Refrigeration system 41 essay questions, too comprehensive!

Refrigeration system 41 essay questions, too comprehensive!

1. What are the three necessary conditions for the safe operation of the refrigeration system? 　　Answer: (1) The refrigerant pressure in the system must not be abnormally high to avoid equipment rupture.

　　 (2) Misoperations such as wet stroke, liquid explosion, and liquid shock shall not occur (may cause) to avoid damage to the equipment.

　　 (3) The moving parts must not have defects or loose fasteners, so as not to damage the machine.

　　 2. What is the evaporation temperature?

　　 Answer: The temperature at which the refrigerant in the evaporator boils and vaporizes under a certain pressure is called the evaporation temperature.

　　 3. What is the condensation temperature?

　　 Answer: The temperature at which the gas refrigerant in the condenser condenses into a liquid under a certain pressure is called the condensation temperature.

　　 4. What is the recooling (or supercooling) temperature?

　　 Answer: (1) The temperature at which the condensed liquid refrigerant is cooled to below the condensing temperature under the condensing pressure is called the recooling temperature (or subcooling temperature).

　　 5. What is the intermediate temperature?

　　 Answer: (1) Two-stage compression system, the saturation temperature of the refrigerant in the intercooler at the intermediate pressure is called the intermediate temperature.

　　 6. (How to detect and how to control) the suction temperature of the compressor?

　　 Answer: The suction temperature of the compressor can be measured from the thermometer in front of the suction valve of the compressor. The suction temperature is generally higher than the evaporation temperature, and the difference depends on the length of the return pipe and the insulation of the pipe. Generally, it should be 5-10 higher than the evaporation temperature. The superheat can be adjusted by changing the liquid supply.

　　 7. (How to detect) the compressor discharge temperature, (what factors affect the discharge temperature)?

　　Answer: The discharge temperature of the compressor can be measured from the thermometer on the discharge line. The exhaust temperature is directly proportional to the (suction and exhaust) pressure ratio and the suction temperature. The higher the suction superheat and the higher the pressure ratio, the higher the exhaust temperature; otherwise the opposite. Generally, the exhaust pressure is slightly higher than the condensing pressure.

　　 8. What is tidal car (liquid hammer)?

　　Answer: Because the refrigerant fails or does not fully absorb heat and evaporate, the refrigerant liquid or wet vapor is sucked into the compressor by the compressor, which is called a tidal car.

　　 9. What can cause the tide of cars?

　　Answer: (1) The liquid level control of the gas-liquid separator or low-pressure circulation barrel fails, causing the liquid level to be extremely high.

　　 (2) The liquid supply is too large and the liquid supply is too rapid. Throttle valve internal leakage or excessive opening.

　　 (3) The evaporator or gas-liquid separator (low pressure circulation barrel) has too much liquid, small heat load, and too fast loading when starting up.

　　 (4) The heat load increases suddenly; or the suction valve is not adjusted in time after frosting.

　　 10. What are the consequences after the tide of cars?

　　Answer: For the piston engine: (1) The refrigerant enters the compressor, causing the lubricating oil to produce a lot of bubbles, destroying the oil film on the lubricating surface, and making the oil pressure unstable.

　　 (2) Make the moving parts run without good lubrication, resulting in picking; in severe cases, the axle holding and the main shaft Waba alloy melt.

(3) Refrigerant enters the compressor, causing the cylinder liner to cool and shrink rapidly and hug the piston; in severe cases, damage the cylinder liner, piston, connecting rod, and piston pin.

(4) Because the liquid is incompressible, the force on the connecting rod and piston in the tide car is far beyond the design value, which is very easy to cause damage; because the liquid is incompressible, in the tide car, the exhaust valve group and the dummy cover It will be lifted by the impact of the liquid; in severe cases, it will cause the safety spring to deform, or even smash the body, cylinder head, and penetrate the gasket to injure the human body.

　　For screw machines: Tide vehicles will cause vibration, increase noise, and damage the rotor and bearings (excessive force); severe tide vehicles will also damage equipment and cause accidents.

