Abstract:
An apparatus and a method for conditioning air has a quantity of liquid desiccant. A first portion of a first airflow is received in a first contact volume such that it contacts a first portion of the liquid desiccant. A second contact volume is in parallel with the first contact volume and receives a second portion of the first airflow. At least a portion of a second airflow is brought into contact with a second portion of the liquid desiccant in a third contact volume. A first heat exchanger is associated with the first portion of the liquid desiccant and configured to transfer heat between the first portion of the liquid desiccant and a first medium. A second heat exchanger is associated with the second portion of the liquid desiccant and configured to transfer heat between the second portion of the liquid desiccant and a second medium.

Description:
TECHNICAL FIELD 
       [0001]    Various embodiments of the invention relate to dehumification and humidification in heating, ventilating, and air conditioning systems. 
       BACKGROUND 
       [0002]    Heating, ventilating, and air-conditioning (HVAC) systems provide temperature and humidity controlled air to residential, commercial, and industrial buildings. Air provided by the HVAC system may need to be at a specified temperature or humidified or dehumidified to meet comfort levels for occupancy, or to be within a range for electronics, or the like. Typically outside air is dehumidified and cooled if using an air conditioning system, and it is humidified and heated if using a heating system. The temperature and humidity mechanisms may be integrated or separate. 
         [0003]    For example, with some conventional air conditioning systems, air is cooled below its dew point by passing it over cooling coils such that water is condensed out of the air. This usually results in air at a temperature below a comfort zone temperature. The air is then heated to bring it to a desired comfort zone temperature by mixing it with warmer air already in the space being cooled or by passing it over a heating coil. The excess cooling used to dehumidify the air decreases efficiency. 
         [0004]    If a desiccant type dehumidifier is used in an air conditioning system, the desiccant removes water to dehumidify air in the dehumidification section. The dried air can then be cooled using a cooling coil to a desired comfort zone temperature. The desiccant is regenerated in a regeneration section where water is removed from the desiccant. The desiccant can then be reused in the dehumidification section. Depending on the capacity and type of the dehumidification and regeneration sections, desiccant can be blown out of the sections at high air flow rates. A high flow rate of air flowing through the chamber containing the desiccant contacts the desiccant, entrains desiccant droplets or vapor, and causes desiccant to be lost from the HVAC system. The loss of desiccant through blow-out from the chamber during high air flow rate conditions can impair the function of the dehumidifier if insufficient desiccant is present, or can cause other problems. 
       SUMMARY 
       [0005]    In some embodiments of the invention, an apparatus for conditioning air is provided with a quantity of liquid desiccant. A first contact volume is provided in which a first portion of a first airflow is received such that it contacts a first portion of the liquid desiccant. A second contact volume is in parallel with the first contact volume in which a second portion of the first airflow is received. A third contact volume is provided in which at least a portion of a second airflow is brought into contact with a second portion of the liquid desiccant. A first heat exchanger is associated with the first portion of the liquid desiccant and configured to transfer heat between the first portion of the liquid desiccant and a first medium. A second heat exchanger is associated with the second portion of the liquid desiccant and configured to transfer heat between the second portion of the liquid desiccant and a second medium. 
         [0006]    In another embodiment, an apparatus for conditioning air is provided with a first chamber having an inlet and an outlet for a first flow of a first fluid. The first chamber contains a first portion of a liquid desiccant for removing water from the first flow moving through the chamber. A second chamber has an inlet and an outlet for a first flow of a second fluid and contains a second portion of the liquid desiccant for evaporating water from the desiccant to the second fluid. The second chamber is in fluid communication with the first chamber such that the desiccant is capable of flowing between the first and second chambers. A third chamber has an inlet and an outlet for a second flow of the second fluid, and is in parallel with the second chamber. 
         [0007]    In yet another embodiment, a method of conditioning a fluid using a system having a first chamber, a second chamber, and a third chamber is provided. A first portion of a first fluid flows through the first chamber. The first portion of the first fluid interacts with a portion of a desiccant and transfers water between the first portion of the first fluid and the portion of the desiccant. A second portion of a first fluid flows through the second chamber. The second portion of the first fluid bypasses the first chamber. A second fluid flows through the third chamber. The second fluid interacts with at least a portion of the desiccant and transfers water between the second fluid and the at least a portion of the desiccant. The first and second portions of the first fluid are combined after the first portion of the first fluid exits the first chamber and the second portion of the first fluid exits the second chamber. 
