Abstract:
A dehumidifier for swimming pool enclosures includes a first circuit having a condenser, an evaporator, and refrigerant, and a second circuit including the evaporator of the first circuit, a second evaporator and a heat sink fluid movable along the circuit. The second evaporator is positioned upstream with respect to the condenser of the first circuit. A bypass directs air around the second evaporator and a second bypass selectively directs air around both the second evaporator and the condenser.

Description:
FIELD OF THE INVENTION 
     The invention relates to a dehumidifier, and more specifically, the invention provides a dehumidifier for removing moisture from the air in a pool enclosure. 
     BACKGROUND OF THE INVENTION 
     Controlling indoor pool environments in a four season setting has been a costly and complicated job. While conventional ventilation systems and heat recovery systems appear to have a cost advantage over energy recycling equipment with respect to equipment cost, there are several problems associated with using a conventional ventilation system for a pool enclosure. First, a ventilation system works only when the humidity outside is substantially lower than the humidity on the inside. An indoor swimming pool can lose as much as 100 gallons of water through evaporation to the adjacent air every day. Traditional ventilation systems cannot remove this amount of moisture in a single day. Second, the operating cost of ventilation systems are higher in colder climates due to the need to heat winter air to an acceptable temperature for the enclosure. Outdoor air must be brought into the enclosure to decrease the humidity in the enclosure. Third, traditional ventilation systems will not control chlorine or eliminate chloramines in the air. 
     Excessive moisture in the air of the pool enclosure can cause several problems. The moist air encounters cooler surfaces such as windows, ceilings, or outdoor walls causing the air to cool and water to condense out of the cool air. The condensed water becomes a haven for fungus, mold and mildew which can contain potentially dangerous biotoxins. Furthermore, humid air is uncomfortable for any one in the swimming pool enclosure, except the swimmers. In addition, gaps in the ceiling or walls provide openings humid air to access building structural members. Condensation can cause water deposits to accumulate on structural members, unseen for years. These deposits can accelerate the deterioration of the structure. 
     One approach to dealing with the problem of humid air in a swimming pool enclosure has been to simply open the doors and windows of the enclosure and let external, relatively dryer air enter the enclosure. This “passive” approach, however, only works on days when the outdoor air is at the same temperature as the air in the enclosure and is of lower humidity. These conditions rarely exist. Furthermore, the passive approach results in substantial energy loss, since the humid air of the enclosure contains latent heat energy lost by the water of the pool. 
     A second approach for dealing with the problem of humid air in a swimming pool enclosure has been to provide a ventilation system. Exhaust fans remove humid air while external air is heated or cooled to a desired temperature and transmitted to the swimming pool enclosure. However, the heating, ventilation, and air conditioning (HVAC) equipment required to accomplish this is expensive and difficult to operate. Furthermore, the equipment typically consists of relatively large and noisy exhaust fans. This approach will not work to dehumidify the air when the outdoor air has the same level of humidity as the air in the swimming pool enclosure. 
     A third approach to solving the problem is referred to as “active dehumidification.” In an active dehumidification system, a blower draws air from the swimming pool enclosure through a dehumidifier coil which is chilled to maintain a surface temperature lower than the dew point. Humidity in the air condenses on the coil and drains. Both sensible and latent heat energy is recaptured by the refrigerant flowing through the dehumidification coil. Refrigerant is drawn into a compressor, compressed and forwarded to a pool water heater. The pool water heater acts as a condenser; heat is transferred from the refrigerant to the pool water. Active dehumidification systems also can include an air reheat coil. Refrigerant exits the pool water heater and travels to the air reheat coil to transfer any remaining heat available to air passing through the system. 
