Abstract:
A temperature control system for a vehicle that defines a load space for supporting cargo. The temperature control system includes a refrigeration unit that has a refrigeration circuit, and a heating system that has a heating circuit. The refrigeration circuit includes a prime mover and a cooling coil that selectively cools an airflow entering the load space. The heating circuit includes a pump that circulates a coolant fluid through the heating circuit, a dedicated heater that heats the coolant fluid, and a heating coil that selectively heats the airflow entering the load space. The temperature control system also includes a controller that detects conditions of the load space, and that engages one of the refrigeration unit and the heating system to condition the load space in response to the detected conditions.

Description:
RELATED APPLICATIONS 
       [0001]    This patent application claims priority to U.S. Patent Application Ser. No. 60/876,449 filed Dec. 21, 2006, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to temperature control systems, and more particularly to a transport temperature control system with a heating circuit and a method of operating the system. 
         [0003]    In conventional mechanical refrigeration units, a diesel/compressor power pack within the unit has been utilized to also provide heat to a load space of a transport unit. However, the existing diesel/compressor power packs often do not provide adequate heat to the load space, particularly in cold ambient temperatures. 
       SUMMARY 
       [0004]    In one embodiment, the invention provides a temperature control system for conditioning at least one load space that supports cargo. The temperature control system includes a refrigeration unit that has a refrigeration circuit, and a heating system that has a heating circuit. The refrigeration circuit includes a prime mover that is operable to circulate a refrigerant through the refrigeration circuit, and a cooling coil that is in communication with the at least one load space to cool the load space. The heating circuit includes a pump that circulates a coolant fluid through the heating circuit, and a dedicated heater that is in communication with the coolant fluid to heat the coolant fluid. The heating circuit also includes a heating coil that is in communication with the at least one load space to heat the load space. The temperature control system also includes at least one air mover and a controller. The air mover directs an airflow across the cooling coil and the heating coil to condition the airflow via heat transfer with one of the refrigerant in the cooling coil and the coolant fluid in the heating coil prior to entry of the airflow into the at least one load space. The controller is in communication with the load space to detect conditions of the load space, and is further in communication with the refrigeration unit and the heating system to engage one of the refrigeration unit and the heating system to condition the load space in response to the detected conditions. 
         [0005]    In another embodiment, the invention provides a method of conditioning at least one load space that supports cargo. The method includes providing a temperature control system that includes a refrigeration unit that has a refrigeration circuit with a prime mover and a cooling coil, and a heating system that has a dedicated heater and a heating coil. The method also includes circulating a refrigerant through the cooling coil, circulating a coolant fluid through the heating coil using a pump, and directing an airflow across at least one of the cooling coil and the heating coil using an air mover. The method further includes detecting conditions of the at least one load space, selectively operating the temperature control system in one of a cooling mode and a heating mode to condition the load space based on the detected load space conditions, and cooling the airflow via heat exchange relationship with the refrigerant flowing through the cooling coil during operation of the temperature control system in the cooling mode. The method also includes heating the coolant fluid in the heating circuit using the dedicated heater and heating the airflow via heat exchange relationship with the heated coolant fluid flowing through the heating coil during operation of the temperature control system in the heating mode, and conditioning the at least one load space using the airflow conditioned by one of the cooling mode and the heating mode. 
         [0006]    In yet another embodiment, the invention provides a vehicle that includes a frame, and an outer wall that is coupled to the frame and that defines at least one load space supporting cargo. The vehicle also includes a temperature control system coupled to the outer wall and in communication with the load space. The temperature control system includes a refrigeration unit that has a refrigeration circuit, a heating system that has a heating circuit, and at least one air mover. The refrigeration circuit includes a prime mover that is operable to circulate a refrigerant through the refrigeration circuit, and a cooling coil that is in communication with the at least one load space to cool the load space. The heating circuit includes a pump that circulates a coolant fluid through the heating circuit, a dedicated heater that is in communication with the coolant fluid to heat the coolant fluid, and a heating coil that is in communication with the at least one load space to heat the load space. The air mover is in communication with the cooling coil and the heating coil to condition an airflow directed across the cooling coil and the heating coil via heat transfer with one of the refrigerant in the cooling coil and the coolant fluid in the heating coil prior to entry of the airflow into the at least one load space. The temperature control system further includes a controller that is in communication with the at least one load space to detect conditions of the load space. The controller is also in communication with the refrigeration unit and the heating system to engage one of the refrigeration unit and the heating system to condition the load space in response to the detected load space conditions. 
