Abstract: A heat exchanger includes an air channel configured to receive air from an equipment rack. A fluid circuit is provided having a bi-phase coolant flowing therethrough. The fluid circuit includes a coolant channel coupled to the equipment rack and positioned adjacent to the air channel. The bi-phase coolant is part liquid and part gas as the bi-phase coolant flows through the coolant channel. The bi-phase coolant is configured to condition the air flowing through the air channel.

Abstract: Assemblies for HVAC systems and methods of operating HVAC systems are disclosed, including a method of operating an HVAC system having a condenser motor operatively coupled to a fan and a controllable bus voltage for powering the condenser motor. The method includes increasing the controllable bus voltage from a first voltage to a second voltage to increase a speed of the condenser motor.

Abstract: Refrigeration systems for machines for making blended iced beverages make ice for use in the beverages and maintain beverage ingredients cold not only as the ingredients are stored in supply containers in the machine but also as they are delivered from the supply containers to a remote point of delivery at a beverage ingredient dispense station. Arrangements are disclosed in which a single refrigeration system makes ice and chills the beverage ingredients; in which a pair of refrigeration systems make ice and chill the beverage ingredients; in which a single refrigeration system makes ice and the ice is used to chill the beverage ingredients; and in which a single refrigeration system makes ice and melt water from the ice is used in chilling the beverage ingredients.

Abstract: A method apparatus and system for implementing a redundant cooling system is disclosed. The system and method include apparatus for providing a plurality of variable refrigerant flow air cooling units, wherein the number of air cooling units is at least one more than required to meet a selected maximum cooling load when operating the air cooling units at up to a maximum cooling capacity; coupling the plurality of variable refrigerant flow air cooling units in thermal communication with the air in a conditioned space; determining a select optimum operating condition for each of the plurality of variable refrigerant flow air cooling units which will result in about a lowest overall energy consumption for the redundant cooling system, while maintaining an average temperature of the air in the conditioned space at a required setpoint; and operating said plurality of air cooling units at about the select optimum operating conditions for each of the air cooling units.

Abstract: A refrigerator having a refrigerator body including a first cooling chamber and a second cooling chamber, a barrier wall located between the first cooling chamber and the second cooling chamber, an evaporator configured to provide cooling air, a first cooling fan configured to provide cooling air of the evaporator to the first cooling chamber, and a second cooling fan configured to provide cooling air of the evaporator to the second cooling chamber is provided. A method of providing cooling air flow in a refrigerator is also provided.

Abstract: A method for operating a heat pump (100) in low ambient air temperatures comprises periodically or temporarily halting flow of refrigerant through an evaporator (170) of the heat pump (100) and providing forced airflow across the evaporator (170) while the refrigerant flow is halted. The method enables operation of the heat pump (100) at low ambient temperatures and provides a means for de-icing the evaporator (170) when operating at low ambient temperatures. The method is particularly applicable to heat pumps having an evaporator located outdoors, such as domestic and industrial water heating systems.

Abstract: A method and apparatus for controlling a vehicle HVAC system to automatically defog a windshield glass and to prevent fogging or condensation of the windshield glass. The ambient air temperature and vehicle speed are measured and used to determine a windshield glass temperature. The in-cabin air temperature and relative humidity are measured and used to determine a dewpoint. An dewpoint margin is calculated to compensate for sensor accuracy and fog predictability. A fog margin, which is based upon calculated windshield glass temperature and dewpoint, is calculated and used, in conjunction with the dewpoint margin, to control the HVAC system to anticipate potential fogging conditions and to scale the intensity of the HVAC system response based upon the severity of fogging conditions.

Abstract: An appliance includes a dispenser having a water valve for controlling a flow of water through the dispenser and a flowmeter for measuring the amount of water dispensed through the dispenser, and a controller operatively coupled to the water valve and the flowmeter. The controller is configured to receive an input relating to a target volume of water, adjust the target volume for a volume error correction to obtain an adjusted target volume, wherein the volume error correction is based on a flow rate, open the water valve, determine a total volume dispensed using the flowmeter, and close the water valve when the total volume dispensed equals the adjusted target volume.

