Abstract:
A Joule heating apparatus with a housing having an internal cavity. The housing has an inlet portal for introducing fluid into the internal cavity and an outlet portal for discharging the fluid form the internal cavity. The internal cavity includes an internal heating section with at least one electrode assembly. The electrode assembly has a supply electrode, a ground electrode, and a space between the supply and ground electrodes. The space of the electrode assembly is in fluid communication with the housing&#39;s inlet and outlet portals. The electrode assembly is adapted to form an electric field to heat via Joule heating the fluid flowing through the annulus. A method for Joule heating of a fluid is provided that uses the aforesaid apparatus to heat the fluid by applying an electric field thereto.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Application No. 61/912,917, filed on Dec. 6, 2013, which is incorporated herein by reference. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
       [0002]      FIG. 1A  is a diagram illustrating a trace heating mechanism. 
         [0003]      FIG. 1B  is a diagram illustrating the Joule heating mechanism. 
         [0004]      FIG. 2  is a side view of an embodiment of the invention. 
         [0005]      FIG. 3  is a cut-away view of the embodiment of the invention shown in  FIG. 2 . 
         [0006]      FIG. 4  is a cross-sectional view of the embodiment of the invention shown in  FIG. 2 . 
         [0007]      FIG. 5  is a perspective view of an embodiment of an electrode assembly of the invention. 
         [0008]      FIG. 6  is a cross-sectional view of the embodiment of the electrode assembly shown in  FIG. 5 . 
         [0009]      FIG. 7  is a perspective view of another embodiment of the invention. 
         [0010]      FIG. 8  in a cross-sectional view of the embodiment of the invention shown in  FIG. 7 . 
         [0011]      FIG. 9  is a partial cross-sectional view of the embodiment of the invention shown in  FIG. 8  depicting the electrode assembly connection to the bus bars and bus plate. 
         [0012]      FIG. 10  is a partial cross-sectional view of the embodiment of the invention shown in  FIG. 7  depicting the junction box and conducting electrode in connection with the bus plate. 
         [0013]      FIG. 11  is a cross-sectional view of another embodiment of the invention depicting the electrode assemblies as including spaced-apart electrode plates. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0014]    The heating principle employed by apparatus  10  is referred to as “Joule” heating. Joule heating has a number of advantages over other forms of heating typically used with respect to fluid such as crude oil. These other forms of heating may include bulk heating with natural gas or electrical trace heating (shown in  FIG. 1A ). Using electrical power to heat has advantages in terms of convenience onboard ships, low emissions in the field (compared to natural gas), and can be transmitted efficiently using electrical power lines. Joule heating is more efficient at converting electrical energy to internal energy in oil, compared to electrical trace heating. Joule heating is about 74% efficient. This value can be increased substantially by optimal design parameters. In comparison, typical efficiencies for tracing heating are about 30%. 
         [0015]    The Joule heating technique (described in  FIG. 1B ) applies “electrical work” to the oil, instead of generating the heat in a resistive heater and then conducting heat into the oil using a thermal gradient (described in  FIG. 1A ). Electrical work through Joule heating is a significantly more efficient process. For example, crude oil can have a widely varying thermal conductivity, but is typically low, as for example, k oil ˜0.147 W/(m K), which is about ⅕ th  of that of water, and about two to three orders of magnitude lower than many common metals. Trace heating relies on using an electrical resistor (A. 1 ) to heat up, and then heat is conducted from the resistor (A. 1 ) into the fluid (A. 2 ). Because of the low thermal conductivity of oil, it is difficult to get the heat to penetrate significantly into the oil. A large fraction of the heat can easily conduct into the metal pipeline material and be transferred to the surrounding environment. 
         [0016]      FIG. 2  shows an embodiment of heating apparatus  10 . Apparatus  10  may include housing  12 . Housing  12  may include inlet section  14 , heating section  16 , and outlet section  18 . Inlet section  14  may be detachably connected to end  20  of heating section  16  by flanges  22   a,    22   b.  Outlet end  18  may be detachably connected to end  24  of heating section  16  by flanges  26   a,    26   b.  When assembled, inlet section  14 , heating section  16 , and outlet section  18  may be in fluid communication. 
