SYSTEM FOR ENVIRONMENTAL PROTECTION OF A HEAT EXCHANGER
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to the protection of heat exchangers  such as air conditioner (AC) heat exchangers  from environmental debris.
[0002] A heat exchanger is a device that is used to transfer heat from one medium to another. For many heat exchanging systems  air serves as the target medium to which heat is transferred from some other hot medium (e.g.  hot refrigerant  hot water  steam  etc.). In such systems  the hot medium is typically passed through one or more metallic coils that maximize the contact surface area for the heat exchanging process. Meanwhile  streams of relatively cool air are drawn over the coils  warming the air while cooling the coils and the medium contained therein. Ideally  the surface of the coils should remain free from environmental debris (e.g.  dust  dirt  pollen  etc.)  since this debris can reduce the contact surface area between the air stream and the coils. For example  the debris essentially creates an undesirable insulation layer (e.g.  coil fouling) that can interfere with the heat transfer process. As the efficiency of the heat transfer process begins to decline due to this coil fouling  the efficiency of the entire system is reduced  and as a consequence  the power consumption of the system increases in an attempt to maintain a similar rate of heat transfer. Over time  system components  such as the compressor  may eventually be stressed to the point of failure in attempting to compensate for the lower efficiency. The problem of coil fouling is further exacerbated in refrigerant-based air conditioning systems  wherein the condenser coils are designed to be located in  and exchange air with  the relatively dirty outdoor environment.

BRIEF DESCRIPTION OF THE INVENTION
[0003] Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention  but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed  the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
[0004] In a first embodiment  a system includes an air conditioning unit having an enclosure  a heat exchanger disposed in the enclosure  and a plurality of louvers coupled to the enclosure. The plurality of louvers is configured to move between an open position and a closed position  and the closed position is configured to protect the heat exchanger from an environment external to the enclosure.
[0005] In a second embodiment  a system includes a heat transfer unit with an enclosure having an air intake and an air exhaust  a heat exchanger disposed in the enclosure  a fan configured to direct air flow across the heat exchanger  and a plurality of louvers coupled to the air intake of the enclosure. The plurality of louvers is configured to move from a closed intake position to an open intake position in response to the air flow.
[0006] In a third embodiment  a system includes a heat transfer unit with an enclosure having an air intake and an air exhaust  a heat exchanger disposed in the enclosure  and a plurality of intake louvers coupled to the air intake. The heat transfer unit also includes at least one drive coupled to the plurality of intake louvers. The heat transfer unit also includes a controller coupled to the at least one drive  wherein the controller is configured to actuate the at least one drive to move the plurality of intake louvers between a closed intake and an open intake position  based on an operational state of the heat transfer unit.

BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features  aspects  and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings  wherein:
[0008] FIG. 1 is a schematic of an embodiment of a heat exchanging unit in an inactive state with intake and exhaust louvers in closed positions;
[0009] FIG. 2 is a schematic of an embodiment of the heat exchanging unit of FIG. 1 in an active state with intake and exhaust louvers in open positions;
[0010] FIG. 3 is a schematic of an embodiment of a heat exchanging unit having multiple intake sides with intake louvers;
[0011] FIG. 4 is a perspective view of an embodiment the active heat exchanging unit of FIG. 3;
[0012] FIG. 5 illustrates a block diagram of an embodiment of a vapor compression refrigeration air conditioning system;
[0013] FIG. 6 is a schematic of an embodiment of a heat exchanging unit with the louvers coupled to drives that are controlled by a controller;
[0014] FIG. 7 is a schematic of an embodiment of a mechanism for opening and closing the louvers using a transfer rod  drive  and controller;
[0015] FIG. 8 is a schematic of the embodiment of FIG. 7  illustrating the louvers in the closed position;
[0016] FIG. 9 is a schematic of an embodiment of a mechanism for opening and closing the louvers using a transmission mechanism  drive  and controller;
[0017] FIG. 10 is a side view of an embodiment of a louver assembly configured to mount to an enclosure having a heat exchanger;
[0018] FIG. 11 is a perspective view an embodiment of the louver assembly of FIG. 10; and
[0019] FIG. 12 is a perspective view of an embodiment of an active heat exchanging unit with the louver assembly of FIGS. 10-11.
DETAILED DESCRIPTION OF THE INVENTION
[0020] One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments  all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation  as in any engineering or design project  numerous implementation-specific decisions must be made to achieve the developers’ specific goals  such as compliance with system-related and business-related constraints  which may vary from one implementation to another. Moreover  it should be appreciated that such a development effort might be complex and time consuming  but would nevertheless be a routine undertaking of design  fabrication  and manufacture for those of ordinary skill having the benefit of this disclosure.
[0021] When introducing elements of various embodiments of the present invention  the articles “a ” “an ” “the ” and “said” are intended to mean that there are one or more of the elements. The terms “comprising ” “including ” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
[0022] The disclosed embodiments describe a method of sealing the enclosure of a heat transfer or heat exchanging unit (e.g.  a central air conditioning unit or a window air conditioning unit) using a plurality of louvers. For example  certain disclosed embodiments may include an intake louver assembly  an exhaust louver assembly  or both. In each of the embodiments  the louvers are configured to close when the heat exchanging unit is inactive in order to seal the enclosure and sequester the enclosed heat exchanger from the environment outside of the enclosure. Certain disclosed implementations may include mechanisms for actively controlling the louver assemblies (e.g.  drives  transfer linkages  belts)  while others may employ passive control mechanisms in which the louvers may automatically close due to gravity or a spring force in the absence of an air flow through the heat exchanging unit enclosure.
[0023] FIG. 1 is a schematic of an embodiment of a heat exchanging or heat transfer unit 10. In the depicted embodiment  unit 10 includes a fan 12 and a heat exchanger 14 located within an enclosure 16 having an air intake 18 and an air exhaust 20. The heat exchanger 14 (e.g.  the evaporator or condenser of an air conditioning system) may include a plurality of coils housing a refrigerant path. The unit 10 includes a plurality of intake louvers 22 (e.g.  intake louver assembly 17) attached to the intake 18 of the enclosure 16  and includes a plurality of exhaust louvers 24 (e.g.  exhaust louver assembly 19) attached to the exhaust 20 of the enclosure 16. As illustrated  the intake and exhaust louver assemblies 17 and 19 have louvers 22 and 24 in respective closed intake and exhaust positions 21 and 23. In one embodiment  the intake louvers 22 or the exhaust louvers 24 are designed to be completely contained within the enclosure 16  while other embodiments may include intake louvers 22 or exhaust louvers 24 that are partially or completely disposed on the outside of the enclosure 16. In some embodiments  the intake louvers 22 or exhaust louvers 24 may include a rotational shaft 26  disposed through the length of the louver near the edge or the center of each louver 22 or 24  about which each louver partially rotates 28. Additionally  some embodiments may include a plurality intake louvers 22 or exhaust louvers 24 having shafts oriented horizontally or vertically.
[0024] The depicted embodiment illustrates an inactive unit (i.e. the fan 12 and heat exchanger 14 are not operational) and accordingly the intake louvers 22 and exhaust louvers 24 are in the closed positions 21 and 23 to block debris in the surrounding environment from entering the enclosure 16 to contaminate (i.e. foul) the surface of the heat exchanger 14. In one embodiment  the intake louvers 22 and exhaust louvers 24 are configured to close in the absence of an air flow as a result a force applied by gravity. Accordingly  the louvers 22 and 24 may be made of a lightweight material  such as plastic. Thus  the air flow may automatically open the louvers 22 and 24  while gravity automatically closes the louvers 22 and 24. In another embodiment  the intake 22 and exhaust 24 louvers remain closed in the absence of an air flow as a result of a closing (e.g.  restoration) force applied by a spring  an elastic band  or the like  disposed about the shaft 26 of each louver. For example  the spring may be compressed or extended into a higher energy state as the air flow forces the opening of the louvers 22 or 24  such that the spring biases the louvers 22 or 24 toward closed positions as the air flow drops below a threshold.
