Abstract:
An underwater thermal connector has mating plug and receptacle units configured for releasable mating engagement to form a sealed thermal connection for transferring heat into or out of subsea equipment housing and pipe lines. The receptacle unit has an inner chamber containing thermally conductive media and having a forward end opening which is sealed in the unmated condition, an outer thermally insulating chamber surrounding the inner chamber, a first thermal contact in the inner chamber, and a thermal conductor or heat pipe communicating with the first thermal contact and extending out of an outer end of the unit. The plug unit has at least one thermal conductor or heat pipe having an outer end and extending forward through a rear manifold and terminating in a thermal contact pin which engages the first thermal contact when the units are in mating engagement.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119(e) of co-pending U.S. Provisional Patent Application No. 62/200,552 filed on Aug. 3, 2015, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to connector assemblies having releasably mateable plug and receptacle units designed for use underwater or in other hostile environments, and is particularly concerned with an underwater thermal connector assembly for connection of heat pipes rather than electrical conductors or optical fibers. 
         [0004]    2. Related Art 
         [0005]    There are many types of submersible connectors for making electrical and fiber-optic cable connections in hostile environments. One type includes connectors for sealed subsea mating and de-mating. Such underwater connectors typically comprise a plug unit containing one or more contact probes and a receptacle unit containing an equivalent number of receptacle contacts or junctions for engagement with the contact probes, which extend into the receptacle unit when the units are connected together. Typically, the contacts or junctions are contained in a sealed chamber containing dielectric fluid, and the probes enter the chamber via one or more normally sealed openings. In U.S. Pat. No. 5,645,442 of Cairns, a submersible fluid-filled electrical connector has a receptacle with a contact chamber sealed with a stopper or plunger, and a plug for mating engagement with the receptacle has a conductive pin which engages through a sealed opening and pushes the plunger back to engage with a contact socket in the receptacle. 
       SUMMARY 
       [0006]    Apparatus and methods for isolated thermal connection between heat pipes in a subsea environment are provided. In one aspect, an underwater thermal connector comprises plug and receptacle (male and female) units configured for releasable mating engagement to form a thermal connection. The receptacle unit has a rear end and a forward end and includes at least one thermal contact chamber containing thermally conductive media and having a sealable forward end opening, a heat pipe having a first end extending into the contact chamber and in thermal communication with a contact socket in the chamber and a second end communicating with a thermal interface at the rear end of the receptacle unit, and a thermally insulating shuttle piston extending through the contact socket and having a forward end in sealing engagement with the forward end opening. The plug unit has at least one thermal interface at a rear end of the unit, a thermally insulating manifold having at least one through bore, and at least one heat pipe extending forward from the thermal interface through the at least one through bore and terminating in a thermal contact pin extending forward from the manifold. The thermal contact pin is configured for sealing engagement through the forward end opening of the contact chamber in the receptacle unit on mating engagement of the units, and urges the shuttle piston inward through the contact socket such that the contact pin is received and directly engaged by the contact socket when the units are in mating engagement, effecting thermal connection between the heat pipes in the two units. 
         [0007]    In one embodiment, the receptacle unit has one contact chamber containing a plurality of contact sockets aligned with respective openings in a forward end wall of the chamber, and a corresponding number of heat pipes extending into the sockets in thermal communication with the respective contact sockets. Alternatively, there may be plurality of separate contact chambers each containing one heat pipe and contact socket and having a forward end opening in which a forward end of a respective shuttle piston is sealed in the unmated condition of the units. 
         [0008]    The underwater thermal connector may be used for various subsea equipment applications, for example heat rejection from subsea components such as VFDs (variable frequency drive motor controller), power electronics, transformers, and motors; heat source and sink for thermal electric generators, and for heat transfer for thermal storage and injection during well shut in and start up. 
         [0009]    Other features and advantages of the present invention should be apparent from the following description which illustrates, by way of example, aspects of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The details of the present invention, both as to its structure and operation, may be gleaned in part by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
           [0011]      FIG. 1  is a schematic illustration of a heat pipe; 
           [0012]      FIG. 2  is a side elevation view, in partial section, of a female or receptacle unit of one embodiment of an underwater thermal connector assembly; 
           [0013]      FIG. 3  is a side elevation view, in partial section, of a male or plug unit of the underwater thermal connector assembly designed for releasable subsea mating engagement with the receptacle unit of  FIG. 2 ; 
           [0014]      FIG. 4  is a side elevation view, in partial section, of the plug and receptacle units of  FIGS. 2 and 3  in the mated condition; 
           [0015]      FIG. 5  is a cross-sectional view illustrating one embodiment of the thermal conductor assembly of  FIGS. 2 to 4  forming a thermal connection for transferring heat out of a subsea electronics or equipment housing; and 
           [0016]      FIG. 6  is a cross-sectional view illustrating an embodiment of the thermal conductor assembly of  FIGS. 2 to 4  forming a thermal connection for transferring heat out of a subsea liquid or gas carrying pipeline. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Certain embodiments as disclosed herein provide for an isolated thermal connection between heat pipes in a subsea or other hostile environment. 