Abstract: A refrigerator includes a main body defining a compartment, the compartment having an access opening and a first wall, a door supported by the main body for selectively closing at least part of the access opening, a sub-compartment on the door, the sub-compartment including a second wall having an opening, a heat exchanger supported by the first wall and positioned so that when the door is closed the heat exchanger is exposed to an interior of the sub-compartment through the opening. The heat exchanger includes a heat exchanging plate. A sealed refrigeration system contains a working medium for cooling the heat exchanger and has one or more segments attached to the heat exchanging plate. A fan is configured to force air over the heat exchanging plate and into the interior of the sub-compartment. A thermistor is coupled to the heat exchanging plate for monitoring a temperature of the heat exchanging plate.

Abstract: An assembly for installation in a refrigerator provides an enclosure for conducting service lines therethrough and an air filter unit mounted to the enclosure. The air filter unit includes an air filter housing that contains an air filter and includes openings for the ingress of air from the refrigerator which, after passing through the air filter, is discharged to the refrigerator interior through discharge openings in the air filter housing. Means such as a fan is provided to establish a flow of air through the air filter housing. The air filter unit has utility separately from the enclosure for conducting service lines in which case the air filter housing includes first and second portions that are pivotally connected to one another. The air filter within the air filter housing is supported by one of the first and second portions of the air filter housing.

Abstract: A refrigerant system is provided that includes a cooling refrigerant circuit, a reheat refrigerant circuit, an evaporator fan, and a controller. The evaporator fan forces indoor air in a first direction and a second direction. The indoor air passes across the evaporator before the reheat coil, in the first direction, but passes across the reheat coil before the evaporator, in the second direction. The controller, when in a conventional cooling mode, controls the reheat refrigerant circuit so that the reheat refrigerant circuit is not in fluid communication with the cooling refrigerant circuit and controls the evaporator fan to force the indoor air in the first direction. Conversely, the controller, when in a defrost mode, controls the reheat refrigerant circuit so that the reheat refrigerant circuit is in fluid communication with the cooling refrigerant circuit and controls the evaporator fan to force the indoor air in the second direction.

Abstract: A method and device for controlling certain two-speed ECMs (Electronically Commutated Motors) used in refrigeration evaporator coils. Said method and device monitors and responds to the status of the cooling system, causing the ECMs to operate at high speed when the cooling system is actively cooling, and at low speed when the cooling system is idle.

Abstract: A galley cooling system comprises a plurality of galley cooling units each to be associated with separate galleys. A sensor senses a condition within each of the galleys. A control determines whether a sensed condition is indicative of efficient operation of a particular galley cooling unit, and the control is operable to decrease cooling capacity delivered to a galley cooling unit which is experiencing inefficient operation. An aircraft galley system incorporating the above cooling unit, and a method of operating a galley cooling unit are also disclosed and claimed.

Abstract: One embodiment comprises an apparatus with an evaporative unit for a refrigerant having a flow direction opposing the airflow direction and an adjustable airflow rate to utilize to produce both cold/dehumidified exit air and warmed exit refrigerant for high efficiency and to maintain an airflow sufficient to avoid freeze-up of evaporative unit or freeze-up to an extent that blocks the airflow. This may produce low humidity even when the room thermostat is set warm (e.g. 85F) and 5%-30% lower A/C bills. Other embodiments comprise systems and methods related to the adjustable airflow. A further embodiment comprises a controller to adjust the humidity in an air-conditioned space to produce air, which is both temperature and humidity controlled.

Abstract: A process for controlling operation of a heating, ventilation and air conditioning system broadly comprises providing a heating, ventilation and air conditioning system having an evaporator, a condenser, a compressor having an inlet and an outlet, and at least one flow control device; measuring a performance parameter of the heating, ventilation and air conditioning system; determining a performance parameter measurement of the flow indicative of onset of surge; determining a surge line of the heating, ventilation and air conditioning system based upon the performance parameter measurement; and independently controlling the at least one flow control device based upon the performance parameter to mitigate an onset of the surge.

Abstract: A refrigerator includes a fresh food compartment, a freezer compartment and a refrigeration system. A duct, exposed to the freezer compartment, leads into the fresh food compartment. A damper is arranged within the duct to selectively allow the passage of cooling air into the fresh food compartment. The refrigerator also includes an air mixing fan arranged in the fresh food compartment, a freezer mounted ice maker, a user interface having a plurality of control elements and a controller operatively associated with the user interface. The controller includes a memory having stored therein a plurality of operating parameters for controlling various aspects or features of the refrigerator, including a temperature control mode, a super cool mode, a food saver mode and a quick ice mode, which can be synergistically combined to efficiently operate the refrigerator.