[0025] FIG. 2 is a schematic of an embodiment of the heat exchanging unit 10 of FIG. 1  illustrating the louvers 22 and 24 in open positions 25 and 27 during operation of the unit 10. As illustrated  both the heat exchanger 14 and the fan 12 are active. Accordingly  the plurality of intake louvers 22 positioned over the intake 18 of the enclosure 16 and the plurality of exhaust louvers 24 positioned over the exhaust 20 of the enclosure 16 have been rotated 28 about their respective shafts 26 to the open positions 25 and 27. The illustrated embodiment depicts streams of relatively cool air 40 entering the enclosure 16 through the open intake louvers 22  passing over and cooling the heat exchanger 14  and exiting the enclosure 16 as warm air 42 through the action of the fan 12. In one embodiment  during operation of the heat exchanging unit 10  the intake louvers 22 remain open in response to the applied force of the air flow 40  and  similarly  the exhaust louvers 24 remain open in response to the applied force of the air flow 42. In such an embodiment  the force applied to the surface of each intake louver 22 or exhaust louver 24 by the air flows 40 and 42 is sufficient to overcome the closing force applied to the louvers by gravity  a spring  an elastic band  or any combination thereof  putting the louvers 22 and 24 in higher positional potential energy states. As such  when the fan 12 is turned off and the force supplied to the surface of the intake and exhaust louvers 22 and 24 by the air flows 40 and 42 relents  a closing (i.e. restoration) force may be supplied by the particular closing mechanism (e.g.  gravity  spring  etc.) employed to return both the intake and exhaust louvers 22 and 24 to their closed (e.g.  lower potential energy) positions 21 and 23.
[0026] FIG. 3 is a schematic of an embodiment of an active heat exchanging unit 60 with multiple air intake sides and a single air exhaust side having louvers 22 or 24. Like the embodiments of FIGS. 1-2  the heat exchanging unit 60 includes a plurality of louvers that are configured to seal the unit 60 when it is inactive to protect it from the external environment. In such an embodiment  the heat exchanger 14 may be positioned centrally within an enclosure 62 between multiple intake faces 64 and an exhaust face 66. Each intake face 64 has an air intake 18 with an intake louver assembly 17  which includes a plurality of intake louvers 22 selectively movable between an open intake position 21 and a closed intake position 25. The exhaust face 66 has an air exhaust 20 with an exhaust louver assembly 19  which includes a plurality of exhaust louvers 24 selectively movable between an open exhaust position 23 and a closed exhaust position 27. In an active state of the unit 60  the fan 12  forces an air flow 40 through the enclosure 62 to cool the heat exchanger 14  and simultaneously forces the louvers 22 from the closed position 21 and 23 to the open positions 25 and 27. Furthermore  the fan 12 is positioned between the intake faces 64 and the exhaust face 66  thereby forcing the air flow 40 through the heat exchanger 14 prior to exiting the enclosure 62 as the warmed air flow 42. In some embodiments  the exhaust face 66 may be on the top side of the enclosure 62 to direct the warmed air flow 42 vertically upward  taking advantage of the rising action of the lower-density  warm air 42 to further encourage air flows 40 and 42 through the enclosure 62.
[0027] FIG. 4 is a perspective view of an embodiment of the heat exchanging unit 60  illustrating louver assemblies on multiple faces of an enclosure 80 (e.g.  a cubic enclosure) that are configured to sequester the internal components of the heat exchanging unit 60 (e.g.  heat exchanger 14 and fan 12) from the external environment when the unit 60 is inactive. In the illustrated embodiment  the unit 60 has an upper exhaust face 82  and lateral intake faces 84 within the enclosure 80  the unit 60 includes the heat exchanger 14 and fan 12 in an active state. Furthermore  each intake face 84 has a plurality of intake louvers 86 (e.g.  intake louver assembly 85)  while the exhaust face 82 has a plurality of exhaust louvers 88 (e.g.  exhaust louver assembly 87). The louvers 86 and 88 are all disposed in open positions 90 and 92 to enable air flows 40 and 42. Thus  the heat exchanging unit 60 has streams of relatively cool air 40 entering the enclosure 80 through the open intake louvers 86 on the various intake faces 84 of the enclosure 80  passing over and cooling the enclosed heat exchanger 14  and exiting from the top of the enclosure 80 as warm air 42. In another embodiment  the heat exchanging unit 60 may not include a fan and may instead be placed in the path of an air flow produced by another system in order to cool the enclosed heat exchanger 14.
[0028] FIG. 5 illustrates a block diagram of a vapor compression refrigeration air conditioning system 100  wherein a refrigerant is cycled between its vapor and liquid phases through a refrigerant path 102 to affect a transfer of heat from the air inside of a building to the air outside of the building. The depicted embodiment includes the refrigerant path 102 connecting a compressor 104  an outdoor condenser unit 106  an expansion valve 108  and an indoor evaporator unit 110. The depicted condenser unit 106 and evaporator unit 110 include respective heat exchangers (i.e. condenser 112 and evaporator 126 ) and fans (i.e. fans 114 and 128) disposed inside of respective enclosures 16  as discussed above with reference to FIGS. 1 and 2. Accordingly  each enclosure 16 has an intake 18 with a plurality of intake louvers 22  as well as an exhaust 20 having a plurality of exhaust louvers 24  that may close when the system 100 is inactive in order to reduce coil fouling in the heat exchangers 14 due to environmental debris.