     Existing active dehumidification systems have several shortcomings. First, existing systems are unable to modify operating conditions to maximize efficiency and capacity. Specifically, existing systems will continue to operate at maximum blower capacity even when efficiency of the system decreases. The capacity of the dehumidifier coil capacity is based on surface area, temperature, and the velocity of air passed over the coil. As air velocity increases, the temperature of the coil will increase, and the capacity of the coil decreases. Therefore, it would be desirable to maintain a constant coil temperature. In addition, existing active dehumidification systems generally include a dehumidifier coil having six or eight rows. The six and eight row evaporator coils are virtually impossible to clean and must be replaced when dirty. Since refrigerant is circulated through the evaporator coil, replacement of a coil requires highly trained personnel. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method for removing moisture from air. The invention includes a refrigerant circuit passing through a first heat exchanger and an evaporator portion of a second heat exchanger. The invention also includes a heat sink circuit passing through the first heat exchanger of the refrigerant circuit and a third heat exchanger. Refrigerant moves along a first path formed by the refrigerant circuit. The first heat exchanger is exposed to an air stream. Heat is transferred from the refrigerant to the air stream as it passes through the first heat exchanger. The evaporator portion of the second heat exchanger is exposed to a heat sink fluid stream moving along a second path formed by the heat sink circuit. Heat is transferred from the heat sink fluid stream to the refrigerant as it passes through the evaporator portion of the second heat exchanger. The heat sink fluid moves from the evaporator portion of the second heat exchanger to the third heat exchanger. The third heat exchanger is exposed to the air stream and is positioned upstream with respect to the first heat exchanger. Heat is transferred from the air stream to heat sink circuit. Water vapor in the air stream condenses on the third heat exchanger. The air stream moves from the third heat exchanger to the first heat exchanger and is heated. 
     The present invention also provides a method and apparatus for directing air around the third heat exchanger to maximize the efficiency of the system. The third heat exchanger and the first heat exchanger can be positioned in a conduit. The conduit can be divided into first, second and third chambers by the first and third heat exchangers. The first chamber can be defined within the conduit between the inlet of the conduit and the third heat exchanger. The second chamber can be defined within the conduit between the third heat exchanger and the first heat exchanger. The third chamber can be defined within the conduit between the outlet of the conduit and the first heat exchanger. The invention can include a second inlet communicating with the conduit adjacent the second chamber to allow a second air stream to bypass the third heat exchanger and enter the conduit. The second air stream entering the second inlet is mixed with the air stream that has passed across the evaporator portion of the third heat exchanger. The invention can include a damper for opening and closing the second inlet and controlling the amount of air bypassing the third heat exchanger. The invention can also include a third inlet communicating with the conduit adjacent the third chamber to allow a third air stream to bypass the third heat exchanger and the first heat exchanger. 
     Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
     FIG. 1 is a schematic view of a refrigerant circuit according to the present invention operating in a first mode; 
     FIG. 2 is a schematic view of a refrigerant circuit according to the present invention operating in a second mode; 
     FIG. 3 is a schematic view of a refrigerant circuit according to the present invention operating in a third mode; 
     FIG. 4 is a schematic view of the environmental control device including an external heat sink fluid stream source according to the present invention; 
     FIG. 5 is a flow diagram illustrating the steps for opening a pair of dampers according to the present invention; 
     FIG. 6 is a flow diagram illustrating the steps for closing a pair of dampers according to the present invention; 
     FIG. 7 is a schematic view of an environmental control device including an alternative water and glycol heat sink circuit according to the present invention; and 
     FIG. 8 is a schematic view of an environmental control device including an optional swimming pool water heater according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides an environmental control device  10  for removing moisture from air. The invention includes a refrigerant circuit  12  and a heat sink circuit  14 . A refrigerant circuit  12  is shown in FIG. 1 according to the present invention. The circuit  12  includes a first heat exchanger  16 , a second heat exchanger  18 , a compressor  20  and an expansion valve  24 . The first heat exchanger  16  includes a condenser portion. The components of the circuit  12  are connected with piping to form a closed loop path  13 . A refrigerant stream  17  moves along the path  13 . 
