Abstract:
A refrigeration system for a mobile unit and a method for operating the same are provided. The method includes the steps of: 1) providing a refrigeration unit having a compressor, an evaporator, and at least one fan operable to move air towards the evaporator, a generator dedicated to the refrigeration unit, and a battery; 2) determining at least one environmental parameter in one or both of the mobile unit and the refrigeration unit; and 3) selectively operating the refrigeration unit in one of a plurality of modes based on the environmental parameter, which plurality of modes includes a first mode wherein at least the fan is powered by the battery, and a second mode wherein the compressor and the fan are powered by the generator.

Description:
[0001]    Applicant hereby claims priority benefits under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/255,318 filed Oct. 27, 2009, the disclosure of which is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    This disclosure relates generally to heat exchange systems and, more particularly, to a hybrid refrigeration system for a mobile unit. 
         [0004]    2. Background Information 
         [0005]    Heat exchange systems can be used to regulate environmental conditions within a mobile unit (e.g., a vehicle, a truck container, a truck trailer, a shipping container, etc.). Typically, heat exchange systems are powered either directly or indirectly by an internal combustion engine. The engine may be operated during high load conditions (e.g. when the heat exchange systems require/draw a relatively large quantity of power), during low load conditions (e.g. when the heat exchange systems require a relatively small quantity of power), and during idle conditions (e.g. when the heat exchange systems are idle and require no power). 
         [0006]    In an effort to reduce energy consumption and costs associated therewith, it is known to operate the engine of a heat exchange system in an operational mode where the engine is subject to periods of operation and periods of rest. This mode of operation can be referred to as a “start and stop” mode of operation. One of the issues with the start and stop mode of operation is that when the engine is needed but the load on the heat exchange system is low, the engine may produce more power than the heat exchange system requires, which negatively effects the efficiency of the system. Another issue with the start and stop mode is that when the system is not operating, the air within the mobile unit is likely to be not circulating. As a result, localized thermal hotspots (and associated steep temperature variances) may form within the mobile unit. The formation of these hotspots can lead to inaccurate temperature readings and reduce the efficiency of the system. For example, if the temperature of the air proximate a sensor within the mobile unit is higher or lower than air elsewhere within the unit, the information provided by the sensor and any actions based on that information may be suspect. To reduce these inaccurate readings, some prior art systems “prime” the sensors within the mobile unit. The term “prime” is used to refer to scenarios where the prior art heat exchange system, including the engine, is run to circulate air within the mobile unit for a period of time until the temperature of the air within the mobile unit is more uniformly distributed. However, similar to low load conditions, the engine used to create the circulation typically produces more power than is required to “prime” the system and energy is consequently wasted. There is, therefore, a need in the art for a heat exchange system that reduces energy consumption during low load conditions. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    According to one aspect of the invention, a method for operating a refrigeration system for a mobile unit includes the steps of: 1) providing a refrigeration unit having a compressor, an evaporator, and at least one fan operable to move air towards the evaporator, a generator dedicated to the refrigeration unit, and a battery; 2) determining at least one environmental parameter in one or both of the mobile unit and the refrigeration unit; and 3) selectively operating the refrigeration unit in one of a plurality of modes based on the environmental parameter, which plurality of modes includes a first mode wherein at least the fan is powered by the battery, and a second mode wherein the compressor and the fan are powered by the generator. 
         [0008]    According to another aspect of the invention, a refrigeration system for a mobile unit is provided. The refrigeration system includes a refrigeration unit, a battery and a controller. The refrigeration unit includes a compressor, an evaporator, a generator, and at least one fan operable to move air through the evaporator. The generator is dedicated to the refrigeration unit. The controller is adapted to selectively operate the refrigeration unit in one of a plurality of modes based on an environmental parameter within the mobile unit, which plurality of modes includes a first mode wherein the fan is powered by the battery, and in a second mode wherein the compressor and the fan are powered by the generator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a diagrammatic illustration of one embodiment of a refrigeration system for regulating environmental conditions in a mobile unit. 