[0029] In the illustrated embodiment  a gaseous refrigerant passes through the compressor 104  which increases the pressure of the gas in the refrigerant path 102 that leads to the condenser unit 106. In the condenser unit 106  the refrigerant passes through a plurality of coils in the condenser 112  wherein the refrigerant is cooled by the air outside of the building by the action of the fan 114 and condenses to a liquid. Then  as the liquid refrigerant traverses the next leg of the refrigerant path 102 to reach the expansion valve 108  it experiences a rapid drop in pressure resulting in a portion of the refrigerant returning to gaseous form. Next  the liquid and gaseous refrigerant mixture travels the refrigerant path 102 to the evaporation unit 110. In the evaporation unit 110  the refrigerant passes through a plurality of coils in the evaporator 126  wherein the refrigerant is heated by air 130 inside the building through the action of the fan 128  evaporating the refrigerant to a gas while producing streams of cool air 132 inside the building. The gaseous refrigerant then returns to the compressor 104 along the refrigerant path 102 to complete the cycle.
[0030] In such an embodiment  the intake louvers 22 attached to the enclosure 16 of the condenser unit 106 may move from the closed intake position 21 to the depicted open intake position 25 during operation of the air conditioning system 110 to enable relatively cooler air 40 from outside of the enclosure 16 to enter through the intake louvers 22. Similarly  exhaust louvers 24 attached to the enclosure 16 of the condenser unit 106 may move from the closed exhaust position 23 to the depicted open exhaust position 27 to enable warm air 42 to exit the exhaust 20 of the enclosure 16 through the exhaust louvers 24. In one embodiment  the intake and exhaust louvers 22 and 24 may move to the closed positions 21 and 23 during system inactivity to limit exposure of the coils of the condenser 112 to environmental debris. In an embodiment  only intake louvers 22 are employed on the condenser unit 106 and the exhaust 20 of the enclosure 16 remains unobstructed when the air conditioning system 100 is inactive. In another embodiment  only exhaust louvers 24 are included on the condenser unit 106 and the intake 18 of the enclosure 16 remains unobstructed when the air conditioning system 100 is inactive.
[0031] Similarly  in the illustrated embodiment  the intake louvers 22 attached to the enclosure 16 of the evaporator unit 106 may move from the closed intake position 21 to the depicted open intake position 25 during operation of the air conditioning system 110 to enable relatively warm air 130 from outside of the enclosure 16 to enter through the intake louvers 22. The exhaust louvers 24 attached to the enclosure 16 of the evaporator unit 106 may move from the closed exhaust position 23 to the depicted open exhaust position 27 to enable cool air 132 to exit the exhaust 20 of the enclosure 16 through the exhaust louvers 24. In one embodiment  the intake and exhaust louvers 22 and 24 may move to the closed positions 21 and 23 during system inactivity to limit exposure of the coils of the evaporator 126 to environmental debris. In an embodiment  only intake louvers 22 are employed and the exhaust 20 of the enclosure 16 of the evaporator unit 110 remains unobstructed when the air conditioning system 100 is inactive. In another embodiment  only exhaust louvers 24 are included on the evaporator unit 110 and the intake 18 of the enclosure 16 remains unobstructed when the air conditioning system 100 is inactive.
[0032] FIG. 6 is a schematic of an embodiment of a heat exchanging unit 150 with an active louver control system 157. As illustrated  the unit 150 includes a heat exchanger 14 and fan 12 within an enclosure 16 having an intake 18 and an exhaust 20. In such an embodiment  the intake 18 may include a plurality of intake louvers 152 (e.g.  intake louver assembly 153) and exhaust 20 may have a plurality of exhaust louvers 154 (e.g.  exhaust louver assembly 155) that close to protect the heat exchanger 14 from environmental debris when the heat exchanging unit 150 is not active. Each intake louver 152 and exhaust louver 154 may be attached to the enclosure 16 using a rotational shaft 26 about which the louver may rotate. In the illustrated embodiment  the active louver control system 151 includes linkages or rods 156  drives 158  and controller 160 to control operation of the louvers 152 and 154. The intake louvers 152 and the exhaust louvers 154 may be attached to one or more transfer linkages or rods156  which may be manipulated by one or more drives 158 based upon signals from the controller 160.
[0033] In the depicted embodiment  the heat exchanging unit 150 is preparing to activate the heat exchanger 14 and fan 12  and accordingly  the controller 160 first activates the drives 158 to impart an upward thrusting motion 162 to the transfer rods 156 of both the intake louvers 152 and the exhaust louvers 154. The upward thrusting motion 162 to the transfer rods 156 causes the attached intake louvers 152 and exhaust louvers 154 to rotate 164 about their respective shafts 26 from a closed position to an open position. In one embodiment  the drives 158 may be one or more of an electric  pneumatic  hydraulic  or similar drive  and may be powered by a power supply within the heat exchanging unit 150  a battery  a solar panel  or the like. In one embodiment  the intake louvers 152 and exhaust louvers 154 may be closed by the drives 158 via a downward pulling motion 166 to the transfer rods 156 based upon a signal from the controller 160 when the heat exchanging unit 150 is inactive. This downward pulling motion 166 causes the intake louvers 152 and the exhaust louvers 154 to rotate 168 about their respective shafts 26 to a closed position. In one embodiment  the controller 160 may determine the operational state of the heat exchanging unit 150 based on temperature feedback  air flow feedback  a control signal  a thermostat signal  or the like  using sensors 170 coupled to the controller 160 and distributed throughout the enclosure 16. In such embodiments  the controller 160 may include circuitry (e.g.  microprocessor executing software or firmware  programmable logic controller (PLC)  or other control circuitry) to determine the operational state of the system 150 and position the intake 152 and exhaust 154 louvers accordingly.