　　11. What should I do if a tidal car is found?

　　Answer: In the event of a damp in the piston compressor, the suction shut-off valve of the compressor should be closed immediately, and the throttle valve should be closed to stop the liquid supply. If the suction temperature continues to decrease, continue to close down or even close the suction valve, and unload at the same time until it reaches zero. The frictional heat between the crankshaft and the bearing bush is used to evaporate the refrigerant in the crankcase. When the pressure in the crankcase increases, a group of cylinders are put into operation, and the pressure drops before unloading. Repeat this process several times until the refrigerant in the crankcase is completely evaporated. After that, slightly open the suction shut-off valve and slowly increase the load. If there is still refrigerant liquid in the suction line, repeat the previous process. Until the liquid is completely drained, slowly fully open the suction shut-off valve, and the compressor is put into normal operation. When a damp occurs, pay attention to observe and adjust the oil pressure. If there is no oil pressure or the oil pressure is too low, stop the machine immediately, release the lubricating oil and refrigerant in the crankcase, and refuel and start the machine. When the screw compressor is dampened, the suction stop valve of the compressor should be closed immediately, and the throttle valve should be closed to stop the liquid supply. If the suction temperature continues to decrease, continue to close the suction valve but not close the suction valve to prevent abnormal noise and vibration from too low suction pressure, and reduce the load until it reaches zero. Taking advantage of the screw compressor's insensitivity to wet stroke, slowly drain the liquid in the return air line into the oil. Then open the suction stop valve and slowly increase the load until the compressor is put into normal operation. In the event of a damp, pay attention to observe and adjust the oil pressure. To prevent the oil temperature from being too low, you can turn on the oil heating equipment or turn off the oil cooling water valve.

　　12. What causes the excessive exhaust pressure and how to eliminate it?

　　Answer: (1) The system and the high-pressure part of the mixed gas will cause excessive exhaust pressure. Air should be released. In the ammonia system, in order to reduce the pollution of ammonia to the atmosphere, an air separator is generally used to discharge the non-condensable gas in the system. The small fluorine system can directly discharge air through the air release valve on the condenser. Slightly open the air release valve for air release. When the exhausted gas is white smoke, indicating that more Freon is released, the valve should be closed to end the air release operation.

　　 (2) Scaling or accumulation of debris on the water side of the condenser heat exchange tube. The water covers on both sides of the condenser should be opened, inspected and cleaned up (wash with a high-pressure water gun, wipe with a brush or cloth strips, please clean by a professional company).

　　 (3) Too much liquid and oil in the condenser. Check whether the condenser outlet valve and balance pipe valve are fully opened (should be fully open), and if necessary, check whether the valve head is off. Excessive refrigerant and accumulated refrigerating machine oil are discharged.

　　 (4) The condenser end cover splitter gasket is damaged, causing the cooling water to circulate in a short circuit. The water cover on both sides of the condenser should be opened to remove the rust on the part of the splitting pad and replace the rubber pad.

　　 (5) The temperature of the cooling water inlet and outlet exceeds the design requirements. Clean up the dirt on the cooling water tower, check whether the water separator falls off and is inclined, and whether the water inlet is blocked by foreign matter.

　　 (6) The cooling water flow is insufficient. It shows that the temperature difference between the cooling water inlet and outlet exceeds the requirement. Check: Whether the pump is mechanically worn excessively; whether there is any blockage in the pump; whether the valve, check valve, and filter are abnormal; whether the head of the pump meets the requirements; whether the direction and specifications of the water pipeline are reasonable.

　　 13. The reason why the compressor does not start and how to deal with it?

　　 Answer: (1) Electrical failure; check and repair.

　　 (2) The pressure relay or the oil pressure relay is out of order; check and adjust the interlock contacts of the pressure relay and the oil pressure relay.

　　 (3) The crankcase pressure or intermediate pressure is too high; check the exhaust valve or reduce the crankcase and intermediate pressure.

　　 (4) (piston engine) unloading mechanism failure; check and repair.

　　14. The cause of the knocking sound in the cylinder of the piston engine and the solution?

　　Answer: (1) The piston hits the exhaust valve during operation; opens the noisy cylinder head and increases the gap between the piston and the inner valve seat

　　 (2) The air valve bolt is loose; tighten the air valve bolt.

　　 (3) The valve plate is damaged and broken and fell into the cylinder, the gap between the piston pin and the small end of the connecting rod is too large, and the gap between the piston and the cylinder is too large; check after dismantling the cylinder, adjust and repair it.

