Abstract: A microwave heat pump defroster system, utilizing a magnetron tube, or other microwave energy generating device, for the application of heat to the external surfaces of the outside coil of an electric heat pump, while the heat pump is operating in the heating mode for the following purposes, (1) to defrost the outside coil of the heat pump, (2) to inhibit the accumulation of frost on the external surfaces of the outside coil of the heat pump, and (3) to allow heat so applied to the external surfaces of the outside coil of the heat pump to be absorbed into the heat pump system via the outside coil of the heat pump, in a manner that will improve the efficiency of the heat pump.

Abstract: A refrigerating exchanger (1) for a refrigeration facility such as a cold storage room or a refrigerated display case, including a refrigerant or heat-removing fluid circulating assembly (5) connected to a heat exchanging assembly (6) with a large surface area. The assemblies (5, 6) form an array of several layers (7) and several rows (8) in the form of a plurality of mutually similar parallel members (9) separated by spacers (10) for providing heat insulation and collecting defrosting runoff water. Each member (9) comprises at least one layer (7) as well as a respective inlet (11) and outlet (12) forming part of the circulating assembly (5).

Abstract: There are described a defrosting method and apparatus for a freezer-refrigerator using a GA-fuzzy theory.A defrosting method for a freezer-refrigerator using a GA-fuzzy theory of the present invention comprises the step of: inputting reference learning data by experiment and actual data to a microcomputer; calculating each frost-quantity on evaporators for a freezing room and a cold-storage room from the input data; inferring each defrosting period for the freezing room and cold-storage room from each frost-quantity on the evaporators for the freezing room and cold-storage room by using a GA-fuzzy theory so that the defrosting periods can be synchronized with each other; and controlling a defrosting heater depending on each defrosting period.

Abstract: A method and apparatus for eliminating the accumulation of moisture condensation on air conditioning supply grills of concentric diffusers which involves the positioning of heat transfer tape around the perimeter of an air conditioning supply grill, a humidistat positioned within the return air duct of the air conditioning system, and a relay located in the electrical component compartment of the air conditioning system which is connected to the humidistat so that when the humidistat senses high levels of moisture in the return air, the relay will allow current to flow through the heat transfer tape for warming of the air conditioning supply grill and prevention of moisture condensation accumulation thereon. Applications may include, but are not limited to, use in commercial air conditioning systems having concentric diffusers.

Abstract: A sealed, closed end heat pipe efficiently warms the drain for an evaporator so that condensation may flow unobstructed away from the evaporator in the refrigeration circuit. An evaporator end of the heat pipe is exposed to ambient air and a condenser end is located close to the drain inlet adjacent the evaporator. Thus, no external power source is required as fluid within the evaporator end is heated to vapor phase and circulates toward the condenser end, and cooled fluid from the condenser end returns to the evaporator end.

Abstract: A refrigerator includes a freezing compartment and refrigerating compartment. Dew prevention heaters are provided for the respective compartments. The dew prevention heater for the freezing compartment cannot be activated if the freezer temperature is above 0.degree. C., but it can be activated if that temperature is below 0.degree. C. as follows: if the compressor is on, then the heater is always on; and if the compressor is off, then the heater will cycle on and off at a frequency dependent upon the magnitude of the temperature outside of the refrigerator. The activation of the dew prevention heater for the refrigerating compartment is independent of the temperature of the refrigerating compartment. Rather, that heater is "off" if the compressor is "off", and if the compressor is "on", the heater will cycle on and off at a frequency dependent upon the temperature outside of the refrigerator.

Abstract: An automated processing freezer system is described that provides a plurality of cooling units to chill the air within a freezing enclosure, whereby the coils of each cooling unit may be defrosted independently, without louvers or other moving mechanisms, while the cooling output of the freezer system is maintained 24 hours a day. Baffles in the freezing enclosure isolate each cooling unit from the airflow associated with the other cooling units, thereby eliminating the need for expensive and less efficient louvers surrounding the coils of each cooling unit.

Abstract: Methods and apparatus for defrosting the outdoor coil in a variable speed heat pump system including determining, after the end of the last preceding defrosting, the optimal time to begin the next defrosting, and then initiating the defrosting responsive to the time interval since the end of the last defrosting tsD, the averages, over time, of liquid line temperature LLT, speed ES of the engine that drives the compressor, and outdoor dry bulb temperature ODT. The defrosting includes switching the system to the defrost mode at a predetermined maximum engine speed, periodically measuring the time taken during the defrosting ttD and the liquid line temperature LLT; periodically computing the rate of change of LLT with respect to time .DELTA.LLT/.DELTA.t, and when .DELTA.LLT/.DELTA.t is greater than the previous maximum value and ttD is greater than a predetermined time, storing the value of each in place of its preceding value.

