The scheme of automatic control of the filling of the evaporator of the refrigeration machine

 

(57) Abstract:

Usage: in automatic feed systems, evaporators, maintain, control and protection of vessels and equipment in refrigeration capacity from 100 000 kcal/h and above, mainly for ammonia get cold. The inventive scheme of automatic control of the filling of the evaporator of the refrigerating machine includes an evaporator with balancing column or other vessel containing a vapor-liquid phase refrigerant, the level Converter, gear and actuator. The Converter is made in the form of a thermometric valve associated pulse tube with a bulb mounted on the balance column at the height of a given level of refrigerant in the evaporator. The transmission mechanism includes a supply line of the diaphragm mechanism regulating valve with compressed air and work the valve thermostatic expansion valve installed on the discharge of compressed air from the membrane of the cavity of the valve. As the Executive body of the submission of the refrigerant in the evaporator is regulating the pneumatic valve. 1 Il.

The invention relates to refrigeration, and bol is about to maintain and alarm preset level in vessels and apparatus, containing the boiling refrigerant and the suction compressors.

The objective power of the evaporator is to regulate supply the optimal amount of refrigerant, providing the maximum possible removal of heat from the cooled object when guaranteeing trouble-free operation of the compressor. The complexity of the solution in this case is that it is necessary to combine two contradictions. On the one hand, to make the compressor run "dry-running", and on the other to ensure good filling of the evaporator with the refrigerant. The first requirement is necessary for the safe operation of the compressor, the second for the heat transfer rate.

Currently, the primary use of have a system based on determining the amount of superheat of the refrigerant at the evaporator outlet or measuring the level of liquid refrigerant in the evaporator.

Automatic feeding system evaporator overheat pair consists of a thermostatic expansion valve (TEV), the bulb that is installed on the outlet of the evaporator. The bulb is connected with a thermostatic expansion valve capillary tube.

Thermostatic expansion valve membrane includes a box with a membrane and a throttling valve with actuator and mounting mechanism. Ter the left gauge thermosysteme, which converts the output of the temperature in the pressure. In a limited range can be considered as the pressure change is proportional to the temperature change. The more steam superheat, the higher the pressure in adminpanel cavity. It forces you to move the diaphragm downward and open the valve, the refrigerant enters the evaporator. When reducing the superheat valve is closed. Under the temperature of superheat refers to the difference between the temperatures of the refrigerant at the outlet of the evaporator and the boiling point.

This system of regulation of the filling of the evaporator is very versatile and has a wide distribution, but bandwidth TEV has a limit, reaching which, it no longer increases with further increase in temperature, therefore, the application schema by using thermostatic expansion valve is limited by the cooling capacity of not more than 500 kW (see "Refrigeration technology", 7.8.92, S. 22-24).

For evaporators high-capacity circuits automatically populate evaporators and level detection preferential spread regulators and transmitters float converters. In General, this circuit consists of a primary Converter, transmitting ele is ectronic block. The regulatory body may be a solenoid valve.

The sensitive element of the float sensor is a steel hollow float is placed inside the camera sensor, which is in communication with the controlled vessel. Converting the level into an electrical signal by using inductors. When changing the level of the float enters the magnetic field of the coil. Due to this change in inductive reactance of the coils that is used to control the actuators. This scheme is selected as the closest analogue of the proposed solution.

The disadvantage of the devices of the float type is the instability of the operation of the sensors due to accumulation of oil. So at least once in 10 days should be warming up and blowing devices, and drain oil. This raises the need to work in manual mode, and this can lead to technological violations.

A well-developed system of relay-contact actuators entails the need for constant monitoring of her condition (see B. P. Akharov, I. C. Smirnov. Reference mechanic and refrigeration installations. L. Agropromizdat, 1989, S. Aly level Converter, electronic gear with electromagnetic Executive body, the proposed system as a level Converter contains gauge thermosysteme, consisting of the bulb of thermostatic expansion valve and capillary tube, uniting namebrand space TEV with the bulb. The transmission mechanism includes a diaphragm actuator control valve with air line and service valve thermostatic expansion valve, throttling the air at the outlet of the membrane boxes regulating valve, and as a regulator on the supply line of the refrigerant in the evaporator is installed control valve with diaphragm actuator.