         [0008]    In another embodiment, an apparatus for conditioning air is provided with a quantity of liquid desiccant, a first contact volume in which a first portion of a first airflow is received such that it contacts a first portion of the liquid desiccant, a second contact volume in parallel with the first contact volume in which a second portion of the first airflow is received, and a third contact volume in which at least a portion of a second airflow is brought into contact with a second portion of the liquid desiccant. A first heat exchanger is in contact with the first portion of the liquid desiccant and configured to transfer heat between the first portion of the liquid desiccant and a first medium. A second heat exchanger is in contact with the second portion of the liquid desiccant and configured to transfer heat between the second portion of the liquid desiccant and a second medium. A vapor compression system includes a compressor, a third heat exchanger not in contact with the liquid desiccant, and a refrigerant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic of a unit for conditioning air according to an embodiment of the invention; and 
           [0010]      FIG. 2  is a schematic of unit for conditioning air according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0012]    A heating, ventilating, and air conditioning (HVAC) system  10  is shown schematically in  FIG. 1 . The system  10  has a dehumidification section or side  14  and a regeneration section or side  16 , and uses a desiccant system  12  to change the humidity level of air flowing through the system  10 . The dehumidification side  14  may be used as a dehumidifier to provide drier air, or as an air conditioner to provide drier, cooler air. Alternatively, the regeneration side  16  may be used as a heating system to provide warmer, higher humidity air. The desiccant is a lithium chloride salt solution. Alternatively, the desiccant includes lithium bromide, magnesium chloride, calcium chloride, sodium chloride, or the like. 
         [0013]    The desiccant system  12  has a dehumidification chamber  18  on the dehumidification side  14  of the system  10 , where a desiccant within the chamber  18  absorbs water from air flowing through the chamber  18  and contacting the desiccant. The air flowing through the chamber  18  is provided through an air inlet  20  to the dehumidification side  14 . Only a portion of air entering through inlet  20  flows through the dehumidification chamber  18 , and the remainder of air bypasses the chamber  18  and flows through ducting parallel to the dehumidification chamber  18  thus allowing for higher flow rates required to achieve the desired cooling in a given space or better control of the humidity level of the air exiting the dehumidification side  14 . Alternatively, all of the air entering through inlet  20  flows through the dehumidification chamber  18 . 
         [0014]    The desiccant system  12  also has a regeneration chamber  22  on the regeneration side  16  of the system  10 , where water is removed from the desiccant through absorption into air flowing through the chamber  22 . The air flowing through the chamber  22  is provided through an air inlet  24  to the regeneration side  16 . Only a portion of air entering through inlet  24  flows through the regeneration chamber  22 , and the remainder of air bypasses the chamber  22  and flows through ducting parallel to the chamber  22 , thus allowing for higher air flow rates or better control of the humidity of air exiting the regeneration side  16 . Alternatively, all of the air entering through inlet  24  flows through the regeneration chamber  22 . 
         [0015]    The dehumidification chamber  18  and the regeneration chamber  22  are connected such that a liquid desiccant may flow between the two. The desiccant with a higher water content from the dehumidification chamber  18  is exchanged with desiccant with a lower or no water content from the regeneration chamber  22 . The desiccant is transported via diffusion flow from differences in desiccant concentration, pumped flow using one or more pumps, gravitational flow using a controlled overflow, or the like. 
         [0016]    Moist air flows through inlet  20  and through the dehumidification, or process, side  14 . Inlet  20  draws air from inside a building or draws outside air to add to a building HVAC system. A fan (not shown) or other device is used to create a pressure difference to provide the air flow through the side  14 . A set of dampers, or additional fans, divides and controls the air flow from the inlet  20  into two air streams. 
         [0017]    One of the air streams from the inlet  20  flows through the dehumidification chamber  18  where water is removed from the air by the desiccant. The desiccant is a liquid desiccant and may be sprayed, contained on a sponge like material, or used as is known in the art to dehumidify the air stream. The stream of air flowing through the dehumidification chamber  18  leaves the chamber  18  with a lower water content, as a dry air portion. 
