Abstract: A hot gas defrost system for a refrigeration cycle, including at least a compressor, reversing valve, condenser and evaporator. During defrost, the reversing valve directs the superheated refrigerant from the compressor to the evaporator. The hot gas traverses the evaporator coil which, in turn, causes the ice or frost to melt. The hot gas defrost refrigeration system may also include a receiver to store the refrigerant during the refrigeration and defrost cycles.

Abstract: A hot gas defrost system for a refrigeration cycle, including at least a compressor, reversing valve, condenser and evaporator. During defrost, the reversing valve directs the superheated refrigerant from the compressor to the evaporator. The hot gas traverses the evaporator coil which, in turn, causes the ice or frost to melt. The hot gas defrost refrigeration system may also include a receiver to store the refrigerant during the refrigeration and defrost cycles.

Abstract: A hot gas defrost system for a refrigeration cycle, including at least a compressor, reversing valve, condenser and evaporator. During defrost, the reversing valve directs the superheated refrigerant from the compressor to the evaporator. The hot gas traverses the evaporator coil which, in turn, causes the ice or frost to melt. The hot gas defrost refrigeration system may also include a receiver to store the refrigerant during the refrigeration and defrost cycles.

Abstract: A refrigeration system is provided with a receiver and a plate attached to the mouth of the outlet tube of the receiver to prevent the formation of a liquid refrigerant vortex. The mouth of the receiver outlet tube has an enlarged cross-sectional area to decrease the velocity of the liquid entering the tube. A deflector for vertical receiver applications interrupts refrigerant downward flow from the receiver inlet to prevent bubble formation in the liquid.

Abstract: The refrigeration system is provided with a bundle of refrigeration tubes extending through heat exchange fins, with the bundle forming a condenser section, a receiver section and a subcooler section. A sight glass is positioned in the line between the receiver and the subcooler to facilitate the refrigerant charging process. The system also includes a floating head arrangement which allows the condenser pressure to fluctuate with the ambient temperature. A solenoid valve leading to an expansion valve cycles on/off in response to compressor suction pressure. A check valve insures that a column of liquid is always immediately upstream from the expansion valve.

Abstract: A hot gas defrost system for a refrigeration cycle, including at least one compressor, condenser, receiver, expansion valve and evaporator. During defrost, a pressure-sensitive valve to the condenser inlet is normally closed, and the flow of refrigerant from the compressor bypasses the condenser and flows to the receiver. However, when the pressure in the system reaches a critical point, the pressure-sensitive condenser inlet valve will open to release the excessive pressure. The condenser inlet valve is also temperature-sensitive and will open if the ambient temperature surrounding the condenser is above a specific point. Opening of the condenser valve permits the utilization of the hot gas in the condenser for defrost and to decrease the thermal shock resulting from the superheated vapor contacting the evaporator coil. The compressor, which needs a constant flow of liquid refrigerant for cooling, is continually supplied with liquid refrigerant.

Abstract: Leaks in tube bundles for a heat exchanger are eliminated or minimized by tube interrelated techniques. A floating tube bundle is constructed with separate support elements also secured to the heat dissipating fins and extending through and supported by the support plates. Thin-walled copper tubing similar to that used for the fluid-carrying tubes is used as support tubes, and steel rods are inserted into these support tubes to provide the necessary strength. To minimize leakage in the area where the tube bundle is joined to a header, connector tubes are provided that have one end joined to the header and the other end extending into one of the tubes of the tube bundle sufficiently far that the end of the connector tube passes through the support plate and at least one fin.

Abstract: Circumferentially spaced bosses concentrically position a male tube end within a female tube end. The bosses have a preferred shape which permits molten brazing material to flow evenly between the tubes, ensuring a void-free joint. The bosses provide a relief clearance at the mouth of the male tube to allow the formation of a continuous annular band of brazing material at this end. Stop tapers on the bosses allow the female tube to be pressed onto the male tube for stability prior to brazing. The bosses also limit the overlap of the two tubes to a maximum distance, ensuring adequate heat conduction to the innermost portion of the male tube. Spacers, integral with the bosses, form an axial gap between the tubes into which the brazing rod more readily melts.

Abstract: An evaporative condenser having a cylindrical fiberglass housing which provides a circumferential air flow across a plurality of concentrically oriented spiral condensing coils. The planar spiral coils are generated through the compression of a conical winding of tubing formed about a multi-tiered platform, to form an evenly-spaced spiral condensing coil. Each layer of tubing is affixed to a plurality of radial braces, which provide the evaporative coils with sufficient structural integrity to be individually employed. A method and apparatus for producing spiral coils having uniform spacing between adjacent revolutions.

Abstract: An improved system for control of defrost in a refrigeration system of the type wherein one or more evaporators are defrosted by hot gas from the compressor while one or more evaporators remain in refrigeration operation. Prior to operating diverting valves to establish defrosting gas flow in an evaporator, a liquid line valve is closed and the system is pumped down to a predetermined amount of refrigerant charge in the defrost loop. In a preferred embodiment, this is accomplished by first opening the liquid line valve to flood the system, then closing it for a predetermined time interval to pump down to the predetermined amount of charge prior to operating the diverting valves.

Abstract: Condensing head pressure in a refrigeration system having its condenser exposed to low outside ambient temperatures is controlled to provide the minimum head pressure required for a given mode of operation. A hierarchy of operating modes, each with its associated pressure is established, including normal refrigeration, evaporator defrost and heat reclaim. The control system prevents system head pressure from going below the minimum required for the operating mode in effect at a given time, with modes requiring higher pressure overriding lower pressure modes when required. In heat reclaim operation, high pressure gas from the compressor is diverted through a heat reclaim coil, and a subcooling sensor or other sensing means controls system head pressure to the minimum pressure that will maintain full condensing in the heat reclaim coil, which is the most economical mode of operation.

Abstract: A control system for a refrigeration system having an air-cooled condenser exposed to normal year round ambient temperatures. Head pressure is controlled in response to sensed subcooling of the refrigerant in the liquid line near the entrance to the expansion device, so as to prevent the occurrence of flash gas at the expansion device, while still allowing minimum head pressures so as to improve energy efficiency. In alternate embodiments, additional controls are provided for assuring at least a predetermined minimum pressure differential across the thermostatic expansion valve. In one preferred embodiment a two-bulb sensing technique is used for subcooling and pressure differential sensing. Both series and parallel condenser-receiver connection systems are disclosed, as are a number of different subcooling sensing and control embodiments.

Abstract: Apparatus for defrosting a heat exchanger, comprises a plurality of spaced parallel heat exchanger fins having sets of circular, collared, axially aligned apertures. The collars of each set coacting to define an essentially continuous tube. Refrigerant tubes pass through the essentially continuous tubes defined by a majority of the sets of apertures and are sized for engagement by the collars of the apertures in intimate heat conductive relation. Axially replaceable electrical heating elements traverse the essentially continuous tubes defined by a minority of sets of apertures instead of refrigerant tubes and the heating elements are sized to fit loosely in the apertures so the heat is transmitted from the element to the collars both by radiation and by conduction and so that axial relative movement between the elements and the collars is enabled.