         [0017]    With reference to  FIG. 2 , inlet section  14  may include inlet portal  28 . Outlet section  18  may include outlet portal  30 . Inlet portal  28  may include flange  32  for detachably connecting inlet portal  28  to inlet conduit  33  for flowing oil into apparatus  10  via inlet portal  28 . Outlet portal  30  may include flange  35  for detachably connecting outlet portal  30  to outlet conduit  37  for flowing heated oil out of apparatus  10  via outlet portal  30 . Electrical power source  39  may be provided to supply electric power (e.g., an electric current) through electrical conduit  41  to apparatus  10 . 
         [0018]    Housing  12  may be formed in a variety of shapes and dimensions. For example, as seen in  FIG. 2 , housing  12  may be cylindrically shaped. Housing  12  may have a length of 5′8″, a width of 3′4″, and a height of 3″6″ as mounted. Inlet and outlet portals  28 ,  30  may each have a 24″ pipe body. Housing  12  may be formed of a variety of materials such as metal, as for example, structural steel or carbon steel. 
         [0019]    With reference to  FIG. 3 , housing  12  may include internal cavity  34 . Internal cavity  34  may be divided into compartments. For example, first support member  36  may be transversely positioned at end  20  of heating section  16  to form internal inlet section  38 . Second support member  40  may be transversely positioned at end  24  of heating section  16  to form internal outlet section  42 . Support members  36 ,  40  also may form internal heating section  44 . 
         [0020]    As seen in  FIGS. 3 and 4 , each of support members  36 ,  40  may include one or more openings or bores  46 . Each of opening  46  in support member  36  may be axially aligned with a corresponding opening  46  in support member  40 . Each opening  46  in support member  36  and its axially aligned corresponding opening  46  in support member  40  may receive and support one electrode assembly  48 . 
         [0021]    With reference to  FIGS. 5 and 6 , electrode assembly  48  may include distal end  50  and proximal end  52 . Electrode assembly may include inner electrode  54  and outer electrode  56  in spaced relation to form annulus  58 . For example, outer electrode  56  may be tubular-shaped (e.g., tubular or a tube) with inner electrode  54  concentrically placed within electrode  56  to form annulus  58 . Outer electrode  56  may have a length in the range of 1 to 360 inches and an inner diameter in the range of 2 to 24 inches Inner electrode  54  may have a length in the range of 1 to 360 inches and a diameter of 1/16″ to 24 inches. The space between the outer surface of inner electrode  54  and the inner surface of outer electrode  56  that forms annulus  58  may be in the range of 1/16″ to 24 inches. Each of inner and outer electrodes  54 ,  56  may be made of conductive metal, as for example, stainless steel. 
         [0022]    Apparatus  10  may include one or more electrode assemblies  48 . For example, apparatus  10  may include from one to  700  electrode assemblies. The embodiment of apparatus  10  shown in  FIG. 3  includes  16  electrode assemblies  48 . 
         [0023]    Again with reference to  FIGS. 3 and 4 , proximal end  52  of each electrode assembly  48  is accommodated within and supported by opening  46  in support member  40  and distal end  50  is accommodated within and supported by the corresponding axially aligned opening  46  in support member  36 . Distal extend  60  of each inner electrode  54  extends past support member  36  and protrudes into internal inlet section  38  terminating at connection point  62 . Each connection point  62  is operatively connected to bus bar  64  positioned transversally within internal inlet section  38 . Bus bar  64  may be in electrical communication with electrical power source  39 . Electrical power source  39  may supply electric power (e.g. an electric current) through electrical conduit  41  to bus bar  64 . Electrical conduit  41  may, for example, be an electrode. Bus bar  64  and conduit  41  may be made of any electrical conductive material, as for example, brass. 
         [0024]    With respect to  FIG. 3 , internal inlet section  38  may include an insulating material  66 . For example, material  66  may be placed or contained in the portion of internal inlet section  38  from and to the right of bottom surface  67  of bus bar  64 . Internal heating section  44  may also include material  66 . Material  66  may be distributed around the portion of each electrode assembly  48  that is longitudinally positioned within internal heating section  44 . Material  66  may function to provide insulation within internal inlet section  38  about bus bar  64  and within internal heating section  44  about electrode assemblies  48 . Material  66  may prevent or retard the transfer of heat generated by bus bar  64  and electrode assemblies  48  to housing  12 . Material  66  may be composed any material that provides insulating properties. For example, material  66  may be a polyurethane. 