         [0007]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a side view of a vehicle including a trailer having a temperature control system. 
           [0009]      FIG. 2  is a side view of the trailer and the temperature control system with portion of an outer wall of the trailer cut-away. 
           [0010]      FIG. 3  is a schematic diagram of a portion of a refrigeration circuit and a heating circuit of the temperature control system of  FIG. 2 . 
           [0011]      FIG. 4  is a schematic diagram of the refrigeration circuit and the heating circuit of the temperature control system of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0013]      FIGS. 1 and 2  illustrate an exemplary vehicle  10  that includes a trailer  12 , and a temperature control system  14  according to an embodiment of the invention. The illustrated vehicle  10  is a semi-tractor that is used to transport cargo, and that is coupled to the trailer  12  in a tractor-trailer combination. In other constructions, the vehicle  10  can be a truck, a shipping container, a rail container, or other transport vehicles (e.g., straight truck, van, etc.) that store and/or carry goods that must be maintained in a temperature controlled environment. 
         [0014]    As shown in  FIG. 1 , the trailer  12  includes a frame  18  and an outer wall  22  supported on the frame  18  for substantially enclosing a temperature controlled load space  26 . Doors  29  are supported on the frame  18  for providing access to the load space  26 . Referring to  FIG. 2 , in some embodiments, the load space  26  can include a partition or an internal wall  24  for at least partially dividing the load space  26  into sub-compartments, including two or more load space zones  38 ,  42 , each of which can be maintained at a different temperature or a different humidity, as described in greater detail below. A plurality of wheels  46  are provided on the frame  18  to permit movement of the vehicle  10  across the ground. In some constructions, wheels and/or rails for a railroad or a boat vessel can be used for transporting temperature controlled containers. 
         [0015]    In the illustrated embodiment of  FIGS. 1 and 2 , the temperature control system  14  includes a mechanical refrigeration unit  50  that conditions the load space  26 . The refrigeration unit  50  includes a refrigeration circuit  48  and a heating circuit  68 .  FIGS. 3 and 4  show a portion of the refrigeration circuit  48  that includes a cooling coil  62 . The temperature control system  14  is provided with a heating system  80  that has a heater  52 . The heater  52  may be a fuel fired heater that provides a source of heat whenever heat is required by the temperature control system  14 . Typically heat is required either for heating the load space  26  or for defrosting evaporator or cooling coils  62  utilized in the refrigeration unit  50  of the temperature control system  14 . The heater  52  can use fuel combustion, electrical resistance, or various other sources to provide heat. 
         [0016]    The heater  52  can be located in several locations. In one embodiment the heater is located within an outer housing  54  of the refrigeration unit  50 . By locating the heater  52  in this region, heat transfer fluid or coolant used for cooling an engine or prime mover  30  that powers the refrigeration unit  50  can be conveniently utilized to transfer heat from the heater  52  to a region adjacent the load space  26 . Utilizing fluid in this manner enables the temperature control system  14  to transfer heat either into or away from the region adjacent the load space  26  at different times depending on requirements of the system  14  and/or requirements in the load space. The heater  52  might also be attached to the outer wall  22  or suspended from the frame  18 , in the load space  26 , or at various other locations. 
         [0017]    The temperature control system  14  will generally direct refrigerant from the refrigeration unit  50  through a continuous loop refrigerant conduit to the load space  26  or the region where the temperature is to be controlled. The temperature control system  14  includes one or more evaporator/heater units or heat exchanger assemblies  58 . In the illustrated embodiment of  FIGS. 1 and 2 , the temperature control system  14  includes a first heat exchanger assembly  58   a  positioned in a first load space zone  38  and a second heat exchanger assembly  58   b  positioned in a second load space zone  42 . In other embodiments, the temperature control system  14  can include one, three, or more heat exchanger assemblies  58  positioned in one, three, or more load space zones. 
         [0018]    In the construction illustrated in  FIGS. 1 and 2 , the first and second units  58   a ,  58   b  are substantially similar. Accordingly, while the following description makes reference to elements of the first heat exchanger assembly  58   a , it should be understood that the second heat exchanger assembly  58   b  can be identical or similar or alternatively include substantially similar elements. Similarly, additional heat exchanger assemblies and additional load space zones will be similar to the heat exchanger assembly  58   a  and the load space  26 . 