[0034] FIG. 7 is a schematic of an embodiment of an active control mechanism 200 for controlling a plurality of louvers 202 (e.g.  a louver assembly 201). In the depicted embodiment  each louver 202 is attached to a support structure 204 with a rotational shaft 206. These shafts 206 extend out of the ends of each louver 202 into the support structure 204  so as to provide each louver 202 with an axis of rotation 208 about its respective shaft 206. In one embodiment  the louvers 202 are intake louvers  and therefore  the support structure 204 is attached to the enclosure 16 near an intake 18. In another embodiment  the louvers 202 are exhaust louvers  and therefore  the support structure 204 is instead attached to the enclosure 16 near an exhaust 20. In the illustrated embodiment  each of the louvers 202 has an edge or end portion 210 (e.g.  a rotational joint offset from the rotational axis of the louver) attached to a common transfer linkage or rod 156 that interfaces with a drive 158 being controlled by a controller 160.
[0035] In operation  the controller 160 may actuate the drive 158  so as to provide a push 212 or pull 214 motion to the transfer rod 156  which transfers the push or pull force to the edge 210 of the louvers 202. In turn  the push 212 or pull 214 causes the louvers 202 to rotate 208 about their respective shafts 206. The depicted embodiment illustrates the louvers 202 in an open position 216  wherein the transfer rod 156 has been positioned by the drive 158 (based upon a signal from the controller 160)  so that the louvers 202 are nearly perpendicular 216 to the support structure 204 and let maximum air flow 218 pass. In one embodiment  the controller 160 may include sensor circuitry configured to detect the position of the transfer rod 156 to determine the direction that the drive 158 is to move in order to adjust the louvers 202 into a particular position. In other embodiments  a stepper motor or other precision motor may be employed in the drive 158  and the controller 160 may cause the drive to perform a calibrated number of steps or rotations in a set direction for each open and close operation. In some embodiments  one or more sensors 170 may be incorporated into the controller 160 to determine the current air flow rate and properly adjust the position of the louvers 202. However  the controller 160 may also adjust the position of the louvers 202 based upon various temperatures within the enclosure 16  a control signal from a system controller or thermostat  or another input signal.
[0036] FIG. 8 is a schematic of the embodiment of FIG. 7  illustrating the louvers 202 in a closed position 218. In the illustrated embodiment  the controller 160 has actuated the drive 158 such that the transfer rod 156 has been pushed up 212 by the drive 158 until the louvers 202 have rotated 220 about their respective shafts 206  thereby moving the louvers 202 to the closed position 218  in which the louvers 202 contact one another along intermediate interfaces 222. For example  each interface 222 may include one or more seals 224 to block the entry of debris. The seals 224 may include a fabric seal  an elastomer seal  or any other type of seal. In some embodiments  the louvers 202 may seal against the support structure 204. For example  a support seal 226 may extend around the perimeter of the louvers 202. In one embodiment  the interface 222 between each pair of adjacent louvers 202 may include a support bar separate from the louvers 202  wherein the support bar may include one or more seals. In each embodiment  the seals help to block the entry of debris  thereby helping to keep the heat exchanger 14 clean.
[0037] FIG. 9 is a schematic of an embodiment of an active control mechanism 240 for controlling the louvers 202. In the illustrated embodiment  a plurality of louvers 202 is attached to an enclosure 16 with a rotational shaft 244. These shafts 244 extend out of the ends of each louver 202 and into the opposite faces of the enclosure 16  so as to provide each louver 202 with an axis of rotation 246 about its respective shaft 244. In one embodiment  the louvers 202 are intake louvers and are attached to the enclosure 16 near an intake 18. In another embodiment  the louvers 202 are exhaust louvers and are attached to the enclosure 16 near an exhaust 20. In the depicted embodiment  each louver shaft 244 includes one or more pulleys or gears 248 connected to a common transmission mechanism 250  such as a belt  a chain  or another loop. In such an embodiment  the loop 250 may be driven by a drive 252 being actuated by a controller 254. In one embodiment  the drive 252 may be one or more of an electric  pneumatic  hydraulic  or similar drive  and may be powered by a power supply within the enclosure 242  a battery  a solar panel  or the like.
[0038] In operation  a signal from the controller 254 may actuate the drive 252 to cause a counter-clockwise motion 256 of the drive 252  which imparts a counter-clockwise motion 258 to the loop 250. In turn  the counter-clockwise motion 258 imparts a counter-clockwise motion 260 to each one of the louvers 202. Similarly  a signal from the controller 254 may actuate the drive 252 to cause a clockwise motion 262 of the drive 252  which imparts a clockwise motion 264 to the loop 250. In turn  the clockwise motion 264 imparts a clockwise motion 266 to the louvers 202. In certain embodiments  the clockwise or counter-clockwise motions may be used to move the louvers between open and closed positions. Furthermore  similar to the embodiments of FIGS. 7-8  the louvers 202 may be substantially sealed in the closed position to block entry of debris into the enclosure 16.