Abstract: A refrigerator and its operation method are disclosed. Cool air ducts guide cool air from a freezing compartment to an ice compartment that is positioned at a refrigerating compartment door. At least a portion of the cool air ducts are located at a barrier that separates the freezing compartment and the refrigerating compartment.

Abstract: A refrigeration apparatus having an evaporator fan motor control includes an evaporator to remove heat energy from the air in a cooled storage space. The evaporator transfers the heat energy to a refrigerant. At least one evaporator fan moves air from the cooled storage space across the evaporator to improve the transfer of heat energy into the refrigerant. The one or more evaporator fans have an energy consumption and generate a waste heat energy. A refrigeration control unit at least controls the operation of the one or more evaporator fans. During an off mode, the one or more evaporator fans are operated in a reduced energy consumption mode to reduce the energy consumption of the one or more evaporator fans and to reduce the waste heat while still defrosting the evaporator in the off mode.

Abstract: Comfort temperature and humidity levels in a conditioned space are controlled by cycling the speed of an evaporator fan motor in such a manner that, during time periods when higher sensible capacity is desired, the time in which the fan motor operates at a higher speed is increased, and during time periods when a higher latent capacity is desired, the time in which the fan motor operates at a lower speed is increased. The fan motor may be a single speed motor that is switched between on and off positions, or it may be a multiple speed motor that is cycled between a higher speed and a lower speed.

Abstract: The invention relates to a method of cooling a metal strip traveling through a cooling section in a continuous heat treatment line. In accordance with the invention, the method consists in projecting a refrigerant medium into the cooling section (4) onto the surface of the strip (1) to be cooled, the medium being constituted for the most part by a phase-change substance that passes into the gaseous phase at a temperature that is lower than the temperature of the strip (1) and without oxidizing said strip so that energy is exchanged within an endothermic process by a change in the phase of said phase-change substance.

Abstract: A system and method of providing a temperature controlled gaseous medium for dermatological applications is described. The gaseous medium may be cooled and applied to an area such as a skin area to provide an analgesic effect thereon. The system and method also include an automated defrost cycle for minimizing the effects of decreased hydraulic diameter due to freezing.

Abstract: A refrigerated display case is provided that includes a display chamber for displaying product. The display chamber includes a product tray for supporting the product. A cooling chamber is arranged beneath the product and is in communication with a surface of the product tray. The cooling chamber is sealed from the display chamber, in one example, and includes a cooling coil. A fan is in communication with the cooling chamber and cooling coil. The fan circulates a cooling flow through the cooling coil. The cooling flow moves across the surface and absorbs heat from the product tray by convection. The cooled product tray removes heat from the product by conduction.

Abstract: A portable air conditioner (10) that has a loading chamber (30) substantially separated from a heat-transfer chamber (32) within a housing (20). Heat-transfer cells (40) for holding a phase-changeable, frozen substance such as ice (3), have an open end that is accessible from the loading chamber (30) and have cell housings (42, 44) disposed within the heat-transfer chamber (32). An air-flow mechanism (62) causes air to be drawn in through at least one air-intake opening (60), circulated among the heat-transfer cells (40) and urged outwardly of the unit housing (20) through at least one air-outlet opening (70, 72).

Abstract: The present invention discloses an apparatus for supercooling and a method of operating the same which can solve supercooling release of a supercooled space and prevent external exposure of energy such as an electric field. The apparatus for supercooling includes a space cooled by cool air, for maintaining an inside object in a supercooled state by supply of energy preventing the object from being converted into a solid phase, a sensing unit for sensing supercooling release of the space or the object, and a heater engaged with the sensing unit, for applying heat to the space or the object.

Abstract: A plate heat exchanger with a condensed fluid separating function, which includes a reheater having plural laminated wrinkled plates and introduction and discharge holes connected to different compressed air channels therein; a chiller having plural laminated wrinkled plates, working fluid inlet and outlet holes connected to a working fluid channel therein, and compressed air channels formed therein; and a wall-shaped pipe configured for partitioning the reheater and the chiller with providing a flow line to communicate a compressed air with he reheater and the chiller. An adiabatic expansion chamber is formed in a lower portion of the chiller on a flow line for the compressed air cooled in the chiller to move toward the reheater. A condensation chamber is formed in a lower portion of the reheater connected to the adiabatic expansion chamber. A condensation mesh sieve and a drainage hole are formed in the condensation hole.

