Patent Publication Number: US-9422147-B2

Title: Fuel or DEF dispenser having fluid temperature conditioning and control system

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     The present application is a continuation of copending U.S. patent application Ser. No. 12/843,976, entitled “Fuel or DEF Dispenser Having Fluid Temperature Conditioning and Control System,” filed on Jul. 27, 2010 and which is incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to fuel dispensers, diesel exhaust fluid dispensers, and other such dispensers. More specifically, the invention provides a system for temperature conditioning and control of a fluid, such as liquid fuel or diesel exhaust fluid, in a fluid dispenser. 
     BACKGROUND 
     Various countries have environmental regulations for vehicles which limit emissions of certain compounds, such as nitrogen oxide. For example, some regulations require that many newly-manufactured diesel-powered vehicle engines significantly reduce nitrogen oxide levels. One technology addressing this concern is selective catalytic reduction (SCR), which involves dosing a reductant into engine exhaust upstream of a catalyst to convert nitrogen oxides into less harmful byproducts. Diesel exhaust fluid (DEF) is a generic term for a reductant that may be used in the process of SCR. An example of a common reductant is a 32.5% solution of aqueous urea. 
     Because many manufacturers have adopted SCR technology, SCR systems will often be installed on new diesel vehicles. Correspondingly, diesel vehicles may now incorporate special DEF tanks, and DEF dispensers are increasingly provided in retail service station environments. 
     However, DEF will crystallize and freeze at a relatively high temperature (approximately 12° F.) compared to liquid fuels such as gasoline. In addition, DEF expands approximately 7% when frozen. This expansion can cause damage to the internal components of a DEF dispenser. 
     One prior art solution to this problem involves mounting a 750 W/120V electric heater in a DEF dispenser&#39;s lower hydraulic cabinet adapted to turn on when the ambient temperature in the cabinet reaches a specified level (e.g., 41° F.). Likewise, the solution may involve providing DEF dispensers with a retractable dispensing hose that is stowed in the dispenser&#39;s cabinet and a sliding cover or access door over the dispenser nozzle. Alternatively, the DEF dispenser may be adapted to suspend operation if the ambient temperature in the hydraulic cabinet reaches 12° F. while the power is energized to prevent damage to the dispenser&#39;s fuel handling components. 
     Temperature effects have also presented problems in prior art liquid fuel dispensers. Liquid fuel dispensers are well known, and these dispensers include flow meters that measure volumetric flow rate of liquid fuel as it is dispensed. Such flow meters are typically required to comply with weights and measures regulatory requirements that mandate a high level of accuracy. This ensures that the customer is neither overcharged nor undercharged for the purchase. Typically, either positive displacement meters or inferential meters have been used for this purpose. 
     The volume of liquid fuel is somewhat dependent on temperature (i.e., it expands when heated and contracts when cooled). In addition, liquid fuels are typically sold by a volumetric measure, such as U.S. gallons. Prior art solutions provide temperature compensation by sending signals from thermometric probes located in a flow meter to a first circuit in the dispenser&#39;s lower fuel handling compartment, to a second circuit in the dispenser&#39;s upper electronics compartment via an intrinsically safe connection, and finally to a computation device designed to combine the temperature data and pulser data. The computation device employs a volume correction factor to compensate the pulser data so as to account for temperature variations. Detailed information regarding temperature compensation of dispensed fuel is disclosed in U.S. Pat. No. 5,557,084 to Myers et al., entitled “Temperature Compensating Fuel Dispenser,” the entire disclosure of which is incorporated herein by reference for all purposes. However, this solution may not be available in many markets due to government regulation. 
     SUMMARY 
     According to one aspect, the present invention provides a fluid dispenser for installation in a forecourt in a fueling environment for dispensing liquid fuel or diesel exhaust fluid from at least one fluid storage tank remote from said fluid dispenser into a vehicle. The fluid dispenser comprises a housing in which fluid flow control components are located and at least one fluid conduit completing first and second fluid flow paths between the at least one fluid storage tank and a nozzle coupled to the housing. The fluid dispenser also comprises a fluid flow meter located along said fluid flow path, a control system, and a recirculation subsystem. The recirculation subsystem comprises a bypass valve located along one of the first and second flow paths. The bypass valve is operative to prevent fluid communication between the first and second fluid flow paths when the fluid dispenser is in use and to allow fluid communication between the first and second fluid flow paths when the fluid dispenser is not in use. 
     According to another aspect, the present invention provides a fluid dispenser for dispensing liquid fuel or diesel exhaust fluid from at least one fluid storage tank into a vehicle. The fluid dispenser comprises a housing in which fluid flow control components are located and a control system. The fluid dispenser also comprises a first fluid conduit completing a first flow path between the at least one fluid storage tank and a nozzle coupled to the housing, and a second fluid conduit completing a second flow path between the nozzle and the at least one fluid storage tank. Further, the fluid dispenser comprises a bypass valve located along one of the first and second flow paths and at least one controllable valve located along the second flow path. The at least one controllable valve is in electronic communication with said control system. 