           [0010]      FIG. 2  is a diagrammatic illustration of one embodiment of the refrigeration system in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]      FIG. 1  illustrates a mobile refrigeration unit  10  operable to regulate environmental conditions (e.g., air temperature) in a truck trailer  12 . Mobile refrigeration units  10  can also be used with box trucks, buses, shipping containers, etc. The portion of the trailer  12  or other container that is to be environmentally maintained by the refrigeration unit  10  is referred to hereinafter as the “control region”. 
         [0012]    A diagrammatic illustration of an embodiment of a refrigeration unit  10  is shown in  FIG. 2 . The refrigeration unit  10  includes a power package  14 , a compressor  16 , a condenser  18 , a refrigerant regulator  20 , an evaporator  22 , at least one fan  24 , and a control system  26  (“controller”). The refrigeration unit  10  is configured such that liquid refrigerant travels through the compressor  16 , the condenser  18 , the refrigerant regulator  20  and the evaporator  22  in a closed loop path  28 . The fan  24  has an alternating current (“ac”) motor or a direct current (“dc”) motor and is configured to direct air  30  from the control region, and/or in some embodiments from outside the control region, through the evaporator  22 , and back into the control region. A detailed example of a refrigeration unit is disclosed within U.S. Pat. No. 5,916,253, which is hereby incorporated by reference in its entirety. 
         [0013]    The power package  14  includes a motor  32  coupled to a generator  34 , and a battery  36 . The power package  14  is adapted to power to one or more of the components of the refrigeration unit  10  (e.g. the compressor  16 , the refrigerant regulator  20 , the fan  24 , the controller  26 , etc.) and, in some embodiments to maintain or replenish the charge of the battery  36 . An example of an acceptable motor  32  is a compact diesel engine of the type that is commonly used to power a refrigeration unit  10 . An example of an acceptable generator  34  is a permanent magnet type DC generator. Alternatively, an AC alternator can be included in the power package  14 . The power package  14  is dedicated to the refrigeration unit  10 . The term “dedicated” is used to indicate that the refrigeration unit  10  derives all or substantially all of its power from the power package  14 . The battery  36  is operable to provide electrical power to one or more of the refrigeration unit components (e.g., the compressor  16 , refrigerant regulator  20 , fan  24 , controller  26 , etc.). In some embodiments, the charge of the battery  36  is maintained or replenished using power received from the generator  34 . Systems for maintaining or replenishing the charge of a battery  36  are well known in the art and further description is not required here for enablement purposes. The battery  36  may be a single unit or multiple units combined. 
         [0014]    The controller  26  includes a processor  38  that is adapted to receive one or more feedback signals from one or more sensors  40 , positioned within the control region and/or the refrigeration unit  10 , indicative of an environmental parameter (e.g., temperature, pressure, humidity, etc.) within the control region, and/or feedback signals indicative of operating parameters of the refrigeration unit  10 . The processor  38  is further adapted to selectively maintain or change the operating mode of the refrigeration unit  10 , using actuators  42  (e.g., switches, valves, etc.) in communication with the refrigeration unit  10  based on the feedback signals, an algorithm, or some combination thereof. For example, a temperature value sensed within the control region may prompt the controller  26  to engage a non-operating refrigeration unit  10  to supply cooling air to the control region, or it may prompt the controller  26  to disengage an operating refrigeration unit  10 . Similarly, an operating parameter value associated with the refrigeration unit  10  may prompt the controller  26  to engage a dormant refrigeration unit  10 , or to disengage an operating refrigeration unit  10 . It should be noted that the functionality of the processor  38  may be implemented using hardware, software, firmware, or a combination thereof. A person skilled in the art would be able to program the processing unit to perform the functionality described herein without undue experimentation. 
         [0015]    The refrigeration unit  10  can be operated in a variety of different modes. In a first mode, for example, the controller  26  directs the refrigeration unit  10  to operate the fan  24  only to circulate air to and from the control region. The power to drive the fan  24  is provided by the battery  36 , and the motor  32  and generator  34  of the power package  14  are maintained in non-operational mode. The other components of the refrigeration unit  10  (e.g., the compressor  16 , etc.) are also maintained in non-operational mode. 
