Classification, principle and use of refrigeration compressors
Classification, principle and use of refrigeration compressors
The function of refrigeration compressor:
The refrigeration compressor is the "heart" of the refrigeration system. It absorbs the refrigerant vapor from the evaporator, increases the pressure and discharges it to the condenser, so that the refrigerant circulates in the system. Can be used in refrigeration systems and heat pump systems
Refrigeration system and heat pump system:
The same point: dissipate heat from low temperature to high temperature while consuming energy.
Differences: The operating temperature range and purpose are different.
The refrigeration system absorbs heat from the cooled medium and releases heat to the ambient medium. In the operating conditions of the compressor, the evaporation temperature is lower than the temperature of the cooled medium, and the condensation temperature is higher than the temperature of the ambient medium.
The heat pump system absorbs heat from the atmosphere and supplies heat to areas with higher temperatures. In the operating conditions of the compressor, the evaporation temperature is lower than the atmospheric temperature, and the condensation temperature is higher than the heating zone temperature. There is no difference in the function of the refrigeration compressor in the two systems.
refrigerating system:
Heat pump system:
Types of refrigeration compressors:Types of refrigeration compressors:
Positive displacement compressor:
A certain volume of gas is first sucked into the cylinder, and then its volume in the cylinder is forcibly reduced and the pressure rises. When a certain pressure is reached, the gas is forcibly discharged from the cylinder. It can be seen that the suction and discharge process of the positive displacement compressor is intermittent, and the flow is discontinuous and stable.
Speed compressor:
The increase in gas pressure is converted from the speed of the gas, that is, the inhaled airflow is first made to obtain a certain high speed, and then slowed down, so that its momentum is converted into the pressure of the gas to increase, and then discharged. It can be seen that the compression process in the speed type compressor can be continuously performed, and the flow is stable.
Classified by evaporation temperature range:
High temperature refrigeration compressor: (-10～0)℃
Medium temperature refrigeration compressor: (-15～0)℃
Low temperature refrigeration compressor: (-40～-15)℃
Classified by sealed structure:
Open type: The prime mover is independent of the refrigerant system.
Semi-closed type: The motor and compressor are installed in the same body and coaxially.
Fully enclosed: The compressor and motor unit connected together are installed in a sealed thin-walled casing.
Open type: The compressor with large refrigeration capacity and independent of the prime mover from the refrigerant system is called an open type compressor. Large cooling capacity. It can be used in refrigeration systems using ammonia as the working medium.
Semi-enclosed type: The cooling capacity is at a medium level, and the enclosed structure is used to connect the motor and the compressor as a whole, and they are installed in the same body and share a main shaft. No shaft seal. The motor is in contact with refrigerant and lubricating oil. All kinds of end covers on the body are tightened with gaskets and bolts to prevent leakage, which is easy to disassemble and repair.
Fully enclosed type: The cooling capacity is small, and the enclosed structure is also adopted. The motor and the compressor are connected as a whole, and they are installed in the same body and share a main shaft. However, the compressor and the motor unit connected together are installed in a sealed thin-walled casing, which is welded together and is not easy to disassemble and repair. Therefore, this type of compressor is required to have high reliability and long life.
Reciprocating compressor: The working chamber of the compressor is a cylinder. The piston reciprocates in the cylinder to complete the processes of compression, exhaust, expansion, and suction. Realize the suction, compression and delivery of refrigerant.
Rolling rotor compressor: belongs to rotary compressor. It is composed of air cylinder, rolling rotor, eccentric shaft and sliding vane. The rotor rolls along the inner wall of the cylinder to form a crescent-shaped working cavity with the cylinder. The end of the sliding vane is in close contact with the rotor under the force of the spring, dividing the crescent-shaped working cavity into two parts. The sliding vane reciprocates along the sliding vane channel as the rotor rolls. movement. The cylinder volume changes with the rotor angle, and the pressure changes accordingly.
Oscillating compressor: The rotor and the sliding vane are cast into one body, which reduces the leakage and friction between the sliding vane and the rotor, and has higher efficiency and reliability. Using frequency conversion, at low and medium speeds, efficiency and energy saving are significant, and it is oriented to alternative working fluids HCFC, 407C and 410A.
Screw compressor: Use the change in the volume and position of the tooth groove of the screw to complete the process of suction, compression and discharge of steam. There are three processes of suction, compression and exhaust in each pair of cogging spaces. In different cogging spaces, there are three processes of suction, compression and exhaust at the same time.
Single screw compressor:
Scroll compressor: mainly composed of moving and static scroll bodies, suction and exhaust ports. A series of crescent-shaped spaces are formed between the moving and static scroll bodies. The orbiting scroll body takes the center of the static scroll body as the center of rotation, and uses a certain radius of rotation to make a rotation and translation without rotation, and the outer crescent-shaped space will continue to the center. Move to reduce the volume.