     In another aspect, the present invention provides a method of measuring the flow rate of a fluid in a fluid dispenser for dispensing liquid fuel or diesel exhaust fluid to a vehicle in a fueling environment. The method comprises providing a fluid dispenser defining at least one fluid conduit connectable to first and second fluid flow paths between at least one fluid storage tank and a nozzle coupled to the fluid dispenser. Also, the method comprises providing a control system, providing a fluid flow meter located along the first fluid flow path, and providing at least one controllable valve located along the second fluid flow path. Further, the method comprises conditioning the temperature of the fluid upstream of the fluid flow meter inside the fluid dispenser and selectively actuating the at least one controllable valve to allow flowing fluid to flow to the at least one fluid storage tank when the fluid dispenser is not in use. 
     According to another aspect, the present invention provides a method of measuring the flow rate of a fluid in a fluid dispenser for dispensing liquid fuel or diesel exhaust fluid to a vehicle in a fueling environment. The method comprises providing a fluid dispenser comprising a housing and a control system. The fluid dispenser defines first and second fluid conduits connectable to first and second fluid flow paths, respectively, between at least one fluid storage tank and a nozzle coupled to the fluid dispenser. The method further comprises providing a first controllable valve located along the first flow path and in electronic communication with the control system. The first flow path defines a fluid inlet for an evacuation fluid downstream of the first controllable valve. In addition, the method comprises providing a recirculation pump coupled to the second flow path and in electronic communication with the control system. Finally, the method comprises closing the first controllable valve and evacuating the fluid from the first and second fluid conduits when the fluid dispenser is not in use. 
     According to another aspect, the present invention provides a method of measuring the flow rate of a fluid in a fluid dispenser for dispensing liquid fuel or diesel exhaust fluid to a vehicle in a fueling environment. The method comprises the steps of providing a fluid dispenser comprising a housing and a control system. The fluid dispenser defines first and second fluid conduits adapted for fluid communication with a nozzle. The first and second fluid conduits respectively complete first and second flow paths through the fluid dispenser. The method also comprises providing a junction at which the first and second fluid conduits are in fluid communication with each other. The junction is spaced apart from the nozzle, and the junction defines an inlet for fluid communication with the at least one fluid storage tank. Additionally, the method comprises providing a valve in fluid communication with the inlet upstream of the junction and providing a recirculation pump coupled to the second fluid conduit. The valve and the recirculation pump are in electronic communication with the control system. Finally, the method comprises actuating the valve and the recirculation pump such that fluid recirculates through the housing when the fluid dispenser is not in use. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which: 
         FIG. 1  is perspective view of a prior art fuel dispenser for use in a retail service station environment. 
         FIG. 2  is a schematic illustration of a prior art fuel dispensing system including the dispenser of  FIG. 1 . 
         FIG. 3  is a perspective view of a prior art DEF dispenser for use in a retail service station environment. 
         FIG. 4  is a schematic illustration of a fluid temperature conditioning and control system according to one embodiment of the present invention. 
         FIG. 5  is a schematic illustration of a fluid temperature conditioning and control system according to an alternative embodiment of the present invention. 
         FIG. 6  is a schematic illustration of a fluid temperature conditioning and control system according to a further alternative embodiment of the present invention. 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     The present invention provides a system for temperature conditioning and control of fluids in fluid dispensers. Embodiments of the present invention may be particularly adapted for use in dispensing DEF and liquid fuels, such as gasoline or diesel fuel. The terms diesel exhaust fluid and DEF are used broadly herein to refer to any reductant used to reduce nitrogen oxide emissions in vehicles, including ammonia and urea. To facilitate explanation of the preferred embodiments, a description of exemplary prior art fluid dispensing systems is first provided below. 
       FIG. 1  is perspective view of a prior art fuel dispenser  10  adapted for use in a retail service station environment. For example, fuel dispenser  10  may be the ENCORE® S fuel dispenser sold by Gilbarco Inc. of Greensboro, N.C. 
     Fuel dispenser  10  includes a housing  12  with a flexible fuel hose  14  extending therefrom. Fuel hose  14  terminates in a manually-operated nozzle  16  adapted to be inserted into a fill neck of a vehicle&#39;s fuel tank. Nozzle  16  includes a fuel valve. Various fuel handling components, such as valves and meters, are also located inside of housing  12 . These fuel handling components allow fuel to be received from underground piping and delivered through hose  14  and nozzle  16  to a vehicle&#39;s tank, as is well understood. 
     The fuel dispenser  10  has a customer interface  18 . Customer interface  18  may include an information display  20  relating to an ongoing fueling transaction that includes the amount of fuel dispensed and the price of the dispensed fuel. Further, customer interface  18  may include a media display  22  to provide advertising, merchandising, and multimedia presentations to a customer in addition to basic transaction functions. The graphical user interface provided by the dispenser allows customers to purchase goods and services other than fuel at the dispenser. 
       FIG. 2  provides a schematic illustration of a prior art fuel dispensing system in a retail service station environment. In general, fuel may travel from an underground storage tank (UST)  28  via main fuel piping  30 , which may be a double-walled pipe having secondary containment as is well known, to fuel dispenser  10  and nozzle  16  for delivery. An exemplary underground fuel delivery system is illustrated in U.S. Pat. No. 6,435,204 to White et al., hereby incorporated by reference in its entirety for all purposes. 
