Abstract:
The present invention comprises an improved refrigerant based heat exchange system useful in air conditioning and refrigeration applications. Improved heat transfer capability is achieved by using a dual heat exchanger with two different heat-transfer mediums, air and water, in one condenser unit and by advancing the water transfer medium ahead of the air transfer medium. Bypass controls are provided for bypassing a selected heat exchange section of the system depending upon existing environmental conditions. The system is optionally housed in a decorative facade which provides an exposed surface adorned with esthetically pleasing artwork.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority from a provisional application Ser. No. 60/654,618, filed Feb. 17, 2005, by Eric Barger, entitled “Heat Exchanger For Evaporative Cooling Refrigeration System.” 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to refrigerant based heat exchange systems employing a compressor, a condenser, an evaporator and associated fluid circuitry used for air conditioning, food storage refrigeration, and similar applications, and to improvements in the condenser sections of such systems.  
         [0004]     2. Description of the Prior Art  
         [0005]     In a typical commercially available air conditioning or refrigeration unit, a condensable refrigerant is compressed, condensed, cooled and then supplied to a metering device and evaporator for cooling a surrounding environment. The condensers of such refrigeration systems are usually cooled by ambient air or by water supplied from an external source. The following references are intended to be merely illustrative or representative of the general state of the art in air, water and air/water cooled condensing heat exchangers.  
         [0006]     U.S. Pat. No. 5,832,739, issued Nov. 10, 1998, to Bacchus, shows an air conditioner operating on a compressor-condenser circuit which utilizes water cooled by air flowing over an evaporative medium through which the water flows to cool a condenser coil located in a continuous serpentine channel in a sump member located at the lower side of the air conditioner unit. This unit is a purely water cooled unit which fails to offer redundancy in the form of an auxiliary water coil in addition to the air coil. At certain times of the year, i.e., under freezing conditions, a water cooled only unit may freeze up or fail to function efficiently. Purely water cooled units are also more likely to fail due to maintenance requirements.  
         [0007]     U.S. Pat. No. 4,182,131, issued Jan. 8, 1980, to Marshall et al., shows an air conditioning system in which the Freon passes first to an air coil, and secondly to a water bath. The water which is heated up in the sump region of the device is passed over evaporative media to provide a cooling effect and make heat transfer over the air coil more effective.  
         [0008]     U.S. Pat. No. 6,862,894, issued Mar. 8, 2005, to Miles, Sr., describes a piggy-back type water cooled auxiliary condenser device used in a food refrigeration system. The water cooled system provides failure detection and a stop-gap solution for failure of the air cooled coil. The refrigerant in the system is circulated first to the air cooled coil and secondly to the water cooled auxiliary coil if the air cooled coil fails.  
         [0009]     U.S. Pat. No. 6,748,759, issued Jun. 15, 2004, to Wu, shows a heat exchanger having vertical cooling fins with a drip-drop type water feeding box for feeding water drops to the top of the cooling fins. The refrigerant is circulated in a path which is acted upon simultaneously by both air and water cooling effects.  
         [0010]     U.S. Pat. No. 6,857,285, issued Feb. 22, 2005, to Hebert, shows a system which achieves an increased refrigeration effect in which the liquid refrigerant line coming off of an air condenser of an air conditioner is serially connected to a water subcool and/or pre-cool heat exchanger before being connected to the line leading to the expansion device of an air conditioning, refrigeration or heat pump system.  
         [0011]     Although certain of the devices shown in the above discussed patent literature utilize a combination of air cooling and water cooling in an air conditioning system, the present invention provides a number of improvements in the operation and design of such systems, as well as providing superior energy efficiency over state of the art systems.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention accordingly has as one object to provide an improved heat exchanger design which improves and facilitates the heat transfer effect achieved within the condenser section of the heat exchanger.  
         [0013]     Another object of the invention is to provide a heat exchanger with improved heat transfer between the condenser and refrigerant circulated through the condenser by using a dual heat exchanger with both air and water heat transfer mediums in one condenser unit and advancing the water transfer medium ahead of the air transfer medium.  
         [0014]     Another object of the invention is to provide an improved air conditioning system which utilizes a condenser section having both a water cooled sub section and an air cooled sub section to provide, improved operating efficiency, redundancy, and the ability to operate in cold ambient conditions where freezing might otherwise inhibit the use of water cooling.  
