A refrigeration compressor is a device responsible for compressing and pumping refrigerant vapor in related equipment. Widely distributed in air conditioning, industrial units. But most often it is used in industry and in deep-freeze refrigerators. According to a number of characteristics, equipment is divided into several varieties.
Device type
There are three groups in this category. The first is the reciprocating compressor of a refrigeration unit. Let us briefly consider the principle of its operation. The gas in such units is compressed by a piston. When it goes down, the refrigerant enters the working space of the compressor. When it is lifted, steam comes out of the unit. A rotary refrigeration compressor is powered by a horn. Thanks to this part, pressure is injected. The horn is in front of the compressor plate. Behind this part, a vacuum occurs, which ensures the circulation of the refrigerant through the cooling system. Centrifugal refrigeration compressorsmachines work with gas compression under the influence of centrifugal force. It is created by the rotation of the impeller blades. Under pressure, the refrigerant penetrates into the diffuser, where its speed decreases due to an increase in the flow area. The result of this is the conversion of kinetic energy into potential energy, and this, in turn, provides an increase in pressure in the system.
Sealing characteristics
Open-view refrigeration equipment is designed so that the electric motor is located outside the case. The motor is connected to the compressor directly or through a transmission. Semi-hermetic refrigeration equipment is 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 in a housing that is tightly closed and one-piece.
Classification by transmission type
In the crank mechanism, the rotational movements of the crankshaft are converted into reciprocating movements of the piston. Under the influence of the pressure difference, gas penetrates into the chamber. When the piston reaches its lowest position, the valve closes and the system starts the suction process. The compressor of the refrigeration unit can be operated by a rocker mechanism. This unit has a lever. In it, rotational movements become reciprocating, and then vice versa. Inside the mechanism, the rocker stone moves. It is equippedstraight or arcuate slot.
Classification by type of refrigerant
The refrigeration compressor can run on ammonia. This compound is subjected to 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 of these types of units use air cooling.
Other classification
The refrigeration compressor is selected according to the application. In plate freezers with high capacity, as well as in designs with several such units, devices are used in which the circulation system is provided by a 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 throughout the unit.
In secondary systems, instead of refrigerants, calcium chloride brine or trichlorethylene is most often used. Such a system requires rather high capital costs, so its use is limited to ship installations. The refrigeration compressor in a unit equipped with gravity circulation makes it possible to achieve an efficient and compactfreezing with the required freezing time. Excellent for both medium and large capacity single freezer systems. The intermediate receiver can be installed directly on the plate freezer. Horizontal plate freezers need to defrost the freezer plates once or twice a day. This need is increased if the operator does not spill liquid on them. But there is also an alternative. Such designs of the refrigeration unit can be equipped with a defrosting or defrosting system. If products containing water are stored in this type of apparatus in cardboard packaging, it is recommended to take care of the defrosting function. In horizontal plates, this system is desirable, but in vertical plate freezers, its presence is mandatory. To remove finished blocks from such an apparatus, it must be pre-thawed.
Screw refrigeration compressors
Today, freezing equipment is often equipped with oil-filled units of this type. When oil is supplied, the leakage of steam between the channels is reduced. The undoubted advantage of such units is the ability to reduce noise.
Operation 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 suction end. The cavities (cavities) are filled with steam due to their rarefaction, whichgets there from the suction pipe through the window. As soon as the cavities at the opposite end of the rotors are completely freed from the teeth located in them, the suction cavity reaches its maximum size in volume. When passing through the suction window, the cavities are separated 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 leading one, the volume of space occupied by the gas 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 these compressors is constant. It is equated to the ratio of the final pressure in an isolated working cavity to the pressure at the moment of cutting it 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 value of the internal compression of the steam varies depending on the size of the injection window. Not only dimensions matter, but also location. Discharge pressure is a reading on the discharge side of the compressor. Its level depends on the temperature of the water cooling the condenser. It may not match the internal compression pressure. When the internal compression ratio p1 becomes lower than in the compressor discharge side p2, thenthere is an "out-of-geometric compression" of the steam to the discharge pressure. If, on the contrary, it is higher than p2, then the gas in the cavities of the rotors expands and the pressure begins to fall. The compressor operating in these modes consumes much more energy.