[0039] In one embodiment  the controller 254 may be equipped with internal or external sensors 268 configured detect the resistance of the louvers 202 to further rotation (e.g.  indicative of the closed position) and respond by stopping the motion of the drive 252accordingly. In some embodiments  one or more sensors 268 (e.g.  flow sensors  temperature sensors  motion sensors  etc.) may be employed in order for the controller 254 to determine the open or closed state of the louvers 202 to achieve the target flow rate or temperature. In some embodiments  the controller 254 may rely upon some other feedback mechanism  such as a control signal  a thermostat signal  or the like  to determine the operational state of the system. In another embodiment  a stepper motor or similar precision motor may be employed in the drive 252 such that  after proper calibration  the controller 254 may move the drive a set number of steps or rotations in a set direction for every open and close operation.
[0040] FIG. 10 is a side view of an embodiment of a louver assembly 280 configured to mount to an enclosure and selectively cover and uncover a flow path (e.g.  intake or exhaust)  thereby blocking entry of debris during an inactive state of the heat exchanger and opening the flow path during an active state of the heat exchanger. In the illustrated embodiment  the assembly 280 has a plurality of louvers 282 attached to a panel or frame 284 with a plurality of rotational shafts 286 supporting the louvers 282. The shafts are connected to the frame 284 at protruding tabs or lips 287  which include openings 288  to support the shafts 286 at opposite ends. In the illustrated embodiment  the louver assembly 280 is a passive unit  which opens and closes the louvers 282 without any drive. For example  the louvers 282 automatically open in response to the presence of an air flow  which forces the louvers 282 to open when the system is active. In turn  gravity automatically closes the louvers 282 in response to an absence of an air flow 290  thereby closing the louvers 282 when the system is inactive. However  some embodiments of the louver assembly 280 may be spring assisted. For example  the shaft 286 may include a spring coupled to each louver 282  thereby biasing the louver 282 toward a closed position. Again  the presence of an air flow 290 may overcome the spring and gravity to open the louver 282  while the absence of the air flow 290 may result in the spring biasing the louver 282 to the closed position. The illustrated louver assembly 280 may be attached to the air intake 18 or air exhaust 20 of any enclosure as discussed above.
[0041] FIG. 11 is a perspective view of an embodiment of the louver assembly 280 of FIG. 10  illustrating details of the frame 284 and louvers 282. In the depicted embodiment  each louver 282 is attached to the frame 284 with a rotational shaft 286 supported by the tabs or lips 287. For example  each shaft 286 may be supported by lips 287 at four locations across the frame 284. Furthermore  each shaft 286 may support one or more louvers 282. In the illustrated embodiment  each shaft 286 supports three louvers 282  e.g.  one louver between each pair of lips 287. In addition  the illustrated assembly 280 includes three rows 302 of louvers 282. However  the assembly 280 may include any number of louvers 282. As a result the louvers 282 in each row 302 are able to rotate 304 about their respective shafts 286. Again  as discussed above  the illustrated louver assembly 280 is a passively controlled system  which may rely entirely on gravity and air flow to control the opening and closing of the louvers 202.
[0042] FIG. 12 is a perspective view of an embodiment of a heat exchanging unit 320 having the louver assembly 280 of FIGS. 10-11. As illustrated  the unit 320 includes a fan 322 and a heat exchanger 324 disposed inside of an enclosure 326 having an intake 18 and an exhaust 20. The intake 18 of the enclosure 326 has a plurality of rows of louvers 302 (e.g.  louvers 282) coupled to the frame 284. In the illustrated embodiment  the fan 322 is actively flowing cool air 40 into the enclosure 326 through the louvers 282  and is actively exhausting warm air 42 from the enclosure 326 downstream of the heat exchanger 324. As the air flows through the enclosure 326  the heat exchanger 324 cools an internal fluid flow (e.g.  gas or liquid)  thereby transferring heat to the cool air 40 to generate the warm air 42. During the presence of air flows 40 and 42 (e.g.  active fan)  the louvers 282 automatically open against the force of gravity (and optionally a spring). In the absence of air flows 40 and 42 (e.g.  inactive fan) the louvers 282 automatically close via gravity (and optionally a spring). Accordingly  the louvers 282 block entry of debris while the fan 322 is inactive.
[0043] Technical effects of the invention include the ability to limit coil fouling with enclosed heat exchanging units by limiting the exposure of the heat exchanger to its surrounding environment when it is not actively in use. Through the use of a plurality of intake and/or exhaust louvers  the enclosure of heat exchanging units (e.g.  central air conditioning units and window air conditioning units) may be effectively sealed when the unit is inactive to prevent the entry of environmental contaminants (e.g.  pollen and dust) that may collect on surface of the heat exchanger and restrict the heat transfer process. Protecting the coils of the heat exchanger  as disclosed herein  helps to ensure that the heat exchanging unit will operate at a high efficiency  without unnecessary strain  and with lower maintenance costs (e.g.  coil cleaning and failed part replacement). Thus  this invention further allows for an improvement in the efficiency  maintainability  and life expectancy of heat exchanging units.
[0044] This written description uses examples to disclose the invention  including the best mode  and also to enable any person skilled in the art to practice the invention  including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims  and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims  or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

