Patent Publication Number: US-2017370332-A1

Title: Fuel cooling system and method

Description:
FIELD OF THE INVENTION 
     The subject matter disclosed herein relates to transportation refrigeration systems and, more specifically, to transportation refrigeration systems for cooling a fuel. 
     BACKGROUND 
     Temperature controlled cargo containers, such as refrigerated trailers, are commonly used to transport food products and other temperature sensitive products. A refrigerated trailer typically includes a refrigeration unit generally mounted on the front wall of the trailer with a portion protruding into the interior of the trailer. 
     In some known trailers, an engine may be used to drive a compressor of the refrigeration system. Fuel for the engine may be located under the trailer and exposed to heat and ambient temperatures. Hot fuel occupies more space at less density of fuel, which may reduce engine power. Increased fuel temperature may also decrease the fuel viscosity, which may increase leakage flow past pistons during injection and allow increased unburned particulates into the atmosphere. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a fuel cooling system is provided. The fuel cooling system includes a refrigeration unit configured to circulate a refrigerant, a bypass cooling circuit fluidly coupled to the refrigeration unit, and a power generation system operably coupled to the refrigeration unit. The power generation system includes a fuel tank fluidly coupled to an engine, and a fuel cooling circuit is fluidly coupled between the fuel tank and the engine. The fuel cooling circuit is thermally coupled to the bypass cooling circuit and is configured to cool a fuel by thermal exchange with the refrigerant. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include: a container configured to store a cargo, wherein the refrigeration unit is coupled to the container and configured to condition an environment within the container; wherein the refrigeration unit comprises a compressor, a condenser, and an evaporator, wherein the bypass cooling circuit is fluidly coupled between the evaporator and the compressor downstream of the evaporator; a heat exchanger thermally coupled between the bypass cooling circuit and the fuel cooling circuit; wherein the bypass cooling circuit comprises an inlet conduit and a return conduit fluidly coupled to the heat exchanger; wherein the bypass cooling circuit further comprises a bypass valve configured to selectively supply the refrigerant to the bypass cooling circuit; wherein the fuel cooling circuit comprises a fuel inlet conduit and a fuel return conduit fluidly coupled to the heat exchanger; wherein the fuel cooling circuit further comprises a bypass valve configured to selectively supply the fuel to the fuel cooling circuit; a controller programmed to selectively switch the bypass valve between a first condition and a second condition when at least one of a predetermined ambient temperature is exceeded and a predetermined fuel temperature is exceeded; and/or a first temperature sensor configured to sense a temperature of ambient air and a second temperature sensor configured to sense a temperature of the fuel. 
     In another aspect, a temperature controlled cargo container is provided. The container includes a plurality of walls defining an interior space configured to store a cargo, a refrigeration unit configured to circulate a refrigerant, and a bypass cooling circuit fluidly coupled to the refrigeration unit. The container further includes a power generation system operably coupled to the refrigeration unit, the power generation system including a fuel tank fluidly coupled to an engine, and a fuel cooling circuit fluidly coupled between the fuel tank and the engine. The fuel cooling circuit is thermally coupled to the bypass cooling circuit and is configured to cool a fuel by thermal exchange with the refrigerant. 
     In addition to one or more of the features described above, or as an alternative, further embodiments may include: wherein the refrigeration unit comprises a compressor, a condenser, and an evaporator, wherein the bypass cooling circuit is fluidly coupled between the evaporator and the compressor downstream of the evaporator; a heat exchanger thermally coupled between the bypass cooling circuit and the fuel cooling circuit; wherein the bypass cooling circuit comprises an inlet conduit and a return conduit fluidly coupled to the heat exchanger; wherein the bypass cooling circuit further comprises a bypass valve configured to selectively supply the refrigerant to the bypass cooling circuit; wherein the fuel cooling circuit comprises a fuel inlet conduit and a fuel return conduit fluidly coupled to the heat exchanger; wherein the fuel cooling circuit further comprises a bypass valve configured to selectively supply the fuel to the fuel cooling circuit; a controller programmed to selectively switch the bypass valve between a first condition and a second condition when at least one of a predetermined ambient temperature is exceeded and a predetermined fuel temperature is exceeded; and/or a first temperature sensor configured to sense a temperature of ambient air, and a second temperature sensor configured to sense a temperature of the fuel. 