         [0025]    Another embodiment of apparatus  10  is depicted in  FIGS. 7-10 . In this embodiment (as shown in  FIG. 7 ), outlet section  18  may be made uniform or integral with heating section  16 . Inlet portal  28  may be positioned at bottom section  68  of housing  12 . Outlet portal  30  may be positioned at top section  70  of housing  12 . Electrical junction boxes  72  may be positioned on each side  74  of heating section  16 . The electrical power source  39  (not shown) that provides electric current to apparatus  10  supplies the electric current through an electric conduit  41  (not shown) that is detachably affixed to each of electrical junction boxes  72 . With the displacement of inlet portal  28  to bottom section  68 , inlet section  14  may be more accurately described as vessel cap section  14 . It is to be understood that the placement of inlet and outlet portals  28 ,  30  and junction boxes  72  about housing  12  may vary without detracting from the functionality of apparatus  10 . 
         [0026]    With reference to  FIG. 8 , inlet portal  28  extends into internal outlet section  42  via internal pipe  75 . The end of internal pipe  75  may be engaged to seal to support member  40  about an opening  46  therein such that fluid entering into apparatus  10  through inlet portal  28  flows, via internal pipe  75 , through opening  46  and into annulus  58  of one of electrode assemblies  48 . The fluid flows through annulus  58  where an electric current may be passed through the fluid from inner electrode  54  (the supply electrode or anode) to the outer electrode  56  (the ground electrode or cathode) causing the fluid to be heated. The heated fluid flows in a first axial direction (e.g., in a left to right direction) through annulus  58  of the electrode assembly  48  and exits through the corresponding axial opening  46  in support member  36  where the heated fluid is deposited within the internal inlet section  38 . Internal inlet section  38  may be better described as internal cap section  38 . From internal cap section  38 , the heated fluid will flow into the annulus  58  of any other electrode assemblies  48  within internal heating section  44  by passing through opening  46  in support member  36  associated with the particular electrode assembly  48 . The heated fluid will then flow in a second direction (e.g., in a right to left direction) through annulus  58  of the respective electrode assembly  48  and undergo further heating as a result of the electric field created by inner electrode  54  and outer electrode  56 . The additionally heated fluid will exit through the corresponding axially positioned opening  46  in support member  40  where the additionally heated fluid will be deposited within internal outlet section  42 . The additionally heated fluid will then flow from internal outlet section  42  through outlet portal  30  and into outlet conduit  37  (not shown). In this embodiment, apparatus  10  does not include insulating material  66  within internal heating section  44  and internal inlet or cap section  38 . 
         [0027]    Again with reference to  FIG. 8 , support member  40  may be configured as an assembly including internal ring member  74  and insulating support piece  76 . Internal ring member  74  may be made of any structural material capable of supporting electrode assemblies  48 . Internal ring member  74  may, for example, be made of metal. Insulating support piece  76  may be detachably affixed to the underside of internal ring member  74 . For example, insulating support piece  76  may be bolted to internal ring member  74 . Insulating support piece  76  may contain preformed supporting recesses  78  that accommodate and support the proximal ends  52 ,  84  of electrode assemblies  48 . 
         [0028]    As illustrated in  FIGS. 8 and 9 , support member  36  may be configured as an assembly including ground bus bars  80  and bus plate  82 . Grounds bus bars  80  and bus plate  82  may be insulated with an insulating material, as for example, a polyurethane coating. Distal end  50  of electrode assemblies  48 , namely, each of the outer electrodes  56  may be directly welded to respective insulated ground bus bars  80 . The distal end  60  of each inner electrode  54  may be operatively connected to insulated bus plate  82 . For example, distal end  60  of each inner electrode  54  may be bolted to insulated bus plate  82  by bolts  86 . The operative connection of each inner electrode  54  to insulated bus plate  82  enables electric current traveling to insulated bus plate  84  via power source  39  to be transferred to each of inner electrodes  54  where the current then passes to the outer electrode  56  within the annulus  58  thereby causing electric work on the fluid within annulus  58  leading to an increase in temperature of the fluid. Both insulated ground bus bars  80  and insulated bus plate  82  may be insulated with any type of material that provides insulation, as for example, a polyurethane coating. This embodiment may use any number of electrode assemblies depending on a variety of factors, as for example, the size of housing  12 , the voltage applied to electrode assemblies  48 , and the flow rate of the fluid being processed by apparatus  10 . For example, seven electrode assemblies may be used. 
