Abstract:
Various refrigerant system schematics incorporate the ability to bypass refrigerant around a condenser, to selectively provide refrigerant of a desired thermodynamic state to downstream system components, including a reheat coil located downstream of the condenser. In addition, the reheat coil may be utilized in combination, or independently from an economizer cycle, that is also incorporated into the system design. The economizer branch can be configured in a sequential or parallel arrangement relative to the reheat coil. Consequently, a wide spectrum of sensible and latent load demands can be satisfied. Furthermore, various schematics provide distinct benefits and flexibility in unloading and temperature and humidity control, also resulting in system performance and reliability enhancement.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This application relates to refrigerant systems that incorporate both an economizer cycle and a reheat coil in several unique configurations to provide better dehumidification performance as well as temperature and humidity control.  
         [0002]     Refrigerant systems are utilized to control the temperature and humidity of air in various environments. In a typical refrigerant system, a refrigerant is compressed in a compressor and delivered to a condenser. In the condenser, heat is exchanged between outside ambient air and the refrigerant. From the condenser, the refrigerant passes to an expansion device, at which the refrigerant is expanded to a lower pressure and temperature, and then to an evaporator. In the evaporator, heat is exchanged between the refrigerant and the indoor air, to condition the indoor air. When the refrigerant system is operating, the evaporator cools the air that is being supplied to the indoor environment. In addition, as the temperature of the indoor air is lowered, moisture usually is also taken out of the air. In this manner, the humidity level of the indoor air can also be controlled.  
         [0003]     In some cases, the temperature level, to which the air is brought to provide a comfort environment in a conditioned space, may need to be higher than the temperature that would provide the ideal humidity level. This has presented design challenges to refrigerant system designers. One way to address such challenges is to utilize various schematics incorporating reheat coils. In many cases, the reheat coils, placed on the way of indoor air stream behind the evaporator, are employed for the purpose of reheating the air supplied to the conditioned space after it has been overcooled in the evaporator, where the moisture has been removed.  
         [0004]     One of the options available to a refrigerant system designer to increase efficiency is a so-called economizer cycle. In the economizer cycle, a portion of the refrigerant flowing from the condenser is tapped and passed through an economizer expansion device and then to an economizer heat exchanger. This tapped refrigerant subcools a main refrigerant flow that also passes through the economizer heat exchanger. The tapped refrigerant leaves the economizer heat exchanger, usually in a vapor state, and is injected back into the compressor at an intermediate compression point (or in between the compressor stages, in case multi-stage compression is utilized). The main refrigerant is additionally subcooled after passing through the economizer heat exchanger. The main refrigerant then passes through a main expansion device and an evaporator. This main flow will have a higher cooling capacity due to additional subcooling obtained in the economizer heat exchanger. An economizer cycle thus provides enhanced system performance. In an alternate arrangement, a portion of the refrigerant is tapped and passed through the economizer expansion device after being passed through the economizer heat exchanger (along with the main flow). In all other aspects this arrangement is identical to the configuration described above.  
         [0005]     As mentioned above, another option available to a refrigerant system designer is to include a reheat coil into the system schematics. As known, at least a portion of the refrigerant upstream of the expansion device is passed through a reheat heat exchanger and then is returned back to the main circuit. At least a portion of a conditioned air, having passed over the evaporator for the moisture removal and humidity control, is then passed over this reheat heat exchanger to be reheated to a desired temperature.  
         [0006]     Recently, the assignee of this application has developed a system that combines the reheat coil and economizer cycle. However, variations of this basic concept have yet to be fully developed.  
       SUMMARY OF THE INVENTION  
       [0007]     In disclosed schematics, a bypass is provided around the condenser, and a tap to lead a refrigerant to a reheat coil is positioned downstream of where the bypass taps refrigerant from the main refrigerant circuit and downstream of the condenser. In this manner, a control can utilize the bypass to achieve a particular thermodynamic state of refrigerant to the reheat coil. Thus, superior control over humidity and temperature is provided.  
