Abstract:
A moisture removal system comprises a plurality of coils each capable of operation as either a condenser or evaporator, and a switching mechanism to cycle the functionality of the coils. The system may cycle the functionality of the coils to alleviate frost development on any one coil and thus speed a moisture removal process.

Description:
BACKGROUND 
       [0001]    The disclosed embodiments relate generally to dehumidification systems, and more particularly to systems directed at removing moisture from agricultural or other moisture-laden products. 
         [0002]    It is often necessary or advantageous to lower the moisture content of certain products, including agricultural commodities. Corn, soybeans, wheat, oats, and even leafcutter bees are examples of products that require moisture removal for shipping, storing, and processing. The process of removing moisture from such commodities may be accomplished by closed-loop refrigeration methods. This involves forcing air over or through the subject product—i.e., the product from which moisture is to be removed—and then extracting moisture from the circulating air. The employed refrigeration systems typically include a heat pump, which comprises a condensing coil and an evaporator coil. Moisture from the circulating air adheres to the evaporator coil, thus lowering the relative humidity of the circulating air. After some time of operation, the moisture content of the subject product is reduced to a desired amount. 
         [0003]    One problem with heat pump-based systems, however, is that the evaporator coil accumulates frost; and, at some point, the coil becomes so frosted that the evaporator coil no longer functions to remove moisture from the air. The typical solution to this frost issue is to cease operation of the heat pump in order to defrost the coil. This, of course, limits the effective operating time of the heat pump. 
       SUMMARY OF THE DISCLOSURE 
       [0004]    Disclosed here is a moisture removal system with a heat pump that employs alternating cycles of operation, reversing functions of the condenser coil and the evaporator coil at certain intervals or when specified conditions are present. This allows the heat pump to continue operating while simultaneously thawing the frosted coil. In this way, the moisture removal process is sped up because there is no need to cease operation of the system to defrost a coil. 
         [0005]    In accordance with some embodiments of the disclosed technology, a moisture removal system employs a dual evaporator. Air is forced through or over the subject product and circulated through a drying enclosure. Within the drying enclosure, the air travels over or through several coils, at least one of which is operated as a condenser and one an evaporator. Moist air enters the removal, or evaporator coil, which is operated at temperature below freezing. The moisture from the air adheres to the coil, which drops the relative humidity of the air. Then, when the evaporator coils is frosted, the system is cycled such that the functions of at least two coils are reversed: at least one coil that initially operated as a condenser changes to an evaporator, and at least one coil the initially operated as an evaporator changes to a condenser. The process continues until the subject product reaches desired moisture content. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  shows a schematic of one embodiment of the disclosed moisture removal system. 
           [0007]      FIG. 2  depicts one cycle of operation of an embodiment of a heat pump in the disclosed moisture removal system. 
           [0008]      FIG. 3  depicts one cycle of operation of an embodiment of a heat pump in the disclosed moisture removal system. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed concepts. It will, however, be apparent to one of ordinary skill in the art that the disclosed concepts may be practiced without these specific details. Well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. 
         [0010]      FIG. 1  shows a moisture removal system  10 , which comprises a product container  12  with an intake side  14  and an exhaust side  16 . The subject product is placed in the product container  10 . There is a drying enclosure  18  with an inlet side  20  and an outlet side  22 . The drying enclosure  18  comprises a heat pump  24 . The heat pump has a first coil  28  and a second coil  30 . Also included are a first expansion valve  32  (which may also be referred to as a thermal expansion valve or TEV) and a switching means  34 . The heat pump has a compressor  26 , which is in fluid communication with the coils via a system of conduit, or conduit means  36 . The conduit means  36  could be copper tubing, polypipe, galvanized piping, or an equivalent fluid conveyance means. 