         [0029]      FIG. 10  depicts an embodiment of the configuration of junction box  72  and its electrical connection to insulated bus bar plate  82 . Junction box  72  may include electrical housing  88  inserted over and affixed to over-molded metal part  90  which may contain external threads. Over-molded metal part  90  may be secured to external mount  94 . Compression nut  92  may be threadedly connected to over-molded metal part  90  to detachably secure housing  88  to external mount  94 . Teflon washer  96  may be included. The threaded connection of compression nut  92  causes compression against the insulated overmold  98 , causing sealing engagement of the insulated overmold  98  against the internal angled wall of the external mount  94 . Insulated overmold  98  (which may be L-shaped) may be positioned on the inner surface  100  of housing  12  and extend in one direction where terminates and abuts insulated bus plate  82 . Insulated overmold  98  may extend in another direction external to housing  12  passing within bore  102  that extends through housing  12 , mount  94 , compression nut  90  and into internal cavity  104  of housing  88 . Insulated overmold  98  may contain central bore  106  in which one or more conducting electrodes  108  are situated and extend from internal cavity  104  of housing  88  to insulated bus plate  82 . At connection point  110 , the end of conducting electrode  108  may be operatively connected to a non-insulating portion of insulated bus plate  82  such that electrical current may travel through conducting electrode  108  and be transported to insulated bus plate  82  at connection point  110 . Electrode  108  may be connected to insulated bus plate  82  via spring assembly  112 . Electrode  108  may be made of brass. 
         [0030]      FIG. 11  depicts an alternative embodiment apparatus  10 . Electrode assemblies  48  may each comprise ground plate electrode  114  parallel to and spaced-apart from supply plate electrode  116 . The fluid flows from inlet portal and into space  118  between each ground plate electrode  114  and supply plate electrode  116 . In space  118 , the fluid is subjected to the electric current flowing from supply plate electrode  116  to ground plate electrode  114  resulting in the heating of the fluid. Bus bar plate  120  transfers electric current to each supply plate electrode  116 . Grounding bus bar plate  122  receives current passing through the fluid from each ground plate electrode  114 . Ground plate electrodes  114  and supply plate electrodes  116  may be positioned parallel to a direction of flow of the fluid through space  118 . Ground plate electrodes  114  and supply plate electrodes  116  may be positioned in a horizontal orientation, a vertical orientation, or any orientation therebetween. 
         [0031]    In operation, fluid (e.g., mildly-conductive fluid, crude or refined oil, or by-products of crude oil) may be transported through inlet portal  28  where the fluid flows (via pressure gradient) into one or more electrode assemblies via annulus  58 . While flowing through annulus  58 , electrical power source  39  is activated to supply an electrical current, through electrical conduit  41 , to bus bar  64 , which transfers the electric current to inner electrodes  54 . The “hot” inner electrode  54  transfers the electric current to the fluid flowing through annulus  58  thereby heating the fluid. Each outer electrode  56  acts a ground member. Heated fluid exits annulus  58  at proximal end  52  of electrode assembly  48  and flows into internal outlet section  42 . From internal outlet section  42 , the heated fluid flows through outlet portal  30  and into conduit  37  where the heated fluid is transported, for example, through a pipeline system. 
         [0032]    With apparatus  10 , an intense electric field is applied to the oil. Due to the small, but finite oil electrical conductivity, electrical work is applied predominantly to the oil, which increases the internal energy of the oil. The increase in internal energy is observed as an increase in oil temperature. 
         [0033]    Because Joule heating is applied through electrical work to the oil, instead of transferring heat through conduction, there is less entropy generated, for a given increase in internal energy of the oil. The result is that oil can be heated with less contact time between the oil and the heating apparatus  10 . This in turn can reduce the length of the heating apparatus  10 , or can allow for higher flow rates of oil through the apparatus  10 . 
         [0034]    With apparatus  10 , the electrical field is delivered to the oil using two concentric annular electrodes  54 ,  56 . In between the electrodes, is an annular region  58 , where the oil flows axially. The annular region  58  can be designed such that the Joule heating is substantially uniform, which allows the oil to be heated substantially uniformly. This is much more advantageous than trace heating, where heat is transferred at the boundaries, and is not uniform. 
         [0035]    The cylindrical electrode design and annular oil flow region is designed to apply an intense electric field to the oil, without significant pressure drop. In addition, the design is relatively easy to manufacture and at a relatively low cost. A 5.5 psi pressure drop may be required to push 100 gallons of oil per minute through the apparatus  10 , assuming the oil has a dynamic viscosity of μ=3.85 Pa s. This design can be further optimized within the guidelines of the claims to increase efficiency. 