     More specifically, a submersible turbine pump (STP)  32  associated with the UST  28  is used to pump fuel to the fuel dispenser  10 . However, some fuel dispensers may be self-contained, meaning fuel is drawn to the fuel dispenser  10  by a pump controlled by a motor positioned within housing  12 . 
     STP  32  is comprised of a distribution head  34  containing power and control electronics that provide power through a riser pipe  36  down to a boom  38  inside the UST  28 , eventually reaching a turbine pump contained inside an outer turbine pump housing  40 . STP  32  may preferably be the RED JACKET® submersible turbine pump, manufactured by the Veeder-Root Co. of Simsbury, Conn. Also, STP  32  may contain a siphon that allows the STP  32  to generate a vacuum using the force of fuel flow. In addition, riser pipe  36  and distribution head  34  may preferably be secondarily contained to capture and monitor leaks. For example, such a system is disclosed in U.S. Pat. No. 7,010,961 to Hutchinson et al., hereby incorporated by reference in its entirety for all purposes. There may be a plurality of USTs  28  and STPs  32  in a service station environment if more than one type or grade of fuel  42  is to be delivered by a fuel dispenser  10 . 
     The turbine pump operates to draw fuel  42  upward from the UST  28  into the boom  38  and riser pipe  36  for delivery to the fuel dispenser  10 . After STP  32  draws the fuel  42  into the distribution head  34 , the fuel  42  is carried through STP sump  44  to main fuel piping  30 . Main fuel piping  30  carries fuel  42  through dispenser sump  45  to the fuel dispenser  10  for eventual delivery. Those of skill in the art will appreciate that dispenser sump  45 , which may also be double-walled, is adapted to capture any leaked fuel  42  that drains from fuel dispenser  10  and its fuel handling components so that fuel  42  is not leaked into the ground. 
     Main fuel piping  30  may then pass into housing  12  through a product line shear valve  46 . As is well known, the product line shear valve  46  is designed to close the fuel flow path in the event of an impact to fuel dispenser  10 . U.S. Patent App. Pub. No. 2006/0260680 to Reid et al., hereby incorporated by reference in its entirety for all purposes, discloses an exemplary secondarily-contained shear valve adapted for use in service station environments. The product line shear valve  46  contains an internal fuel flow path to carry the fuel  42  from the main fuel piping  30  to internal fuel piping  48 , which may also be double-walled. 
     After the fuel  42  exits the outlet of the shear valve  46  and enters into the internal fuel piping  48 , it may encounter a flow control valve  50  positioned upstream of a flow meter  52 . In some prior art fuel dispensers, the valve  50  may be positioned downstream of the flow meter  52 . The valve  50  may preferably be a proportional solenoid controlled valve, such as described in U.S. Pat. No. 5,954,080 to Leatherman, hereby incorporated by reference in its entirety. 
     The flow control valve  50  is under control of a control system  54  via a flow control valve signal line  56 . In this manner, the control system  54  can control the opening and closing of the flow control valve  50  to either allow fuel to flow or not flow through meter  52  and on to the hose  14  and nozzle  16 . Control system  54  may be a microprocessor, microcontroller, or other electronics with associated memory and software programs running thereon. Control system  54  typically controls other aspects of the fuel dispenser  10 , such as valves, displays, and the like as is well understood. For example, the control system  54  typically instructs the flow control valve  50  to open when a fueling transaction is authorized. In addition, control system  54  may be in electronic communication with a site controller  56  via a fuel dispenser communication network  58 . The site controller  56  communicates with control system  54  to control authorization of fueling transactions and other conventional activities. The site controller functions may preferably be provided by the PASSPORT® point-of-sale system manufactured by Gilbarco Inc. 
     The flow control valve  50  is contained below a vapor barrier  60  in a hydraulics compartment  62  of the fuel dispenser  10 . The control system  54  is typically located in an electronics compartment  64  of the fuel dispenser  10  above vapor barrier  60 . After the fuel  42  exits the flow control valve  50 , it typically flows through meter  52 , which measures the volume and/or flow rate of the fuel. 
     Flow meter  52  is typically a positive displacement or inferential flow meter. Meter  52  typically comprises a pulser  66  that generates a pulse series indicative of the volumetric flow rate of fuel and periodically transmits the pulse series to control system  54  via a pulser signal line  68 . In this manner, the control system  54  can update the total gallons dispensed and the price of the fuel dispensed on the information display  20 . 
     As fuel leaves the flow meter  52  it enters a flow switch  70 . The flow switch  70 , which is preferably a one-way check valve that prevents rearward flow through fuel dispenser  10 , generates a flow switch communication signal via the flow switch signal line  72  to the control system  54  to communicate when fuel is flowing through the flow meter  52 . The flow switch communication signal indicates to control system  54  that fuel is actually flowing in the fuel delivery path and that subsequent signals from flow meter  52  are due to actual fuel flow. 
     After the fuel  42  enters flow switch  70 , it exits through internal fuel piping  48  to be delivered to a blend manifold  76 . Blend manifold  76  receives fuels of varying octane levels from the various USTs and ensures that fuel of the octane level selected by the customer is delivered. After flowing through blend manifold  76 , the fuel passes through fuel hose  14  and nozzle  16  for delivery to the customer&#39;s vehicle. 