         [0011]    The moisture removal system  10  has one or more sections of duct for conveying air through the system. In a preferred embodiment, there is a first section of duct  38  that is connected between the exhaust side  16  of the product container  12  and the inlet side  20  of the drying enclosure  18 . There is a second section of duct  40  which is connected between the outlet side  22  of the drying enclosure  18  and the intake side  14  of the product container  12 . At least one blower  42 , which, in  FIG. 1 , is shown in the first section of duct  38 , circulates air  43  through the system. The blower  42  could be located in either the first section of duct  38  or the second section of duct  40 . The blower  42  circulates air  43  through the moisture removal system  10 , thus force air over or through the subject product within the product container  12  and through the drying enclosure  24 . The moisture removal system  10  could employ a plurality of blowers  24 , as may be required by specific designs and embodiments. 
         [0012]    The heat pump  24  may be equipped with a third coil  44  and a second expansion valve  45 . Additionally, it may be equipped with a four-way valve  46  and a plurality of flow control devices  48 . 
         [0013]    In one embodiment, in which the heat pump  24  comprises three coils, there is a first coil  28  having a condenser inlet  50 , an evaporator inlet  52 , and a valve outlet  54 . There is also a second coil  30  having a first outlet  56 , a second outlet  58 , and a valve inlet  60 . There is a third coil  44  having a condenser inlet  62 , an evaporator inlet  64 , and a valve outlet  66 . In such an arrangement, the first coil  28  and the third coil  44  are each capable of operating as either a condenser or evaporator. The compressor  26  has a suction inlet  68  and a discharge outlet  70 . The four-way valve  46  has a first coil inlet  72 , a second coil outlet  74 , a third coil inlet  76 , and a compressor outlet  78 . The first expansion valve  32  has an inlet  80  and an outlet  82 , and the second expansion valve  45  has an inlet  84  and outlet  86 . 
         [0014]    In this embodiment, the heat pump  24  is operated in either of two cycles.  FIG. 2  depicts a first cycle. In  FIG. 2 , the first coil  28  and the second coil  30  operate as a condenser, while the third coil  44  operates as an evaporator. During the first cycle, the compressor  26  provides refrigerant to the first coil  28  via a conduit means  36 . The conduit means  36  is connected from the discharge outlet  70  of the compressor  26  to the condenser inlet  50  of the first coil  28 . Within the conduit means is a flow controlling device  48  ( FIG. 1 ). The flow controlling device could be either a solenoid or a check valve, or any other similar means of controlling the flow in a conduit or pipe. 
         [0015]    The refrigerant leaves the first coil  28  at valve outlet  54  and moves to the second coil  30 , which acts as a secondary condenser, via the four-way valve  46 . The second coil outlet  74  of the four-way valve  46  is connected to the valve inlet  60  of the second coil  30  via conduit means  36 . Next, the refrigerant moves from the second coil  30  to the third coil  44 , which operates as an evaporator, via a second expansion valve  45 . The second outlet  58  of the second coil  30  is connected to inlet  84  of the second expansion valve  45  via a conduit means  36 . Within the conduit means  36  is a flow-controlling device  48  which, again, could be either a solenoid or a check valve, or any other similar means of controlling the flow in a conduit or pipe. The outlet  86  of the second expansion valve  45  is connected to the evaporator inlet  64  of the third coil  44  via a conduit means  36 . 
         [0016]    The refrigerant is then circulated back to the compressor  26  by way of the four-way valve  46  and the accumulator  88 . The valve outlet  66  of the third coil  44  is connected to the third coil inlet  76  of the four-way valve  46 . The compressor outlet  78  of the four-way valve  46  is connected to the valve inlet  90  of the accumulator  88  via conduit means  36 ; and the compressor outlet  92  of the accumulator  88  is connected to the suction inlet  68  of the compressor  26  via conduit means  36 . The preferred embodiment includes an accumulator  88 ; however, those skilled in the art will recognize that a compressor with an internal or integral accumulator may also be used. 
         [0017]      FIG. 3  depicts a second cycle of the heat pump  24 . The compressor  26  is connected to the third coil  44 , which acts as a condenser, as does the second coil  30 . During the second cycle, the compressor  26  provides refrigerant to the third coil  44  via a conduit means  36 . The conduit means  36  is connected from the discharge outlet  70  of the compressor  26  to the condenser inlet  62  of the third coil  44 . Within the conduit means is a flow controlling device  48  ( FIG. 1 ). The flow controlling device could be either a solenoid or a check valve, or any other similar means of controlling the flow in a conduit or pipe. 