         [0018]    The other portion of air from inlet  20  is cooled by a heat exchanger  26 , such as a cold water coil or a glycol coil. The heat exchanger  26  may be directly connected to a groundwater source, or may be integrated into a larger cooling system  28  or thermodynamic system  29 , such as a vapor compression cycle. The dry air portion and the other cooled portion of air are recombined before exiting the dehumidification side  14 . Heat exchanger  30  is a part of the vapor compression cycle  29 , or alternatively, is connected to a ground water source and integrated into cooling system  28 . The heat exchanger  30  is located on the regeneration side  16  to keep the lines in vapor compression cycle  29  on the regeneration side  16 , and out of the dehumidification side  14 . The air flow is conditioned on the dehumidification side  14  through cooling and the removal of water moisture. Vapor compression cycle  29  has a compressor  31  to circulate a refrigerant fluid through the cycle  29 , and additionally has a throttle (not shown). The heat exchangers described within the system  10  are associated with a medium such as various flows of air, desiccant, or circulating fluids, meaning that there is either direct heat transfer between a fluid flowing through the heat exchanger and the medium or there is indirect heat transfer between the fluid flowing through the heat exchanger and the medium using intermediary heat exchangers or additional mediums. 
         [0019]    Alternatively, after the water removal in the dehumidification chamber  18 , the dry air portion and the other portion of air from inlet  20  are recombined and then flow across and are cooled by a medium flowing in the heat exchanger  26 . 
         [0020]    By reducing the air flow through the chamber  18  by providing a bypassed air portion, blow-out of desiccant from the chamber  18  is prevented or reduced and higher flow rates are attainable. The flow rate through the chamber  18  is limited based on when the air flowing through the chamber begins to entrain desiccant. The flow rate of air through the dehumidification side  14  is increased by bypassing air around the chamber  18 , thereby providing an air flow that is greater than what is attainable using the chamber  18  alone. 
         [0021]    If a cooling system  28  is present, a flow of cooling fluid, such as glycol or another refrigerant, leaves the heat exchanger  30  and flows in parallel or in series to heat exchanger  26  and heat exchanger  32 . The cooling fluid in heat exchanger  32  may be used to cool the desiccant before use in the dehumidification chamber  18 , which additionally cools the air. 
         [0022]    A second flow of air enters through inlet  24  and through the regeneration side  16  of the system  10 . Inlet  24  may draw air from outside a building if the system  10  is used as an air conditioning system. A fan (not shown) or other device is used to create a pressure difference to provide the air flow through side  16 . The air is preheated by a medium in heat exchanger  34  before it enters the regeneration chamber  22  containing the desiccant. The air is preheated to increase the amount of water that may be evaporated into the air from the desiccant. Heat exchanger  34  is a part of the vapor-compression cycle  29 , or alternatively, is connected to an external heat source. The air flows through the regeneration chamber  24  where water is removed from the desiccant. The desiccant may be sprayed, contained on a sponge like material, or used otherwise as is known in the art. The desiccant is heated by a medium in heat exchanger  36  before entering the regeneration chamber  22  to aid in the evaporation water from the desiccant. Heat exchanger  36  is connected into vapor compression cycle  29 , or alternatively, is connected to an external heat source. The heated air flowing through the regeneration chamber  22  leaves the chamber  22  as moist air with an increased water content. 
         [0023]    In an embodiment, a set of dampers, or additional fans, divides the air flow through inlet  24  into two air streams, often after the heat exchanger  34 . One of the air streams flows through the regeneration chamber  22 , while the other air stream bypasses the chamber  22 . By limiting the air flow through the chamber  22 , blow-out of desiccant from the chamber  22  is prevented or reduced. The flow rate of air through the regeneration side  16  is increased by bypassing air around the chamber  22 , thereby providing an air flow that is greater than what is attainable using the chamber  22  alone. The two air streams may be recombined in a mixing chamber or the like downstream of the regeneration chamber  22 . 
