True or false
1. The refrigerant represented by the symbol R22 is Freon 22.
2. R22 has a slight destructive effect on the atmospheric ozone layer and produces a greenhouse effect.
3. In the ammonia refrigeration equipment, additional safety membranes are allowed on the outlet side of the safety valve.
4, R22 refrigerant refrigeration equipment does not need to set up dryers.
5. R12 emits chloride ions under ultraviolet light, and chlorine ions consume ozone in the thermal layer around the earth.
6. The ozone layer is an umbrella of life on the earth, blocking 99% of ultraviolet radiation and protecting Earth's creatures from UV rays.
7. When R12 is a CFCS refrigerant, its large amount of emissions will contribute to the greenhouse effect and accelerate global warming.
8. Among the Freon-based refrigerants, refrigerants containing chlorine or bromine atoms in their molecules have the potential to consume atmospheric ozone.
9. The GWP value represents the potential value of ozone depletion in the atmosphere.
10. The ODP value shows the global warming effect caused by the greenhouse climate.
11. Three indicators that examine the impact of refrigerants on the environment are atmospheric life, potential for greenhouse effect, and potential for ozone depletion.
12. The chlorine in the CFCS refrigerant has no major damage to the ozone layer.
13, R22 has a strong swelling effect on organic matters, and the seal of the refrigeration system should be made of fluorine-resistant material.
14. CFCS refrigerant has a long atmospheric life, even up to several hundred years, and is a banned refrigerant.
15. The presence of hydrogen in the CFCS refrigerant greatly weakens the destructive effect on the ozone layer.
16. CFCS refrigerants are chlorine-free refrigerants and will certainly damage the ozone layer.
17. All countries have stipulated standards for the safety of refrigerants and require no harm to human health, food, etc.
18. The recent international standards have made major adjustments to the safety classification of refrigerants, combining toxicity and flammability, and stipulating six safety levels.
19, the exhaust process is an overheating process, so the exhaust pressure and exhaust temperature are in a one-to-one relationship.
20. The refrigerant is saturated in the condenser, so the condensation pressure and condensation temperature are not in a one-to-one relationship.
21. R22 can partially dissolve with mineral oil, and its solubility varies with the type and temperature of mineral oil.
22, R22 in the high temperature side of the system (condenser, reservoir) R22 and oil completely dissolved, not easy to form an oil film on the heat transfer surface and affect heat transfer.
23. Refrigerants such as R12, R13, R600a, R134a are all substances that are banned from use.
24. For Freon refrigeration system compressors, energize the heater before starting to vaporize the liquid refrigerant dissolved in the oil.
25, refrigerant liquid is easily compressed, the refrigerant liquid into the compressor will not accident.
26. Replacement of R22 refrigerant mainly includes R407C or R410a.
27. R407C is an azeotropic mixture refrigerant.
28. In practical applications, the big problem with non-azeotropic refrigerants is that when the refrigerant leaks, the speed of dispersion in each group is different, and the concentration of the mixture remaining in the system will change.
29. Refrigerants are customarily classified into three categories based on their boiling temperature at a standard atmospheric pressure and condensing pressure at 30°C, namely high-temperature refrigerants, medium-temperature refrigerants, and low-temperature refrigerants.
30, R134a, R404a belongs to CFCS refrigerant.
31, R123 belongs to high temperature refrigerant (low pressure refrigerant).
32. Water is used not only in compression chillers but also in absorption chillers and steam jet chillers.
33, water as a refrigerant is suitable for the refrigeration temperature above 0 °C, and the system is often in a high vacuum state.
34. Ammonia is widely used medium-temperature and medium-pressure refrigerants. Ammonia has good thermodynamic properties and thermophysical properties.
35, ammonia in the normal temperature and normal low temperature range of relatively moderate pressure, its evaporation pressure in the evaporator is generally 0.098 ~ 0.49MPa.
36. The pressure of ammonia in the normal temperature and normal low temperature range is relatively moderate. The condensing pressure in the condenser is generally 0.981 to 1.57 MPa.
