The compressor in a refrigeration system is controlled solely by a variable speed drive which controls the motor of the compressor by virtue of the varying of the frequency of the electricity provided to the motor. To minimize the initial cost and to minimize operating costs, the variable speed drive is cooled by refrigerant from the refrigeration system which permits the use of a smaller drive, and the variable speed drive is operated at, or approaching, a unity power factor.

Variable speed drive chiller system

A variable capacity vapor compression cooling system is presented. In the system of the present invention, air conditioning requirements are entered into a microprocessor which controls the system. Liquid phase refrigerant entering an evaporator is regulated by a microprocessor controlled electronic expansion valve. Evaporated refrigerant is delivered to a pair of compressors from the evaporator. The motors for the compressors are controlled by a controller. Each of the compressors has a feed back loop attached thereto for feeding back some of the inducted vapor phase refrigerant. The amount of vapor fed back in each loop is regulated by a corresponding microprocessor controlled multi-purpose valve. The compressed vapor phase refrigerant is then presented to a condenser which condenses the refrigerant to the liquid phase which is used for cooling, as is well known in the art. Thereafter, liquid phase refrigerant is presented to an economizer where vapor phase refrigerant (i.e., flash gas) is drawn off. The amount of vapor phase refrigerant drawn off is regulated by a microprocessor controlled electronic expansion valve. This vapor phase refrigerant is presented to the multi-purpose valves where it is directed to the respective compressors. The liquid phase refrigerant is delivered to the evaporator with the flow thereof being regulated by a microprocessor controlled electronic expansion valve. Accordingly, the above describes a complete cycle which can be capacity varied without unloading of the compressors, as described more completely below. It is an important feature of the system of the present invention that capacity is varied without unloading the compressors.

Variable capacity vapor compression cooling system

A compressor (90) includes a male rotor (42) which is axially aligned with and in communication with two female rotors (44, 46). The male rotor is driven by a motor (92), in other words the male rotor is the drive rotor. The male rotor has a plurality of lobes (48-55) which intermesh with a plurality of flutes (56-67) on each of the female rotors. The male rotor comprises an inner cylindrical metal shaft (82) with an outer composite material ring (84) mounted thereon. The ring includes the lobes of the male rotor integrally depending therefrom. The lobes of the male rotor being comprised of a composite material allows positioning of the female rotors at a small clearance from the male drive rotor. This clearance is small enough that the liquid refrigerant itself provides sufficient sealing, cooling and lubrication. The positioning of the female rotors on opposing sides of the male rotor balances the radial loading on the male rotor thereby minimizing radial bearing loads.

Multi-rotor helical-screw compressor

A heat recovery system includes a first air cooler for cooling compressed air from a compressor, a first oil cooler for cooling a lubricant from the compressor, and a second air cooler and/or a second oil cooler serving as a heat recovering heat exchanger. The second air cooler heats water with the heat of the compressed air to be fed to the first air cooler. In contrast, the second oil cooler heats water with the heat of a lubricant to be fed to the first oil cooler.

Heat recovery system

A positive displacement compressor designed for near isothermal compression. A rotor includes a curved sealing portion that coincides with a in an interior rotor casing wall. Liquid injectors provide cooling liquid. A gate moves within the compression chamber to either make contact with or be proximate to the rotor as it turns. Gate positioning systems position the gate in this manner, taking into account the shape of the rotor. Outlet valves allow for expulsion of liquids and compressed gas. The unique geometry and relationship between the parts provides for efficiencies and higher pressures not previously found in existing compressor designs.

Compressor with liquid injection cooling

In a compression system which incorporates a rotary helical screw compressor, and for any type of gas or refrigerant, the working liquid oil is atomized through nozzles suspended in, and parallel to, the suction gas flow, or alternatively the nozzles are mounted on the suction piping In either case, the aim is to create positively a homogeneous mixture of oil droplets to maximize the effectiveness of the working liquid oil in improving the isothermal and volumetric efficiencies The oil stream to be atomized may first be degassed at compressor discharge pressure by heating within a pressure vessel and recovering the energy added by using the outgoing oil stream to heat the incoming oil stream The stripped gas is typically returned to the compressor discharge flow In the preferred case, the compressor rotors both contain a hollow cavity through which working liquid oil is injected into channels along the edges of the rotors, thereby forming a continuous and positive seal between the rotor edges and the compressor casing In the alternative method, working liquid oil is injected either in the same direction as the rotor rotation or counter to rotor rotation through channels in the compressor casing which are tangential to the rotor edges and parallel to the rotor centerlines or alternatively the channel paths coincide with the helical path of the rotor edges

Anthony N. Fresco

Papers

Apparatus and methods for cooling and sealing rotary helical screw compressors