Abstract: The present invention describes a method and apparatus for controlling the operating pressure of a Reverse Brayton type refrigeration device 70 for the purposes of regulating cooling capacity and coolant inventory control.

Abstract: A system (10) for cooling a thermally loaded device on board an aircraft comprises a distribution line (12) which is in communication with an installation space (14) of the thermally loaded device, a coolant supply line (20) which is in communication with a coolant source, and a heat removal line (28) which is in communication with a source of pressure below atmospheric pressure. A shut-off control device (34) is adapted so as, in a first position, to separate the distribution line (12) from the coolant supply line (20) and connect the distribution line (12) to the heat removal line (28) and, in a second position, to connect the distribution line (12) to the coolant supply line (20) and separate the distribution line (12) from the heat removal line (28).

Abstract: The invention relates to a method and equipment for dispersing the air flowing out of air conditioning systems and mixing it with the ambient air of the enclosure to be conditioned. The quick mixing of the conditioned air jets will create better comfortable feeling of people in front of the conditioned air outlet.

Abstract: A refrigerator that is capable of achieving smooth flow of cool air therein and improving cooling efficiency of a cooled evaporator (10) and a control method of the same that is capable of controlling operation time of an evaporator (10) and a fan (20), thereby improving cooling efficiency of the refrigerator are disclosed.

Abstract: A ventilated merchandising system for products displayed in merchandise coolers such as refrigerator or freezer cases. One embodiment of the merchandising system includes a base member and a platform coupled to the base member such that air can flow between the platform and the base member. One or more plenum plates can be coupled to the base for directing air between the platform and the base member. A pusher plate may also be coupled to and movable along the platform for advancing products along the platform. A baffle system that may be coupled to a merchandising tray and a method of distributing air flow within a merchandise cooler unit are also provided.

Abstract: Disclosed embodiments include systems for heating and cooling the interior climate of a vehicle. In some embodiments, the system comprises a conduit having a first fluid channel, a second fluid channel, a fluid diversion channel configured to divert fluid flow between the first and second channels, and a thermoelectric device operatively connected to the fluid conduit. In certain embodiments, the thermoelectric device comprises a plurality of thermal zones. In some embodiments, the plurality of thermal zones comprises a first thermal zone connected to a first electric circuit switchable between a first polarity and a second polarity and a second thermal zone connected to a second electric circuit switchable between the first polarity and the second polarity independent of the polarity of the first electric circuit.

Abstract: A method is provided for operating a refrigerant vapor compression system, for example an air-cooled chiller or air-cooled condensing unit, at optimal energy efficiency rating. The method includes the steps of: determining the instantaneous values of a plurality of selected operating parameters of the system's refrigeration unit, calculating a desired control parameter set point indicative of an optimal energy efficiency rating for the refrigeration unit as a function of the selected operating parameters, sensing the instantaneous value of the control parameter, comparing the sensed instantaneous value of the control parameter to the calculated control parameter set point, and adjusting the operating speed of the condenser fans associated with the air-cooled condenser of the refrigeration unit in response to that comparison.

Abstract: A refrigeration apparatus includes an air chiller including a fan, a storage enclosure defining a compartment, and a duct system. The air chiller blows chilled air into the duct system. The compartment has first and second openings, each of which is coupled to the duct system. Chilled air enters the first opening and exits the second opening, and vice versa. In one implementation, the first opening is at the top of the compartment and the second opening is at the bottom of the compartment. A control circuit may periodically cause the fan to change the direction of the chilled air flow. This effectively maintains a relatively uniform temperature throughout the compartment.

Abstract: The invention relates to an air-conditioning unit (1) comprising an air circuit with an air inlet (5), a main fan (10) and an air outlet (6) designed to be connected to a chamber such as, for example, an aircraft parked on the ground, preferably via one or more flexible ducts, and a refrigerant circuit comprising a heat exchanger/evaporator (12) positioned in said air circuit to cool the air by evaporating the refrigerant, a compressor (17) and a condenser (18) for condensing the refrigerant before it is returned to the heat exchanger/evaporator (12). Said heat exchanger/evaporator (12) comprises several parallel circuits (19) each having at least one regulator valve (20).

