Refrigeration compressor is a device responsible for compressing and pumping refrigerant vapors in appropriate equipment. Widely distributed in air conditioning, industrial units. But most often it is used in industry and in deep-freezers. According to a number of characteristics, the equipment is divided into several varieties.
Device view
In this category there are three groups. The first includes a piston compressor of the refrigeration unit. Let us briefly consider the principle of its action. The gas in such units is compressed by a piston. When it goes down, the refrigerant enters the compressor working space. When it is lifted, steam escapes from the unit. The rotary refrigeration compressor is powered by a speaker. Thanks to this part, pressure is injected. The horn is in front of the compressor plate. Behind this part, a vacuum occurs, which circulates the refrigerant through the cooling system. Centrifugal compressors of refrigeration machines work with gas compression under the influence of centrifugal force. It is created by rotating the impeller blades. Under pressure, the refrigerant enters the diffuser, where its speed decreases due to an increase in the flow area. The result is the conversion of kinetic energy into potential, and this, in turn, provides an increase in pressure in the system.
Sealing characteristics
Open-type refrigeration equipment is designed so that the electric motor is located outside the housing. The motor is connected directly to the compressor or via a transmission. Semi-hermetic refrigeration equipment was assembled differently. Compressors are located in containers, in the same place as the electric motor. The connection is direct. The sealed unit is designed so that the electric motor is located in a body tightly closed and integral.
Gear Type Classification
In the crank mechanism, the rotational movements of the crankshaft are converted into reciprocating piston movements. Under the influence of the pressure difference, gas penetrates into the chamber. When the piston reaches its lowest position, the valve closes and the suction process begins in the system. The compressor of the refrigeration unit can operate due to the rocker mechanism. In such an assembly there is a lever. In it, rotational movements become reciprocating, and then vice versa. Inside the mechanism, the rocker moves. It is equipped with a rectilinear or arched slot.
Refrigerant Classification
The refrigeration compressor can run on ammonia. This compound undergoes adiabatic compression, due to which the temperature reaches 105 degrees Celsius. Such an installation requires additional equipment. For this, a cooling jacket is suitable, which will lower the temperature in the system. In freon systems, the working gas is freon. When compressed, its temperature is 45 degrees. Many units of this type use air cooling.
Other classification
The refrigeration compressor is selected according to the purpose of the application. In tiled high-speed freezers, as well as in designs with several such units, devices are used in which the circulation system is provided by the pump. Due to the forced flow of liquid through the plate, such a system has good heat transfer. And this makes it easy to achieve turbulence. Recirculation through the pump ensures the same freezing time in the entire apparatus.
In secondary systems, instead of
refrigerants, calcium brine or trichlorethylene is most often used. Such a system needs rather high capital expenditures; therefore, its use is limited by ship installations. A refrigeration compressor in a unit equipped with gravity circulation allows efficient and compact freezing with the necessary freezing time. Great for both medium and high capacity single freezer systems. An intermediate receiver can be installed directly on a tiled freezer. Horizontal tiled quick-freezing units need to defrost freezer plates once or twice a day. This need is enhanced if the operator does not spill liquid on them. But there is an alternative. Such refrigeration unit designs may be equipped with a defrost or defrost system. If products containing water are stored in cardboard packaging in this kind of apparatus, it is recommended to take care of the defrosting function. In horizontal plates this system is desirable, but in vertical tiled freezers, its presence is mandatory. To extract the finished blocks from such an apparatus, it is necessary that it be previously thawed.
Screw refrigeration compressors
Today, often freezing equipment is equipped with oil-filled units of this type. When oil is supplied, steam leakage between the channels is reduced. The undoubted advantage of such units is the ability to reduce noise.
Operating principle
When the screws begin to rotate, then on the exit side of the teeth, the depressions between them are gradually released from engagement. The process starts from the end of the suction. Hollows (cavities) due to their discharge are filled with steam, which enters there from the suction pipe through a window. As soon as the cavities at the opposite end of the rotors are completely free of the teeth located in them, the suction cavity reaches the maximum value in volume. When passing through the suction window, the cavities are disconnected from the suction chamber. The circulating oil is supplied to that part of the housing where the cavity between the rotors has ceased to communicate with the suction side. As the tooth of the driven rotor descends into the cavity of the lead, the amount of space that the gas occupies will decrease. As a result, vapor compression will begin. This process in the cavity will continue until the gas reaches the edge of the discharge window.
Unit Performance
The internal compression of such compressors is constant. It is equal to the ratio of the final pressure in the isolated working cavity to the pressure at the time it is cut off from the suction line in the same cavity. A screw compressor differs from a piston compressor in that the latter is equipped with a self-acting valve. But in the first, the amount of internal compression of the vapor varies depending on the size of the discharge window. Not only dimensions matter, but also location. Discharge pressure is a measure on the discharge side of the compressor. Its level depends on the temperature of the water cooling the condenser. It may not coincide with the internal compression pressure. When the internal compression ratio p1 becomes lower than in the discharge side of the compressor p2, an “non-geometric compression” of the steam to the discharge pressure occurs. If, on the contrary, it is higher than P2, then the gas in the cavities of the rotors expands and the pressure begins to drop. A compressor operating in these modes consumes significantly more energy.