Abstract:
A refrigeration apparatus having an evaporator fan motor control includes an evaporator to remove heat energy from the air in a cooled storage space. The evaporator transfers the heat energy to a refrigerant. At least one evaporator fan moves air from the cooled storage space across the evaporator to improve the transfer of heat energy into the refrigerant. The one or more evaporator fans have an energy consumption and generate a waste heat energy. A refrigeration control unit at least controls the operation of the one or more evaporator fans. During an off mode, the one or more evaporator fans are operated in a reduced energy consumption mode to reduce the energy consumption of the one or more evaporator fans and to reduce the waste heat while still defrosting the evaporator in the off mode.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to a method and apparatus for the operation of evaporator fans and more particularly to the operation of evaporator fans in refrigerated merchandisers. 
       BACKGROUND OF THE INVENTION 
       [0002]    Merchants of refrigerated beverages, snacks, and perishable foods typically use refrigerated merchandisers to market these products. Refrigerated merchandisers generally comprise a cooled storage space with shelves and a compressor, an evaporator, and a condenser to carry out a refrigeration cycle to cool the storage space. One or more evaporator fans blow storage space air over an evaporator, typically transferring heat energy from the storage space air to a circulating refrigerant in the evaporator coil to facilitate the refrigeration process. Also, one or more condenser fans blow ambient room air to cool the condenser, removing heat energy from the refrigerant. 
         [0003]    When the refrigerator is actively cooling the storage space in an “on mode”, both the condenser and evaporator fans are commanded on. Following a cooling on mode, the evaporator fan is typically left running to defrost the evaporator, but the time required to defrost the evaporator is usually shorter than the compressor off cycle that follows each on mode. Also, the operation of the evaporator fan motor itself adds heat to the refrigerated merchandiser cabinet. The problem is that operation of the evaporator fan beyond what is needed to defrost the evaporator wastes the energy needed to run the fan and needlessly adds heat to the refrigerated merchandiser, much of which ultimately ends up in the cooled storage space. 
         [0004]    Therefore, there is a need for an evaporator motor control that can reduce evaporator fan motor energy consumption during the compressor off cycle. 
       SUMMARY OF THE INVENTION 
       [0005]    A refrigeration apparatus having an evaporator fan motor control includes an evaporator to remove heat energy from the air in a cooled storage space. The evaporator transfers the heat energy to a refrigerant. At least one evaporator fan moves air from the cooled storage space across the evaporator to improve the transfer of heat energy into the refrigerant. The one or more evaporator fans have an energy consumption and generate a waste heat energy. A refrigeration control unit at least controls the operation of the one or more evaporator fans. During an off mode, the one or more evaporator fans are operated in a reduced energy consumption mode to reduce the energy consumption of the one or more evaporator fans and to reduce the waste heat while still defrosting the evaporator in the off mode. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    For a further understanding of these and objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, where: 
           [0007]      FIG. 1  shows a refrigerated merchandiser; 
           [0008]      FIG. 1A  shows a refrigerated merchandiser cassette; 
           [0009]      FIG. 2  a block diagram including refrigeration electrical controls; 
           [0010]      FIG. 3  shows an embodiment of evaporator fan control using two fan speeds; 
           [0011]      FIG. 4  shows an embodiment of evaporator fan control using control of multiple fans; 
           [0012]      FIG. 5  shows an embodiment of evaporator fan control based on defrosting; 
           [0013]      FIG. 6  shows a graph of power consumption versus time for an evaporator fan control using two fan speeds; and 
           [0014]      FIG. 7  shows a table of energy savings for the evaporator fan control of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]      FIG. 1  shows a refrigerated merchandiser  10  suitable for the system and method of inventive evaporator fan operation. Refrigerated merchandiser  10  can cool storage space  17  using the well known refrigeration cycle. Three of the major components used to carry out the refrigeration cycle are evaporator  14  (typically including an evaporator coil), condenser  16 , and compressor  18 . In operation (the “on mode”) one or more evaporator fans  13  draw air from interior storage space  17  over evaporator  14  removing heat from the air and returning cooler air to interior storage space  17 . A refrigerant circulated through evaporator  14  (not shown) is thus heated. The heated refrigerant is later cooled by condenser  16  working in conjunction with one or more condenser fans  15  to remove heat from the refrigerant and dissipate it into a flow of cooler ambient room air. The majority of the refrigeration components of refrigerated merchandiser  10  can be assembled into a refrigeration cassette  12  as shown in  FIG. 1A . Refrigeration cassette  12  can be made conveniently removable from refrigerated merchandiser  10  for ease of servicing. Such an exemplary refrigerated merchandiser is explained in more detail in PCT/US05/33078, “Evaporator fan/motor assembly support bracket”, filed Sep. 16, 2005 and incorporated herein by reference in its entirety. 