     In this case, fuel dispenser  10  comprises a vapor recovery system to recover fuel vapors through nozzle  16  and hose  14  to return to UST  28 . An example of a vapor recovery assist equipped fuel dispenser is disclosed in U.S. Pat. No. 5,040,577 to Pope, incorporated herein in its entirety for all purposes. More particularly, flexible fuel hose  14  is coaxial and includes a product delivery line  78  and a vapor return line  80 . Both lines  78  and  80  are fluidly connected to UST  28  through fuel dispenser  10 . Lines  78  and  80  diverge internal to dispenser  10  at manifold  76 , such that product delivery line  78  is fluidly coupled to internal fuel piping  48  and vapor return line  80  is fluidly coupled to internal vapor return piping  82 . During delivery of fuel into a vehicle&#39;s fuel tank, the incoming fuel displaces air in the fuel tank containing fuel vapors. Vapor may be recovered from the vehicle&#39;s fuel tank through vapor return line  80  and returned to the UST  28  with the assistance of a vapor pump  84 . A motor  86  operates vapor pump  84 . Internal vapor return piping  82  is coupled to a vapor flow meter  88 . Vapor flow meter  88 , which measures vapor collected by the nozzle  16  when fuel  42  is dispensed, may be used for in-station diagnostics and monitoring or control of vapor recovery as is well known. 
     After the recovered vapor passes through the vapor flow meter  88 , the recovered vapor passes to vapor line shear valve  90  (which is analogous to product line shear valve  46 ). Finally, the recovered vapor returns to UST  28  via vapor return piping  92 . Vapor return piping  92  is fluidly coupled to the ullage  94  of UST  28 . Thus, the recovered vapor is recombined with the vapor in the ullage  94  to prevent vapor emissions from escaping to the atmosphere. The vapors recombine and liquefy into fuel  42 . 
       FIG. 3  is a perspective view of a prior art DEF dispenser  100  for use in a retail service station environment. For example, dispenser  100  may be the ENCORE® S DEF dispenser, sold by Gilbarco Inc. DEF dispenser  100  is in many respects similar to fuel dispenser  10  and comprises a housing  102  containing fluid handling components. These fluid handling components allow DEF to be received from above- or below-ground piping and delivered through hose  104  and nozzle  106  to a vehicle&#39;s DEF tank, as is well understood. In addition, DEF dispenser  100  comprises a customer interface  108 , information display  110 , and media display  112  analogous to those described above. 
     However, DEF is corrosive to some materials, such as aluminum and carbon steel, and the purity of DEF must be maintained as it is dispensed. Thus, many DEF dispenser fluid handling components are plated or formed of stainless steel or composite plastic. One example of a hose  104  and a nozzle  106  that may be utilized for dispensing DEF is the 21Gu™ DEF filling system, sold by OPW of Hamilton, Ohio. 
     As explained above, DEF is known to have a relatively high freezing temperature. Thus, fuel hose  104  is an automatically retractable hose that is stored in a compartment of DEF dispenser  100  when not in use. Further, nozzle  106  is stowed in an insulated and/or heated nozzle boot  114  that is enclosed by a slidable access door  116 . When DEF dispensing is desired, a customer may slide the access door  116  upward so that nozzle  106  and hose  104  may be extracted. Other prior art DEF dispensers may employ “hanging” hoses and nozzles that are insulated to prevent DEF that resides in the system while not in use from freezing. 
     Those of skill in the art will appreciate that the fluid handling components of a prior art DEF dispensing system are in many respects analogous to those of the prior art fuel dispensing system illustrated in  FIG. 2 . By way of additional background, however, a brief discussion of some notable differences between the two systems follows. 
     First, although DEF may be provided to DEF dispenser  100  from a UST, it may also be delivered from an above-ground tank, such as an intermediate bulk carrier (IBC) or a larger “skid tank.” In such a case, DEF may be delivered to the dispenser  100  via above-ground piping, which may be insulated and/or heated. Both wet-pit (i.e., submersible) and dry-pit pumps may be used to deliver DEF from the tank DEF dispenser  100 . 
     Embodiments of the present invention provide a system to condition fluid, including both liquid fuel and DEF, to be dispensed to a desired temperature and maintain this temperature even while dispensing is not ongoing. Thereby, a fluid dispenser may both obtain an accurate measurement of the volume of fluid dispensed and avoid inoperability and/or component damage at low temperatures. Moreover, the system may be used to sell fluid at a specific temperature as compensated wholesale sales. 
     In preferred embodiments described in more detail below, the system comprises two subsystems. First, the system preferably comprises a temperature conditioning subsystem inline to the fluid flow path at a location upstream of a flow meter. This subsystem may comprise either or both of a heating device and a cooling device. Second, the system preferably comprises a recirculation subsystem to recirculate the fluid through the dispenser and/or back to a storage tank. The recirculation may be continuous or intermittent, and in some embodiments the internal dispenser piping may be evacuated to prevent freezing. However, depending on the climate at the location of the fluid dispenser, the type of fluid dispensed, and the needs of an operator, the recirculation subsystem may not be provided. For example, where the cooling device is needed to lower the temperature of the fluid dispensed, the fluid dispenser may not include a recirculation subsystem. This could be the case in some warmer climates where liquid fuel is dispensed. 