In this case, the income amount of refrigerant in the evaporator provides a pneumatic valve with diaphragm actuator, which in comparison with valve thermostatic expansion valve has virtually no limited bandwidth. The degree of filling of the evaporator is determined as a function of state termobarometricheskim system in contact with the vapor-gas phase.

The drawing shows the scheme of automatic control of the filling of the evaporator of the refrigeration machine.

The schema contains: 3 bulb 4. Balance column 1 through valves 5, 6, top-bottom, connected to the evaporator. The bulb 4 capillary tube 7 is connected with namebrands cavity 8 of thermostatic expansion valve (TEV) 9, 10 main pipeline compressed air line 11 for supplying air into the diaphragm cavity 12 of the regulating valve 13, 14 operating valve thermostatic expansion valve regulating the air outlet of the membrane cavity 12 of the regulating valve 13, valve 15 air sampling on the main pipeline 16 air filter, 17 - reducing valve 18 safety valve, 19, 20, 21 levels of Assembly connecting the bulb height of the evaporator, respectively, not less than 50% strictly 80% and 100%

The scheme works as follows.

Balance column 1 and the evaporator 2 communicating vessels. The temperature of the liquid refrigerant are the same, the temperature of the gaseous refrigerant is different. So, in working with the load, the evaporator temperature of the liquid and gas up to suchoparek almost identical, and in the balance column for the mirror surface of the liquid phase vertically upwards there is a small pillar of the order of 40 to 60 mm liquid-vapor-gas phase changes greatly with temperature towards its improvement and next is mperature, 5 to 10ogreater than the boiling temperature in the apparatus. Therefore TEV works on contact with the vapor-gas phase or close to it, but not on superheat.

For example, in the case of complete absence of the refrigerant in the evaporator bulb 4 adopts the temperature of its surroundings, and this corresponds to the maximum pressure on the membrane thermostatic expansion valve 9, which in this case will open the service valve thermostatic expansion valve 14. Line 11 is open to free air flow. The pressure in the diaphragm cavity 12 of the regulating valve 18 is missing. Regulating the pneumatic valve is fully open for admission of refrigerant into the evaporator.

Upon receipt of the refrigerant temperature in the evaporator 2 and, respectively, in the balance column 1 is reduced. The pressure in the system: the bulb 4, the capillary tube 7, namebrand cavity 8 TEV is reduced, resulting in a working valve thermostatic expansion valve 14 begins to close, creating resistance at the air outlet of the membrane cavity 12 of the regulating valve 13. The pressure in line 11 is increased, the membrane valve moves the valve 13 to close. On filling of the evaporator 2 to the maximum level (typically 80% item 20), the liquid refrigerant comes into contact with tarmac the minimum value, working valve 14 will completely block the air vent of the membrane cavity 12, the pressure in the diaphragm cavity takes the maximum value, and regulating the pneumatic valve 13 will block the flow of refrigerant into the evaporator. As the suction of the refrigerant from the evaporator in the further course of the process level in the evaporator is reduced, the temperature of the bulb increases, which leads to the opening of the valve 14 TEV, which in turn will reset the air pressure in the line 11. The pressure in the diaphragm cavity regulating valve 13 drops, the valve opens again, allowing the flow of refrigerant into the evaporator.

With a steady heat gain scheme regulates itself in the smooth flow of the refrigerant in the evaporator by means of the regulating valve.

The use of a scheme of automatic control of the filling of the evaporators of refrigerating machines ensures reliable operation of the power system evaporator, expands the scope of a proportional regulator overheating, allows the use of EWM control schemes in high-performance ammonia plants.

The scheme of automatic control of the filling of the evaporator refrigerating machines, containing an evaporator unabatedly mechanism and an Executive body, to ensure the delivery of refrigerant to the evaporator, characterized in that the Converter is made in the form termobarometricheskim system consisting of namebrands cavity expansion valve associated pulse tube with a bulb mounted on the balance column at the height of a given level of refrigerant in the evaporator, and the transmission mechanism includes a supply line of the diaphragm mechanism regulating valve with compressed air and work the valve thermostatic expansion valve installed on the discharge of compressed air from the membrane of the cavity of the pneumatic valve, and as the Executive of the refrigerant in the evaporator is regulating the pneumatic valve.

 

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