         [0008]     In various embodiments, an economizer cycle is also incorporated into the system design, with the economizer cycle being either in a sequential arrangement with the reheat coil (upstream or downstream of the reheat coil tap) or in a parallel configuration. The economizer cycle and the reheat coil can be selectively operated in conjunction or independently from each other to satisfy a wide spectrum of external sensible and latent capacity demands as well as enhance system performance characteristics.  
         [0009]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1A  is a first schematic of a refrigerant system according to this invention.  
         [0011]      FIG. 1B  is a second schematic of a refrigerant system according to this invention.  
         [0012]      FIG. 1C  is a third schematic of a refrigerant system according to this invention.  
         [0013]      FIG. 2A  is a fourth schematic of a refrigerant system according to this invention.  
         [0014]      FIG. 2B  is a fifth schematic of a refrigerant system according to this invention.  
         [0015]      FIG. 3A  is a sixth schematic of a refrigerant system according to this invention.  
         [0016]      FIG. 3B  is a seventh schematic of a refrigerant system according to this invention.  
         [0017]      FIG. 4A  is an eighth schematic of a refrigerant system according to this invention.  
         [0018]      FIG. 4B  is a ninth schematic of a refrigerant system according to this invention.  
         [0019]      FIG. 5A  is a tenth schematic of a refrigerant system according to this invention.  
         [0020]      FIG. 5B  is an eleventh schematic of a refrigerant system according to this invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]     A refrigerant system  20  is illustrated in  FIG. 1A . A compressor  22  compresses a refrigerant and delivers a compressed refrigerant into a main refrigerant line  23 . A condenser  26  is positioned downstream of the compressor  22 . A bypass line  28  bypasses from the main refrigerant line  23  and around the condenser  26 , returning refrigerant to the main refrigerant line  23  at a point  29 . As shown, a flow control device  30  is positioned on the bypass line  28 . A control for the refrigerant cycle  20  may operate the flow control device  30  (through modulation or pulsation techniques) to bypass either a portion or all of the refrigerant around the condenser  26 , for a purpose to be disclosed below. In case it is desired to bypass the entire refrigerant amount around the condenser, a flow control device  21  upstream of the condenser  26  has to be closed and the flow control device  30  must be open.  
         [0022]     A three-way valve  32  communicates with the main refrigerant line  23  and selectively taps refrigerant into a line  33  from the main refrigerant line  23 , and through a reheat coil  34 . Downstream of the reheat coil  34 , refrigerant passes through a check valve  36 , and at a point  38  is returned to the main refrigerant line  23 .  
         [0023]     As also shown, an economizer cycle includes a tap at point  39  from the return line for the reheat coil  34 . Tap  39  communicates refrigerant into a tap line  42 , through an economizer expansion device  40 . The main refrigerant line  23  passes through an economizer heat exchanger  44 , as does the tap line  42 . While the two flows are shown going in the same direction through the economizer heat exchanger  44 , in practice, it may be preferable to have the two streams flowing in the counter-flow arrangement, however, for ease of illustration purposes, the refrigerants are shown flowing in the same direction. A line  43  returns refrigerant, preferably in the vapor state, from tap line  22  downstream of economizer heat exchanger  44  to the compressor  22  at an intermediate compression point. In some modes of operation, it is desirable to shutoff the economizer circuit, and if the auxiliary expansion device  38  is not capable to perform such a function, then addition shutoff valve may be added to the economizer loop.  
         [0024]     A main expansion device  46  is positioned on the main refrigerant line  23 , downstream of the economizer heat exchanger  44 . Downstream of the main expansion device  46  is an evaporator  48 . As is known, an air moving device, such as a fan  50 , passes air over the evaporator  48 , and at least a portion of that air flows over the reheat coil  34 .  
         [0025]     As known, refrigerant is passed to the reheat coil  34  at a temperature warmer than the temperature of refrigerant in the evaporator  48 . In some cases, air passing over the evaporator  48  can be cooled below a temperature desirable by an occupant of the environment to be conditioned by the refrigerant system  20 , and such that a significant amount of moisture can be removed from the air. That dehumidified air is then passed over the reheat coil  34 , where its temperature is increased to a comfort level by utilizing the warmer refrigerant flowing through the reheat coil  34 .  