         [0024]    The system  10  is described previously as an air conditioning unit where the dehumidification side  14  provides a high flow rate of cooler air at an appropriate humidity level to a building, and the regeneration side  16  is used to cycle desiccant for reuse in the desiccant system  12 . In other embodiments, the system  10  as described above is used as a heating unit with the regeneration side  16  providing a high flow rate of warmer air at an appropriate humidity level to a building, and the dehumidification side cycling the desiccant for reuse in the desiccant system  12 . The system  10  may be used to provide air as a HVAC system using the side  14 ,  16  which corresponds to the HVAC purpose or requirements. 
         [0025]      FIG. 2  illustrates another HVAC system  50  having a dehumidifying chamber  52  and a regenerator unit  54 . The dehumidifying chamber  52  and the regenerator unit  54  provide chambers or contact volumes where air interacts and comes into contact with a desiccant. In one embodiment, the system  50  provides cooler, drier, conditioned air from the dehumidifying chamber  52 , while the desiccant is regenerated in unit  54  for reuse. In another embodiment, the system  50  provides warmer, moister, conditioned air from the regenerator unit  54 , while the desiccant is regenerated using the chamber  52  for reuse. The system  50  is described below as an air conditioning unit; however, the use of the system as a heater or ventilator is contemplated and functionally would also operate as described below. Differences between the system  50  as an air conditioner and as a heater are the sources of inlet air for the chamber  52  and the unit  54 , and where the air from the chamber  52  and unit  54  is directed after leaving the system  50 . 
         [0026]    Moist air enters the dehumidifying chamber  52  through a moist air inlet  56 , and cooler, dried air or partially dried air exits chamber  52  through a dry air outlet  58 . A bypass duct  60  allows a portion of the air entering through inlet  56  to be bypassed around the dehumidifying chamber  52 . The bypass duct  60  acts as a chamber or contact volume for the bypassed portion of air. A series of fan or dampers  62  control the relative portions of air flowing through the chamber  52  and the duct  60 . The respective portions of air may be recombined using a mixing chamber  64  downstream of the chamber  52  and the duct  60 . The bypass duct  60  allows for a higher flow rate of air (cubic feet per minute, cfm) to be provided by outlet  58  and to flow through the system  50 . The addition of the duct  60  provides a mechanism to obtain higher overall flow rates at outlet  58 , while maintaining air flow through the chamber  52  at a lower flow rate. The flow rate through chamber  52  is limited by when the desiccant begins to be entrained by the air flowing through the chamber  52 . Without a bypass duct  60  and at high flow rates, desiccant from chamber  52  blows out of the chamber and is entrained in the exiting air at outlet  58 . 
         [0027]    Desiccant  66  is pumped from a desiccant reservoir  70  through a pipe  72  to a series of nozzles  74  using a pump  68 . The nozzles  74  spray the desiccant into the interior of chamber  52 . The chamber  52  may be filled with a cellulose sponge material through which the desiccant percolates downward to the reservoir  70 . The portion of moist air entering the chamber  52  through inlet  56  contacts the desiccant droplets. The hygroscopic desiccant absorbs water vapor from the moist air. Drier air exits the chamber  52 , mixes with the bypass air from duct  60 , and exits through outlet  58 . 
         [0028]    The desiccant in the sump  70  connected to chamber  52  increases in water content as air is dried. The desiccant is regenerated for reuse by having water removed from it in a regeneration unit  54 . Air enters through inlet  76  of the regeneration unit  54  and exits through outlet  78 . The air flow may be divided into two portions, with one portion flowing through the regeneration unit  54 , and the other portion flowing through a bypass duct  80 . The bypass duct  80  acts as a chamber or contact volume for the bypassed portion of air. A series of dampers  82  or fans are used to control the relative portions of air between the unit  54  and the duct  80 . The portion of air flowing through the unit  54  carries away moisture evaporated from the desiccant through outlet  78 . The portions of air flowing through the unit  54  and the bypass duct  60  may be recombined in a mixing chamber  84  before exiting the outlet  78 . 
