geothermal heat exchange apparatus  10  is structured for flexibility that includes the bending and coiling of assembled plurality of pipes  14  in the assembled twisted preferably helical arrangement around flexible center conduit  12 . Geothermal heat exchange apparatus  10  can also be readily uncoiled into a linear alignment. This flexibility and compactness makes the geothermal heat exchange apparatus  10  easy to store, transport and install. Once uncoiled, the linearly extended assembly  10  can be readily installed down a borehole. The plurality of pipes  14  can have one or more joints  30  installed while coiled as well as one or more manifolds  28 . The combination of manifolds  28  and joints  30  connected to the first end portion  22  and second end portion  24 , respectively of the plurality of pipes  14  can be used to retain the plurality of pipes  14  in direct contact with conduit  12  and retain the desired separation between individual pipes  15  of the plurality of pipes  14  without the need for bands  34 . 
         [0041]    As shown in  FIGS. 5 and 6 , geothermal heat exchange apparatus  10  has been extended from the coiled position to a linear position in an approximately vertical borehole  6  in the ground. It is understood that borehole  6  is not required to be vertical and can be angled from the vertical. Once positioned in borehole  6 , an external source of grout  9  is used to supply grout  40  into center conduit  12  aperture  20  in first end portion  16 . Grout  40  is preferably pumped under pressure down conduit  12  and out through aperture  20  in the second end portion  18 . Grout  40  surrounds the geothermal heat exchange apparatus  10  in borehole  6  through the primary loading of the grout at the bottom of the borehole and filling the borehole  6  vertically upward as is common practice. In addition, grout  40  advantageously passes through apertures  38  in the tubular wall of conduit  12  in order to provide grout  40  transverse to the longitudinal axis in order to properly fill the spaces  32  between the pipes  15  of the plurality of pipes  14  in approximately fixed spaced separation. As required for a given application, bands  34  can be applied around the plurality of pipes  14 . 
         [0042]    The relatively thin walled structure of central conduit  12  and each pipe  15  of the plurality of pipes  15  of geothermal heat exchange apparatus  10  that facilitates coiling also advantageously provides less thermal resistivity and correspondingly better heat transfer when the geothermal heat exchange apparatus  10  is installed in the earth or ground  6 . 
         [0043]    Referring now to  FIG. 7 , grout  40  fills center conduit  12  and surrounds geothermal heat exchange apparatus  10  in borehole  6  to include filling spaces  32 . Geothermal heating exchange apparatus  10  has an advantageous level of heat transfer due to the helical twist in the plurality of pipes  14  and the creation of secondary effects in the fluid flow in the plurality of pipes  14 . Secondary effects occurs in curved pipes  15  as the laminate flow against the boundary layer on the inside of each pipe  15  becomes a cross flow between the inner and outer pressure gradients experienced by the heat exchange fluid in the plurality of pipes  14 . The secondary flow results in elevated levels of heat transfer at relatively low Reynolds numbers in the range of 1,000 or less without the high turbulence and greater pump pressure demands required by straight pipes to achieve the approximately same level of heat transfer at Reynolds number in the range of approximately 2,500—approximately 3,000. Further, the combination of multiple relatively small diameter plurality of pipes  14  provides for increased surface area for heat transfer. 
         [0044]    In the preceding specification, the present disclosure has been described with reference to specific exemplary embodiments thereof. It will be evident, however, that various modifications, combinations and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims that follow. While the present disclosure is described in terms of a series of embodiments, the present disclosure can combine one or more novel features of the different embodiments. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.