     More specifically,  FIG. 4  shows a fluid temperature conditioning and control system in accordance with one embodiment of the present invention. Fluid dispenser  200  is preferably adapted to dispense either liquid fuel or DEF and comprises a housing  202  with a coaxial fluid hose  204  extending therefrom. Hose  204  terminates in a manually-operated nozzle  206  adapted to be inserted into a vehicle&#39;s fuel or DEF tank. As explained above, those of skill in the art will appreciate that the materials used in constructing the fluid handling components (including hose  204  and nozzle  206 ) of dispenser  200  may depend on whether liquid fuel or DEF will be dispensed. 
     Fluid dispenser  200  comprises a control system  208  which is preferably positioned in an electronics compartment  210 . As described in more detail below, in this embodiment control system  208  controls the fluid temperature conditioning aspects of the present invention. Control system  208  preferably also controls various other functions of fluid dispenser  200 , such as valves, displays and the like, as is well understood. Control system  208  may preferably be communicatively coupled to a site controller  212 , for example by a suitable dispenser communication network  214 . 
     Generally, an STP  216 , which is preferably analogous to STP  32 , is associated with a UST  218  containing fluid  220  to pump fluid  220  along a fluid flow path to fluid dispenser  200  for eventual delivery. However, as explained above, in alternative embodiments an above-ground storage tank may be provided and/or a dry-pit pump may be used to pump fluid  220  to the fluid dispenser  200 . In addition, fluid  220  may preferably be either liquid fuel or DEF. Additionally, in some embodiments fluid dispenser  200  may be self-contained, meaning fluid  220  is drawn to the fluid dispenser  200  by a pump  221  controlled by a motor positioned within housing  202 . Those of skill in the art will appreciate that where STP  216  is used to pump fluid  220 , pump  221  may not be provided. 
     Fluid  220  flowing through main fluid piping  222  enters housing  202  and first encounters a fluid temperature conditioning subsystem  224 . In some embodiments, main fluid piping  222  may be double-walled and may be above- or below-ground. Also, those of skill in the art will appreciate that where main fluid piping  222  is provided below-ground, main fluid piping  222  and any associated valves or manifolds are typically buried below the “frost line.” Further, in some embodiments, main fluid piping  222  may first enter housing  202  via a shear valve analogous to shear valve  46 . Temperature conditioning subsystem  224 , which in this case is positioned in a fluid handling compartment  226  of fluid dispenser  200 , is adapted to condition the fluid to maintain it at a desired temperature. In preferred embodiments, temperature conditioning subsystem  224  may comprise a heating device  228  and/or a cooling device  230 , each in electronic communication with control system  208 . This may be accomplished via communication line  231 . 
     As explained above, fluid temperature conditioning subsystem  224  may perform several functions. For example, it may condition liquid fuel or DEF to a predetermined temperature upstream of a flow meter  234  to facilitate accurate volumetric measurement. Also, it may condition DEF to prevent the DEF from crystallizing and freezing at low temperatures. 
     Although fluid temperature conditioning subsystem  224  is illustrated in  FIG. 4  internal to fluid handling compartment  226 , those of skill in the art will appreciate that fluid temperature conditioning subsystem  224  may be located at any location along the path of fluid flow between UST  218  and nozzle  206 . In some embodiments, for example, temperature conditioning subsystem  224  may be located in UST  218  and provide temperature conditioning functionality for a plurality of fluid dispensers  200  located at a retail service station. However, temperature conditioning subsystem  224  is preferably located immediately upstream of flow meter  234  so that meter  234  may measure the fluid  220  at a constant temperature and volume. 
     Heating device  228  is preferably an electrical, on-demand heater situated in-line to the fluid flow path. A suitable heating device is selected based on various factors, such as the type of fluid dispensed, the location of the heating device along the fluid flow path, and the ambient temperatures to which the fluid dispenser is exposed, among other factors. Many different types of devices may be used for heating device  228 , including tubular, immersion, circulation, and impedance heaters. 
     However, in preferred embodiments, heating device  228  may be an induction heater. Induction heaters have several desirable characteristics. For example, induction heaters provide for precise temperature control and rapid adjustment of temperature. In addition, heat is provided uniformly along the length of the pipe being heated. Induction heaters may be used to heat a conductive pipe by subjecting the pipe to a time-varying magnetic field which surrounds a coil carrying high frequency alternating current. Heating of the pipe occurs via the electrical resistance of the pipe and, where the pipe is formed of a magnetic material, hysteresis losses. 
     Several induction heating arrangements are possible. The coil is typically provided having one or more windings surrounding the section of the pipe to be heated. Often, the coil is formed of copper tubing and may be cooled by circulating water therethrough. In this arrangement, the pipe is heated via resistance and hysteresis losses and heat is conducted to the fluid flowing in the pipe. However, in alternative embodiments, a magnetic wire may be provided internal to a nonconductive conduit or hose in the fluid flow path. The coil again has one or more windings surrounding the section of the conduit to be heated. In this case, however, the conduit itself is not heated. Instead, the wire generates heat via electrical resistance and hysteresis losses and heat is conducted to the fluid in the conduit. 