         [0029]    Desiccant  66  is pumped by a pump  86  from a desiccant reservoir  88  through a pipe  90  to a series of nozzles  92 . The nozzles  92  spray the desiccant into the interior of unit  54 , which may be filled with a cellulose sponge material through which the desiccant percolates downward to reservoir  88 . The portion of air entering the unit  54  through inlet  76  contacts the moisture laden desiccant droplets. Water vapor is evaporated from the desiccant into the drier air, and moist air exits the chamber  54 , mixes with the bypass air, and exits through outlet  78 . By reducing the water content in the desiccant, the desiccant  66  is regenerated for reuse in the dehumidifying chamber  52 . 
         [0030]    The bypass duct  80  allows for a higher flow rate of air (cubic feet per minute, cfm) to be provided by outlet  78 . 
         [0031]    The addition of the duct  80  provides a mechanism to obtain higher overall flow rates at outlet  78 , while maintaining air flow through the unit  54  at a lower flow rate which prevents desiccant from becoming entrained into the air flowing through the unit  54 . Without a bypass duct  80  and at high air flow rates, desiccant may blow-out of unit  54  and be entrained in the exiting air. 
         [0032]    A heat transfer mechanism often occurs between the desiccant flowing through the dehumidifying side and the regenerative side. For example, a vapor compression cycle  94 , such as a heat pump or refrigeration cycle, is used for the heat transfer between the high and low water content desiccants and is additionally used to cool or heat air flowing through the system  50 . Of course, other cycles or heat exchangers operating independently using heat sources and sinks are also contemplated. The heat exchangers described within the system  50  are associated with a medium such as various flows of air, desiccant, or circulating fluids, meaning that there is either direct heat transfer between two mediums flowing through the heat exchanger or there is indirect heat transfer between two mediums flowing through the heat exchanger through intermediary heat exchangers or additional mediums. 
         [0033]    The vapor compression cycle  94  includes a compressor  96 , a first condenser  98 , a second condenser  100 , a throttle or expansion valve  102 , and an evaporator  102 . The heat pump  94  uses a refrigerant such as R-134a, R-1234, or others as are known in the art. The compressor  96  circulates the refrigerant through the cycle  94 . The first condenser  98  acts as a heat exchanger to heat the desiccant in pipe  98 . By preheating the desiccant before regenerating it in unit  54 , water is more easily evaporated from the desiccant. The second condenser  100  acts as a heat exchanger to heat the air flowing through inlet  76 . Warmer air flowing through unit  54  is able to retain a higher level of moisture or water at a higher temperature, which additionally assists regeneration of the desiccant  66 . The evaporator  104  provides a heat exchanger which acts as a heat sink to directly or indirectly cool desiccant and air on the dehumidifying side of the system  50 . 
         [0034]    The order of the first and second condensers  98 ,  100  may be reversed depending on the heating requirements of the air and the desiccant. Additionally, the second heat exchanger  100  could be positioned to heat only the portion of air flowing through the unit  54 , as opposed to the air flowing through inlet  76 . 
         [0035]    The evaporator  104  may be a two-stage evaporator, or two evaporators in series to directly cool the desiccant and the air on the dehumidifying side of the system  50 . Alternatively, the evaporator  104  is connected to a cooling loop  106 , which contains glycol, water, or another fluid. Flow within the cooling loop  106  leaves the evaporator  104 , and divides at valve  108 . One line in the cooling loop  106  flows through a heat exchanger  110 , which is directly or indirectly in contact with the desiccant in the pipe  72  to pre-cool the desiccant before it enters chamber  52 . The other line in the cooling loop  106  flows through a heat exchanger  112 , in parallel with the first heat exchanger  110 . The medium in the heat exchanger  112  cools the air in the bypass duct  60 . By cooling the air in the bypass duct, cooler moist air from duct  60  is mixed with drier air from chamber  52  at mixing chamber  64 , which allows for control over the air temperature and humidity level at outlet  58  through use of the dampers  62 , fans, and a controller (not shown). Heat exchanger  112  may also be positioned at inlet  56  to cool all of the air flowing through the dehumidifying side of the system  50 . Other cooling loops  106  are also contemplated, such as those having heat exchangers in series. 
         [0036]    Cooling the desiccant on the dehumidifying side with heat exchanger  110 , reduces the temperature of the desiccant in chamber  52 , which contacts the air being dried in the chamber  52  and additionally reduces the temperature of the dried air. 