         [0015]     Another object of the invention is to provide a condenser circuit for an air conditioning system having both water and air cooled subsections, in which the water cooled sub section is always located before the air cooled subsection to provide an initial cooling effect using water, thereby increasing the efficiency of the system.  
         [0016]     Another object of the invention is to provide a condenser circuit for an air conditioning system having both water and air cooled subsections which is provided with appropriate by-pass circuitry for optionally by passing a selected one of the cooling subsections.  
         [0017]     In one broad aspect, the present invention comprises a refrigerant based heat exchange system including a condensing heat exchanger and an evaporating heat exchanger connected in a refrigerant circuit. A compressor circulates refrigerant between the condensing heat exchanger and the evaporating heat exchanger in the refrigeration circuit. The condensing heat exchanger includes both a water cooled subsection and an air cooled subsection for redundancy. By pass means are provided, as a part of the refrigerant circuit, for alternately directing the flow of refrigerant in the refrigerant circuit through either or both of the water cooled subsection and the air cooled subsection of the condensing heat exchanger.  
         [0018]     In one case, the water cooled subsection and the air cooled subsection are located in series in the refrigerant circuit and the water cooled subsection precedes the air cooled subsection.  
         [0019]     In another case, the water cooled subsection and the air cooled subsection are arranged in parallel fashion within the refrigerant circuit and wherein a control valve is located in the refrigerant line ahead of each subsection, the valves being operable to direct refrigerant first to the water cooled subsection when both the subsections are being utilized.  
         [0020]     Both the water cooled subsection and the air cooled subsection of the condensing heat exchanger include heat exchange surface areas, and wherein air flow from a source of forced air is used to provide a cooling effect over at least the air cooled heat exchange surface area, and wherein the source of forced air is arranged so that the air flow always contacts the heat exchange surface area of the air cooled subsection prior to contacting the heat exchange surface area of the water cooled subsection of the condensing heat exchanger.  
         [0021]     In one version of the refrigerant circuit, each of the water cooled subsection and the air cooled subsection of the condensing heat exchanger has a refrigerant line in and a refrigerant line out and a by pass line connecting the two and a check valve located downstream of the respective heat exchanger subsection, and wherein a valve means precedes each subsection for directing flow of refrigerant to the heat exchanger subsection or to the by pass line.  
         [0022]     In another version of the refrigerant circuit, each of the water cooled subsection and the air cooled subsection of the condensing heat exchanger has a refrigerant line in and a refrigerant line out and a by pass line connecting the two and a check valve located downstream of the respective heat exchanger subsection, and wherein a T-junction is located upstream of each heat exchanger subsection, the T-junction being isolated by a pair of solenoid valves for directing flow of refrigerant to the heat exchanger subsection or to the by pass line.  
         [0023]     In yet another version of the refrigerant circuit, a header is located downstream of the compressor, the refrigerant flow being split at the header and directed to the water cooled subsection and the air cooled subsection in parallel fashion, and wherein a check valve is located downstream of each subsection, the flow of refrigerant from the respective subsections being recombined in a second header located in the refrigeration circuit.  
         [0024]     Preferably, the water cooled subsection and the air cooled subsection are both packaged within a common housing. Most preferably, at least the water cooled subsection is housed within an artistic facade which is selected from the group consisting of water falls and decorative fountains. The artistic facade which houses at least the water cooled subsection can be comprised of a base enclosure and a frame which extends upwardly from the base enclosure, the frame forming an exposed surface or plane for presenting artwork selected by a user of the system. Preferably, the base enclosure houses at least the compressor, the water and air cooled subsections and a receiver. The base can also be provided with an exposed water basin on an upper surface thereof and with the frame supporting selected evaporative cooling media. In this case, the system can further comprise a water source and associated piping for supplying cooling water to the evaporative cooling media, the water being collected downstream in the water basin.  
         [0025]     In the method of the invention an air conditioning apparatus is provided wherein a refrigerant is circulated between a condensing heat exchanger and an evaporating heat exchanger in a refrigerant circuit by a compressor. The efficiency of the apparatus is improved by providing both a water cooled subsection and an air cooled subsection in a redundant arrangement as a part of the condensing heat exchanger, and by providing a by pass means for alternately directing the flow of refrigerant in the refrigerant circuit through either or both of the water cooled subsection and the air cooled subsection of the condensing heat exchanger.  