         [0018]    After reading this description it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this detailed description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention. 
         [0019]      FIG. 1  is a schematic illustration of a heat pipe  10  for transfer of heat between two interfaces at different temperatures T 1 &gt;T 2 . Heat pipe  10  comprises an outer shell  19  having opposite ends  12 ,  16 , an annular wick  18  of suitable wicking material extending along the inside of shell  19  between the ends, and an interior lumen  15  inside wick  18 . At the hot or heat source end  12  of the heat pipe, a liquid in contact with the thermally conductive end face  14  at temperature T 1  absorbs heat so that it evaporates and turns into a vapor which travels along the interior lumen  15  of the tube towards the colder or heat sink end  16  of the heat pipe at temperature T 2 . The vapor is condensed back into a liquid at the colder end of the pipe extending up to end face  17 , releasing the latent heat. The liquid then returns to the heat source end of the pipe via annular wick  18  surrounding the inner lumen  15 , and the cycle repeats to transfer thermal energy from one end of the pipe to the other. The direction of heat transfer is reversed if T 1  is lower than T 2  (T 1 &lt;T 2 ). 
         [0020]      FIGS. 2 to 4  illustrate one embodiment of an underwater thermal connector assembly  20  shown in the mated condition in  FIG. 4 . In the mated condition, connector assembly  20  is designed to transfer heat into or out of subsea equipment, as described in more detail below.  FIG. 2  illustrates the receptacle or female unit  22  of the connector assembly, while  FIG. 3  illustrates the mating plug or male unit  24  of the assembly. The connector assembly is similar to prior underwater electrical connectors as described in U.S. Pat. Nos. 5,645,442 and 7,959,454, the contents of which are incorporated herein by reference, but electrical conductors are replaced by high thermal conductivity heat pipes, conductive materials are replaced by thermally conductive materials, and electrically insulating materials are replaced by thermal insulating materials. 
         [0021]    In this embodiment, the female connector unit  22  comprises a housing or shell  25  which may be made of a relatively low thermal conductivity metal such as titanium or 316 stainless steel, and one, two or more socket assemblies  26  (one of which is visible in  FIG. 2 ) extending from the rear or outer end  27  towards the forward or inner end  29  of shell  25 . Although plural socket assemblies  26  are illustrated, a single socket assembly may be provided in other embodiments, depending on heat transfer requirements. Shell  25  has a through bore  28 , a base or stopper  30  secured in a rear or outer end portion of through bore  28 , and a forward or inner end wall or plate  31  having openings  32  aligned with respective socket assemblies  26 . Base or stopper  30  is of rigid thermal insulating material such as Ultem™, PEEK™ or the like. An outer bladder  33  extends from the rear end wall  30  through bore  28  and has a forward or inner end seal  34  behind end plate  31  having a plurality of sealable openings each aligned with a respective opening  32  in forward end plate  31 . Each socket assembly  26  comprises a heat pipe  36  having a rear or outer end  83  thermally connected to external thermal interface  38 , shown schematically in  FIG. 2 . Heat pipe  36  extends from interface  38  through an aligned bore  40  in end wall or stopper  30  and into the shell. Where there is more than one heat pipe  36  in the connector unit, each heat pipe may terminate at a separate thermal interface  38 , or all heat pipes may terminate to the same thermal interface. Heat pipe  36  is similar to heat pipe  10  of  FIG. 1 , and has an inner lumen  80  surrounded by an annular wick  82  extending along the length of heat pipe  36  between thermally conductive end walls  83 ,  84 . End wall  84  is in thermal communication with socket  44  via thermally conductive sleeve  42 . 
         [0022]    A thermally conductive sleeve  42  extends from the forward or inner end of heat pipe  36  towards the inner end of the shell, and terminates at a thermal contact socket  44  of thermally conductive material. Sleeve  42  may be in thermal contact with inner or forward end  84  of heat pipe  36  or may be formed integrally with the inner end of heat pipe  36 , and may be an annular extension of the heat pipe. A thermally insulating shuttle piston  45  of Ultem™, PEEK™ or the like extends slidably through the contact socket  44  and has a forward end in sealing engagement in one of the sealable openings  37  in the forward or inner end wall or seal  34  of outer bladder  33  in the unmated condition of  FIG. 2 . Piston  45  is biased into the extended position of  FIG. 2  by spring  46  which acts between inner end  84  of heat pipe  36  and an adjacent end of shuttle piston  45 . In one embodiment, the sleeve  42  and contact socket  44  are of a suitable thermally conductive material such as copper. 
