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Do you know all this knowledge about the screw refrigerator system?

I. Classification of Screw Freezers

A total of six different classifications can be made according to the air conditioning function, the refrigerant, the condensation method, the sealing structure method of the compactor, the structure of the evaporator, and the screw type refrigeration compactor:

1. Divided into single cooling type and heat pump type according to air conditioning function.

2. It is divided into R134a and R22 according to different refrigerants.

3. According to its condensation method, it is divided into water-cooled screw freezer and air-cooled screw freezer!

4. According to the sealing structure method of the compactor, it is divided into open type, semi-closed type and fully closed type.

5. Divided into ordinary type and full liquid type according to the structure of the transpiration device

6. According to different screw refrigeration compactors used in screw refrigerators, they are classified. Screw refrigeration compactors are divided into two types of twin screw and single screw. The twin screw refrigeration compactor has a pair of rotors with helical teeth that are coupled to each other and rotate in opposite directions. The single screw refrigeration compactor has a rotor screw with six spiral grooves machined on the outer cylindrical surface. On the left and right sides of the butterfly and lever, the identical planetary gears with 11 racks are installed vertically! Specific understanding of the classification of screw chiller For friends who need to buy screw chiller is undoubtedly a great help!
Second, the principle and use of screw freezer
1 Principle of Screw Freezer

Because of its key component-the compactor, the screw-type freezer uses the screw-type screw-type freezer. The condition of the unit from the evaporator is gas refrigerant. After the adiabatic contraction of the compactor, it will become high-temperature and high-pressure. The condensed gas refrigerant is cooled and condensed at constant pressure in a condenser. After the condensation, the liquid refrigerant is changed to a liquid refrigerant, which is then expanded to a low pressure by a throttle valve and becomes a gas-liquid mixture. In the meantime, the liquid refrigerant at low temperature and low pressure absorbs the heat of the material to be cooled in the transpiration device, and becomes a gaseous refrigerant from the beginning. The gaseous refrigerant enters the compactor from the beginning through the pipeline and starts a new cycle. These are the four processes of the refrigeration cycle. It is also the primary operating principle of screw freezers.
The screw chiller used in the 2 screw chiller has a relatively large power compared to the scroll type, and is mainly used in central air conditioning systems or large industrial refrigeration.

(1) Twin screw refrigeration compactor

The twin screw refrigeration compactor is an energy adjustable fuel injection compactor. Its three successive processes of suction, contraction and exhaust are completed by a periodic volume change when a pair of meshing male and female rotors in the body rotate. Generally, the male rotor is a driving rotor, and the female rotor is a driven rotor. Primary components: double rotor, body, main bearing, shaft seal, balance piston and energy conditioning equipment. The capacity is 15 ~ 100% stepless conditioning or two or three-stage conditioning. The hydraulic piston is used to increase or decrease the load. Conventional selection: radial and axial are rolling bearings; open type is equipped with oil separator, oil storage tank and oil pump; closed type is used for differential pressure oil supply for lubrication, fuel injection, cooling and driving piston valve capacity adjustment. Inspiratory process: the gas enters the interdental volume of the yin-yang rotor through the suction port. Tightening process: When the rotor rotates, the volume between the male and female rotor teeth is connected (V-shaped space), because the teeth mesh with each other, the volume gradually decreases, and the gas is tightened. Exhaust process: The condensed gas is moved to the exhaust port to complete an operation cycle.

(2) Single screw refrigeration compactor

Contraction is created by the engagement of one active rotor and two star wheels. Its three successive processes of suction, tightening and exhaust are completed by the periodic volume change when the rotor and the star wheel rotate. The rotor has six teeth and the star wheel has eleven teeth. The main components are a rotor, two star wheels, a body, a main bearing, and an energy conditioning device. The capacity can be adjusted from 10% to 100% stepless and three or four stages. Inspiratory process: The gas enters the rotor slot through the intake port. Following the rotation of the rotor, the star wheel sequentially enters the state of meshing with the cogging of the rotor, and the gas enters the constriction cavity (closed space formed by the surface of the rotor cogging, the inner cavity of the casing and the tooth surface of the star wheel). Compaction process: As the rotor rotates, the volume of the compaction chamber decreases continuously, and the gas follows the compaction until the front of the compaction chamber turns to the exhaust port. Exhaust process: the front of the tightening chamber is turned to the exhaust port, and the exhaust is started to complete an operation cycle. Because of the symmetrical arrangement of the star wheel, the cycle will contract twice each revolution, and the exhaust volume will be twice the exhaust volume of the aforementioned cycle.
3. Analysis of common problems of screw chiller For the use of screw chiller, friends will be familiar with some of the common problems are high pressure problems, low pressure problems, low valve temperature problems, compactor overheating problems, communication problems, etc. However, in order to effectively deal with these problems, the first principle of the screw chiller must be linked first, and the four processes of the refrigeration cycle are the most important among them. After adiabatic contraction of the compactor, it will become high temperature and high pressure in the future. The condensed gas refrigerant is cooled and condensed at constant pressure in a condenser. After the condensation, the liquid refrigerant is changed to a liquid refrigerant, which is then expanded to a low pressure by a throttle valve and becomes a gas-liquid mixture. In the meantime, the liquid refrigerant at low temperature and low pressure absorbs the heat of the material to be cooled in the transpiration device, and becomes a gaseous refrigerant from the beginning. The gaseous refrigerant enters the compactor from the beginning through the pipeline and starts a new cycle.
1 high pressure problems