         [0018]    The refrigerant leaves the third coil  44  at valve outlet  66  and moves to the second coil  30 , which acts as a secondary condenser, via the conduit means  36  and the four-way valve  46 . The second coil outlet  74  of the four-way valve  46  is connected to the valve inlet  60  of the second coil  30  via conduit means  36 . Next, the refrigerant moves from the second coil  30  to the first coil  28 , which operates as an evaporator, via a first expansion valve  32 . The first outlet  56  of the second coil  30  is connected to inlet  80  of the first expansion valve  32  via a conduit means  36 . Within the conduit means  36  is a flow-controlling device  48 , which, again, could be either a solenoid or a check valve, or any other similar means of controlling the flow in a conduit or pipe. The outlet  82  of the first expansion valve  32  is connected to the evaporator inlet  52  of the first coil  28  via a conduit means  36 . 
         [0019]    The refrigerant is then circulated back to the compressor  26  by way of the four-way valve  46 , and the accumulator  88 . The valve outlet  54  of the first coil  28  is connected to the first coil inlet  72  of the four-way valve  46 . The compressor outlet  78  of the four-way valve  46  is connected to the valve inlet  90  of the accumulator  88  via conduit means  36 ; and the compressor outlet  92  of the accumulator  88  is connected to the suction inlet  68  of the compressor  26  via conduit means  36 . 
         [0020]    Referring again to  FIG. 1 , the switching means  34  operates to change the operation of the heat pump  24  between the first cycle and second cycle discussed above. The switching means  34  accomplishes this by adjusting the four-way valve  46  and opening and closing flow-controlling devices  48  such that the flow of refrigerant changes course and thus alternates the respective functions of the first coil  28  and the third coil  44 . Those skilled in the art will recognize that some of the flow-controlling devices  48  will begin in a normally open state and some in a normally closed state. The switching means  34  thus changes the respective states of the flow-controlling devices  48 . 
         [0021]    In the preferred embodiment, the switching means comprises a timer that operates the flow-controlling devices to alternate the function of the first coil  28  and the third coil  44  in set increments. In the best mode presently known, the switching means comprises a timer set to fifteen-minute increments. The switching means could, however, comprise a temperature gauge and the cycling of the first coil  28  and the third coil  44  could be based on the temperature at a given point in the system. In one embodiment, the temperature gauge could reference refrigerant temperature at the outlet  82  of the first expansion valve  32  or the outlet  86  of the second expansion valve  45 . (Whether to measure at the first expansion valve  32  or the second expansion valve  44  of course depends in which cycle the heat pump is operating.) Or, a switching means comprising a pressure gauge that could measure pressure at a given point in the system and switch the functionality of the first coil  28  and the third coil  44  when the pressure reaches a certain limit. 
         [0022]    As the circulating air  43  travels through the coils, moisture adheres to the coil operating as an evaporator and the relative humidity of the circulating air  43  is reduced. This moisture removal occurs because the temperature of the refrigerant in the coil, and thus the coil itself, is below freezing. In one embodiment, the temperature of the system refrigerant is about −11 degrees Fahrenheit, as measured at outlet  82  or outlet  86 , depending on the cycle of operation. But those skilled in the art will recognize that a range of temperatures will be suitable for moisture removal. 
         [0023]    The disclosed technology may be operated using a method with the following. First, provide a moisture removal system  10 , as described above. Then, circulate air through the system with the blower  42 . Next, run the heat pump in a first cycle, as depicted in  FIG. 2 , with a switching means  34  configured for automatically switching the system  10  to operate in  FIG. 3 . When a predetermined condition is met—an expiration of time or a certain temperature or pressure measured—automatically switch operation of the system  10  to run the heat pump as depicted in  FIG. 3 . Finally, continue alternating between the first and second cycle until the subject product is at desired moisture content. 
         [0024]    The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. The illustrative discussion above, however, is not intended to be exhaustive or to limit the disclosed concepts to any particular form. The embodiments were chosen and described in order to best explain the principles of the disclosed concepts in order to enable others skilled in the art.