         [0036]    The voltage applied to inner electrode  54  may vary. For example, a voltage of 0-10000 V may be applied to inner electrode  54 . More preferably, a voltage of 8000 V may be applied to inner electrode  54 . 0V may be applied to outer grounding electrode  56 . 
         [0037]    Because the electrical conductivity of the oil is about 12 orders of magnitude lower than that of the electrodes  54 , 56 , nearly all the electric field will reside in oil annulus  58 . Here, Joule heating is given by {dot over (Q)} e =σ|E| 2 , where |E| is the magnitude of the electric field. The oil in annulus  58  is represented as {dot over (Q)} e ˜3×10 5  [W/m 3 ]. In the electrodes  54 ,  56 , Joule heating is 10 orders of magnitude lower at approximately {dot over (Q)} e ˜9×10 −6  [W/m 3 ] and 7 orders of magnitude greater than what occurs in the bus bar. 
         [0038]    With a flow rate of 100 gallons per minute the maximum velocity is indicated by U max =0.174 m/s. 
         [0039]    A large voltage drop (i.e. electric field) may occur in the oil annulus. 
         [0040]    Very little Joule heating occurs in bus bar  64  and electrodes  54 ,  56  (7-10 orders of magnitude lower than in the oil), because oil is such a poor thermal conductor. It is very inefficient for the oil to convect heat away from the bus bar  64  and electrodes  54 ,  56 . As a result, the bus bar  64  heats up to about 12° C. above ambient conditions of T amb =0° C. The inner electrodes  54  heat up to about 7° C. above ambient. 
         [0041]    Inner electrodes  54  reach a temperature of 1-50° C. above ambient, but do not contribute to heating of the oil. Bulk material  66  to the right of the bus bar  64  may reach a temperature of 50° C. above ambient. This is due to Joule heating of the bulk material  66  (e.g., polyurethane) that occurs between the bus bar  64  and the surrounding pipe material. Poor thermal conduction of the bulk material will allow the temperature to become high; however, this does not heat the oil, but instead can create some inefficiency due to thermal losses to the surrounding pipe material and surrounding environment. This can be improved by different material choices and placing the bus bar  64  further away from the pipe housing. 
         [0042]    The oil temperature at the outlet reaches 0.1-30° C. above the inlet and ambient oil temperatures. The heating is achieved using V applied =8000 V. When the electrical conductivity is σ=1×10 −6  S/m, the draw is I=2.96 A. The rate of electrical work applied to the apparatus is therefore, {dot over (W)}=23.68 [kW]. 
         [0043]    The oil in annulus  58  has a heat flux of q″=7×10 7  [W/m 2 ], which is 50,000 times higher than the heat flux through the electrode  54 . 
         [0044]    The oil has an inlet temperature of T in =0° C. and an outlet temperature T out =3° C. The velocity profile of the annular region  58  may have a maximum velocity of 0.172 m/s. 
         [0045]    The total rate of energy transfer flux of oil at 100 gallons per minute entering the Joule heating apparatus  10  is ink {dot over (m)}h in =2.7765×10 6  [W], where {dot over (m)} is the mass flow rate and h in  is the specific enthalpy of oil at the inlet. The oil is heated by 3° C. in the apparatus  10 . The total rate of energy transfer at the outlet is {dot over (m)}h out =2.7789×10 6  [W]. The net change in enthalpy is therefore {dot over (m)}(h out −h in )=17.4 [kW]. Alternatively, the oil may enter the Joule heating apparatus  10  at a rate of 1-1000 gallons per minute. 
         [0046]    Joule heating is achieved using V applied =8000 V. When the electrical conductivity is σ=1×10 6  S/m, the current draw is I=2.96 A. The rate of electrical work applied to the apparatus  10  is therefore, {dot over (W)} e =23.68 [kW]. As a result, the thermodynamic efficiency of the 
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         [0047]    Apparatus  10 , which employs direct fluid electric heat transfer or Joule Heating, achieves multiple benefits for the production, transportation, and storage of petroleum products through the direct application of electrical potential to the fluid. The desired benefits include, for example, the lowering of viscosity, prevention of paraffin deposition, efficient heat transfer, destruction of living biomass such as bacteria, and water molecule aggregation facilitating separation. Apparatus  10  will make transportation by pipeline, tanker truck, tanker train and marine crude carrier more efficient, more economical, and with increased margins of safety. This list is meant to be illustrative. Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.