     Cooling device  230  is also situated in-line to the fluid flow path. Cooling device  230  preferably comprises a suitable on-demand refrigeration system. For example, cooling device  230  may comprise a closed-circuit vapor-compression refrigeration system. Alternatively, a heat exchanger suitable for cooling fluid flowing in a pipe may be used, such as a shell and tube or plate and fin heat exchanger. 
     Depending on the fluid dispensed and the environment in which fluid dispenser  200  operates, those of skill in the art will appreciate that either heating device  228  or cooling device  230  may not be provided in temperature conditioning subsystem  224 . For example, cooling device  230  is not typically provided if fluid dispenser  200  dispenses DEF. Further, where both devices are provided, heating device  228  and cooling device  230  may be arranged in the fluid flow path in any order. 
     Control system  208  is adapted to selectively operate temperature conditioning subsystem  224  based on the temperature of fluid  220  and the ambient temperature. (Typically, both devices  228 ,  230  will not be operating simultaneously.) Thus, control system  208  is preferably in electronic communication with one or more thermometric probe located at various locations along the fluid flow path and associated with fluid dispenser  200 , such as thermometric probe  235 . Although not shown in  FIG. 4 , those of skill in the art will appreciate that the one or more thermometric probes may communicate with control system  208  via suitable communication lines. Thermometric probes may preferably be provided at least in the UST  218 , dispenser sump  236 , and flow meter  234 . Control system  208  receives temperature information from the thermometric probes and determines whether the temperature of the fluid needs to be conditioned. For example, when the ambient temperature falls below a predetermined level, control system  208  may determine that fluid  220  should be heated to prevent freezing. Alternatively, when temperatures are at a suitable level, temperature conditioning subsystem  224  is not operated and fluid  220  will simply flow through subsystem  224  without being conditioned. 
     In many embodiments, fluid leaving temperature conditioning subsystem  224  next encounters flow meter  234 . Flow meter  234  may be any suitable flow meter for fluid dispensing, but meter  234  may preferably be a positive displacement or inferential flow meter. Other types of flow meters are contemplated, however, including Coriolis mass flow meters. Meter  234  is preferably analogous to meter  52 , and thus it may comprise a pulser in electronic communication with control system  208 . 
     After the fluid  220  exits the outlet of flow meter  234 , it flows through internal fluid piping  238  to a flow control valve  240  and a flow switch  242 . Flow control valve  240  may be a proportional solenoid valve analogous to flow control valve  50  and may preferably be located below a vapor barrier  244 . In some embodiments, flow control valve  240  may be located upstream of flow meter  234 . Flow switch  242 , which is preferably analogous to flow switch  70 , is preferably a one-way check valve that prevents rearward flow through fluid dispenser  200 . As with flow control valve  50  and flow switch  70  above, flow control valve  240  and flow switch  242  are in electronic communication with control system  208  to allow fluid dispensing and communicate when fluid is flowing through flow meter  234 . 
     Fluid  220  exiting flow switch  242  is carried via internal fluid piping  238  to a flow manifold  246 . Manifold  246  is fluidly coupled to internal fluid piping  238  and fluid dispensing hose  204  to direct fluid  220  from flow switch  242  to hose  204 . In many embodiments, fluid dispenser  200  is not adapted for vapor recovery. Nevertheless, hose  204  may preferably comprise concentric outer hose  248  and inner hose  250 , which define a fluid delivery line  252  and a fluid return line  254 . As explained in more detail below, coaxial fluid hose  204  facilitates recirculation of fluid, such as when fluid dispenser  200  is not in use. Those of skill in the art will appreciate that where it is desirable that fluid dispenser  200  be adapted for vapor recovery, for example where fluid  200  is liquid fuel, a three-channel hose may be provided. 
     Internal fluid piping  238  is fluidly coupled to fluid delivery line  252  at manifold  246 . Thus, after flowing through manifold  246 , fluid  220  passes through fluid delivery line  252  of fluid hose  204  to nozzle  206  for delivery to a customer&#39;s vehicle. To initiate fluid flow, the customer manually activates a trigger on fluid nozzle  206  which opens a dispensing valve in nozzle  206  so that fluid is dispensed into the vehicle. Manifold  246  also provides a fluid coupling between fluid return line  254  and internal fluid return piping  256 , which may be double-walled. As explained in more detail below, this coupling facilitates recirculation of fluid  220  through dispenser  200  or return of fluid  220  to UST  218 . 
     In this regard, in one embodiment of the present invention, a recirculation subsystem may cooperate with fluid temperature conditioning subsystem  224  to condition the fluid  220 . Specifically, the recirculation subsystem comprises a one-way bypass valve  257  situated at the distal end of fluid return line  254  of fluid hose  204 , which is connected to nozzle  206 . The bypass valve  257 , which may be a spring loaded poppet valve, is biased to close fluid return line  254  during fluid dispensing, when the fluid pressure in nozzle  206  and fluid hose  204  is relatively low. 