　　 (4) The spring of the false cover is deformed, and the elasticity is not enough; add pad to increase spring force or replace.

　　 (5) Refrigerant liquid enters the cylinder to cause liquid shock; close the suction stop valve, the liquid supply throttle valve, or temporarily close it to drain the liquid.

　　 15, the reason and treatment of the knocking sound in the crankcase of the piston engine? 　　Answer: (1) The gap between the big end bearing bush of the connecting rod and the crank pin is too large; check and adjust the gap or replace it.

　　 (2) The gap between the main journal and the main bearing is too large; check and adjust the gap.

　　 (3) Flywheel and shaft or key fit loosely; check and adjust the gap and repair.

　　 (4) The connecting rod bolt cotter pin is broken and the connecting rod nut is loose; tighten the connecting rod nut and lock it with a cotter pin.

　　 16. The reason and treatment of no oil pressure after the piston compressor is started?

　　Answer: (1) The oil pump transmission parts are out of order; disassemble for maintenance.

　　 (2) The oil pump inlet is blocked; check and remove dirt.

　　 (3) The oil pressure gauge fails; replace the oil pressure gauge.

　　 (4) The oil fine filter and shaft seal are free of oil; you should add oil to the oil fine filter and shaft seal before driving to prevent emptying during driving.

　　17. Reasons and solutions for low oil pressure of piston compressors?

　　Answer: (1) The oil suction filter is blocked; remove it for cleaning.

　　 (2) The oil pressure regulating valve fails; repair or replace.

　　 (3) The gap between the oil pump gear and the pump cover is too large and worn; repair or replace.

　　 (4) The crankcase oil level is too low; add oil or return oil from the oil separator.

　　 (5) The bearings of various parts are seriously worn and the gap is too large or part of the oil circuit leaks; check and repair.

　　 18. Reasons and solutions for the increase in oil consumption of piston compressors?

　　Answer: (1) The refrigerant liquid enters the crankcase; turn the suction shut-off valve and the liquid supply throttle valve down or temporarily close (refer to the method of handling tide cars).

　　 (2) The seal ring, oil scraper ring or cylinder is severely worn or the piston ring lock is in a line; check, adjust, and replace severely worn parts if necessary.

　　 (3) The crankcase oil level is too high or the exhaust temperature is too high; part of the lubricating oil is released or measures are taken to reduce the exhaust temperature.

　　19. The cause and treatment of oil or gas leakage in the shaft seal?

　　Answer: (1) The shaft package is poorly matched or the shaft seal sealing surface is rough; check and adjust, replace or grind the seal ring.

　　 (2) The "O" ring of the dynamic and static rings is aging and deformed or the tightness is inappropriate; replace the sealing rubber ring.

　　 (3) There is a lot of liquid refrigerant in the oil; increase the oil temperature or discharge the refrigerant.

　　 (4) The crankcase pressure of the piston compressor is too high; reduce the crankcase pressure.

　　 20. Reasons and solutions for the failure of the unloading device of the piston compressor? 　　Answer: (1) The oil pressure is not enough; adjust the oil pressure so that the oil pressure is 0.12~0.2MPa higher than the suction pressure.

　　 (2) The tubing is blocked; disassemble and clean.

　　 (3) There is dirt stuck in the cylinder; disassemble and clean.

　　 (4) The oil distribution valve is improperly assembled, the tie rod or the rotating ring is incorrectly assembled, and the rotating ring is stuck; disassemble and repair.

　　 21. What is the reason for the overheating of the compressor suction (the suction temperature is higher than the evaporation temperature) and how to deal with it?

　　 Answer: (1) The refrigerant in the refrigeration system is insufficient; supplement the refrigerant.

　　 (2) The refrigerant in the evaporator is insufficient; open a large throttle valve and increase the liquid supply.

　　 (3) The suction pipe of the refrigeration system is not well insulated; check and repair.

　　 (4) The water content of the refrigerant exceeds the standard; check the water content of the refrigerant.

　　(5) The throttle valve has a small opening and the liquid supply is small; open the throttle valve to increase the liquid supply.

　　 22. Reasons and solutions for the high exhaust temperature of piston compressors?

　　 Answer: (1) The temperature of the inhaled gas is too high; adjust the degree of inhalation superheat (refer to Question 21).