         [0019]    As shown in  FIG. 2 , the first heat exchanger assembly  58   a  can include an evaporator housing  60 , a cooling coil  62 , and a heating coil  66 . The coils  62 ,  66  are contained in the evaporator housing  60 . The cooling coil  62  is fluidly connected to and positioned along a refrigeration circuit  48 . The heating coil  66  is connected to and positioned along the heating circuit  68 . The housing  60  can include an air inlet  86  and an air outlet  88  for receiving air from, and returning air to, the load space  26 . The housing  60  can also support a fan or blower or air mover  72  for drawing load space air into the evaporator housing  60  through the air inlet  86 . The air mover  72  moves the air across the coils  62 ,  66  and returns the air to the load space  26  through the air outlet  88 . In some constructions, the cooling coil  62  and the heating coil  66  can be positioned within a compartment of the housing  60  as an integral unit. 
         [0020]    As mentioned above, and in contrast to the cooling coil  62 , the heating coil  66  is connected to and positioned along a different fluid heating circuit  68 . The heating circuit  68  is provided to integrate an efficient and controllable means of transferring heat to the heating coil  66  when it is necessary to either heat the load space  26  or to defrost the cooling coils  62  and the heating coils  66 . Through utilization of a specific purpose heating circuit  68  with the separately powered heater  52 , the heating process can be accomplished more efficiently. The heating circuit  68  may be wholly self-contained or it may be a circuit that is extended from an existing fluid circuit (e.g., a cooling circuit for the prime mover  30 ). 
         [0021]      FIG. 3  shows a portion of the heating circuit  68 . In one construction, the fluid used for the heating circuit  68  comes from the prime mover  30 . This is commonly a diesel engine of conventional design. However, the prime mover  30  that is used for the cooling circuit  62  can be of various types and may not necessarily be appropriate for providing coolant for a different purpose (e.g., heating). Using the coolant from the prime mover  30  is not necessary, but it can be a convenient source. One advantage of this arrangement is it avoids duplication of cooling fluids. The coolant fluid of the prime mover  30  will generally have appropriate thermodynamic characteristics so that the coolant fluid can be used to cool or heat the prime mover via heat exchange relationship, and to selectively heat the load space  26 . However, other embodiments might use a separate independent fluid source for the heating circuit  68  for various reasons. 
         [0022]    The heating circuit  68  as shown in  FIG. 3  provides heat to a single area or load space  26 .  FIG. 4  shows the heating circuit in configuration for delivering heat to two areas or load space zones  38 ,  42 . 
         [0023]    Referring back to  FIG. 3 , the coolant fluid used to cool the prime mover  30  is drawn from the prime mover  30  through the heating circuit  68 . The heating circuit flow path continues from the prime mover  30 , through a pump  32  and a flow control valve  34  and adjacent or into the heater  52  where the coolant fluid is heated. In one embodiment, heating the coolant fluid in the heater  52  is accomplished through a conventional and relatively direct fuel-fired heating process. After the coolant fluid is heated and passed through the heater  52 , it continues on to the heat exchanger assembly  58  and into the heating coil  66 . At the heating coil  66 , an airflow is directed from the air mover  72  over the heating coil  66  and into the load space  26 . This is an efficient means of heating air that is directed into the load space  26  for the purpose of maintaining conditions of the load space  26  within desired parameters without operating the prime mover  30 . 
         [0024]    In the event that heating is required for defrosting the cooling coil  62 , the airflow is interrupted and not directed into the load space  26 . Rather, an entry area into the load space  26  is closed, and heat is retained in the region of the cooling coil  62  to provide greater heat transfer to the cooling coil  62  in order to defrost the cooling coil  62 . In the same manner, the heating coil  66  can be defrosted. 
         [0025]    After passing through the heating coil  66 , the coolant fluid is then returned through a complete circuit to the prime mover  30  and the process continues as the coolant fluid is continuously circulated through the continuous loop heating circuit  68 . 
         [0026]    The heating process is initiated when a control unit or controller  70  of the vehicle  10  calls for a heating process, either to heat the load space  26  or to defrost the cooling coil  62 . When the controller  70  calls for heating, the supplemental cooling pump  32  is activated, the valve  34  is opened, and begins circulating coolant fluid. The heater  52  is activated and heats the coolant fluid. In some constructions, a coolant pump coupled to the prime mover cooling system may suffice to provide circulation. In these constructions, the coolant pump may replace the pump  32 . 