     The refrigerant circuit can operate in several modes. In a first mode, the heat exchanger  16  acts as a condenser to condense vaporized refrigerant and transfer heat from the refrigerant stream  17  to an air stream  19 , increasing the temperature of the air stream  19  flowing relative to the first heat exchanger  16 . In the first mode, the refrigerant stream  17  is compressed by the compressor  20  and directed to the first heat exchanger  16  by a direction valve  25  in a first position and a reversing valve  26  in a first position. The direction valve  25  can be moved between two positions. The reversing valve  26  can be moved between two positions. The refrigerant stream  17  can move from the compressor  20 , through the direction valve  25 , and through the reversing valve  26  to enter the first heat exchanger  16 . 
     Refrigerant in the form of high pressure vapor transfers heat to an airstream  19  flowing across the first heat exchanger  16  to increase the temperature of the airstream  19 . After passing through the first heat exchanger  16 , the refrigerant stream  17  moves through a three-way valve  28 , the expansion valve  24  and enters the second heat exchanger  18 . The second heat exchanger  18  includes a heat transfer wall  34  separating the refrigerant stream  17  from a water stream  21 . The water stream  21  moves along the heat sink circuit  14 . The water stream  21  enters the second heat exchanger  18  at an inlet  38  and exits the second heat exchanger  18  at an outlet  36 . Heat is transferred from the water stream  21  to the refrigerant stream  17  passing through the second heat exchanger  18 , through the wall  34 . The refrigerant stream  17  moves to the compressor  20  to be compressed after passing through the second heat exchanger  18 . 
     Referring now to FIG. 2, in a second mode of operation of the refrigerant circuit, the direction valve  25  can be moved to a second position and the reversing valve  26  remains in the first position. The refrigerant stream  17  can move from the compressor  20  and through the direction valve  25  to a fourth heat exchanger  30 . The fourth heat exchanger  30  includes a heat transfer wall  31  separating the refrigerant stream  17  from a water stream  116 . The water stream  116  enters the fourth heat exchanger at an inlet  37  and exits the fourth heat exchanger  30  at an outlet  39 . Heat is transferred from the refrigerant stream  17  to the water stream  116  passing through the fourth heat exchanger  30  through the wall  31 . The hot or heated water stream  116  can be directed to a swimming pool after passing through the fourth heat exchanger  30 . The refrigerant stream  17  moves through the three-way valve  28 , the expansion valve  24  and enters the second heat exchanger  18  after passing through the fourth heat exchanger  30 . The second heat exchanger  18  includes a heat transfer wall  34  separating the refrigerant stream  17  from a water stream  21 . The water stream  21  moves along the heat sink circuit  14 . The water stream  21  enters the second heat exchanger  18  at an inlet  38  and exits the second heat exchanger  18  at an outlet  36 . Heat is transferred from the water stream  21  to the refrigerant stream  17  passing through the second heat exchanger  18  through the wall  34 . The refrigerant stream  17  moves to the compressor  20  to be compressed after passing through the second heat exchanger  18 . 
     Referring now to FIG. 3, in a third mode of operation of the refrigerant circuit, the direction valve  25  is in the first position and the reversing valve  26  is in a second position. The refrigerant stream  17  can move from the compressor  20 , through the direction valve  25 , and through the reversing valve  26  to enter the second heat exchanger  18 . In the third mode of operation of the refrigerant circuit, the second heat exchanger  18  acts as a condenser to condense the refrigerant stream  17  by transferring heat to the water stream  21  to increase the temperature of the water stream  21 . The second heat exchanger  18  includes a heat transfer wall  34  separating the refrigerant stream  17  from a water stream  21 . The water stream  21  moves along the heat sink circuit  14 . The water stream  21  enters the second heat exchanger  18  at an inlet  38  and exits the second heat exchanger  18  at an outlet  36 . Heat is transferred from the refrigerant stream  17  to the water stream  21  passing through the second heat exchanger  18 , through the wall  34 . The refrigerant stream  17  moves through the expansion valve  24 , the three-way valve  28  and enters the first heat exchanger  16 . In the third mode of operation of the refrigerant circuit  12 , the first heat exchanger  16  acts as an evaporator to evaporate the refrigerant stream  17  to transfer heat to the refrigerant stream  17  to decrease the temperature of the air stream  19  flowing relative to the first heat exchanger  16 . The refrigerant stream  17  passes through the reversing valve  26  and enters the compressor  20  to be compressed after passing through the first heat exchanger  16 . 