　　 (2) The exhaust valve plate is broken; open the cylinder head, check and replace the exhaust valve plate.

　　 (3) The safety valve is leaking; check the safety valve, adjust and repair.

　　 (4) Piston ring leaks; check piston ring, adjust and repair.

　　 (5) Cylinder liner gasket is broken or leaking; check and replace.

　　 (6) The top dead center gap of the piston is too large; check and adjust the top dead center gap.

　　 (7) Insufficient cooling capacity of the cylinder head; check the water volume and temperature, and adjust.

　　 (8) The compressor compression ratio is too large; check the evaporation pressure and condensing pressure.

　　23. The reason and treatment for the low suction pressure of the compressor?

　　Answer: (1) The liquid supply throttle valve or the suction filter is blocked (dirty blockage or ice blockage); disassemble, inspect and clean.

　　 (2) Insufficient refrigerant in the system; supplement refrigerant.

　　 (3) The refrigerant in the evaporator is insufficient; open a large throttle valve and increase the liquid supply.

　　 (4) There is too much refrigerating oil in the system and in the evaporator; find out where the oil accumulates in the system and drain the oil.

　　 (5) Small heat load; adjust the compressor energy level and properly unload.

　　 24. The reason and treatment of abnormal vibration of screw unit?

　　Answer: (1) The anchor bolts of the unit are not tightened or loose; tighten the anchor bolts.

　　 (2) The compressor shaft and the motor shaft are misaligned or not concentric; realign.

　　 (3) The vibration of the pipeline causes the vibration of the unit to increase; add support points or change the support points.

　　 (4) The compressor sucks in too much oil or refrigerant liquid; when it is stopped, the cranking will cause the liquid to drain out of the compressor.

　　(5) The spool valve cannot stop at the required position, but vibrates there; check whether the oil piston, four-way valve or the solenoid valve for increasing/decreasing load is leaking and repair it.

　　 (6) The suction chamber vacuum is too high; open the suction shut-off valve and check whether the suction filter is blocked.

　　 25. Reasons and solutions for insufficient refrigeration capacity of screw unit?

　　Answer: (1) The position of the spool valve is improper or other faults (the spool valve cannot be placed on the fixed end); check the position of the indicator or angular displacement sensor, and repair the spool valve.

　　 (2) The suction filter is blocked, the suction pressure loss is too large, the suction pressure is reduced, and the volumetric efficiency is reduced; remove the suction filter and clean it.

　　 (3) The machine has abnormal wear and tear, causing the gap to be too large; check, adjust or replace parts.

　　 (4) The resistance loss of the suction line is too large, and the suction pressure is too much lower than the evaporation pressure; check the suction stop valve and suction check valve, and repair if there is a problem.

　　 (5) Leakage between high and low pressure systems; check the bypass valve and oil return valve when driving, parking, and repair if any problems are found.

　　 (6) Insufficient fuel injection volume can not achieve sealing effect; check oil circuit, oil pump, oil filter, and increase fuel injection volume.

　　 (7) The exhaust pressure is much higher than the condensing pressure, and the volumetric efficiency drops; check the exhaust system piping and valves to remove the resistance of the exhaust system. If the system seeps into air, it should be discharged.

　　 26. The cause and treatment of abnormal noise during operation of the screw unit?

　　Answer: (1) There is debris in the rotor teeth; check the rotor and suction filter.

　　 (2) The thrust bearing is damaged; replace the thrust bearing.

　　 (3) The main bearing is worn and the rotor is rubbed against the body; repair and replace the main bearing.

　　 (4) The spool valve is skewed; repair the spool valve guide block and guide post.

　　 (5) Loose joints of moving parts; disassemble the machine for maintenance and strengthen relaxation measures.

　　 27. The cause and treatment of excessive exhaust temperature or oil temperature?

　　Answer: (1) The compression ratio is too large; check the suction and discharge pressures and reduce the pressure ratio.

　　 (2) The cooling effect of the water-cooled oil cooler decreases; clean the oil cooler, lower the water temperature or increase the water volume.

　　 (3) Insufficient liquid supply of the liquid ammonia oil cooler; analyze the reason and increase the liquid supply.

　　 (4) Inhalation of severely overheated steam; increase