         [0016]      FIG. 2  shows refrigeration controls (refrigeration control unit)  21  used to at least control the operation of one or more evaporator fan(s)  13  and typically to also control the one or more condenser fans  15  and the operation of compressor  18 . During a refrigeration cooling cycle (“on mode”), compressor  18  is powered and both evaporator fans  13  and condenser fans  15  are in operation. In conventional operation, at the end of a refrigeration cycle (“off mode”), the compressor and condenser fans are turned off, but the evaporator fans continue to operate. During the off mode, evaporator fan operation is used to defrost evaporator coil  14 . However, in most instances, the time required to defrost evaporator  14  is shorter than the compressor off cycle. Therefore the evaporator fan is running much longer than required. 
         [0017]    The heat added to refrigerated merchandiser by evaporator fan  13  is approximately 30% to 50% of the total cooling load of the merchandiser. According to the invention, power to evaporator fan(s)  13  can be reduced when full operation of the fan(s)  13  is not required during the off cycle to defrost evaporator coil  14 . The energy savings is two fold. First there are direct savings by the reduction in electrical power consumption by fan(s)  13  and secondly, fan(s)  13  create less waste heat that ultimately ends up in cooled storage space  17  because refrigeration cassette  12  is located in the merchandiser below cooled storage space  17 . 
         [0018]    According to a preferred embodiment of the invention, as shown in  FIG. 3 , during a cooling on cycle, the compressor is on and one or more evaporator fans  13  are operating at high speed. At the completion of the on cycle, active cooling of storage space  17  ends when compressor  18  is shut off. During the off cycle, the one or more evaporator fan(s)  13  are set by refrigeration controls  21  to a low speed. The low speed operation of evaporator fans  13  reduces the direct electrical energy needed to run the fan(s)  13  as well reduces the waste fan heat that is introduced into storage space  17  as a result of the heat energy generated by the operation of fan(s)  13 . It should be noted that while the electrical energy to fan(s)  13  is significantly lower during an off cycle, there is still sufficient air flow through evaporator  14  to defrost it. 
         [0019]    An additional improvement in efficiency (not shown in  FIG. 3 ) can be gained by adding a third fan speed, such that the one or more evaporator fan(s)  13  are set by refrigeration controls  21  to a third higher fan speed, during an initial cool down period (“pull down”) of storage space  17 . The third higher fan speed can be especially useful during high refrigeration loading situations, such as when new products are added to refrigerated merchandiser  10 . One method to detect the addition of newly added products is to detect a temperature rise in storage space  17 . 
         [0020]    In another embodiment of the invention, shown in  FIG. 4 , during a cooling on cycle, the compressor is on and N evaporator fans  13  are operating at an operating speed. At the completion of the on cycle, active cooling of storage space  17  ends when compressor  18  is shut off. During the off cycle, the one or more (M) evaporator fans  13  are turned off leaving (N−M) fans still running at the operating speed. The reduced number of operating evaporator fan(s)  13  reduces the direct electrical energy needed to run the remaining (N−M) fan(s)  13  as well reducing the amount of waste fan heat introduced into storage space  17  as compared to the heat energy generated by the operation of N fan(s)  13 . It should be noted that while the electrical energy to fan(s)  13  is significantly lower during an off cycle, there is still sufficient air flow through evaporator  14  to defrost it. 
