The problem of refrigeration system is too comprehensive. Collect it quickly (I)

1. What are the three necessary conditions for the safe operation of refrigeration system?

Answer: (1) the refrigerant pressure in the system shall not have abnormal high pressure to avoid equipment rupture.

(2) Misoperation such as wet stroke, liquid explosion and liquid hammer shall not occur (may lead to) to avoid equipment damage.

(3) Moving parts shall be free from defects or loose fasteners to avoid damage to the machinery.

2. What is 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 condensation temperature?

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

4. What is the re cooling (or supercooling) temperature?

Answer: (1) the liquid refrigerant after condensation is cooled to a temperature lower than the condensation temperature under the condensation pressure, which is called the re cooling temperature (or supercooling temperature).

5. What is intermediate temperature?

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

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

A: 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 pipe insulation. Generally, it should be 5 ~ 10 higher than the evaporation temperature. Changing the liquid supply can adjust the superheat.

7. (how to detect) compressor exhaust temperature, (what factors affect the exhaust temperature)?

A: the exhaust temperature of the compressor can be measured from the thermometer on the exhaust pipeline. The exhaust temperature is directly proportional to the pressure ratio (suction and exhaust) and suction temperature. The higher the suction superheat and pressure ratio, the higher the exhaust temperature; Otherwise, the opposite is true. Generally, the exhaust pressure is slightly higher than the condensation pressure.

8. What is tide car (liquid hammer)?

Answer: the refrigerant liquid or wet steam is sucked into the compressor by the compressor due to failure or insufficient heat absorption and evaporation of the refrigerant.

9. What causes damp cars?

Answer: (1) the liquid level control of gas-liquid separator or low-pressure circulating drum fails, resulting in ultra-high liquid level.

(2) The liquid supply is too large and urgent. Internal leakage of throttle valve or excessive opening.

(3) Too much liquid is stored in the evaporator or gas-liquid separator (low-pressure circulating drum), the heat load is small, and the load is too fast when starting up.

(4) Sudden increase of heat load; Or the suction valve is not adjusted in time after frost flushing.

10. What are the consequences of a wet car?

Answer: for the piston machine: (1) the refrigerant enters the compressor, causing a large number of bubbles in the lubricating oil, damaging the oil film on the lubricating surface, and making the oil pressure unstable.

(2) Make the moving parts run without good lubrication, resulting in galling; In case of serious, Babbitt alloy of holding shaft and main bearing bush melts.

(3) The refrigerant enters the compressor to make the cylinder liner cool and shrink sharply and hold the piston; If it is serious, damage the cylinder liner, piston, connecting rod and piston pin.

(4) Because the liquid is incompressible, the force on the connecting rod and piston under the condition of wet car far exceeds the design value, which is very easy to cause damage; Because the liquid is incompressible, the exhaust valve group together with the false cover will be lifted by the liquid impact in the case of wet vehicle; In serious cases, it will lead to the deformation of the safety spring, and even the malignant accident of crashing the machine body and cylinder head, breaking through the gasket and hurting people.

For screw machine: damp car will cause vibration, increase noise, and damage rotor and bearing (too much force); Serious damp vehicles will also damage equipment and cause accidents.