     Referring now to FIG. 4, the water stream  21  moves from the second heat exchanger  18  along a second path defined by the heat sink circuit  14 . The heat sink circuit  14  includes the inlet  38 , the second heat exchanger  18 , the outlet  36 , a temperature sensor  40  and a third heat exchanger  42 . The circuit  14  also includes appropriate piping to form a closed loop path between the second heat exchanger  18  and the third heat exchanger  42 . The chilled water stream  21  leaving the outlet  36  has a lower temperature relative to the water stream  21  entering the inlet  38 . The water stream  21  travels along the heat sink circuit  14  to the sensor  40  for measuring a temperature of the water stream  21 . The sensor  40  can be in communication with a controller  66 . 
     The water stream  21  enters the third heat exchanger  42  from the outlet  36 . The third heat exchanger  42  can include a coil having three or four rows. The air stream  19  passes across the third heat exchanger  42  and heat is transferred from the air stream  19  to the water stream  21  causing water to condense from the airstream  19 . The air stream  19  is cooled at the third heat exchanger  42 . The condensed water can drain from the third heat exchanger  42  through drain  44 . The water stream  21  moves from the third heat exchanger  42  to the second heat exchanger  18 . The air stream  19  passes across the first heat exchanger  16  after passing across the third heat exchanger  42 . The air stream  19  is heated at the first heat exchanger  16  when the refrigerant circuit  12  is operating in the first mode. 
     The present invention can also include a conduit  46 . As shown in FIG. 4, the conduit  46  is formed of a first portion  48  and a second portion  50 . The conduit  46  includes an inlet  52  and an outlet  54 . The inlet  52  receives the air stream  19  and the outlet  54  expels the air stream  19 . The conduit  46  also includes a first chamber  56 , a second chamber  58  and a third chamber  60 . The first chamber  56  is positioned between the inlet  52  and the third heat exchanger  42 . The second chamber  58  is positioned between the third heat exchanger  42  and the first heat exchanger  16 . The third chamber  60  is positioned between the outlet  54  and the first heat exchanger  16 . 
     The conduit  46  also includes a second inlet  62 . The inlet  62  communicates with the conduit  46  adjacent the second chamber  58 . A second air stream  23  can enter the conduit  46  through the inlet  62  and bypass the third heat exchanger  42 . Bypassing at least a portion of the air stream  19  around the third heat exchanger  42  can be desirable when the third heat exchanger  42  exceeds a predetermined temperature sufficient to cause condensation of water vapor in the air stream  19 . As the temperature of the third heat exchanger  42  increases, the capacity and efficiency of the third heat exchanger  42  can decrease. Bypassing at least part of the air stream  19  can return the operating temperature of the third heat exchanger  42  to below an upper threshold value. 