The exhaust pressure of the compactor is too high, causing the high-voltage maintenance relay to operate. The exhaust pressure of the compactor reflects the condensing pressure, the normal value should be 1.40 ~ 1.60MPa, and the maintenance value is set to 2.00MPa. If the pressure is too high for a long period of time, it will cause the compressor to run too much current, burn the motor easily, and easily cause damage to the valve of the compressor exhaust port. What should be done is to control the size of the compressor exhaust pressure to a safe scale. Inside!
2 Low-pressure failure: The suction pressure of the compactor is too low, causing the low-pressure maintenance relay to operate. The suction pressure of the compactor reflects the transpiration pressure, the normal value should be 0.40 ~ 0.60MPa, and the maintenance value is set to 0.20MPa. If the suction pressure is low, the return air volume will be small, and the cooling capacity will be lacking, resulting in the deterioration of electrical energy. The motor of the compactor motor with regard to the return air cooling has poor heat dissipation and is easy to damage the motor! And the treatment method is the same as the high pressure problem, try to keep the compactor within the normal pressure scale.
3 Low valve temperature and faulty expansion valve The outlet temperature reflects the transpiration temperature, which is a factor that affects heat transfer. Generally, the temperature difference between the outlet temperature of the refrigerant and the refrigerant water is 5.0 ~ 6.0 ° C. When a low valve temperature problem occurs, the tightening machine will stop. When the valve temperature rises, it will automatically resume operation. The maintenance value is -2.0 ° C.
4 Tightening machine overheating problems

A thermistor is embedded in the motor winding of the compactor, and the resistance is generally 1kΩ. When the winding is overheated, the resistance value will increase rapidly. When the temperature exceeds 141kΩ, the thermal maintenance module SSM will be activated to cut off the operation of the unit. At the same time, an overheating fault will appear and the TH fault indicator will be on.
5Communication problems

The control of each module by the computer controller is completed through the communication line and the main interface board. The primary cause of communication problems is poor contact or disconnection of the communication line, especially the interface is exposed to moisture and oxidation to form a poor contact. The interface board is faulty, the address dial switch is not selected properly, and the power supply fault can form a communication fault. The above five kinds of fault phenomena are the most common, and understanding these fault phenomena, judgment ability, and treatment methods have an irreplaceable effect on the service life of the extended screw chiller!
Fourth, the key to the selection of screw freezer

1. The main operating parameters of screw refrigerators are the cooling function coefficient, rated cooling capacity, input power and refrigerant type.

2. The selection of chiller should be considered based on the cold load and its use. Regarding the refrigeration system with low load and long working time, it is better to choose a multi-head piston compactor or screw compactor to facilitate conditioning and energy saving.

3. When selecting a chiller, priority should be given to the unit with a higher functional coefficient. According to statistics, the operating time of a general chiller at 100% load throughout the year accounts for less than 1/4 of the total operating time. 100%, 75%, 50%, 25% within the total operating time

The load moment share is approximately 2.3%, 41.5%, 46.1%, and 10.1%. Therefore, when selecting a chiller, priority should be given to models with relatively flat efficiency curves. At the same time, the load conditioning scale of the chiller should be considered in the design and selection. The multi-head screw chiller has excellent partial load function and can be selected according to the actual situation.

4. When choosing a chiller, pay attention to the conditions of nominal working conditions. The actual cooling output of chiller is related to the following factors:

a) cold water outlet temperature and flow;

b) Inlet temperature, flow rate and fouling factor of cooling water.

5. When selecting a chiller, pay attention to the normal operation scale of this type of unit. The main limitation is that the current limit of the main motor is the current value of the shaft power under nominal conditions.

6. Please pay attention to the design and selection: under nominal operating flow, the outlet temperature of cold water should not exceed 15 ℃, and the outdoor dry bulb temperature of air-cooled units should not exceed 43 ℃. Whether the scale of use is allowed, and whether the power of the main motor is sufficient.

The control of each module by the computer controller is completed through the communication line and the main interface board. The primary cause of communication problems is poor contact or disconnection of the communication line, especially the interface is exposed to moisture and oxidation to form a poor contact. The interface board is faulty, the address dial switch is not selected properly, and the power supply fault can form a communication fault.

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