10 heat transfer unit
12 fan
14 heat exchanger
16 enclosure
18 air intake
20 air exhaust
22 intake louvers
17 intake louver assembly
24 exhaust louvers
19 exhaust louver assembly
21 exhaust positions
23 exhaust positions
26 shaft
25 open positions
27 open positions
28 rotate
40 relatively cool air
42 warm air
60 active heat exchanging unit
62 enclosure
64 multiple intake faces
66 exhaust face
80 enclosure
82 upper exhaust face
84 lateral intake faces
86 intake louvers
85 intake louver assembly
88 exhaust louvers
87 exhaust louver assembly
90 open positions
92 open positions
100 air conditioning system
102 refrigerant path
104 compressor
106 outdoor condenser unit
108 expansion valve
110 indoor evaporator unit
112 condenser
126 evaporator
114 fans
128 fans
130 air
132 cool air
150 heat exchanging unit
157 active louver control system
152 intake louvers
153 intake louver assembly
154 exhaust louvers
155 exhaust louver assembly
151 active louver control system
156 rods
158 drives
160 controller
162 upward thrusting motion
164 rotate
166 downward pulling motion
168 rotate
170 sensors
200 control mechanism
202 louvers
201 louver assembly
204 support structure
206 rotational shaft
208 rotation
210 end portion
212 push
214 pull
216 open position
218 air flow
220 rotated
222 intermediate interfaces
224 seals
226 support seal
240 active control mechanism
244 shaft
246 rotation
248 gears
250 transmission mechanism
252 drive
254 controller
242 enclosure
256 counter-clockwise motion
258 counter-clockwise motion
260 counter-clockwise motion
262 clockwise motion
264 clockwise motion
266 clockwise motion
268 external sensors
280 louver assembly
282 louvers
284 frame
286 shafts
287 lips
288 openings
290 air flow
302 three rows
304 rotate
320 heat exchanging unit
322 fan
324 heat exchanger
326 enclosure