         [0026]     The economizer cycle provides the refrigerant system designer with superior control flexibility. The economizer is operable to increase the sensible and latent capacity of the evaporator  48 , as disclosed above. Should increased latent capacity be desired (while the sensible capacity is preserved), the economizer cycle may be utilized in combination with the reheat coil  34 .  
         [0027]     On the other hand, if cooling is not particularly demanded but dehumidification is desired, some or all of the refrigerant may be bypassed around the condenser  26 . The refrigerant reaching the reheat coil  34  will now be in a two-phase state (or even in a vapor state, if flow control device  21  is predominantly closed) and has more re-heating capacity, than if it had passed through the condenser  26 . That higher heating capacity refrigerant will re-heat the air passing over the reheat coil  34  to a higher temperature, than if that same refrigerant had passed through the condenser  26 . Once again, the economizer cycle can be utilized to improve the system performance and to satisfy a wider spectrum of latent and sensibly capacity demands, if desired. As discussed above, the bypass flow control device  30  can be controlled to provide variable performance characteristics over a range of sensible heat ratios. Again, this system operation flexibility provides the designer of the refrigerant system  20  with additional control options, to satisfy a wider range of temperature and humidity levels. Obviously, the economizer circuit tap point  39  can be located downstream of the economizer heat exchanger  44  but upstream of the main expansion device  46  or downstream of the return point  38  of the reheat circuit but upstream of the economizer heat exchanger  44 .  
         [0028]      FIG. 1B  shows a refrigerant system  51  that operates and performs similar functions to the refrigerant system  20  illustrated in  FIG. 1A . In other words, the economizer heat exchanger  42  and the reheat coil  34  are arranged sequentially, with the reheat coil located upstream of the economizer heat exchanger. However, the tap  52  for the tapped refrigerant passing through the economizer heat exchanger  44  is selected from a location upstream of the three-way valve  32 , but downstream of the return point  29  of the bypass line  28 . This tap point  52  can be also located downstream of the three-way valve  32  but upstream of the return point  38  of the reheat circuit.  
         [0029]      FIG. 1C  shows a refrigerant system  53  wherein the economizer tap  54  is upstream of both the three-way valve  32 , and the return point  29  of the bypass line  28 . The location of the economizer tap  39 ,  52 , and  54  can be selected based upon the application of a particular refrigerant system. By selecting the particular position, a particular thermodynamic state of the refrigerant passing into the tap line can be achieved. Lastly, the three-way valve  32  can be either a conventional or a regulating flow control device. Also, a pair of conventional or regulating valves can be utilized instead.  
         [0030]      FIG. 2A  shows a refrigerant cycle  60 , wherein the three-way valve  62  for the reheat coil  34  is located downstream of the return point  29  of the condenser bypass line  28  and upstream of the economizer tap  64 . As shown, the reheat coil returns refrigerant to a point  138  that is downstream of the economizer heat exchanger  44 . Notably, in the  FIG. 1A -LC schematics, the return point  38  is upstream of the economizer heat exchanger  44 . In this sense, the economizer heat exchanger  42  and the reheat coil  34  are in a parallel arrangement now and if both reheat and economizer circuits are in operation, the refrigerant flow has to split between these two branches. As discussed before, the economizer tap point  64  can be located anywhere downstream of the economizer heat exchanger  44  but upstream of the expansion device  46 . Once again, selectively operating the economizer heat exchanger  44 , in conjunction or independently from the reheat coil  34 , provides advantages analogous to those mentioned above. Also, system reliability can be enhanced through a precise external heat load satisfaction and consequent reduction of the start-stop cycles.  