         [0027]    Once the heating process is started, components of the vehicle  10  that are powered by electricity are generally supplied with electricity from an alternator or generator powered by a vehicle engine (not shown). Alternatively, these items can be powered by a battery or other source of electrical power. Electrically powered components can include the motorized air mover  72  located at the cooling and heating coils  62 ,  66  to move the airflow over the cooling and heating coils  62 ,  66  into the load space  26 , as well as other components described herein. When a defrost mode of the controller  70  is utilized, the air movers  72  can be turned off, and in some constructions, a damper can be used to stop warm air from entering the load space  26 . 
         [0028]    Throughout the heating process, the heater  52  provides efficient and continuous heat transfer to the coolant fluid. As mentioned above, the heater  52  requires a source of heat energy. In some constructions, a fuel tank  74  may be carried beneath the trailer  12  (See  FIGS. 1 and 2 ). In other constructions, the fuel tank  74  for the heater  52  can be disposed at various other locations on the vehicle  10 . A fuel line  76  directs fuel to the heater  52 . It may be advantageous to utilize the same fuel that is used to power the prime mover  30  to also power the heater  52 . Typically, both the prime mover  30  and the heater  52  use diesel fuel. In the event that both of them are diesel fuel powered, it is very convenient to use the same fuel tank (e.g., fuel tank  74 ) and the same fuel circuit. As shown in  FIGS. 3 and 4 , a fuel circuit  78  extends from the fuel tank  74  and carries fuel directly to the heater  52  and the prime mover  30  The illustrated heater  52  can be, for example, an Espar Hydronic Model 5™, although other heaters are possible and considered herein. 
         [0029]    The controller  70  can be programmed to operate the temperature control system  14  in a cooling mode or a heating mode to maintain or achieve a desired set point temperature and/or set point humidity level in the load space zones  38 ,  42 . Each load space zone  38 ,  42  can be independently maintained and at different set point conditions. 
         [0030]    During operation of the temperature control system  14  in the cooling mode by the controller  70 , the refrigerant circulates through the refrigeration circuit  48  to the cooling coil  62  of the first heat exchanger assembly  58   a  and/or the second heat exchanger assembly  58   b . The air mover  72  draws air from the load space  26 , into the evaporator housing  60  through the inlet  86 . The air mover  72  then directs the airflow across the cooling coil  62  to cool the airflow via heat exchange between the cooling coil  62  and the airflow, and returns the cooled or conditioned airflow to the load space  26  through the air outlet  88 . As the refrigerant travels through the cooling coil  62 , the refrigerant absorbs heat energy from the airflow directed across the cooling coil  62 . The refrigerant is then circulated through the remaining portions of the refrigeration circuit  48 . 
         [0031]    The prime mover  30  is cooled by the coolant fluid flowing through a coolant circuit (not shown) during operation of the temperature control system  14  in the coolant mode. The coolant fluid is bypassed around the heating coil  66  via the coolant circuit to avoid heating the airflow entering the load space  26  during operation of the temperature control unit  14  in the cooling mode. 
         [0032]    During operation of the heating system  80  in the heating mode by the controller  70  (shown schematically in  FIG. 3 ), the heater  52  heats the coolant fluid in the heating circuit  68 . The heated coolant fluid flows through the heating coil  66 , and heats the airflow via heat exchange relationship. The coolant fluid then circulates through the heating circuit  68  to be reheated by the heater  52  as necessary. 
         [0033]    During operation of the temperature control system  14  in the defrost mode, the controller  70  may cause the dampers adjacent the air inlet  86  and the air outlet  88  of each heat exchanger assembly  58   a ,  58   b  to be closed, and/or the air movers  72  to be shut down to prevent and/or limit movement of heat from the respective heat exchanger assembly  58   a ,  58   b  into the load space zones  38 ,  42 . Alternately, the speed of the air movers  72  can be decreased during the defrost mode. The heater  52  then heats the coolant fluid in the heating circuit  68 , and the coolant fluid is then pumped by the pump  32  through the heating circuit  68  to the heating coil  66  of the first heat exchanger assembly  58   a  and/or the second heat exchanger assembly  58   b . Heat from the heating coil  66  then defrosts and/or thaws the adjacent cooling coil  62  in the first heat exchanger assembly  58   a  and/or the second heat exchanger assembly  58   b , as well as the heating coil  66  if frost has built up on the heating coil  66 . 