     The recirculation subsystem also comprises a second bypass valve  258  located downstream of manifold  246  in the fluid return path along internal fluid return piping  256 . Second bypass valve  258  may preferably be a solenoid-controlled valve in electronic communication with control system  208  via communication line  259 . In this embodiment, valve  258  is located in fluid handling compartment  226 , but those of skill in the art will appreciate that it may be located at any point downstream of manifold  246  along the fluid return path to UST  218 . Second bypass valve  258  is normally in the closed position when the recirculation subsystem is not in use. 
     Finally, the recirculation subsystem comprises main fluid return piping  260 , which may be double-walled. In some embodiments, main fluid return piping  260  may be fluidly coupled to internal fluid return piping  256  via a shear valve, as described above. Main fluid return piping  260  is in fluid communication with UST  218 , extending from housing  202  through dispenser sump  236  and STP sump  262 . Thus, as described below, in this embodiment fluid  220  may be continuously recirculated back to UST  218  to maintain the temperature of fluid  220  when not being dispensed. 
     In operation, once dispensing is complete, the customer manually releases the trigger on nozzle  206  and its internal dispensing valve closes. Normally, at this point control system  208  closes flow control valve  240  to stop the flow of fluid to nozzle  206 . However, if control system  208  determines that the temperature of the fluid  220  and/or the ambient temperature is below a predetermined level, it will activate the recirculation subsystem of the present invention. Specifically, in this embodiment, control system  208  allows the flow control valve  240  to remain open, causing fluid pressure to build in nozzle  206  and fluid supply line  252 . As a result, the one-way valve  257  in fluid return line  254  opens and fluid  220  will enter fluid return line  254 . 
     Control system  208  also causes second bypass valve  258  to open, and fluid  220  flows from fluid return line  254  through manifold  246 , internal fluid return piping  256 , and main fluid return piping  260 . Finally, fluid  220  is returned to UST  218 . Therefore, the recirculation subsystem will maintain the temperature of the fluid  220  and may improve the flexibility of hose  204  at low temperatures. Those of skill in the art will appreciate that continuous recirculation of fluid  220  may be sufficient to prevent freezing of fluid  220 , in which case temperature conditioning subsystem  224  would not be operated. However, in colder climates it is contemplated that temperature conditioning subsystem  224  may operate in conjunction with the recirculation subsystem. Control system  208  will continue to operate the recirculation subsystem until dispensing is resumed or it determines that the fluid and/or ambient temperatures have risen to an acceptable level. When either event occurs, control system  208  will cause flow control valve  240  and second bypass valve  258  to close. 
       FIG. 5  provides a schematic illustration of a fluid temperature conditioning and control system according to an alternative embodiment of the present invention. The fluid dispensing system illustrated in  FIG. 5  is in many respects identical to the fluid dispensing system illustrated in  FIG. 4 . However, in this embodiment, once fluid dispensing is complete, fluid  220  recirculates through fluid dispenser  200  instead of returning to UST  218 . 
     In particular, the recirculation subsystem illustrated in  FIG. 5  comprises the bypass valve  257  in fluid return line  254  described above and a second bypass valve  264 , which is preferably analogous to valve  258 . Thus, valve  264  is in electronic communication with control system  208  via communication line  265 . However, valve  264  may be located upstream of a fluid recirculation pump  266 . Valve  264  is normally in the closed position when the recirculation subsystem is not in operation. Recirculation pump  266  is in electronic communication with control system  208  via communication line  267 . In some embodiments, pump  266  may comprise a controlled valve, in which case second bypass valve  264  may be unnecessary. 
     In the recirculation subsystem of this embodiment, main fluid piping  222  extends from STP  216  through STP sump  262  and dispenser sump  236  to a recirculation manifold  268 . In addition, main fluid piping  222  includes a stop valve  270 . A junction (i.e., recirculation manifold  268 ) fluidly couples main fluid piping  222  to internal fluid piping  238  and internal fluid return piping  256 . Stop valve  270  is in electronic communication with control system  208  via communication line  271  and may preferably be a solenoid controlled valve. As described below, stop valve  270  is normally in the open position. 
     In operation, once dispensing is complete and control system  208  determines that temperatures are below a predetermined level, it will activate the recirculation subsystem. Control system  208  again allows flow control valve  240  to remain open so that fluid  220  will enter fluid return line  254 . Control system  208  causes second bypass valve  264  to open and stop valve  270  to close, thus trapping fluid  220  in a recirculation loop. Control system  208  also activates recirculation pump  266  to cause fluid  220  to recirculate through fluid dispenser  200 . Temperature conditioning subsystem  224  typically operates in conjunction with the recirculation subsystem to heat the fluid  220  as it flows along the fluid flow path, as needed. 
     As explained above, this recirculation will continue until dispensing is commenced or fluid and/or ambient temperatures reach a predetermined threshold. Upon occurrence of either event, control system  208  causes bypass valve  264  to close, deactivates pump  266 , and causes stop valve  270  to open. Where the temperatures reach the predetermined threshold but dispensing is not desired, control system  208  may additionally cause flow control valve  240  to close. 
       FIG. 6  provides a schematic illustration of a fluid temperature conditioning and control system according to a second alternative embodiment of the present invention. The fluid dispensing system illustrated in  FIG. 6  is in many respects identical to the fluid dispensing system illustrated in  FIG. 4 . However, in this embodiment, once fluid dispensing is complete, fluid  220  is evacuated from fluid dispenser  200  and returned to UST  218 . Then, when dispensing is desired, air in the internal fluid piping and fluid handling components of fluid dispenser  200  is removed and the system is primed with fluid. 