         [0023]    Socket assembly  26  also includes an outer bladder  48  of flexible thermal insulating material such as flexible elastomer material extending from the forward end wall  34  of outer bladder  33  rearwards over the shuttle piston  45 , contact socket  44 , and sleeve  42  up to the inner end  84  of heat pipe  35 . Bladder  48  may be formed integrally with the forward end wall  34  of bladder  33 . Inner chamber  50  within bladder  48  communicates with the interior of sleeve  42  via opening  51 , and may be filled with a mobile thermally conductive medium such as the synthetic ester Midel® 7131, manufactured by M&amp;I Materials Limited of Manchester UK, or other high thermal conductivity transformer fluid. A second chamber  53  is formed between bladders  48  and  33  and contains a mobile thermal insulating medium such as Dow Corning 200 or the like, and a third, outer chamber  52  is formed outside bladder  33  and exposed to the surrounding medium via ports  54  in shell  25 , for pressure compensation purposes during mating and de-mating. Bladder  48  has an annular inner rib  55  secured to contact socket  44 , and has one or more inwardly directed annular nibs  56  between ribs  55  and end wall  34  which are in sealing engagement with the outer surface of shuttle piston  45  in the unmated condition of  FIG. 2 . 
         [0024]    Plug unit  24  of  FIG. 3  has an outer cylindrical shell  60  which is of the same material as shell  25 , for example relatively low thermal conductivity metal such as titanium or 316 stainless steel. Shell  60  has a through bore  62  and a rear portion in rotating engagement with rear or outer manifold  64  which has a forwardly extending sleeve, and one or more plug probes or pins  65  which extend through bores in rear manifold  64  into hollow forward or inner end portion  66  of the plug through bore. Each plug probe  65  is a high thermal conductivity heat pipe of similar or identical construction to the heat pipe  10  of  FIG. 1  and heat pipe  65  has an inner lumen  85  surrounded by annular wick  86  extending from thermally conductive rear or outer end wall  88  to forward or inner end  70  of the heat pipe. In one embodiment, the heat pipes  40  and  65  are copper. Rear end wall  88  is terminated at a thermal interface  68  (shown schematically in  FIG. 3 ). Forward or inner end or tip  70  of heat pipe  65  is spaced inward from the forward end  72  of plug shell  60  and also comprises a thermal interface. Manifold  64  is also formed of a suitable rigid thermal insulating material such as Ultem™, PEEK™ or other rigid thermoplastic material. The hollow forward end portion  66  is of larger diameter than a corresponding forward end portion  74  of the receptacle manifold so that portion  74  is slidably engaged inside forward end portion  66  as the two parts are brought into engagement. Internal screw threads  75  at the forward or inner end of bore portion  66  are designed for threaded engagement with external screw threads  76  on the outer surface of receptacle shell  22  to secure the parts together in the mated condition of  FIG. 4 . 
         [0025]    Thermal interfaces  38  and  68  are shown schematically in  FIGS. 2 and 3 . In practice, one of the interfaces is in communication with a heat sink which may be provided by deep seawater surrounding a subsea equipment installation or wellhead, or a heat rejection connector on a vessel or surface installation such as an oil rig. The other interface is in communication with a heat source, such as subsea components in a subsea equipment housing, for example VFDs, power electronics, transformers, and motors, or an oil pipe where oil flowing through the pipe is the heat source. Heat transfer from the thermal interfaces to the heat sources and sink is accomplished using conventional heat transfer systems. This is includes direct conduction heat transfer, passive convective heat transfer with extended surface fins, circulating fluid systems and heat pipes. If interface  38  is the heat source and interface  68  is the heat sink, then T 1  (temperature at end  83  of heat pipe  36 ) is greater than T 2  (temperature at end  84  of heat pipe  36 ), and heat flux direction is from  83  to  84  or left to right as viewed in  FIG. 4 . For the heat pipe in plug  24 , T 1  (at outer end  88  of heat pipe  65 ) is less than T 2  (temperature at end  70 ), and the heat flux direction is towards interface  68 . These directions are reversed if interface  68  is the heat source and interface  38  is the heat sink. 
         [0026]    In the embodiment illustrated in  FIG. 4 , the receptacle is mounted in a threaded opening or port in a wall or pressure barrier  90  of a subsea pressure vessel or other enclosure, as indicated in dotted outline in  FIG. 2  and  FIG. 4 . In this embodiment, thermal interface  38  communicates with one or more heat sources inside the enclosure, and the parts of connector  20  outside the enclosure are surrounded by the seawater environment forming a heat sink, while thermal interface  68  of plug unit  24  communicates directly or indirectly with the heat sink for heat transfer out of the equipment housing or subsea pressure vessel. In other embodiments, the heat pipes and thermal interfaces may alternatively be configured for heat transfer into the equipment housing, or the thermal interface  38  at the opposite end of the connector may be surrounded by seawater. 