     The operating temperature of the third heat exchanger  42  can be monitored by monitoring the temperature of the water stream  21  with the sensor  40 . As the circuit  14  operates over time, the temperature of the water stream  21  can increase based on the capacity and efficiency of the system. In particular, the amount of heat absorbed by the water stream  21  at the third heat exchanger  42  may not be completely transferred to the refrigerant stream  17  at the second heat exchanger  18 . If a net heat gain occurs, the temperature of the water stream  21  will increase and will cause the temperature of the third heat exchanger  42  to increase. As the temperature of the third heat exchanger  42  increases, the efficiency of the third heat exchanger  42  will decrease and less humidity will condensate on the third heat exchanger  42 . Therefore, it is desirable in the present invention to reduce the likelihood that the temperature of the water stream  21  will increase. An air stream  23  can be received in the second chamber  58  to reduce the flow rate of air stream  19  passing relative to the third heat exchanger  42  if the temperature of the water stream  21  increases. Reducing the flow rate of air stream  19  will reduce the thermal load of the third heat exchanger  42  while being less efficient in removing water vapor from the combined air stream. In other words, the temperature of the water stream  21  is monitored to ensure that the temperature is maintained below the dew point of the air stream  19 . 
     The invention can also include a damper  64  for controlling the air stream  23  entering the second chamber  58  of the conduit  46  through the inlet  62 . The damper  64  can be moveable to a plurality of positions between an open position and a closed position, for generating a range of airflows through the inlet  62 . The controller  66  can control the damper  64  to move in response to the temperature of the water stream  21  entering the third heat exchanger  42 . In operation, the sensor  40  senses the temperature of the water stream  21  entering the third heat exchanger  42  and emits a signal to the controller  66  corresponding to the temperature of the water stream  21 . As the temperature of the water stream  21  increases, the controller  66  can move the damper  64  from a relatively closed position to a more open position to increase the flow rate of the air stream  23  bypassing the third heat exchanger  42 . 
     The conduit  46  can also include a third inlet  68 . The third inlet  68  communicates with the conduit  46  adjacent the third chamber  60 . A third airstream  25  can enter the third chamber  60  through the inlet  68  to bypass both the third heat exchanger  42  and the first heat exchanger  16 . If the temperature of the water stream  21  increases after the damper  64  has been moved to the open position, the third air stream  25  can be received by the third chamber  60  to bypass both the third heat exchanger  42  and the first heat exchanger  16 . The invention can also include a damper  70  for controlling the air stream  25  entering the third chamber  60  of the conduit  46  through the inlet  68 . The damper  70  can be moveable to a plurality of positions between an open position and a closed position for generating a range of airflows through the inlet  68 . The controller  66  can control the damper  70  to move in response to the temperature of the water stream  21 . In operation, the sensor  40  senses the temperature of the water stream  21  entering the third heat exchanger  42  and emits a signal to the controller  66  corresponding to the temperature of the water. As the temperature of the water stream  21  increases, the controller  66  can move the damper  70  from a relatively closed position to a more open position to increase flow rate of the air stream  23  bypassing the third heat exchanger  42 . By diverting air around the third heat exchanger  42 , the temperature of the third heat exchanger  42  will be less likely to increase beyond the upper threshold value sufficient to cause condensation of water vapor in the air stream  19 . 
     FIG. 4 shows a first portion  48  of a conduit  46  having a common inlet  52  and a plurality of conduits  106 ,  108  and  110  extending from the inlet  52  to the third heat exchanger  42 , the inlet  62  and the inlet  68 , respectively. However, the conduit  46  can be formed as a single conduit  106  having apertures forming inlets  62  and  68  without conduits  108  and  110  if desired. The embodiment of the invention as shown in FIG. 4 is illustrative and not restrictive. 
     The simplified flow diagram of FIG. 5 shows the steps for opening the dampers  64  and  70  with the sensor  40  and the controller  66 . The process starts at step  72 . Step  74  monitors the temperature of the water stream  21  entering the third heat exchanger  42 . If the temperature has increased, the process continues to step  76  as shown in FIG.  5 . Step  76  monitors whether the primary damper  64  is in the open position. If the primary damper  64  is not in the fully open position, step  78  opens the primary damper  64  a predetermined amount. The primary damper  64  can be moved incrementally to the fully open position when a temperature increase is detected by the controller  66  or can be moved to a proportional position between the open and closed positions depending on the magnitude of the temperature variance from the upper threshold value. If the primary damper  64  is in the fully open position when monitored at step  76 , step  80  monitors whether the secondary damper  70  is in the fully open position. If the secondary damper  70  is in the fully open position, the process returns to step  74 . If the secondary damper  70  is not in the fully open position, step  82  incrementally opens the secondary damper  70  a predetermined amount. The secondary damper  70  can be moved to the fully open position at step  82  by the controller  66  or can be moved incrementally or proportionally moved to a position between the open and closed positions depending on the magnitude of the temperature variance from the upper threshold value. The process returns to step  72  after step  82 . If both dampers  64  and  70  are in the fully open position, a maximum amount of air is being bypassed with respect to the third heat exchanger  42  and the first heat exchanger  16 . 