         [0026]     In a particularly preferred version of the invention, the system comprises a heat exchanger for an air conditioner system using a combination of air-cooling and water-cooling with appropriate motor controls for adjusting the speeds of the compressor, the condenser water pump and fan and the evaporator fan. The heat exchanger is adapted for use in a typical compressor-condenser-evaporator air conditioning system and specifically to the condenser unit of the system. A networking feature can also be provided to enable such features as system status, statistics gathering and an alarm functionality. A two way communication feature would also allow remote control and configuration.  
         [0027]     Additional objects, features and advantages will be apparent in the written description which follows.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is a schematic diagram of a heat exchange system of the invention showing the water subsection and the air cooling subsection of the system arranged in series.  
         [0029]      FIG. 2  is a schematic diagram, similar to  FIG. 1 , but showing a heat exchange circuit in which the water and air cooling subsections are arranged in parallel fashion.  
         [0030]      FIG. 3A  is a schematic representation of one arrangement of the air flow pattern in the heat exchange system of the invention.  
         [0031]      FIG. 3B  is a schematic representation of an alternative air flow pattern in the system of the invention.  
         [0032]      FIG. 4  is a schematic representation of one embodiment of the by pass circuitry used with one of the heat exchange subsections of the system of the invention.  
         [0033]      FIG. 5  is a schematic representation, similar to  FIG. 4 , showing another embodiment of the by pass circuitry used with the heat exchanger subsection.  
         [0034]      FIG. 6  is a similar view of the by pass circuitry in the parallel version of the heat exchange subsection of the invention.  
         [0035]      FIG. 7  is a top view, partly schematic, of one embodiment of the heat exchange system of the invention showing the principal components of the refrigerant circuit with a cooling tower as the water subsystem implementation.  
         [0036]      FIG. 8  is a side view of one form of the heat exchange system of the invention which is housed in a decorative fountain or waterfall.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]     The refrigerant based heat exchange system of the invention can be utilized to improve the efficiency of a conventional refrigerant type air conditioning system where a refrigerant such as Freon is circulated by compressor between an evaporator section and a condenser section, wherein it is respectively changed between liquid and gaseous states to effect cooling in the evaporator unit.  
         [0038]     The conventional Freon type air conditioning circuit includes a compressor, condenser, a metering device and an evaporator connected in series in a refrigerant circuit. The system is charged with refrigerant, which circulates through each of the components in order to remove heat from the evaporator and transfer heat to the condenser. The compressor compresses the refrigerant from a low pressure superheated vapor state to a high pressure superheated vapor state, thereby increasing the temperature and pressure of the refrigerant. The refrigerant medium leaves the compressor and enters the condenser as a vapor at an elevated pressure. The condenser condenses the refrigerant vapor at substantially constant pressure to a saturated liquid state as a result of the heat transfer in the condenser, typically accomplished with either cooling water or to ambient air. The refrigerant then leaves the condenser as a high pressure liquid. The pressure of the liquid is decreased as it flows through a metering device, such as an expansion type valve, causing the refrigerant to change to mixed liquid-vapor state. The remaining liquid, now at low pressure, is vaporized in the evaporator section of the system as a result of heat transfer from the space being cooled. This vapor then enters the compressor to complete the cycle.  
         [0039]     The above described type vapor-compression refrigeration cycle has, for many years, been the pattern for the majority of commercially available air conditioning and refrigeration systems in the marketplace. The present invention is directed to improvements in such systems, and particularly to the condenser sections of such systems.  
         [0040]     Turning to  FIG. 1 , there is shown one version of the refrigerant based heat exchange system of the present invention. As described with respect to the conventional Freon-type air conditioning system, the system includes a compressor  11 , a condensing heat exchanger section, designated generally as  13 , a receiver  15 , a metering device such as an expansion valve  17 , and an evaporator section  19 .  
         [0041]     The compressor  11  circulates refrigerant, such as Freon or another suitable compressible refrigerant, between the condensing heat exchanger section  13  and the evaporating heat exchanger  19  in the refrigeration circuit. The receiver  15  stores liquid refrigerant. If multiple condenser modes of the system require multiple refrigerant charges, the receiver acts as a buffer. The receiver  15  also provides storage that may be used at startup when a conventional system would require additional time to build up pressures sufficient to facilitate the required heat exchange.  