         [0027]    In order to connect the units, the forward ends of the receptacle and plug units are first aligned, and the hollow forward end portion  66  of plug shell  60  is engaged over the forward end portion  74  of receptacle unit  25 . The forward ends  70  of plug pins  65  enter the aligned openings  32  in the receptacle shell end plate or wall  31  and engage the forward ends of shuttle pistons  45 , pushing the pistons inward and compressing return springs  46 . As the receptacle unit continues to be advanced into plug shell  60 , the shuttle pistons are retracted inward from contact sockets  44 , and the contact pins or heat pipes  86  move into sealing engagement with sealable openings  37  in place of shuttle pins  45 , while the tips  70  of contact pins or heat pipes  65  move into thermal engagement with the respective sockets  44 . This effectively connects heat pipes  35  and  65  together in series via a thermal connecting portion comprising sleeve  42  and socket  44  between the forward or inner ends  70 ,  84  of the heat pipes. 
         [0028]      FIGS. 5 and 6  illustrate some embodiments or examples of the thermal connector assembly  20  of  FIGS. 2 to 4  with different thermal interfaces  38  and  68  and heat sources. It will be understood that different heat sources or heat sinks may be connected via the thermal connector assembly in other embodiments. In the embodiment of  FIG. 5 , the thermal interface  38  at the outer ends of heat pipes  80  of receptacle or female connector unit  22  comprises a subsea housing or enclosure  95  of thermally conductive material having an internal chamber  96  holding electronics  97  or other heat generating equipment on thermally conductive mount  91 . Chamber  96  may be a gas filled one atmosphere chamber as known in the field. The thermal interface  68  at the opposite end of assembly  20  comprises a finned heat exchanger  98  which is thermally coupled to the outer ends  88  of heat pipes  85  of the plug or male connector unit  24 . The finned heat exchanger  98  is surrounded by the seawater environment which acts as the heat sink. 
         [0029]    In the embodiment of  FIG. 5 , T enclosure  equals the temperature of the electronics equipment or heat source  97  inside electronics housing  95  and T seawater  is the temperature of the seawater or heat sink surrounding the heat exchanger  98 , and T enclosure &gt;T 1 &gt;T 2 &gt;T seawater , where T 1  is the temperature at the outer ends  83  of heat pipes  80  and T 2  is the temperature at the outer ends  88  of heat pipes  85 . 
         [0030]      FIG. 6  illustrates an embodiment in which thermal connector assembly  20  communicates between a heat source comprising oil or petroleum liquid or gas carried by pipe  100  from an underwater well, and a heat sink comprising sea water surrounding the opposite end of the assembly. Pipe  100  has an outer, thermally insulating layer  105  and an inner layer  104  of thermally conductive material comprising thermal interface  38 . The oil or gas travels along the interior  102  of pipe  100 . Thermal interface  38  is formed between the outer end portion of connector unit  22  and the inner, thermally conductive pipe layer  104 . As illustrated, the outer ends  83  of the heat pipes  80  of unit  22  extend through the insulation layer  105  and terminate in thermally conductive layer  104 . 
         [0031]    The thermal interface at the outer end of connector unit  24  is surrounded by seawater, and comprises connector or adapter  106  of thermally conductive material in which the outer ends  88  of heat pipes  85  are terminated, a thermoelectric generator or thermopile  108  suitably connected to connector or adapter  106  on one side, and to a finned heat exchanger  110  on the other side. Thermoelectric generator  108  has an electric power output  112  which may be connected to a subsea power cable or the like. 
         [0032]    In the embodiment of  FIG. 6 , T liquid &gt;T 1 &gt;T 2 &gt;T seawater , where T liquid  is the temperature of oil or liquid carried in pipe  100  (heat source). 
         [0033]    This arrangement permits releasable mating engagement between heat pipes in subsea mateable thermal connector units, while maintaining a seal against seawater ingress into the receptacle unit both in the mated and unmated conditions of the units. This allows heat to be transferred more easily into or out of subsea equipment. The underwater mateable thermal connector described above is configured to maintain thermal conduction while reducing or minimizing convection heat losses by means of suitable thermal insulating materials used in the connector units. The connector may be used for heat rejection from subsea components such as variable frequency drives or motor controllers, power electronics, transformers and motors as used in the subsea oil and gas industry and from oil or gas traveling along a subsea pipeline, as well as in other subsea applications such as communication systems, and for use as a heat source and sink for thermoelectric generators, as well as to provide for heat transfer for thermal storage and injection during well shut in and start up. The thermal connector assembly may also be used for heat transfer in other harsh environments. 
         [0034]    The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly limited by nothing other than the appended claims.