Abstract: A defrost cycle controller for modifying the total length of time a compressor operates before a defrost cycle is initiated, wherein the time the compressor is on between defrost cycles is referred to herein as a frost accumulation period. A microprocessor includes means for deenergizing the compressor and coupling the defrost heater to a power supply when a continuous compressor run time exceeds a predetermined demand defrost time. The microprocessor further includes means for determining the time required to actually defrost the evaporator during a defrost operation, referred to herein as a defrost time, and means for modifying the frost accumulation period in response to the time to complete the defrost operation.

Abstract: An air conditioning apparatus includes an air duct having an inlet and an outlet supplying conditioned air, and an air conditioner for cooling and heating air using a refrigeration cycle. In the refrigeration cycle, the air conditioner includes a first heat exchanger, a second heat exchanger disposed on a downstream side of the first heat exchanger, and a compressor. The air conditioner selectively operates in a cooling mode where cool air cooled by the first heat exchanger is supplied through the outlet of the air duct, in a heating mode where hot air heated by the first heat exchanger is supplied through the outlet of the air duct, and in a dehumidifying mode where air cooled by the first heat exchanger and subsequently heated by the second heat exchanger is supplied through the outlet of the air duct.

Abstract: The disclosure involves a method for defrosting an inner door of a laboratory freezer having (a) a plurality of inner doors, each closing a separate compartment, and (b) an outer door covering the inner doors. The method includes the steps of opening the outer door, removing at least one inner door, closing the outer door and defrosting the removed inner door. In that way, an inner door is defrosted without disturbing the contents of the freezer and, particularly, the contents of the compartment from which the door is removed. Optionally, the freezer user may keep a spare inner compartment door on hand and use it to immediately replace the removed door before closing the outer door. Door defrosting steps and a new hinge mechanism facilitating quick door removal are also disclosed.

Abstract: A method for controlling a defrosting operation of a refrigerator by providing a defrosting operation control method wherein a refrigerator use pattern by the user is learned. The defrosting operation control method based on the learning of the refrigerator use pattern comprises the steps of dividing a day, namely, 24 hours into a plurality of time intervals each corresponding to a predetermined period, for example, one hour, calculating the number of refrigerator door openings by time intervals, repeating the calculating step for predetermined days, storing information about arithmetic average values of the number of door openings calculated by time intervals, and performing a defrosting operation during the period that the refrigerator is not used by the user, based on the arithmetic average value information.

Abstract: Defrosting tool for maintaining the temporarily exposed cold head interface of a cryostat in frost-free condition. A plurality of electrically heated heat exchange surfaces of the tool simultaneously contacts a like plurality of cold head interface surfaces to vaporize frost formed on the latter. The tool further provides a passage for venting the vaporized frost to the surrounding environment.

Abstract: A defrost cycle for a heat pump system which optimizes the efficiency of the heat pump by initiating defrost depending upon the relationship of both the outdoor coil ambient temperature and the outdoor coil refrigerant temperature with a predetermined temperature reference level.

Abstract: A method is described for the performance optimization of refrigeration devices fed with refrigerant, in particular of air refrigeration devices in which a setting value is formed for an electrically or electronically operatable expansion valve in dependence on different temperature measurements continually ensures the ideal filling of the vaporizer. The invention includes a method of optimising the performance of a fan air refrigerator and of determining the ideal timepoint for defrosting is described, with the time for defrosting being determined by a comparative monitoring of a temperature difference, on the one hand, and a time related monitoring of the refrigerant throughflow, on the other hand. In addition the cold room temperature is regulated by the supply air sensor by switching on and switching off the compressor.

Abstract: A refrigerator is defrosted by comparing a sensed temperature in the refrigerator with a predetermined temperature when a defrost start time is reached. If the sensed temperature is too high, a compressor is caused to operate in order to reduce the temperature to the predetermined temperature. Then, the open/closed conditions of the refrigerator doors are sensed, and the defrost heater is activated if the doors are sensed as being closed.

Abstract: An automatic operation control method automatically controls the temperature setting of a chamber, the defrost cycling and the operation of a compressor and a fan motor according to the door open/close frequency and open time. The defrost cycling is operated during a predetermined time period or an auxiliary time period according to the usage frequency of a refrigerator and the door open time before entering into the defrost cycle while being started after dropping the chamber temperature according to the current state of a temperature adjuster and the average value of the chamber temperature. The operation of a compressor and a fan motor is retarded to prevent the chamber temperature from increasing after the completion of the defrost cycling, thereby minimizing the temperature change of the chamber to protect the stored food.

Abstract: A system for conditioning working fluid in environmental control systems includes arrangements for minimizing icing from a variable flow velocity turbine exit flow at subfreezing conditions, wherein the turbine is very closely located to the downstream heat exchanger, including a backpressure plate for minimizing flow velocity stratification, an internal bypass passage arranged to produce a relatively predictable bypass flow ratio regardless of the flow velocity stratification, and other anti-icing techniques.

Abstract: A system for controlling the operation of an HVAC system which includes a direct expansion coil, a condenser, a pre-cool coil, and a control system. The control system includes a controller and sensors. The controller receives signals indicative of air flow through the direct expansion coil from the sensors, compares the received signal to a stored air flow rate, and disables the compressor if the stored air flow rate is equal to or greater than the stored value. The controller is also adapted to vary air flow into an occupied space for small changes in the cooling load. In addition, the controller can artificially load the compressor during periods of small cooling load by restricting flow of a cooling agent between the cooling tower and the condenser, or by directing warm water from the condenser through the pre-coil coil.

Abstract: A system for controlling the operation of an HVAC system which includes a direct expansion coil, a condenser, a pre-cool coil, and a control system. The control system includes a controller and sensors. The controller receives signals indicative of air flow through the direct expansion coil from the sensors, compares the received signal to a stored air flow rate, and disables the compressor if the stored air flow rate is equal to or greater than the stored value. The controller is also adapted to vary air flow into an occupied space for small changes in the cooling load. In addition, the controller can artificially load the compressor during periods of small cooling load by restricting flow of a cooling agent between the cooling tower and the condenser, or by directing warm water from the condenser through the pre-coil coil.

Abstract: A heat pump system selectively operable in cooling and heating modes of operation and having an internal combustion engine prime mover which produces refrigerant vapor compression, and which produces excess heat for rejection, is provided with a first heat exchanger that evaporates compressed refrigerant in the system heating mode of operation, with a second heat exchanger which uses prime mover rejected heat to heat a working fluid, and with a fluid distribution arrangement which is selectively operable to flow the heated working fluid in heat exchange relation to said first heat exchanger also, in the system heating mode of operation to provide a defrost capabilities and to improve heat pumping heating capacity at low ambient temperatures.

Abstract: A detachable heat bonnet for mounting over and around a conventional heat pump which confines and electrically heats air confined in spaced areas between the enclosure means and the exterior surfaces of the heat pump. This supplementary heat supplied by a small, high capacity electrical heater, prevents the actuating of the auxiliary heat strips of the heat pump, when the coolness of the inside air calls for the heating cycle.

Abstract: Apparatus and method for defrosting a refrigerator in an operator actuated vacation mode wherein, after the operator actuation, the next defrost cycle is executed in accordance with the previously existing schedule in the normal defrost mode. If the time duration to execute the next defrost cycle is greater than a predetermined time period, the controller continues to defrost in the normal mode. However, if the next of a subsequent defrost cycle is executed in a relatively short time duration, the interval between defrost is significantly increased to a fixed interval of compressor run time hours.

Abstract: The present invention is an adaptive method and apparatus for detecting the formation of frost in a heat pump. The compressor cycle is interrupted and a defrosting operation is begun if the difference between the exterior ambient temperature and exterior heat exchanger temperature exceeds a difference function of the exterior ambient temperature. The length this defrosting cycle is measured and the difference function is altered if the measured length deviates from a predetermined length of time. The frost formation difference function is initially set as a linear approximation. Thereafter the difference function value at the particular exterior ambient temperature is increased if the length the defrosting is greater than an upper limit value of six minutes and decreased if the length the defrosting is less than a lower limit value of four minutes.

Abstract: There is disclosed a method for the removal of a coating of mist at the interior face of a glazing panel, especially of high thermally insulating glass, of a refrigerating cabinet, operating with forced air circulation, after the opening and closing of a door of the cabinet. In order to remove the coating, the speed of circulation of the air after closing of the door is temporarily increased until decomposition of the coating has taken place and thereafter is reduced back to the level required for normal cooling operation.

Abstract: An air cooler having coolant tubes, a drain, a pair of coolant tube supports and a defroster for preventing condensate in the drain from freezing. The coolant tube supports include a vertical plate provided with a pair of horizontally spaced notches for supporting the defroster. The notches open to the lower edge of the plate and converge towards one another.

Abstract: A refrigeration control system with self-adjusting defrost interval is provided. The system includes an improved control circuit including an external comparator and a microprocessor having a compressor output drive function and a defrost output drive function. The comparator is linked with the microprocessor with circuit elements for detecting the time period of a defrost operation, comparing the time period with predetermined defrost period limits, generating an output control signal in response to a predetermined relationship between the time period and the limits, and adjusting the defrost interval in response to the control signal whereby the defrost operation is maintained within a preferred preselected time period.

Abstract: An improved duty cycle timer provides a duty cycle control signal having alternate "on" and "off" intervals of different logic states. The timer utilizes integrated circuitry having first and second independent clock sources respectively driving first and second multistage, binary counters. One counter measures the "off" interval and the other counter measures the "on" interval. Each counter provides a signal representative of the completion of the interval which it measures, and that signal is connected to a resetting input of the opposite counter for initiating the measuring interval of that opposite counter. Typically, one interval is longer than the other. The duty cycle control signal is provided by the output of one of the counters. In an illustrated embodiment, the duty cycle timer controls operation of a defrost mechanism for a refrigeration circuit and the "off" interval is longer than the "on" interval.

Abstract: Disclosed are refrigeration system control systems and methods for compressor motor protection and defrost control. The disclosed systems and methods are generic in the sense that they are self-calibrating and so may be employed in a variety of different air conditioner or heat pump models of different sizes and capacities, without being specifically tailored for a particular model. The disclosed systems and methods sense loading on the compressor and evaporator fan motors, preferably by sensing the voltage across the capacitor-run winding of an AC induction motor and normalizing with respect to line voltage. The self-calibrating capability is implemented by taking advantage of the changing loads as a function of time on both the compressor and fan motors during both normal and abnormal operation of a refrigeration system. In overview, a reference value of motor loading is established for each motor at certain times during an ON cycle.

Abstract: The icing of the evaporator for refrigerant in a refrigeration system is checked by an air-permeable web of wire mesh which is moved along an endless path extending in front of the inlet of the evaporator to collect moisture from the flow of atmospheric air which is conveyed into the evaporator. Successive increments of the web are thereupon regenerated by melting or mechanically removing the ice and frost and by thereupon drying and cooling the increments before they return into the portion of the endless path in front of the inlet of the evaporator. Cooling of the web can be effected in a discrete cooling device or by causing a portion of the path to extend behind the outlet of the evaporator so that the web is cooled by cool atmospheric air which leaves the evaporator.

Abstract: Apparatus and a method for determining the appropriate time-to-initiate a defrost cycle in conjunction with a refrigeration circuit having a heat exchanger upon which frost may accumulate. The elapsed time period from a previous defrost cycle is used to adjust the time between defrost cycles such that the time period between defrost cycles is varied as a function of the length of the previous deforst cycle.

Abstract: In an air conditioning system having a condensate tube interconnecting a condensate pan and a trap, a vent is provided in the condensate tube for relieving any internal pressure which would otherwise cause a restriction of condensate flow within the condensate tube.

Abstract: An apparatus and process for frost control for the ambient air heat exchanger of a space conditioning apparatus. The ambient air heat exchanger is immersed in a fluidized bed enhancing the heat transfer and physically reducing frost formation. In a preferred embodiment, the fluidized bed is supported by a support bed of non-fluidized solid particles. In one of the embodiments the particulate beds may be desiccant materials. The space conditioning apparatus and method of frost control of this invention permits smaller ambient air heat exchangers and accommodates greater transient conditions due to the enhanced heat transfer and physical prevention of ice formation resulting from the fluidized bed.

Abstract: A flashing lamp for vehicles incorporates a base with an upstanding integral boss defining a worm gear. The base and the boss are of plastic or equivalent material. A frame is rotatable about the axis of the worm gear, the frame supporting at least one lamp. A motor is supported from the frame and directly rotates a worm which engages the worm gear. Brush and ring elements are provided to transmit electrical energy through the stationary base to the rotating frame and its electrical components.

Abstract: A method of removing particulate or aggregate frost deposits from cooling-coil batteries or the like in a freezing plant during operation while maintaining the state of aggregation of the removed frost deposit, recurrently removing the frost deposits by a current of compressed air directed towards and brought to sweep over the cooling-coil batteries. The apparatus for carrying out the method includes at least one compressed-air nozzle which is adapted to be recurrently directed towards and brought to sweep over said cooling-coil batteries in order to blow away the frost deposit.

Abstract: The current outdoor ambient temperature and outdoor coil temperature in a heat pump are sensed when the heat pump's outdoor coil is clean and frost-free, and from those current temperatures the split or difference that will later exist between the temperatures, when sufficient frost has built up on the outdoor coil to necessitate defrosting, may be determined. When that defrost temperature split, called the Defrost Value or DV, is reached, defrost is initiated and the frost that has accumulated on the coil is melted. Before defrost occurs, however, changing weather conditions (namely, changing outdoor temperature and/or changing outdoor relative humidity) may effectively invalidate the previously determined defrost temperature split or DV, and a frost condition may be reached at a substantially different temperature split, either greater or smaller than that previously calculated.

Abstract: This invention relates to a method of removing frost deposits from cooling-coil batteries or the like in a freezing plant during operation, while maintaining the state of aggregation of the removed frost deposit. According to the invention the frost deposit is recurrently removed by a current of compressed air being directed towards and brought to sweep over the cooling-coil batteries.The invention also concerns an apparatus for carrying out the method, said apparatus including at least one compressed-air nozzle which is adapted to be recurrently directed towards and brought to sweep over said cooling-coil batteries in order to blow away the frost deposit.

Abstract: In a freezer with a chamber, in which refrigerated surfaces tend to collect frost, with a moisture absorbing regenerable filter in order to lower the relative humidity of the freezing chamber air and counteract forming of frost therein, the filter has had to be removed and regenerated outside the freezer. This can be avoided if the air of the freezing chamber is conducted through a first flow path having a motor driven fan and a filter and ambient air is conducted through the fan and the filter in a second flow path for regeneration of the filter. An arrangement for the purpose is characterized in that the filter is arranged in a first heat-insulated flow path, intended for freezing chamber air and containing a motor driven fan, that a second heat-insulated flow path, intended for ambient air, is connected to the first one before and after a part thereof containing the filter and the fan, and that valves are arranged for shifting of the flow paths.

Abstract: An apparatus and process for frost control for the ambient air heat exchanger of a space conditioning apparatus. The ambient air heat exchanger is immersed in a fluidized bed enhancing the heat transfer and physically reducing frost formation. In a preferred embodiment, the fluidized bed is supported by a support bed of non-fluidized solid particles. In one of the embodiments the particulate beds may be desiccant materials. The space conditioning apparatus and method of frost control of this invention permits smaller ambient air heat exchangers and accommodates greater transient conditions due to the enhanced heat transfer and physical prevention of ice formation resulting from the fluidized bed.

Abstract: Method and apparatus are disclosed wherein a circuit for detecting the phase angle of a motor is disclosed. This circuit utilizes zero crossing detectors to compare the voltage and current signals such that a digital signal indicating the value of the phase angle by the duration of the signal is generated. Additionally, a method and apparatus for comparing the phase angle to the reference phase angle value is disclosed. Means for updating the reference value and for comparing the detected value to the reference value to determine appropriate defrost initiation time are additionally disclosed.

Abstract: A drain assembly including a drain pipe and a heater oriented to heat the drain pipe, in combination with a defrosting type refrigeration evaporator intended for use within an enclosure whose temperature is maintained lower than the freezing point of water. The drain pipe has a discontinuity positioned in an upper portion so that defrost meltage traversing the drain tube in the ordinary course will not leak out of the pipe through the discontinuity, but that meltage backing up in the drain pipe because the drain pipe has been plugged by ice or dirt, will flow out of the discontinuity onto the freezer floor rather than backing up further into the drain pan, and the discontinuity will be maintained free of ice because it is heat transfer relation to the heater.

Abstract: An air cooling evaporator for use in refrigeration systems under conditions where frost is deposited on the cooling surfaces having a drain pan positioned under the cooling surface and a water distributing pan positioned over the cooling surface. The water distributing pan has as a distribution device holes positioned in the bottom of the pan, with the holes so positioned or sized that more water is distributed to the portions of the coil.

Abstract: A refrigerated display case having a display space and an access opening, reversible fans for circulating air through an inner air conduit and across the access opening between a first outlet and a first inlet in a refrigeration mode to establish a primary air band; a second set of fans for circulating air through a second air conduit and across the access opening adjacent to and outwardly of the inner primary air band between a second outlet and second inlet to establish a secondary air band; and defrost cycle control means for reversing the air flow direction of the primary air band during a defrost cycle while maintaining the air flow direction of the second air band continuously in the same direction during both refrigeration and defrost cycles.

Abstract: A method and apparatus for promoting effective heat transfer between refrigerant flowing through a heat exchanger and air flowing thereover and for providing a method of defrost of a portion of the heat exchanger wherein frost has accumulated. A headering arrangement is provided such that during defrost a portion of the heat exchanger is isolated and the fluid being supplied to the frosted portions of the coil is directed to the frosted portions to make the most effective use of the heat energy therein. Valve means are provided for regulating the flow of refrigerant to an intermediate header during defrost.

Abstract: A control and method for defrosting the outdoor heat exchanger of an air source heat pump. A defrost cycle is initiated when ice and frost have accumulated on the outdoor heat exchanger sufficiently such that, as a function of the indoor temperature of a comfort zone, the maximum permissible heat transfer degradation at which the efficiency and reliability of the temperature conditioning system are optimized, has occurred. Heat transfer degradation is determined from the outdoor ambient air temperature and the temperature of either the outdoor heat exchanger, or the compressor suction line. If the temperature of the outdoor heat exchanger or the suction line is less than a predetermined value, a deferred defrost cycle is initiated wherein the defrost cycle starts after a fixed time interval has elapsed.

Abstract: A defrost system for refrigerating apparatus having a refrigerating mode and a defrosting mode including an evaporator and an electric resistance heater in heat transfer relationship with the evaporator. There is provided a timer to actuate a normally open defrost initiation switch to energize the heater periodically and initiate a defrosting mode. A defrost terminating thermostat switch is in the heater circuit and will open at a predetermined elevated temperature to deenergize the heater and close at a lower temperature. A voltage sensor across the normally open defrost initiation switch senses periodically and provides a signal when voltage in the heater circuit is interrupted. The multiple voltage sensor signals are stored in a memory bank over a predetermined period of time and when the voltage is interrupted for the predetermined period of time, an alarm is actuated to indicate failure of the defrost system.

Abstract: A device for preventing icing in a thermostat-controlled evaporator in an air conditioning unit for motor vehicles including a first sensor for sensing the speed of the air through the evaporator and preferably also a second sensor for sensing the humidity of the air. A control unit sets the thermostat to a lowest permissible evaporator temperature which is dependent on the speed and humidity of the air.

Abstract: A control and method for defrosting the outdoor heat exchanger of an air source heat pump. A defrost cycle is initiated when ice and frost have accumulated on the outdoor heat exchanger sufficiently such that, as a function of the indoor temperature of a comfort zone, the maximum permissible heat transfer degradation at which the efficiency and reliability of the temperature conditioning system are optimized, has occurred. Heat transfer degradation is determined from the outdoor ambient air temperature and the temperature of either the outdoor heat exchanger, or the compressor suction line. If the temperature of the outdoor heat exchanger or the suction line is less than a predetermined value, a deferred defrost cycle is initiated wherein the defrost cycle starts after a fixed time interval has elapsed.

Abstract: Food thawing apparatus is disclosed specifically adapted for use in a refrigeration appliance. An enclosure having good thermal communication with surrounding environment is provided with a pair of planar electrodes defining a food thawing zone. One of the electrodes is movable to allow insertion of a frozen food load. A high frequency, relatively low wattage power supply provides uniform energy distribution throughout the feed load for gentle heating (thawing). Frequencies of 27.12 MHz or 43 MHz are suggested along with a power level of 100 watts or below, preferably 35-80 watts.

Abstract: In a compressed air powered refrigeration system for aircraft containing a refrigeration turbine and associated heat exchangers for supplying cool air to the aircraft cabin, air is recirculated from the cabin by a recirculation means and combined with the turbine discharge air to simultaneously melt ice present in the turbine discharge and provide cooling to the recirculated air. The lack of ice in the turbine discharge allows the use of an ice-free regenerative heat exchanger, in heat exchange relation with the mixture of the turbine discharge air and recirculated cabin air, to condense moisture from the air entering the turbine. The use of heat from the cabin air to melt ice coupled with maximum utilization of the recirculation means supplying the recirculating cabin air enables the turbine to provide air at a temperature below freezing and results in improved cycle efficiency as well as maximum possible ventilation rate to the load.