         [0037]    Alternatively, the heat exchangers in the vapor compression cycle  94  and cooling loop  106  may be directly plumbed to heat sinks or sources, such as groundwater or waste heat from an associated air-conditioner or other system. 
         [0038]    Desiccant may be transferred between the two reservoirs  70 ,  88  using a diffusive aperture  114 , pumps, a float system, or the like. Desiccant in reservoir  70  increases in water content as the dehumidifying chamber  52  operates compared to the desiccant in reservoir  88 , which equates to a higher concentration of desiccant in reservoir  88  than in reservoir  70 . The desiccant needs to be regenerated for the efficiency and drying capacity of the dehumidifying chamber  52 . 
         [0039]    In the system  50  as shown in  FIG. 2 , the desiccant is transferred between the dehumidifying reservoir  70  and the regeneration reservoir  88  through diffusion transport. Alternatively, pumping or another system may be used. Aperture  114  allows for transfer of ions of water and desiccant salt between the reservoirs while minimizing the amount of heat transfer between the reservoirs. The dehumidifying chamber  52  continuously adds water content to the desiccant  66  in the reservoir  70 . The regenerating unit  54  continuously removes water from the desiccant. During operation, the concentration of salt ions in the reservoir  88  is generally higher than that in reservoir  70  because the desiccant the regeneration reservoir  88  is being concentrated while the desiccant in reservoir  70  is being diluted. The difference in concentration causes a flow of salt ions from reservoir  88  to reservoir  70  by diffusive transport, through aperture  114 , which is balanced by the flow of water ions from reservoir  70  to reservoir  88  caused by the flow of solution in this direction. This results in steady state levels of desiccant concentrations, although during changing air flow rate, start up conditions, or other system  50  transients, there will be corresponding transient period for the desiccant concentrations. 
         [0040]    In one embodiment, the system  50  has a dehumidifying chamber (or contact volume)  52  and a regeneration chamber  54 . A bypass duct (or contact volume)  60  is provided in parallel with the dehumidifying chamber  52 . Liquid desiccant  66  is used in the chambers  52 ,  54  to change the humidity level of air flowing through the chambers  52 ,  54 . A portion of an airflow entering inlet  56  flows into chamber  52  such that it contacts a first portion of the liquid desiccant  66  and is dehumidified. A second portion of an airflow entering inlet  56  flows through the bypass duct  60 . At least a portion of a second airflow entering through inlet  76  flows into chamber  54  such that it contact a second portion of the liquid desiccant  66  and water is removed from the desiccant to regenerate the desiccant. The system  50  has a heat exchanger  110  in contact with the first portion of the liquid desiccant  66 . Another heat exchanger  98  is in contact with the second portion of the liquid desiccant  66 . Yet another heat exchanger  112  is not in contact with the liquid desiccant  66 . In one embodiment, the heat exchanger  112  is in contact with the second portion of the first airflow in bypass duct  60 . In some embodiments, the system has a vapor compression system  94  including heat exchangers  110 ,  98 ,  112 , a compressor  96 , and a refrigerant. In other embodiments, the heat exchangers  110 ,  112 ,  98  may be run to independent heat sources or sinks. Alternatively, the heat exchangers  110 ,  112  are a part of a cooling loop  106  in communication with the vapor compression cycle  94 . Heat exchangers  110 ,  112  are arranged in parallel such that the refrigerant or cooling fluid flows in parallel to the heat exchangers  100 ,  112 . 
         [0041]    Heat exchanger  110  transfers heat from the desiccant  66  to the vapor compression cycle  94 . Heat exchanger  112  transfers heat from the bypass air in duct  60  to the vapor compression cycle  94 . This provides two sources of heat to the vapor compression cycle  94 , the bypass air in duct  60  and the desiccant flowing through piping  72 . The increased energy transferred into the vapor compression leads to additional energy (or heat) that may be transferred or used on the regeneration side, increasing the heat capacity available for regeneration. This additionally increases the system  50  efficiency and allows for higher airflows through the system  50 . By arranging the heat exchangers  110 ,  112  in parallel, a higher airflow may be attained through inlet  56  and outlet  58  without blow-out of the desiccant  66  from the chamber  52 . 
         [0042]    While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, features of various implementing embodiments may be combined to form further embodiments of the invention.