Abstract: A refrigerated merchandiser including a case defining a product display area, and a shelf supported by the case within the product display area. The case includes a base that is disposed below the product display area and a canopy that is disposed substantially above the product display area. The shelf includes an air discharge duct that is configured to direct a first air curtain generally downward from the shelf into the product display area toward the base, and an air return duct that is configured to receive at least a portion of a second air curtain discharged into the product display area from above the shelf.

Abstract: A refrigerated case (20) includes a body (22) having a left and a right side, a top, and a back. A refrigerated compartment (24) is located within the body. At least one vertical array (120, 122) of shelves is within the refrigerated compartment. A base compartment (44) is below the refrigerated compartment. A refrigeration module (50) is located within the base compartment. A cold air flowpath (512) extends from the module upward through a rear duct (146,147) of the body and returns to the module. The cold air flowpath includes a number of branches extending through apertures in the rear duct. The cold air flowpath returns downwardly through the shelf array.

Abstract: There is disclosed a liquid discharge method in a temperature controller having a refrigerant circulation line circulating a refrigerant to a target of temperature control and a heater heating the target, wherein the refrigerant is circulated so as to control the temperature of the target with the refrigerant and the heater in the case where the temperature of the target is controlled to be a first temperature lower than or equal to a room temperature, wherein the circulation of the refrigerant is stopped so as to control the temperature of the target with the heater in the case where the temperature of the target is controlled to be a second temperature higher than the room temperature, wherein in the case of changing the setpoint of the target from the first temperature to the second temperature, when the temperature of the refrigerant rises to reach a first predetermined temperature lower than or equal to the boiling point of the refrigerant, the circulation of the refrigerant is stopped, one of air and an

Abstract: A heat pump refrigerant system is provided with a pulse width modulation control for a fan moving air over the indoor heat exchanger. When it is determined that there is insufficient heat rejected by the indoor heat exchanger to heat the volume of air being delivered by the fan into the conditioned environment, the volume of air supplied to the conditioned environment is reduced by utilizing one of pulse width modulation techniques to cycle the indoor fan motor to reduce the average volume of supplied air. Therefore, a precise control over the temperature of air delivered to the conditioned space is achieved, temperature of the delivered air is increased to the target value, and so-called “cold blow” conditions are avoided.

Abstract: A multi-zone HVAC&R system has its control programmed to provide diagnostic testing of air handling components and refrigerant components associated with each climate controlled zone in sequence. The control changes the original position of the corresponding component and a resultant change in a relevant operational parameter is sensed. If the actual change is outside of the tolerance band associated with the expected change, then the determination is made that the component under consideration is malfunctioning. The periodicity of a diagnostic procedure for a particular component is typically defined by its criticality and reliability level. If the change in the corresponding operation parameter is recorded and stored in the database, the component degradation can be observed over time and a prognostic prediction can be made when a particular component requires preventive maintenance or replacement.

Abstract: Method for cool drying gas containing water vapour, whereby this gas is led through the secondary part of a heat exchanger (2), whose primary part is the evaporator (3) of a cooling circuit (4), whereby the temperature or the dew point is measured in the environment of the place where, when cool drying, the temperature of the gas to be dried is the lowest, and whereby the above-mentioned method comprises the step of switching off the cooling circuit (4) when the decrease of the lowest measured gas temperature (LAT) or the dew point during a predetermined period of time amounts to less than a preset value (y).

Abstract: Air-conditioning system (10) for aircraft, in particular for commercial aircraft, with a bleed air source (12), a bleed air line (22-30) comprising a main valve (16), and an air-conditioning unit (32), wherein a mass air flow conveyed from the bleed air source (12) through the bleed air line (22-30) to the air-conditioning unit (32) can be controlled by means of the main valve (16). According to the invention it is envisaged that a by-pass line (36-50, 58, 60) comprising a by-pass valve (34) and by-passing at least a part (22-26, 16) of the bleed air line, is present between the bleed air source (12) and the air-conditioning unit (32).

Abstract: A refrigerator incorporates an air filter for filtering an airflow passing along at least one refrigeration component into surrounding spaces. The air filter is positioned in an upper machine compartment which houses refrigeration components associated with maintaining temperatures in the refrigerator. At least one sensor is arranged adjacent the air filter to determine a parameter of the air flow. A control, including an air filter analyzer, determines a need for an air filter change based on the sensed parameter. In addition to removing impurities from the airflow, the air filter includes scented media which adds fragrance to the airflow.