         [0042]     As will be apparent from  FIG. 1 , the condensing heat exchanger section  13  includes both a water cooled subsection  21  and air cooled subsection  23 . The air subsystem  23  can conveniently comprise a finned coil arrangement, of the type previously described, over which air from an air source is forced. It will be appreciated that any other type of conventional heat exchanger component, known to those skilled in the relevant arts, could be used, as well. The water subsystem  21  can also comprise a finned coil or plate, but also comprise a cooling tower, cooling pads, or an external water source that serves as a heat sink. The heat sink embodiment would include, for example, a swimming pool, pond, lake, ground water source, or the like. As will be described in greater detail, the water subsystem can also comprise a decorative or artistic facade in the form of a water fountain or water fall, or similar design. One preferred heat exchange media for the water subsystem is a resin coated corrugated-type cardboard “pad” over which water is allowed to flow.  
         [0043]     As will be apparent from  FIG. 1 , the water subsystem  21  and air subsystem  23  are both equipped with bypass means  27 ,  29  for alternately directing the flow of refrigerant in the refrigerant circuit  25  through either or both of the water cooled subsection  21  and the air cooled subsection  23  of the condensing heat exchanger.  
         [0044]     In the version of the invention illustrated schematically in  FIG. 1 , note that the water cooled subsection  21  and the air cooled subsection  23  are located in series in the refrigerant circuit  25  with the water cooled subsection  21  preceding the air cooled subsection. The system shown in  FIG. 1  thus utilizes both an air cooled subsystem and a water cooled subsystem to achieve an improved operating efficiency, redundancy, and the ability to operate in cold ambient conditions where freezing might otherwise inhibit the use of water cooling. The water cooled subsection  21  is placed before the air cooled subsection  23  in the refrigeration circuit  25  to facilitate speedy heat exchange using water, thereby maximizing reduction in compressor load. The bypass means  27 ,  29  will be described later in greater detail.  
         [0045]      FIG. 2  shows another version of the refrigerant based heat exchanger of the invention wherein the water cooled subsection  31  and the air cooled subsection  33  are arranged in parallel fashion within the refrigeration circuit  35 . Otherwise, the remaining components of the receiver  37 , expansion valve  39 , evaporator  41  and compressor  43  are identical to the components previously described with respect to  FIG. 1 . In this case, a control valve  45 ,  47 , is located in the refrigerant line  35  ahead of each subsection  31 ,  33 . Check valves  32 ,  34  are located downstream of each subsection. The valves  45 ,  47  can be operated to selectively control the flow of refrigerant to the respective cooling subsections  31 ,  33 . In normal operations, the valves  45 ,  47  split the flow or refrigerant to the respective subsections  31 ,  33 . As a practical matter, more refrigerant will tend to flow to the water subsection  31  because it cools faster and therefore has a lower temperature than the air subsection  33 . In other words, a high temperature difference dictates that the path of least resistance will be the water subsection  31 , similar to parallel resistors in an electrical circuit.  
         [0046]     As illustrated schematically in  FIGS. 3A and 3B , both the water cooled subsection  49  and the air cooled subsection  51  of the condensing heat exchanger include heat exchange media with heat exchange surface areas. The surface areas could comprise, for example, finned coils, corrugated pads, and other suitable heat transfer surface materials, commercially available in the air conditioning and refrigeration industries. The materials used in conventional air cooled refrigerant heat exchangers risk corrosion in the presence of water and, therefore, the ultimate reliability of the system could be jeopardized. The system of the invention addresses this potential problem through the arrangement or placement of the respective heat exchanger subsections.  
         [0047]     In the present system, air flows from a source of forced air  53  (for example provided by a fan) to provide a cooling effect over the heat exchange surfaces before being returned as outdoor ambient air  54 . To avoid corrosion of the air subsection heat transfer elements (e.g., the air coil), the source of forced air  53  will always be arranged so that the air forced over the water subsystem will never be directed over the air coil. This is accomplished by either having the air subsystem and water subsystem  51 ,  49  respectively arranged in series as shown in  FIG. 3A  or by having an air flow isolator  56  (such as a baffle) which separates the subsystems, as shown in  FIG. 3B . Thus, the air may flow from outside the unit, through the air coil first, and then through the wet evaporative media. Alternatively, two separate fans and openings in the system enclosure may allow for the selective introduction of air flow across one heat exchanger or the other. A third variation of the system would be to provide multiple fans and dampers to direct the flow of air to the air coil only or to the water evaporative media only. Finally, a single fan and baffle arrangement, such as that shown in  FIG. 3B  can be utilized.  