37, ammonia standard evaporation temperature is -13.4 °C, low viscosity, small flow resistance, good heat transfer performance. In addition, ammonia is inexpensive and easy to obtain.
38. The main disadvantage of ammonia is its greater toxicity to the human body and its flammability. The safety classification is B:2.
39, ammonia liquid fertilizer can cause swelling and even frostbite when it is on the skin.
40. Ammonia vapor is colorless and has a strong irritating odor. It can stimulate people's eyes and respiratory organs.
41. When the volume concentration of ammonia vapor in the air reaches 0.5% to 0.6%, people can poison in the gas for half an hour.
42, ammonia will not cause combustion and explosion, when the volume concentration in the air reaches 11% to 14% can be ignited (a yellow flame when burning).
43. When the concentration of ammonia in the air reaches 16% to 25%, it will cause an explosion. Safety regulations: The concentration of ammonia vapor in the work area of ​​the workshop must not exceed 0.02 mg/L.
44. The interior of the refrigeration system contains air and gradually accumulates to a certain concentration, which is very explosive. Therefore, an air separator must be installed in the ammonia system.
45. Ammonia vapors have an adverse effect on the food and make it smell bad.
46. ​​The final temperature of ammonia compression is high, so the compressor cylinder can not take cooling measures.
47. The solubility of ammonia in mineral oils is very small. In condensers, reservoirs and evaporators, the oil will deposit in the lower part and need to be released regularly.
48. Pure ammonia does not corrode steel, but when it contains moisture, it is necessary to corrode zinc, copper, bronze and other copper alloys, and even phosphor bronze is not listed.
49. Copper and copper alloy components are not used in ammonia refrigerating machines. When using copper materials, high-tin-phosphor bronze materials are restricted.
50. Ammonia can be dissolved with water in any ratio. At low temperatures, water does not precipitate out of the solution and freeze into ice. Therefore, a dryer must be installed in the ammonia system.
51. The presence of moisture in the ammonia system not only exacerbates the corrosion of the metal, but also reduces the amount of refrigeration, so the water content in ammonia is generally limited to no more than 0.1%.
52, ammonia leak detection method: From the pungent odor is easy to find the system ammonia leakage. The litmus test paper or phenolphthalein test paper can be used for chemical leak detection.
53. At present, ammonia is mainly used in single- and dual-stage compression refrigerators of large and medium-sized cold storages.
54. R134a (tetrafluoroethane) is an alternative refrigerant to R12. Its ODP value is not 0, GWP is 875.
55, R134a (tetrafluoroethane) standard evaporation temperature of -26.2 °C; freezing point of -101.0 °C.
56. R134a has a large molecular weight, large flow resistance loss than R12, and better heat transfer performance than R12.
57. When R22 refrigerant is used for cooling operation, when air is used as a cooling medium, the condensing pressure should generally not exceed 2.16 MPa.
58. When R22 refrigerant is used as a cooling medium for cold storage refrigeration operation, its condensing pressure generally does not exceed 1.53 MPa.
59. The toxicity of R134a is very low and it is flammable in the air. It is a very unsafe refrigerant.
60. R134a dissolves well with mineral oils.
61. The chemical stability of R134a is good, but because it is much more soluble than R12, it is not good for the refrigeration system.
62, R134a refrigeration system must be used for R134a compatible desiccants, such as XH-7 or XH-9 type molecular sieve.
63. A mixture of n-butane, isobutane or n-butane and isobutane can be used in domestic refrigerators.
64. Methane can be combined with ethylene, ammonia (or propane) to form a ternary refrigerating system, obtaining a low temperature of around -150°C due to the natural gas liquefaction plant.
65. The refrigeration temperature range of ethane and ethylene is comparable to that of R13, and it is only used in the low-temperature part of the refrigerating system.