         [0021]    An additional improvement in efficiency (not shown in  FIG. 4 ) can be gained by adding additional fans P, such that (N+P) fan(s) evaporator fan(s)  13  are turned on by refrigeration controls  21 , during an initial cool down period (“pull down”) of storage space  17 . The additional airflow caused by the operation of (N+P) fan(s) evaporator fan(s)  13  can be especially useful during high refrigeration loading situations, such as when new products are added to refrigerated merchandiser  10 . 
         [0022]    In yet another embodiment of the invention, shown in  FIG. 5 , during a cooling on cycle, the compressor is on and N evaporator fan(s)  13  are operating at an operating speed. At the completion of the on cycle, active cooling of storage space  17  ends when compressor  18  is shut off. During the off cycle, the one or more evaporator fan(s)  13  are still running at the operating speed until the temperature of evaporator  14  rises to a level indicating that evaporator  14  is defrosted, or some other method of defrost detection as known in the art indicates that evaporator  14  defrosted. One way to detect a defrost condition at evaporator  14  is by temperature sensing to determine when the temperature of evaporator  14  has risen a predetermined amount above the freezing point of water as can be accomplished using temperature sensors, including bimetal switch, bimetallic sensor, thermistors, resistance temperature devices (RTDs), thermocouples, and infrared (IR) sensors. When it is detected that evaporator  14  is defrosted, evaporator fan(s)  13  can be turned off by refrigeration controls  21 . 
         [0023]    It should be noted that refrigeration controls  21  can comprise electromechanical switches, relays, or contactors to control fan(s)  14 , fan(s)  15 , and compressor  18 . Fan speeds can also be set by using multi-speed fans with dedicated power leads for each fan speed, or by a passive or active electronic fan speed control. Power semiconductor switches including SCRs, TRIACs, transistors, FETs, MOSFETs, and insulated gate bipolar transistors (IGBTs) can also be used for both on-off power controls as well as being used in electronic fan speed controls. Refrigeration controls  21  can also comprise a microcontroller, microcomputer, logic board using standard function digital logic chips or programmable logic elements, including gate arrays, programmable gate arrays, field programmable gate arrays (FPGA), ASICs, or other suitable electronic controls including a programmable logic controller (PLC). Typically refrigeration controls  21  will comprise a mix of both digital electronic control elements and power electrical switching elements as described above. 
         [0024]    It should also be noted that any type of fan suitable to move air across evaporator  14  can be used to practice off cycle energy savings afforded by the various embodiments of the invention. Suitable fan types include propeller blade fans, blowers, and squirrel cage fans. 
         [0025]    It should be noted that the inventive method and apparatus for controlling evaporator fan operation in refrigerated merchandisers is not limited to refrigerated merchandisers and can more generally be applied to other types of refrigeration equipment. 
       Example 
       [0026]    A simulation of the preferred embodiment where evaporator fan speed is reduced during the cooling off mode was carried out. The graph of  FIG. 6  shows a comparison of standard operation of refrigerated merchandiser according to the prior art compared to operation of the evaporator fans at a reduced speed during the off mode according to the invention. The graph is a plot of electrical power consumption (in Watts) plotted versus relative units of time, such as numbered sample points (on a scale of 0 to 1200). The solid curve shows the power consumption of an exemplary refrigerated merchandiser operated with the evaporator fans always on at a single fixed motor speed. The dotted curve, overlapping the solid curve during common operation over the on cycle, shows the dramatic power savings with a two speed evaporator motor dropped to a low speed during the off mode.  FIG. 7  is a table that shows the cost savings achieved by the reduced need for electrical power by a refrigerated merchandiser operated according to the invention. In this simulation example, it can be seen that with an overall 2.8% reduction in energy consumption, a cost savings of approximately $6 per year or at least $73 can be achieved over a 12 year product life cycle. 
         [0027]    The power and cost figures of the example are merely an illustration of one simulated case and do not reflect any limits on the potential energy saving possible using any of the aforementioned embodiments of the invention. 
         [0028]    While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.