     In yet another aspect, a method of fabricating a fuel cooling system is provided. The method includes providing a refrigeration unit configured to circulate a refrigerant, providing a bypass cooling circuit fluidly coupled to the refrigeration unit, and providing a power generation system operably coupled to the refrigeration unit, the power generation system including a fuel tank fluidly coupled to an engine. The method further includes providing a fuel cooling circuit fluidly coupled between the fuel tank and the engine, thermally coupling a heat exchanger between the bypass cooling circuit and the fuel cooling circuit to provide thermal exchange between the refrigerant and the fuel, and operably coupling a controller to the bypass cooling circuit and the fuel cooling circuit. The controller is programmed to selectively operate between a first mode and a second mode. In the first mode the refrigerant bypasses the bypass cooling circuit and the fuel bypasses the fuel cooling circuit, and in the second mode the refrigerant is circulated through the bypass cooling circuit and the fuel is circulated through the fuel cooling circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic view of an exemplary cargo container having a fuel cooling system; and 
         FIG. 2  is a schematic view of an exemplary fuel cooling system that may be used with the cargo container shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a temperature controlled cargo container  10  configured to maintain a cargo  12  located inside the cargo container  10  at a selected temperature through the use of a temperature control unit  14 . Cargo container  10  is utilized to transport cargo  12  via, for example, a truck, a train or a ship. 
     Container  10  generally includes an interior space  16  formed by thermally insulated walls including a top wall  18 , a front wall  20 , a rear wall  21 , a floor  22 , and side walls  24 . Temperature control unit  14  is mounted at front wall  20 . In the exemplary embodiment, temperature control unit  14  is a refrigeration unit that includes an exterior condenser  26  and an interior evaporator section  28 . Refrigeration unit  14  is powered by a power generation system  30 , which generally includes an engine  32  that is fluidly coupled to a fuel tank  34 . Although described as a refrigeration unit, temperature control unit  14  may be any suitable environment conditioning system. For example, temperature control unit  14  may be a cab air conditioning unit for a truck. 
       FIG. 2  is a schematic illustration of a fuel cooling system  100  that includes refrigeration unit  14  and power generation system  30 . 
     Refrigeration unit  14  generally includes a compressor  112 , a condenser  116 , a liquid suction heat exchanger  118 , an expansion valve  120 , and an evaporator  122 . In the exemplary embodiment, compressor  112  is a scroll or reciprocating type and evaporator  122  is a flooded-type evaporator. However, compressor  112  may be any suitable type of compressor (e.g., centrifugal), and evaporator  122  may be any suitable evaporator that enables unit  14  to function as described herein. 
     Refrigeration unit  14  is a closed loop system through which refrigerant is circulated in various states such as liquid and vapor. As such, a low temperature, low pressure superheated gas refrigerant is drawn into compressor  112  through a conduit  124  from evaporator  122 . The refrigerant is compressed and the resulting high temperature, high pressure superheated gas is discharged from compressor  112  to condenser  116  through a conduit  126 . 
     In condenser  116 , gaseous refrigerant is condensed into liquid as it gives up heat. The superheated gas refrigerant enters condenser  116  and is de-superheated, condensed, and sub-cooled through a heat exchanger process with, for example, engine coolant flowing through condenser  116  (or thermally coupled heat exchanger) to absorb heat. However, condenser  116  may be air cooled or evaporatively cooled. The liquid refrigerant is discharged from condenser  116  and supplied through a conduit  128  to liquid suction heat exchanger  118 . 
     In the exemplary embodiment, liquid suction heat exchanger  118  cools liquid refrigerant from condenser  116  against vaporized and/or vaporizing refrigerant from evaporator  122 . The cooled liquid refrigerant is subsequently supplied to evaporator  122  through a conduit  130 . The cooled liquid refrigerant passes through a metering device or expansion valve  120 , which converts the relatively higher temperature, high pressure sub-cooled liquid to a low temperature saturated liquid-vapor mixture. 
     The low temperature saturated liquid-vapor refrigerant mixture then enters evaporator  122  where it boils and changes states to a superheated gas as it absorbs the required heat of vaporization from chilled water (or other heat exchange fluid). The low pressure superheated gas then passes in heat exchange relation with heat exchanger  118 , where it is further heated to increase the superheat of the gas and vaporize any residual liquid droplets that may pass evaporator  122 . The superheated gas is then drawn into the inlet of compressor  112  and the cycle is repeated. 