         [0016]    In a second mode, the controller  26  directs the refrigeration unit  10  to operate the fan  24  to circulate air to and from the control region, and to operate at least one of the other components (e.g., the compressor  16 , etc.) of the refrigeration unit  10 . The power to drive the fan  24  and the other component is provided by the battery  36 , and not by the motor  32  and generator  34  of the power package  14 . 
         [0017]    In a third mode, the controller  26  directs the refrigeration unit  10  to operate the fan  24  to circulate air to and from the control region, and operate at least one of the other components (e.g., the compressor  16 , etc.) of the refrigeration unit  10 . The power to drive the fan  24  and the other component is provided by motor  32  and generator  34  of the power package  14 . 
         [0018]    The above described modes of operation are examples of how the present refrigeration unit  10  may be operated, and the present refrigeration unit  10  should not be construed as being limited to these particular modes. Additional information regarding circumstances when these modes may be implemented is provided below. 
         [0019]    In operation of the present refrigeration unit  10 , the controller  26  receives the feedback signal(s) indicative of the environmental parameter(s) in the control region and/or the operational parameter(s) of the refrigeration unit  10 . If, for example, the feedback signals indicate that the refrigeration unit  10  should be operating in a low load condition (e.g., temperature sensed within the control region is equal to or below the desired temperature for a cooling application), the controller  26  may operate the refrigeration unit  10  according to the first mode, wherein the battery  36  is used to power the fan  24  alone to circulate air to and from the control region. In some applications, the controller  26  may dictate a variable air flow rate created by the fan  24  based on feedback signals. 
         [0020]    While operating in the first mode, the circulation of the air may reduce or prevent the formation of regional thermal hotspots within the control region. The speed and extent to which the air circulation will eliminate the regional hotspots will depend upon factors including the volumetric flowrate of the fan  24 , the configuration of objects within the control region, the size of the control region, etc. Once an effective flow rate of air is circulated, the sensors  40  are apt to determine temperature values that are more representative of the average temperature within the control region, as opposed to a disparate regional temperature values. Consequently, it may be possible to reduce or eliminate associated sensor priming periods. In the first mode, the refrigeration unit  10  can be operated for a period of time without running the motor  32  and generator  34  of the power package  14 . Consequently, whatever fuel would have been consumed by the motor  32  is saved. What constitutes a “low load” condition can be determined for the particular application and the controller  26  can be appropriately adapted. 
         [0021]    If the feedback signals are indicative of a medium load condition (e.g., when the temperature sensed in the control region is within a predetermined temperature range), the controller  26  may operate the refrigeration unit  10  according to the second mode, wherein the battery  36  is used to power the fan  24  and one or more of the other components of the refrigeration unit  10 . In the second mode, the fan  24  and one or more other components of the refrigeration unit (e.g. the compressor  16 , etc.) are operated for a period of time without engaging the motor  32 . Hence, whatever fuel would have been consumed by the motor  32  is saved. What constitutes a “medium load” condition can be determined for the particular application and the controller  26  can be appropriately adapted. 
         [0022]    If the feedback signals are indicative of a high load condition (e.g., the sensed environmental temperature in the control region above the first predetermined range of temperatures), the controller  26  may operate the refrigeration unit  10  according to the third mode, wherein the motor  32  is operated to power the entire refrigeration unit  10 . In the third mode, the charge of the battery  36  can be replenished. What constitutes a “high load” condition can be determined for the particular application and the controller  26  can be appropriately adapted. 
         [0023]    The controller  26  can also be adapted to sense the level of charge within the battery  36 . If the charge within the battery  36  drops below a predetermined value, the refrigeration unit  10  can be operated within the third mode until the battery  36  is charged. 
         [0024]    While various embodiments of the present invention have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the present invention is not to be restricted except in light of the attached claims and their equivalents.