         [0031]      FIG. 2B  is similar to  FIG. 2A , however, the tap point  68  for the tapped line  42  is located downstream of the return point  29  of the condenser bypass line  28 , but upstream of the three-way valve  62 . Again, the particular location can be selected to provide enhanced control of the refrigerant system. Obviously, a less desirable location downstream of the condenser  22  and upstream of the return point  29  of the condenser bypass line  28  can be selected as well.  
         [0032]      FIG. 3A  shows a refrigerant system  70 , wherein a tap point  72  for directing refrigerant into the tap line  42  is positioned upstream of the return point  29  for the condenser bypass line  28 . The main refrigerant flow is either passed at point  80  into line  74  passing through the economizer heat exchanger  44 , or into line  75  leading to a three-way valve  78 . If the three-way valve  78  is a regulating flow control device, then the refrigerant could simultaneously flow through both aforementioned paths. From the three-way valve  78 , refrigerant may be passed through the reheat coil  34 , and back through a line  76  to a return point  139 , or alternatively, directly to the main expansion device  46 . As can be appreciated, the line  74  passing through the economizer heat exchanger  44  rejoins line  76  at point  149  and then at point  139  rejoins main flow line  23 . Obviously, the point  149  can be located on line  76  or on line  23  between the three-way valve  78  and the main expansion device  46 . In this sense, the reheat and economizer branch are once again in a parallel arrangement. Obviously, the tap point  72  can be located anywhere between the condenser  26  and the main expansion device  46 . Similarly, the abovementioned benefits can be obtained for this system configuration as well.  
         [0033]      FIG. 3B  exhibits a refrigerant system  82  that is similar to the  FIG. 3A  embodiment, however, the location of the tap  84  for the main flow passing through the economizer heat exchanger  44  is downstream of the point  29  for the condenser bypass line  28 . Again, a refrigerant system designer can control the amount of refrigerant passing through the bypass line  28 , and through the condenser  26  such that the refrigerant reaching the economizer loop is of a desired thermodynamic state, thus providing a wider range for the system performance control.  
         [0034]     Refrigerant system  90  is illustrated in  FIG. 4A . Refrigerant system  90  has refrigerant passing from a tap point  92  into line  42  at a location upstream of the return point  29  of the condenser bypass line  28 . The three-way valve  94  for directing refrigerant into the reheat coil  34  is located downstream of the economizer heat exchanger  44 . A return line  239  for returning the refrigerant to the main line  23  from the reheat coil  34  is also downstream of the economizer heat exchanger  44 , downstream of the three-way valve  94  and upstream of the main expansion device  46 . In this sense, although the reheat coil  34  and economizer heat exchanger  44  are configured in a sequential arrangement, now the reheat coil is located downstream of the economizer heat exchanger. As before, the tap point  92  can be located anywhere between economizer heat exchanger  44  and main expansion device  46 . Similarly, the aforementioned advantages are obtained form this system schematic as well.  
         [0035]      FIG. 4B  shows a refrigerant system  100  that is similar to the  FIG. 4A  embodiment. However, the return line  102  from the reheat coil  34  provides the point  103  to tap refrigerant into the tap line  42 . Again, a refrigerant system designer would recognize when such a schematic would be desirable to achieve flexibility in temperature and humidity control.  
         [0036]      FIG. 5A  shows a refrigerant system  110 , wherein the point  112  at which refrigerant is tapped into the line  42  is located downstream of the return point  29  of the condenser bypass line  28 . The  FIG. 5A  embodiment differs from the  FIG. 4A  embodiment in that the tap point is downstream of the return point  29 .  
         [0037]      FIG. 5B  shows a schematic similar to the  FIG. 5A  schematic, in which a refrigerant system  120  has its connection point  122  for delivering a main flow of refrigerant through the economizer heat exchanger  44  located upstream of the return point  29  of the condenser bypass line  28 . Again, a refrigerant system designer would recognize when such a schematic would be desirable in providing a particular degree of control over refrigerant reaching the reheat coil  34 , the economizer heat exchanger  44 , and the evaporator  48 .  
         [0038]     Although preferred embodiments of this invention have been disclosed, a worker of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.