WE CLAIM:
1. A system  comprising:
an air conditioning unit  comprising:
an enclosure;
a heat exchanger disposed in the enclosure; and
a plurality of louvers coupled to the enclosure  wherein the plurality of louvers is configured to move between an open position and a closed position  and the closed position is configured to protect the heat exchanger from an environment external to the enclosure.

2. The system of claim 1  wherein the plurality of louvers is disposed over an air intake of the enclosure.

3. The system of claim 1  wherein the plurality of louvers is disposed over an air exhaust of the enclosure.

4. The system of claim 1  wherein the air conditioning unit comprises a fan configured to provide an air flow across the heat exchanger  and the plurality of louvers is configured to move from the closed position to the open position in response to the air flow.

5. The system of claim 4  wherein the plurality of louvers is configured to move from the open position to the closed position in response to an absence of the air flow.

6. The system of claim 1  wherein the air conditioning unit comprises a drive configured to move the plurality of louvers between the closed position and the open position.

7. The system of claim 6  wherein the air conditioning unit comprises a controller coupled to the drive  and the controller is configured to actuate the drive to move the plurality of louvers between the closed position and the open position based on an operational state of the air conditioning unit.

8. The system of claim 6  wherein the air conditioning unit comprises a transmission mechanism between the drive and the plurality of louvers  and the transmission mechanism is coupled to a rotational shaft of the plurality of louvers.

9. The system of claim 6  wherein the air conditioning unit comprises a transmission mechanism between the drive and the plurality of louvers  and the transmission mechanism is coupled to the plurality of louvers at an offset from a rotational axis of the plurality of louvers.

10. The system of claim 1  wherein the heat exchanger comprises a refrigerant path.

11. The system of claim 1  wherein the air conditioning unit comprises a window air conditioning unit or a condenser unit of a central air conditioning system.

12. A system  comprising:
a heat transfer unit  comprising:
an enclosure comprising an air intake and an air exhaust;
a heat exchanger disposed in the enclosure;
a fan configured to direct an air flow across the heat exchanger; and
a plurality of intake louvers coupled to the air intake  wherein the plurality of intake louvers is configured to move from a closed intake position to an open intake position in response to the air flow.

13. The system of claim 12  wherein the plurality of intake louvers is configured to move from the open intake position to the closed intake position in response to an absence of the air flow.

14. The system of claim 12  comprising a plurality of exhaust louvers coupled to the air exhaust  wherein the plurality of exhaust louvers is configured to move from a closed exhaust position to an open exhaust position in response to the air flow.

15. The system of claim 14  wherein the plurality of intake louvers is configured to move from the open intake position to the closed intake position in response to an absence of the air flow  and the plurality of exhaust louvers is configured to move from the open exhaust position to the closed exhaust position in response to the absence of the air flow.