66. There is no chlorine atom in the R134a molecule, which can be detected by a traditional electronic leak detector.
67. The high greenhouse effect of R134a is a worrying issue.
68. R134a is mainly used for household refrigerators, refrigerators, freezers, car air conditioners and some central air conditioning refrigeration systems.
69, R600a is a natural refrigerant; R600a has a boiling point of -11.73 °C.
70. R600a is used as a permanent replacement for R12 in low refrigeration temperatures (eg refrigerators).
71. R600a has a destructive effect on the atmospheric ozone layer without greenhouse effect.
72, R600a flammable, explosive, in the air explosion volume fraction of 1.8% to 8.4%, so there is R600a existing refrigeration pipeline, does not allow the use of gas welding or welding.
73, R600a very low toxicity, but flammable in the air, so the safety category is A3, in the use of R600a should pay attention to fire and explosion protection.
74, R600a can be miscible with mineral oil, vaporization of latent heat, so the system charge more.
75, R600a high thermal conductivity, compression ratio, to improve the compressor's gas transmission coefficient and compressor efficiency has an important role.
76, R600a is low in entropy index, low in temperature, and the unit volume of refrigeration is only about 50% of R12.
77, R600a is cheap. Due to its excellent environmental characteristics and no pollution to the atmosphere, it is currently widely used as one of the alternative refrigerants for R12.
78, inorganic salt solution is mainly used in applications where the operating temperature is above 0 °C. An aqueous solution such as calcium chloride, sodium chloride, magnesium chloride, and the like.
79, the use of R600a seat refrigerant system, its electrical insulation requirements higher than the general system, in order to avoid sparks caused by the explosion.
80, R600a and mineral oil can be mutually soluble, without expensive synthetic lubricants.
81. The leak detection of R600a cannot be detected by a conventional leak detector. A leak detector specially designed for R600a should be used.
82. The boiling points of R407C and R22 are relatively close. When the pressure is at the standard atmospheric pressure, the bubble point temperature is -43.4°C and the dew point temperature is -36.1°C.
83. Like other HFC refrigerants, R407C is also compatible with mineral oils and can be dissolved in polyester synthetic lubricants.
84, R22's air conditioning system replaced by R407C, as long as the lubricant and refrigerant can be replaced, without the need to replace the refrigeration compressor, which is R407C as a substitute for R22 big advantage.
85, fire damper is a normally open air duct valve, in the event of a fire, used to cut off the air inside the duct.
86. Sodium dichromate must not be added to salt water for frozen foods to prevent poisoning. For example, sodium chloride may not be added to poplar production brine tanks.
87, R407C can not be miscible with mineral oil, but can be dissolved in polyester synthetic lubricants.
88, R407C is mainly used in air conditioning and refrigeration systems.
89. At low temperature conditions, compared to R407C, the refrigeration system using R410A has a smaller volume.
90, in the use of R410A to use a dedicated refrigeration compressor, and can not directly use the R22 refrigeration compressor.
91. Like other HFC refrigerants, R410A can not be miscible with mineral oil, but can be dissolved in polyester synthetic lubricants.
92. The opening pressure of the safety valve has been set before leaving the factory. When the user is using it, it cannot be unsealed and adjusted.
93. The safety valve must be opened within more than 10% of the container and have enough discharge capacity.
94. When R22 is selected in the refrigeration system of the refrigerator, the single-stage compression ratio is large, and the exhaust gas temperature is too high, so that the compressor has to be protected by high temperature.
95, three-phase thermal relay in the control circuit as a long-term overload protection.
96, the temperature of the refrigerant vapor sucked by the compressor is called the suction temperature.
97. The refrigerant is saturated in the evaporator. Therefore, there is a one-to-one relationship between evaporation pressure and evaporation temperature.
98. The pressure at which the compressor draws refrigerant vapor is referred to as exhaust pressure.
99. The pressure of the refrigerant in the evaporator is called the condensing pressure.
100. In the safety protection device, a temperature controller is used to control the low allowable suction temperature, ie, low temperature protection.
Refrigerator air conditioning exercises
February 22 18:10:51, 2019
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