     In the exemplary embodiment, refrigeration unit  14  includes a bypass cooling circuit  132  that branches off from conduit  124  and generally includes an inlet conduit  134 , a bypass valve  136 , a heat exchanger  138 , a return conduit  140 , and a valve  142  (e.g., a check valve). A second bypass valve  144  may be disposed on conduit  124  between inlet conduit  134  and return conduit  140 . When bypass valve  136  is closed (and second bypass valve  144  is open), refrigerant is supplied directly from heat exchanger  118  to compressor  112 . When bypass valve  136  is open (and second bypass valve  144  is closed), refrigerant is supplied via inlet conduit  134  to heat exchanger  138  for thermal exchange with a fuel flowing through power generation system  30 , as is described herein in more detail. The warmed refrigerant is then supplied via return conduit  140  to conduit  124  and back to compressor  112 . 
     Power generation system  30  generally includes engine  32  fluidly coupled to fuel tank  34 . A conduit  150  supplies a coolant between engine  32  and a heat exchanger  152  (e.g., a radiator) to cool engine  32  during operation. A fuel supply conduit  154  supplies a fuel (e.g., diesel fuel) to engine  32  for operation thereof, and any unused or unburnt fuel is returned to tank  34  via a fuel return conduit  148 . 
     Power generation system  30  includes a fuel cooling circuit  160  that branches off from supply conduit  154  and generally includes an inlet conduit  162 , a bypass valve  164 , heat exchanger  138 , a return conduit  166 , and a valve  168  (e.g., a check valve). A second bypass valve  146  may be disposed on supply conduit  154  between inlet conduit  162  and return conduit  166 . When bypass valve  164  is closed (and second bypass valve  146  is open), fuel is supplied directly from fuel tank  34  to engine  32 . When bypass valve  164  is open (and second bypass valve  146  is closed), fuel is supplied via inlet conduit  162  to heat exchanger  138  where the fuel is subsequently cooled by thermal exchange with the refrigerant passing through bypass circuit  132 . The cooled fuel is then supplied via return conduit  166  to engine  32 . Alternatively, fuel cooling circuit  160  may branch off a return fuel conduit  148  from engine  32  to fuel tank  34 . 
     As such, the cooled fuel supplied through fuel cooling circuit  160  facilitates increased engine efficiency and power, cleaner exhaust, and reduced fuel consumption. 
     Fuel cooling system  100  may include one or more sensors (e.g., temperature sensors) to determine when to utilize bypass circuit  132  and fuel cooling circuit  160  to cool fuel supplied to engine  32 . For example, as illustrated, a first temperature sensor  170  senses the ambient temperature, and a second temperature sensor  172  senses the temperature of the fuel in fuel tank  34 . A controller  174  may be in signal communication with sensors  170 ,  172  and bypass valves  136 ,  164 . If a predetermined temperature is sensed by one of temperature sensors  170 ,  172 , controller  174  may be programmed to open bypass valves  136  and  164  to commence cooling of fuel supplied to engine  32 . For example, if the ambient temperature reaches a predetermined temperature, controller  174  may open bypass valves  136 ,  164 . Alternatively, or in addition, if the fuel temperature reaches a predetermined temperature (e.g., an increased amount of warmed, unused fuel is returned to tank  34 ), controller  174  may open bypass valves  136 ,  164 . As used herein, the term controller refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     Fuel cooling system  100  is configured to switch between a normal operation first mode and a fuel-cooling second mode. In the first mode, bypass valves  136 ,  164  are closed and valves  144 ,  146  are open such that bypass circuit  132  and fuel cooling circuit  160  are not utilized. At a predetermined time or after a predetermined condition, fuel cooling system  100  is switched to the second mode (e.g., by controller  174 ) and bypass valves  136 ,  164  are opened and valves  144 ,  146  are closed such that bypass circuit  132  and fuel cooling circuit  160  are utilized to cool fuel being supplied to engine  32 . 
     Described herein are systems and methods for cooling a fuel used to operate an engine for a transport refrigeration unit. The system includes a refrigeration unit bypass circuit that is thermally coupled to a fuel cooling circuit attached to the engine. At a predetermined time, fuel is selectively supplied to the fuel cooling circuit to be cooled by refrigerant supplied to the bypass circuit. Cooling the fuel and its physical properties facilitates increased engine efficiency and power, cleaner exhaust, and reduced fuel consumption. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.