     The simplified flow diagram of FIG. 6 shows the steps for closing the dampers  64  and  70  with the sensor  40  and the controller  66 . With reference to FIGS. 5 and 6, if the temperature of the water has not increased at step  74 , step  84  monitors whether the temperature of the water stream has decreased. If the temperature has not decreased, the process returns to step  72 . Whether the temperature has decreased can be determined based on a preferred temperature or an upper threshold temperature and a lower threshold temperature. The controller can be programmable for the threshold value of temperature of the water stream. The temperature can be selected based on the temperature of water entering the circuit, such as water drawn from a geothermal source. 
     If the temperature has decreased at step  84 , step  86  monitors whether the secondary damper is at least partially open. If the secondary damper is at least partially open, the process continues to step  88  and the secondary damper is incrementally closed a predetermined amount. The predetermined amount can be completely closed or partially closed or proportionally closed depending on the magnitude of the temperature variance from the threshold value. If the secondary damper is not at least partially open when monitored at step  86 , the process continues to step  90 . Step  90  monitors whether the primary damper is at least partially open. If the primary damper is not at least partially open, the process returns to step  72 . If the primary damper is at least partially open when monitored at step  90 , the process continues to step  92 . Step  92  incrementally closes the primary damper a predetermined amount. The predetermined amount can be fully closed or partially closed or proportionally controlled depending on the magnitude of the temperature variance from the threshold value. The process then returns to step  72 . As the temperature of the water entering the third heat exchanger increases, the efficiency and the dehumidification capacity of the third heat exchanger decreases. The temperature of the water stream can increase as the system operates over a period of time depending on the refrigeration capacity of the refrigerant circuit. 
     The invention can include a blower  112 , as shown in FIG.  1 . The blower  112  can direct the air stream  19  across the first heat exchanger  16  and can direct the air stream  19  across the third heat exchanger  42 , as shown in FIG.  4 . The blower  112  can be operated by the controller  66  in accordance with a control program stored in memory. The controller  66  can control the blower  112  to generate a forced air stream  19 . The circuit  12  can also include a heater  114 . The heater  114  can generate heat to be transferred to the air stream  19 . The heater  114  can be operated by the controller  66  in accordance with a control program stored in memory to control the operation of the heater  114 . The circuit  12  can also include a filter  32  for the refrigerant. 
     As shown in FIG. 4, the second circuit  14  can receive water from an external source  97 , shown schematically. The second circuit  14  can include an inlet  94  and an outlet  96  in communication with the source  97 . The source  97  can be an open loop geothermal source, a closed loop geothermal source, or a boiler/cooling tower. The heat sink circuit  14  can also include a pump  98  for moving the water stream  21  along the heat sink circuit  14 . The heat sink circuit  14  can also include a check valve  100  to control the flow of the water stream  21  and prevent backflow with respect to the pump  98 . The pump  98  can be operated by the controller  66  in accordance with a control program stored in memory. The heat sink circuit  14  can include a solenoid valve  117  and a flow controller  118 . The valve  117  can be opened to discharge water from the source  97  into the heat sink circuit  14 , or closed to prevent water from leaving the heat sink circuit  14  through outlet  96 . The flow controller  118  can be adjusted to control an exiting flow rate of the water stream  21 . When valve  117  is closed and check valve or back-flow preventer  100  is open water will be circulated through the heat sink circuit  14  by operation of pump  98 . 