         [0048]     The previously described refrigerant based heat exchange system can be implemented in any of a number of ways. The following examples are intended to be merely illustrative.  FIG. 4  shows a heat exchange sub  57  which could be either the air subsystem  51  or water subsystem  49 , previously described. The heat exchange sub  57  has a refrigerant line in  59 , a refrigerant line out  61  and a bypass line  63  connecting the two. Valve means are provided to selectively effect a by pass of refrigerant around the respective heat exchange sub. In the embodiment illustrated in  FIG. 4 , a three-way valve  67 , precedes each subsection  57  for directing the flow of refrigerant to the heat exchanger subsection or to the bypass line  63 . That is, the valve  67  opens on one side and closes on the other in one action to direct the flow of refrigerant to the subsystem or to the bypass. A check valve  65  is located downstream of the respective heat exchanger subsection  57 .  
         [0049]      FIG. 5  shows another means of bypassing refrigerant about a heat exchange sub  69 . This sub  69  again has refrigerant line in  71 , a refrigerant line out  73  and a bypass line  75  connecting the two.  
         [0050]     A check valve  77  is located downstream of the respective heat exchanger subsection  69 . A T-junction  79  is located upstream of each heat exchanger subsection  69 . The T-junction is isolated by a pair of solenoid valves  81 ,  83  for directing the flow of refrigerant to the heat exchanger subsection or to the bypass line. That is, one of the solenoid valves  81 ,  83  is normally open while the other is normally closed. Both valves can be connected to the same control signal.  
         [0051]      FIG. 6  shows the parallel version of the system in which the water sub  85  and the air sub  87  are located in parallel fashion within the refrigerant circuit  89 . Hot refrigerant gas leaves the compressor  91  and enters a T-junction, which in this case is represented as a header  93 . The header  93  splits the path of the refrigerant between the air sub  87  and the water sub  85  of the system. Solenoid valves  95 ,  97  on either side of the header determine which subsystem  85 ,  87  will operate, or if both subsystems will operate simultaneously. Following each subsystem,  85 ,  87  is a check valve,  99 ,  101  which insures that refrigerant flows in only one direction. Each branch of the parallel subsystem is then attached to a second header  103  which recombines the refrigerant flow and leads the receiver  105 . Following the receiver is a metering device, such an expansion valve  107  and the traditional evaporator sub  109 , previously described.  
         [0052]      FIG. 7  of the drawings illustrates one physical embodiment of the principles of the invention which have been previously described. Many of the components of the system can be varied in accordance with knowledge in the industry generally. For example, the air cooled heat exchange media can comprise a finned coil, a spined coil or plate, etc. The example is merely intended to be illustrative of one possible implementation of the concepts of the invention.  
         [0053]     In the system illustrated in  FIG. 7 , the hot compressed refrigerant in conduit  113  first passes from the compressor  115  through the water cooled subsection of the apparatus which, in this case, is located in a synthetic housing  119 . In the particular apparatus illustrated, the housing  119  is a “roto-mold” plastic housing. However, it will be understood that any material suitable for continuous contact with contaminated water could be utilized. In the housing  119 , a pump  121  causes water to be circulated through cooling “pads”  123  of the type previously described. The roto-molded housing  119  also has a drain means  125  to purge coolant water through a valve or other device for drainage of the housing. The refrigerant then passes out of the housing  119  and through an air-over plate-fin condenser/coil  127  that cools it a second time by virtue of air flowing over an evaporative medium.  
         [0054]     The unit uses a condenser fan  129  to draw air over both the air and water heat exchange media. After passing through the plate-fin condenser/coil  127 , the refrigerant returns to the evaporator coil  123  and then back to the compressor  115 . A supply fan  131  returns supply air cooled by the evaporator coil. A commercially available TRIAC  133  or other digital controller can be implemented to optimize system efficiency.  
         [0055]     The housing  119  is designed to maintain a uniform level of water in the system and the evaporative media (cooling pads) of the system. It can conveniently be designed as a plastic apparatus to keep the water from rusting materials subject to corrosion. In the preferred example shown, the heat exchanger components are incorporated in a plastic apparatus to which a sump pump  135  and a water distributing apparatus  137  are added. A float switch  139  keeps the water level constant. A cut off valve  141  is provided in the water supply line to cut off the water in freezing weather.  
         [0056]     The exemplary system can be equipped with a pressure temperature switch (thermostat) and/or humidistat and/or thermister (thermocouple temperature probe) or other controls to control the fan speeds to maintain the appropriate refrigerant pressure. The fan speed is preferably digitally controlled to provide optimum condensation, temperature difference and pressures. A control system using a microprocessor can be provided to manage the mechanical operation of the unit.  