Abstract: A transport refrigeration system, which uses the heat of compression to selectively provide heat to a cargo space by way of the evaporator coil, is provided with enhanced heating capacity during lower ambient conditions by causing the heat from an engine radiator to flow over the condenser coil to thereby increase the condensing pressure and temperature and thereby increase the heat of compression and the heat being provided to the space. Provision is also made to cause the hot air from the engine itself to flow over the engine radiator and the condenser coil to further enhance the heating capacity. Various damper and shutter arrangements are also provided as alternative embodiments.

Abstract: An appliance system including a module removably mounted to an appliance, one or more removable gas canisters operably connected to the module, and a food retaining enclosed space operably connected to the module. The one or more gas canisters supply a modified atmosphere in the food retaining enclosed space to produce a modified atmosphere that enhances preservation of the food contained in the food retaining enclosed space.

Abstract: An aircraft air-conditioning unit (10) includes a compressor (18) and a motor (20) driving the compressor (18). A fuel cell system (24) is connected directly to a control unit (22) for controlling the motor (20) driving the compressor (18), wherein the control unit (22) is adapted to convert electrical energy directly generated by the fuel cell system (24) into corresponding electrical control signals for controlling the motor (20) driving the compressor (18). In a method for operating an aircraft air-conditioning unit (10), which includes a compressor (18) and a motor (20) driving the compressor (18), a control unit (22) for controlling the motor (20) driving the compressor (18), which is directly connected to a fuel cell system (24), converts electrical energy directly generated by the fuel cell system (24) into corresponding electrical control signals for controlling the motor (20) driving the compressor (18).

Abstract: A system for removing heat from heat load equipment including a re-circulating air handling unit for establishing an air curtain that flows up from and around the heat load equipment and one or more roof-mounted heat stratification housings disposed over the heat load equipment for receiving heat from the equipment. The heat generated from the equipment travels upwardly inside of and propelled by the air curtain. The heat stratification housing includes a plurality of heat transfer plates that extend between interior and exterior areas thereof. Water nozzles direct a spray on the heat transfer plates.

Abstract: A pre-riding air conditioning method in which if an intention of a passenger to ride in a vehicle is detected, an inside air fan (3) is operated to stir air in a passenger room, and an air conditioner comprising the inside air fan (3) which can stir air in the passenger room, and a control (21) which operates the inside air fan (3) when the intention of a passenger to ride in the vehicle is detected.

Abstract: Hydrogen gas at a hydrogen refueling site is cooled below liquid nitrogen temperature (e.g., about 80K) for more efficient adsorption of hydrogen on hydrogen adsorbent particles in the fuel storage of a hydrogen powered vehicle. When compressed hydrogen gas is available it may be cooled with liquid nitrogen and then sub-cooled below about 70K by a Joule-Thompson expansion. When liquid hydrogen provides hydrogen gas it may be cooled below liquid nitrogen temperatures by mixing with liquid hydrogen or by heat exchange with liquid hydrogen.

Abstract: A system (20) for conditioning air (30) includes conditioning circuits (26, 28). Each of the circuits (26, 28) includes a heat transfer coil (54, 60) residing in a supply section (22) of the system (20), and a heat transfer coil (56, 62) residing in a return section (24) of the system (20). A controller (50) in communication with the circuits (26, 28) determines one of a heating mode (78, 110) and a cooling mode (148, 150) for an interior space (34). The controller (50) selectively actuates the conditioning circuits (26, 28) to condition outside air (30) entering the supply section (22) to produce conditioned supply air (36) for provision into space (34) and to recover heating and cooling energy from return air (38) entering the return section (24) from the space (34) prior to its discharge from the system (20) as exhaust air (44).

Abstract: A refrigeration apparatus includes an air chiller, a storage enclosure defining a compartment, a duct system, and a valve system. The air chiller blows chilled air into the duct system. The compartment has a first and a second opening, each of which is coupled to the duct system. The valve system has valves that can be moved to route the chilled air so that it enters into the first opening and exits the second opening, or vice versa. In one implementation, the first opening is at the top of the compartment and the second opening is at the bottom of the compartment, and the valve system is controlled by a control circuit that periodically switches the valves (via an actuator) to change the direction of the chilled air. This effectively maintains a relatively uniform temperature throughout the compartment.