     Referring now to FIG. 7, the heat sink circuit  14   a  can include a hydronic pump  104  for moving a mixture of water and glycol along the heat sink circuit  14   a.  The hydronic pump  104  can be controlled by the controller  66   a.  The heat sink circuit  14   a  can include a valve  120  to divert the water/glycol stream  21   a  from the third heat exchanger  42   a  to a fifth heat exchanger  122 . The fifth heat exchanger  122  can transfer heat from the water stream  21   a  or transfer heat to the water/glycol stream  21   a.  The other components illustrated in FIG. 7, namely refrigerant circuit  12   a,  first heat exchanger  16   a,  second heat exchanger  18   a,  conduit  46   a,  and dampers  64   a  and  70   a,  are operated as previously described with respect to FIGS. 1-6 except for the changes as noted. 
     Referring now to FIG. 8, a fifth heat exchanger  123  can transfer heat from the water stream  21   b  to water from a swimming pool  124 . The other components illustrated in FIG. 8, namely refrigerant circuit  12   b,  first heat exchanger  16   b,  second heat exchanger  18   b,  conduit  46   b,  and dampers  64   b  and  70   b,  are operated as previously described with respect to FIGS. 1-6 except for the changes as noted. 
     The apparatus dehumidifies the airstream  19  while the refrigerant circuit  12  is operated in the first mode. The blower  112  can generate the airstream  19  across the third heat exchanger  42  and the first heat exchanger  16 . The pump  98  (shown in FIG. 4) pumps the water stream  21  through the heat sink circuit  14 . The water stream  21  is directed through the third heat exchanger  42 . In an alternative embodiment of the invention, pump  104  (shown in FIG. 7) pumps the water/glycol stream  21   a  through the heat sink circuit  14   a.  Valve  120  can be selectively switched to direct the water/glycol stream  21   a  through the third heat exchanger  42   a  or the fifth heat exchanger  122 . As shown in FIG. 1, the refrigerant circuit  12  can include a heater  114 . The heater  114  can be operated to heat the air stream  19  after water vapor has been removed from the air stream  19  prior to discharge into the pool area. 
     The apparatus can be used to heat the airstream  19  without removing water vapor from the air stream  19  while the refrigerant circuit  12  is operated in the first mode. The blower  112  generates the airstream  19  across the third heat exchanger  42  and the first heat exchanger  16 . The pump  98  (shown in FIG. 4) is disengaged and solenoid valve  117  is opened to discharge the water stream  21  out of the outlet  96 . The air stream  19  can be heated by passing across the first heat exchanger  16 . The heater  114  can be engaged to further heat the air stream  19 . 
     The apparatus can be used to heat the water stream  116  and remove water vapor from the air stream  19  while the refrigerant circuit  12  is operated in the second mode. The blower  112  generates the airstream  19  across the first heat exchanger  16  and the third heat exchanger  42 . The pump  98  (shown in FIG. 4) pumps the water stream  21  through the heat sink circuit  14  and solenoid valve  117  is closed. Water vapor will be removed from the air stream  19  at the third heat exchanger  42 . The heater  114  can be operated to further heat the air stream  19  after water vapor has been removed from the air stream  19  in the third heat exchanger  42  and the air stream  19  has been preheated by passing through first heat exchanger  16 . 
     The apparatus can be used to cool and dehumidify the airstream  19  while the refrigerant circuit  12  is operated in the third mode. The blower  112  generates the airstream  19  across the first heat exchanger  16  and the third heat exchanger  42 . The pump  98  (shown in FIG. 4) is disengaged and solenoid valve  117  is opened to discharge the water stream  21  out of the outlet  96 . The air stream  19  can be cooled and water vapor can be removed from the air stream  19  by passing across the first heat exchanger  16 . 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.