         [0034]    The controller  70  can be programmed to initiate operation of the refrigeration unit  50  in the defrost mode based upon one or more sensed conditions (e.g., a pressure change of air flowing across the cooling coils  62 , a temperature change in the evaporator housing  60 , etc.). Alternatively, the defrost mode can be initiated by the controller  70  at predetermined time intervals (e.g., every 4 hours, etc.). Each heat exchanger assembly  58   a ,  58   b  can be independently defrosted by the associated heating circuit  68  based upon the sensed conditions of the associated load space zone, or at the predetermined time interval(s). 
         [0035]    In  FIG. 2 , the heating system  80  is in communication with two load space zones  38 ,  42 . Similarly, the refrigeration unit  50  is in communication with the two load space zones  38 ,  42 . Various modes of operation are possible with the circuits shown in  FIG. 4 . For example, the heating system  80  and the refrigeration unit  50  can be selectively operated by the controller  70  to cool the load space zones  38 ,  42 . Alternatively, the heating system  80  and the refrigeration unit  50  can be operated by the controller  70  to heat the load space zones  38 ,  42 , to defrost the two cooling coils  62 , or any combination thereof (e.g., heat one load space zone and cool the other load space zone, etc.). Each portion of the heating circuit  66  is provided with an independent heating coil  66  and an independent flow control valve  34  for the purpose of controlling the flow of the coolant fluid through the two circuits  66  in order to accommodate various modes of operation. 
         [0036]    In some constructions, a separate, independent coolant fluid can be used in heating circuit  68 . It is not necessary to utilize the coolant fluid of the prime mover  30 . For example, a food grade coolant fluid can be used in the heating circuit  68 . In this construction, the prime mover  30  is not in communication with the heating circuit  68 . 
         [0037]    It may be advantageous to use the prime mover  30 , at various times, to keep a battery pack (e.g., a deep cycle battery pack) charged for powering electrical components of the vehicle  10 . Commonly, the battery pack can be charged during operation of the truck or trailer through a circuit carried from a main vehicle engine electrical system (not shown) and/or an engine of the trailer  12  (e.g., the prime mover  30 ). For tractor-trailer applications, the tractor  10  is coupled to the trailer  12  to provide the electrical power for lights and other accessories, and an engine (e.g., the prime mover  30 ) of the trailer  12  provides power to the electrical components of the trailer  12 . In some constructions, the main vehicle engine drives an alternator sufficiently sized to power an electrically-driven compressor, condenser, and evaporator fan or blower unit, and to power electrical components for cooling, heating, and defrosting. However, there are times when the main vehicle engine is not operating, and in these circumstances, the prime mover  30  may be used to charge the battery pack. Thus, continuous operation of a vehicle engine and/or alternator can be avoided. 
         [0038]    Alternatively, or in addition, the temperature control system  14  can include a dedicated power source  90  (e.g., a fuel cell, etc.), for supplying power to the controller  70 , the air movers  72 , and other electrical power-consuming elements. In the illustrated construction, the power source  90  includes a deep cycle battery pack. In other constructions, fuel cells and/or other dedicated power sources can be located in other locations in the vehicle  10  (e.g., on the frame  18 , under the load space  26 , in the load space  26 , on the outer wall  22  of the vehicle  10 , etc.). 
         [0039]    In some constructions, the temperature control system  14  can include a receptacle  92  for receiving power from external power sources. In these constructions, an engine or battery of the vehicle  10  can supply electrical power to the controller  70 , the air movers  72 , and/or other electrical power-consuming elements. As shown in  FIGS. 1 and 2 , the temperature control unit  14  can also, or alternatively, use the receptacle  92  for receiving power from a land-based power network (e.g., the power network of a truck depot) for supplying electrical power to the controller  70 , the air movers  72 , and/or other electrical power-consuming elements of the temperature control system  14 . 
         [0040]    In constructions that include the receptacle  92  for receiving power from a land-based power network, the temperature control unit  14  may include an adaptor to facilitate an electrical connection between the receptacle  92  and various land-based power networks. For example, the adaptor can be engageable with a 120 volt alternating current (“VAC”) circuit and/or with a 230 VAC circuit. In other constructions, the temperature control system  14  can include separate receptacles for engaging various standard land-based power networks. 
         [0041]    Various features and advantages of the invention are set forth in the following claims.