     Those of skill in the art will appreciate that this embodiment may be additionally useful in the event of a protracted loss of power at fluid dispenser  200 . Because fluid  220  is returned to UST  218  when the recirculation subsystem of this embodiment is operated, no fluid  220  will remain in the dispenser  200  if power is lost. As a result, the fluid  220  will not freeze inside the dispenser. 
     In this regard, the recirculation subsystem illustrated in  FIG. 6  comprises the bypass valve  257  in fluid return line  254  described above and a second bypass valve  272 , which is preferably analogous to valves  258 ,  264 . Valve  272  is in electronic communication with control system  208  via communication line  273 . Valve  272 , which is also normally closed, may be located upstream of a fluid recirculation pump  274 , which is preferably analogous to recirculation pump  266 . Pump  274  is in electronic communication with control system  208  via communication line  275 . In some embodiments, pump  274  may comprise a controlled valve, in which case second bypass valve  272  may be unnecessary. 
     In the recirculation subsystem of this embodiment, main fluid piping  222  may extend from STP  216  through STP sump  262  and dispenser sump  236  to an ON/OFF valve  276 , which may preferably be a solenoid controlled valve in electronic communication with control system  208  via communication line  277 . It will be appreciated that valve  276  need not be located in dispenser sump  236 ; for example, it may also be located in fluid handling compartment  226 . Main fluid piping  222  is in fluid communication with internal fluid piping  238 . In this embodiment, internal fluid piping  238  also comprises a fluid inlet  278  and a fluid inlet valve  280 . However, those of skill in the art will appreciate that fluid inlet  278  and fluid inlet valve  280  may be located at other locations downstream of valve  276 . Valve  280 , which is preferably a proportional solenoid controlled valve in electronic communication with control system  208  via communication line  281 , is normally in a closed position. As described below, fluid inlet  278  is adapted to introduce a second fluid into internal fluid piping  238  as fluid  220  is evacuated. In the illustrated embodiment the second fluid is air, but those of skill in the art may select other suitable evacuation fluids, such as an inert gas or the like. 
     In operation, once dispensing is complete and control system  208  determines that the fluid and/or ambient temperatures have fallen below a predetermined threshold, control system  208  activates the recirculation subsystem. Control system  208  again allows flow control valve  240  to remain open so that fluid  220  will enter fluid return line  254 . Control system  208  causes ON/OFF valve  276  to close, second bypass valve  272  to open, and fluid inlet valve  280  to open. Control system  208  also activates recirculation pump  274  to evacuate fluid  220  from dispenser  200 . Those of skill in the art will appreciate pumping fluid  220  from fluid dispenser  200  while ON/OFF valve  276  is closed creates a pressure in internal fluid piping  238  that is lower than the atmospheric pressure, thus drawing air into the fluid dispenser  200 &#39;s internal fluid piping and fluid handling components via fluid inlet  278 . In this embodiment, temperature conditioning subsystem  224  is not typically operated as fluid  220  is evacuated. 
     After all of the fluid  220  has been evacuated from fluid dispenser  200  and returned to UST  218 , control system  208  deactivates recirculation pump  274 . In addition, control system  208  causes fluid inlet valve  280 , flow control valve  240 , and second bypass valve  272  to close. At this point, no fluid  220  remains in fluid dispenser  200 ; thus, freezing and associated component damage is not a problem. 
     When fluid dispensing is desired, a customer removes nozzle  206  from its nozzle boot. Before dispensing may commence, however, fluid dispenser  200  must be primed with fluid  220 . Thus, control system  208  causes ON/OFF valve  276 , flow control valve  240 , and second bypass valve  272  to open. In addition, STP  216  is activated to pump fluid  220  to dispenser  200 . (Recirculation pump  274  is not typically operated during priming.) Control system  208  may determine that fluid dispenser  200  is primed, for example, by measuring a predetermined amount of fuel pumped through the system using meter  234 , waiting a predetermined amount of time prior to allowing fluid dispensing, or receiving a signal from a pressure transducer. In the latter case, the pressure transducer may preferably be associated with recirculation pump  274 , although other locations for the pressure transducer along the fluid flow path are contemplated. 
     As fluid  220  is reintroduced into fluid dispenser  200 , fluid  220  displaces the second fluid (air, in this example) and causes it to flow to ullage  282  of UST  218 . To prevent an undesirable rise in pressure in UST  218 , an ullage pressure reducing system may be provided. Such systems are well known to those of skill in the art. For example, a vent pipe capped with a pressure relief valve may be fluidly coupled to UST  218  and ullage  282 . Thereby, the second fluid that is transferred to ullage  282  may be safely dissipated to the atmosphere. After control system  208  determines that fluid dispenser  200  is primed with fluid  220 , control system  208  causes second bypass valve  272  to close. Finally, control system  208  zeroes the display and allows dispensing to commence. 
     While one or more preferred embodiments of the invention have been described above, it should be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. The embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention. Thus, it should be understood by those of ordinary skill in this art that the present invention is not limited to these embodiments since modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the scope and spirit thereof.