         [0057]     This following discussion is intended to be illustrative of a simple control system, which could be used to manage the mechanical operation of the unit.  
         [0000]     Inputs:  
         [0058]     Float switch or water level sensor to sense water level in the sump basin.  
         [0059]     Detection of external thermostat/control system turning the condenser unit on.  
         [0060]     A temperature sensor to sense outdoor ambient temperature.  
         [0000]     Water Flow Malfunction Detection:  
         [0061]     For example a high pressure switch on the hot gas refrigerant. If the water system is failing, the compressor head pressure will rise, signaling to switch to the air subsystem.  
         [0000]     Outputs:  
         [0062]     Switched output to turn the compressor on and off.  
         [0063]     Switched output(s) to start the condenser fan(s).  
         [0064]     Switched output to start the water pump.  
         [0065]     Switched output to open the fill valve.  
         [0066]     Switched output to open a drain valve or drain pump.  
         [0067]     Switched output to control water subsystem bypass.  
         [0068]     Switched output to control air subsystem bypass.  
         [0000]     Alarm Light or Sound Indicator:  
         [0069]     Signaling water flow malfunction or other detected problem in the system operation.  
         [0000]     Communication:  
         [0070]     Optionally, a communication interface that enables the control system to indicate status and alarm conditions to the consumer, facilities manager, or service provider (contractor). This can comprise, for example, an onboard control module using “Blue Tooth,” TCIP, cellular infrared, or other similar technology to provide a communication interface. The type of interface is customer-specific. 802.11 standards are common in most homes today. Energy management and building automation systems may also be used (such as LonWorks, Modbus, Zigbee, etc.)  
         [0071]     The above described system is intended to be merely illustrative of a simple control system to manage the mechanical operation of the system. A separate motor controller and fan controller(s) may also be provided.  
         [0072]      FIG. 8  shows a particular type of packaging or housing for a preferred system of the invention. In this embodiment of the invention, at least the water cooled subsection of the refrigerant based heat exchange system is housed within an artistic facade which is selected from the group consisting of water falls and decorative fountains. For example,  FIG. 8  shows an artistic facade comprised of a base enclosure  143  and a frame  145  which extends upwardly from the base enclosure, the frame forming an exposed surface or plane  147  for presenting artwork selected by a user of the system.  
         [0073]     Preferably, the base enclosure  143  houses at least the compressor (shown as  149  in  FIG. 8 ), the water and air cooled subsections and a receiver. For example, with respect to  FIG. 8 , the base  143  includes an exposed water basin  151  on an upper surface  153  thereof and wherein the frame  145  supports selected evaporative cooling media  155 . The system further comprises a water source and associated piping  157  for supplying cooling water to the evaporative cooling media  155 , the water being collected downstream in the water basin  151 . The water source can be, for example, the water supply line and control valve  141  and the sump pump  135  described in  FIG. 7 .  
         [0074]     The control system for this embodiment of the invention may be implemented in any convenient fashion. For example, a mechanical or electrical float switch ( 139  in  FIG. 7 ) is used to determine if the water basin  151  needs to be filled to make up for water loss due to evaporation, or if the basin is empty for any reason. The control system operates a fill valve to fill the basin. The control system can utilize a temperature sensor to determine if water is to be used at all, that determination being a part of the decision criteria of the fill valve. A drain valve is used to empty the basin if the previously mentioned temperature sensor determines that there is a risk of equipment damage due to freezing.  
         [0075]     An invention has been provided with several advantages. The refrigerant based heat exchange system of the invention can be used in a variety of air conditioning and refrigeration type settings to provide improved efficiency, thereby saving on energy costs. By having a condensing heat exchanger with a water cooled subsection which precedes the air cooled subsection, more efficient cooling can be achieved using water for the heat exchange medium. The provision of appropriate bypass means for the subsections allows the water subsection to be diminished or eliminated under selected conditions, for example, in freezing weather. Air flow through the unit is always over the air cooled heat exchange media prior to passing to the water cooled subsection, thereby eliminating the possibility of corrosion or deterioration of the components of the system in contact with tap water or other contaminants. The major components of the system can be housed in a decorative facade which presents a pleasing esthetic appearance for the user. For example, the housing can comprise a decorative waterfall or decorative fountain.  
         [0076]     While the invention has been shown in only two of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof.