Abstract: A self-cleaning heat exchanger (10) has a reversible fan (12) located between two tube banks (14, 16) with a pressure switch (24) connected thereto. The fan (12) rotates in one direction blowing across the first tube bank (14) and drawing air over the second tube bank (16). The pressure switch and fan are interconnected by two relays (28, 30). When the refrigerant pressure in the tube banks exceeds the threshold pressure, the relay (28) is closed and grounded and electric current flows through the relay (30). The change in direction of current flow will reverse the polarity of the windings in motor (13) and thus the rotation of the motor (13) and the fan (12) thereby reversing air flow to remove debris from one tube bank while withdrawing heat from the other without loss of cooling efficiency.

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 compact, air cycle air conditioning system including compressor, turbine, heat exchanger and high speed electric motor is thermostatically controlled to supply either hot or cold conditioned air to a load air space. In a second arrangement, compact, exhaust gas driven air cycle air conditioning system including a compressor, turbine, two heat exchangers and an exhaust turbine is controlled by means of an exhaust gas bypass arrangement and supplies either hot or cold conditioned air to a load air space. In a third arrangement compact, exhasut gas driven air cycle air conditioning system includes an expansion turbine, two compressors, two heat exchangers and an exhaust turbine which is preferably controlled by means of an exhaust gas bypass arrangement and supplies either hot or cold conditioning air to a load air space.

Abstract: A transport refrigeration system including a refrigerant compressor which is alternatively driven by an internal combustion engine or an electric induction motor. The transport refrigeration system achieves and maintains a predetermined set point temperature in a served space by heating and cooling cycles. When additional heat is required during a heating cycle while the internal combustion engine is driving the compressor, capacitors are connected across the induction motor, to cause the motor to function as an induction generator and build up an output voltage. The output voltage is monitored, and when it is sufficient to sustain a load, resistors located to aid the heating cycle are connected to receive the output voltage.

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 refrigeration system including a compressor, condenser, capillary tube and evaporator includes a hot gas bypass defrosting capability provided by a bypass means around the capillary tube. Defrosting is achieved by the use of hot, uncondensed refrigerant, without requiring a reversal of the flow of refrigerant through the system. An exemplary bypass means includes a solenoid valve and associated tubing to form an alternate, low restriction path for the refrigerant to bypass the capillary tube. When the solenoid valve is closed, refrigerant is forced through the capillary tube for normal refrigeration. However, when the solenoid valve is open, condensation of refrigerant in the condenser is inhibited, and hot refrigerant gas is delivered directly to the evaporator for defrosting. The solenoid valve is controlled in response to the total accumulated running time of the compressor for improved control of the defrosting cycles.

Abstract: A hot gas defrost refrigeration system has a compressor, a condenser, a receiver, an evaporator, interconnected by fluid passage means and incorporating valve means to cause refrigerant to flow sequentially through the compressor, condenser, receiver and evaporator to the compressor during the refrigeration cycle. The refrigeration system includes a superheater and defrost passage means, including valve means, connecting the evaporator outlet to the condenser inlet and connecting the condenser outlet through the superheater to the compressor inlet, bypassing the receiver. The passage means connecting the compressor outlet with the evaporator inlet includes a superheat passage in heat exchange relationship with the superheater for transferring heat from the refrigerant discharged from the compressor outlet to the refrigerant delivered to the compressor inlet during the defrost cycle.

Abstract: A fiber optic frost sensor for use in a refrigerating apparatus having evaporator coils is used to determine when ice or frost has accumulated on the evaporator coils to an extent that the air around the evaporator coils cannot be cooled efficiently. The frost sensor includes a fiber optic cable located adjacent to the evaporator coils, the fiber optic cable extending between a light transmitter and a light receiver. As ice and frost accumulate on the evaporator coils, the ice and frost also accumulate on the outer surface of the fiber optic cable resulting in a change in the amount of light traveling from the transmitter to the receiver through the fiber optic cable. When the amount of light received by the receiver changes a preselected amount, the receiver determines that a defrost cycle needs to be initiated to melt the accumulated ice or frost. In one embodiment, a serpentine fiber optic cable is looped along the evaporator coils.

Abstract: A refrigeration unit comprising a cooling circuit having a compressor, a condenser and an evaporator, and said unit including a hot gas valve and a hot gas bypass passage bypassing the condenser and forming a defrost circuit, so that when the evaporator is frosted upon operation by means of the cooling circuit, constant quantity refrigerant is circulated around the defrost circuit to perform a defrosting operation.

Abstract: A refrigeration system, and a method for operating the system, having a two-stage compressor for supplying refrigerant to a cooling coil, and having a desuperheater unit disposed between the two compressor stages. This desuperheater unit includes a container having heat exchange fluid therein and a coil, disposed in the heat exchange fluid, through which the refrigerant passes. During normal operation of the refrigeration system, both compressors are running. The desuperheater unit between the two compressor stages reduces the temperature of the compressed refrigerant before it reaches the second stage. The temperature of the heat exchange fluid is correspondingly increased in the course of the heat exchange. Also during normal operation, frost accumulates on the cooling coil, which is removed by a control device initiating a defrost cycle. When the defrost cycle begins, the first stage compressor is turned off while the second stage compressor continues to run.

Abstract: A sensing and control device is provided for monitoring the build up of frost, ice and condensate on the cooling coils of refrigeration unit. The microwave unit is placed a fixed distance away from a cooling coil and provides an emitted wave and reflected wave. The reflected wave, and the resulting standing wave, shift in spacial phase which differs due to the accumulation of ice or frost and provides a voltage change which is observed by an electronic circuit to shut off the cooling unit while activating a defrost cycle or merely keeping the refrigeration shut off until the ice melts. The sensing and control unit is also used to sense the removal of ice and frost by heating of the defrost cycle and thus establish the termination of defrost cycle and restoration of refrigeration.

Abstract: In one exemplar embodiment, a method and apparatus are disclosed for detecting the accumulation of frost on the evaporator coils of refrigerating equipment. An emitter or source of electromagnetic radiation having a selected narrow band of wavelengths and a selected intensity directs the electromagnetic radiation at the frost. A detector, spaced from the frost and emitter, receives the narrow band of electromagnetic radiation and detects changes in the intensity of the radiation due to absorption or scattering of the radiation by the frost in a relation proportional to the thickness of the frost. Control means responding to the detected change in intensity of the radiation is provided to initiate a defrost cycle and control the accumulation of the frost on the evaporator coil surfaces. Other embodiments of the invention include a liquid level detector and a physical state phase change detector.

Abstract: In one exemplar embodiment, a method and apparatus are disclosed for detecting the accumulation of frost on the evaporator coils of refrigerating equipment. An emitter or source of electromagnetic radiation having a selected narrow band of wavelengths and a selected intensity directs the electromagnetic radiation at the frost. A detector spaced from the frost and emitter receives the narrow band of electromagnetic radiation and detects changes in the intensity of the radiation due to absorption or scattering of the radiation by the frost in a relation proportional to the thickness of the frost. Control means responding to the detected change in intensity of the radiation is provided to initiate a defrost cycle and control the accumulation of the frost on the evaporator coil surfaces. Other embodiments of the invention include a liquid level detector and a physical state phase change detector.

Abstract: A control system for a refrigeration heat pump having an outdoor coil through which air is blown by a fan for extracting heat from outdoor air with means to defrost the coil periodically has a differential pressure responsive means responding to the differential air pressure across the outdoor coil. A time control means periodically operates the heat pump for a time controlled operation for predetermined time period (such as 90 minutes of elapsed operating time) and measures and stores the value of the differential pressure across the coil at the end of the time period in memory. A control means controls the heat pump between the periodically time controlled operations for normal operations for a total elapsed time operation in a pressure controlled operation until the pressure differential as previously stored occurs at which time a defrost cycle is initiated. Periodically a time controlled operation is initiated to update the pressure stored in the memory.

Abstract: A dehumidifier for converting warm moist air to dry cool air. The dehumidifier includes a fan for delivering warm moist air to a plenum chamber, a dehumidifier chamber mounted adjacent to and communicating with the plenum chamber and provided with a condensing surface, a device for supplying a refrigerant to the dehumidifier chamber, and a structure for supplying short bursts of heat to the condensing surface. The condensing surface can be tapered or straight lengthwise and can be of any cross-sectional shape. Further, the condensing surface can comprise a plurality of air passages, again tapered or straight and of any cross-sectional shape.

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: An open top refrigerated display case having mechanisms for establishing an inner refrigerated air band encircling the display portion of the case and an outer air band also encircling the display portion and being positioned outside of the inner air band. An inner air conduit passes around the side and bottom walls of the cabinet of the display case and has an outlet opening at one end of the opening in the top of the cabinet and an inlet opening at the other end of the top opening in the cabinet. A fan circulates air through this inner air conduit with the air leaving the outlet opening and being directed toward and received by the inlet opening of the conduit, thereby establishing an inner air band along with an inner air curtain across the opening in the top of the cabinet. An evaporator coil arranged within the inner air conduit serves to refrigerate the air passing along the inner air band during a refrigeration cycle of operation.

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 refrigeration system having an increased efficiency of operation and reduction in power consumption. Low head pressure and subcooling the liquid refrigerant emitted from the remote condenser, the efficiency of operation of the compressor of the refrigeration system can be substantially increased. The particular type of refrigeration system of concern generally includes a compressor for compressing a gaseous refrigerant, a condenser for condensing the gaseous refrigerant and subcooling the liquid refrigerant, a receiver for receiving the liquid and a plurality of display cases having evaporators for evaporating the liquid refrigerant. The gaseous refrigerant passing through the condenser is first condensed into a liquid at a condensing temperature of approximately 10.degree. to 25.degree. F. above a preselected cooling temperature. The condensed liquid is then subcooled to the preselected cooling temperature which should be preferably either approximately 50.degree. F.

Abstract: The invention provides a heat pump system employing a refrigerant charged space and including at least two evaporators, one of which is an ambient air head absorber, and the other of which can be of the same type, or of the type obtaining heat from solar insolation, water, ground heat, etc. The coil or coils of an ambient air absorber must be defrosted periodically. In the system of the invention defrost heat is applied to the evaporator coil or coils while the compressor is operating, such defrost heat causing vaporization of the refrigerant therein. The system includes a pressure containment valve between the evaporator and the compressor that maintains the vapor pressure of the vaporizing liquid in the coil above the value at which the ice will readily melt, the valve releasing excess vapor to the compressor and then to the condenser which discharges the heat to the space to be heated. Thus, the only part of the defrost heat lost from the system is that required to melt the ice.

Abstract: A demand defrost system in which a high resistive epoxy resin hermetically seals a capacitive sensor plate and a noise immune phase detector detects a phase shift caused by the build up of frost.

Abstract: A reverse air cycle type heat pump is provided that utilizes a refrigeration system having a unidirection refrigerant flow wherein the condenser and evaporator retain their functions, but the air directed across them is redirected for different operations. The refrigeration system employed in the air cycle type heat pump is further provided with a secondary defrost circuit that includes the system liquid line and a conduit having a valve which permits refrigerant flow to bypass the compressor upon termination of compressor operation. A sensing means associated with the system expansion device is arranged on the suction line in a manner that allows the expansion device to regulate the flow of refrigerant through the liquid line in the normal manner when the compressor is operating, while allowing unrestrictive refrigerant flow through the liquid line when compressor operation terminates and the system pressure differential is equalized.

Abstract: An open front refrigerated display case having mechanisms for establishing an inner refrigerated air band encircling the display portion of the case and secondary air band also encircling the display portion and being positioned outside of the inner air band. An inner air conduit passes around the cabinet of the display case and has an outlet opening at one end of the access opening in the front of the cabinet and an inlet opening at the other end of the front access opening in the cabinet. A fan circulates air through this inner air conduit with the air leaving the outlet opening and being directed toward and received by the inlet opening of the conduit, thereby establishing an inner air band along with an inner air curtain across the access opening in the front of the cabinet. An evaporator coil arranged within the inner air conduit serves to refrigerate the air passing along the inner air band during a refrigeration cycle of operation.

Abstract: Apparatus and method for defrosting a dual refrigeration circuit refrigeration system. During defrost one of the refrigeration circuits is operated to supply heat energy to the frosted heat exchanger of the other circuit and the fan circulating heat transfer media through a heat exchanger of each circuit is reversed such that heat transfer fluid is heated by one refrigeration circuit and then used to defrost a heat exchanger of the other circuit.

Abstract: An evaporator coil defrost control system for a refrigeration system comprising refrigerant compression means, a condenser coil, an evaporator coil, and an electric motor operated fan positioned adjacent to said evaporator coil and adapted, when energized, to blow air through said evaporator coil, said defrost control system comprising: strain sensing means connected to said fan blades and adapted to measure force applied to said fan and to produce a signal indicative of said measured force; controller means connected to said strain sensing means to receive the signal therefrom and having operative connections to said system, said controller being adapted to place said system in a defrost mode of operation upon said signal of said strain sensing means having a characteristic indicative of a significant frost build-up on said evaporator coil.

Abstract: A method and apparatus for defrosting cooling elements in a freezer chest of the type displaying frozen food items. The chest, having an open top, is provided with a channel around the food items through which air is circulated by means of a fan. The air is also directed over the open top of the freezer. Upon the defrost cycle, the cooling elements are shut down, and the air flow is reversed and directed away from the food items whereby air is drawn into the channel from the atmosphere outside of the freezer chest.

Abstract: A freezing refrigerator has a freezing chamber for accommodating food to be freezed and a cold chamber for accommodating food kept at low temperature, those chambers being separated by a heat insulative member and provided with doors, respectively. The cold chamber is provided therein a cold chamber cooler for cooling the inside thereof and the freezing chamber is provided therearound with a first freezing chamber cooler for cooling the inside therein. A second freezing chamber cooler is provided close to the rear side of the freezing chamber but is separated from the inner surface of the freezing chamber. The surface temperature of the second cooler is kept lower than that of the first freezing chamber cooler. A shield plate is further provided to blind one from seeing the second cooler when the door for the freezing chamber is open, the shield plate being disposed close to the second cooler.

Abstract: A refrigeration system having an increased efficiency of operation and reduction in power consumption. By maintaining a low head pressure and subcooling the liquid refrigerant emitted from the remote condenser, the efficiency of operation of the compressor of the refrigeration system can be substantially increased. The particular type of refrigeration system of concern generally includes a compressor for compressing a gaseous refrigerant, a condenser for condensing the gaseous refrigerant and subcooling the liquid refrigerant, a receiver for receiving the liquid and a plurality of display cases having evaporators for evaporating the liquid refrigerant. The gaseous refrigerant passing through the condenser is first condensed into a liquid at a condensing temperature of approximately 10.degree. to 25.degree. F. above a preselected cooling temperature. The condensed liquid is then subcooled to the preselected cooling temperature which should be preferably either approximately 50.degree. F.

Abstract: Apparatus and a method for operating a refrigeration system without reverse cycle defrost are disclosed. A heat exchanger is divided into a plurality of zones, one zone being constantly utilized as a subcooler to both defrost said zone and to subcool the refrigerant. The remaining zones of the heat exchanger are utilized as an evaporator as is known in the art. A selector valve which is capable of indexing liquid refrigerant flow between zones and receiving gaseous refrigerant from the remaining zones is also disclosed. Additionally, a header arrangement having both expansion means and a conduit controlled by check valve is utilized to direct refrigerant flow from the subcooled zones to the remaining zones of the heat exchanger which act as an evaporator.

Abstract: A refrigerator cabinet having a chamber divided by a mullion into a freezer and fresh food compartment, each having a front door open. Arranged in the mullion and front door opening of the freezer is auxiliary liquid line loop arrangement whichprevents condensation from forming on the freezer front door openings. A valve is provided in the auxiliary line arrangement for controlling flow through the auxiliary liquid line in response to the ambient relative humidity conditions.

Abstract: A cooling unit for refrigeration systems having a substantially vertically disposed air cooling element, utilizing either a volatile or a non-volatile refrigerant, upon which element frost accumulates during the course of the refrigeration process. The element includes heaters to periodically warm the element to a temperature above 32.degree. F. to thaw the frost. These heaters have their heating capacity adjusted so that more heat is applied at the bottom portion of the frost-collecting air cooling element and less heat is supplied to the upper portion.

Abstract: An energy conserving refrigerated display case having a control circuit that diverts electrical energy from the antisweat heaters operable during the refrigeration mode of the display, to an evaporator defrost heater during the defrost mode of the display.

Abstract: In a frost detector mounted proximate cooling fins of refrigeration apparatus, an emitter directs pulses of infrared radiation in the direction of the fins. When there is frost buildup on the fins, the frost reflects the radiation back towards a detector, the detector and emitter being mounted at a slight angle to each other.

Abstract: An open show case of cold-air-circulation type having a front access opening, a passage with a cooler and an air fan for circulating cold air therethrough and forming a cold air curtain across the access opening, and at least one other air passage with an air fan for circulating air and forming another protective layer of air curtain outside of the cold air curtain is defrosted by controllably operating the fans respectively in mutually adjacent air passages to blow air in mutually opposite directions thereby to cause air to flow in short-circuited flow at passage openings at the access opening, whereby air ejected from one passage at the access opening is immediately sucked into the adjacent passage without crossing the access opening, thereby to draw in warm outside air into the cold air passage and thereby to accomplish defrosting.

Abstract: A refrigeration system including at least one compressor, a condenser for receiving hot gaseous refrigerant from the compressor and condensing same, a discharge line for supplying hot gaseous refrigerant from the compressor to the condenser, a plurality of expansion valves associated with a plurality of evaporators, a liquid line for passing condensed refrigerant from the output of the condenser to the expansion valves and evaporators, a return line extending from the evaporators to the input of the compressor to supply refrigerant thereto, a receiver for holding a reservoir of refrigerant, a bypass line connecting the receiver to the liquid line, a hot gas defrost means for selectively passing hot gaseous refrigerant through one or more of the evaporators for defrost and a balancing line operable during defrost responsive to a pressure within the receiver greater than within the discharge line to provide fluid flow communication therebetween to equalize refrigerant pressure between the receiver and discharge

Abstract: In an apparatus for defrosting an evaporator in a heat pump which is driven by a compressor, the evaporator consists of a fan and a heat exchanger through which the fan drives air for heat exchange with the heat transport medium flowing through the heat exchanger. A pressure sensitive switch is arranged to actuate a member for reversal of the pumping direction of the compressor when the pressure differential .sigma. p of the air over the heat exchanger has reached a predetermined value, and a temperature sensitive switch which senses the temperature at the heat exchanger, is arranged to actuate the reversal member to maintain the reversed pumping direction of the compressor as long as the temperature at the heat exchanger is less than or equal to 0.degree. C.

Abstract: A device to be used e.g. in cooling radiators, for monitoring the formation of frost and for defrosting. Frost formed on the cooling radiator causes a change in the quantity of light received by a light receiver from a light transmitter, and when the quantity of light received by said light receiver reaches a predetermined value a unit controlled by the light receiver initiates the drfrosting which continues until all of the frost has molten.

Abstract: A refrigeration system having an improved defrost control including a thermal relay, a bimetal thermostat, and a thick film/hybrid microelectronic element responsive to cumulative humidity of the refrigerated air comprising a moisture sensor/cumulator portion and a control circuit portion on a ceramic substrate. The sensor/cumulator absorbs water vapor at a rate proportional to the relative humidity of the refrigerated air and activates a heater element of the thermal relay to initiate a defrost period. The element is reset by thermally removing a preselected amount of the absorbed water vapor. The defrost period is terminated by a bimetal thermostat. Alternatively, a thermal responsive resistor may be included in the control circuit to terminate the defrost period.