【 Weak current College 】 air conditioning requirements on what refrigerant

In thermodynamic requirements thermodynamic requirements including refrigerant evaporating temperature, condensing pressure and unit volume cooling capacity, critical temperature, freezing temperatures, condensing temperature, etc.

Refrigerant evaporating temperature (boiling point) is a very important performance indicators, in atmospheric pressure, the lower the temperature, the lower the temperature of the cooling, while at the same time can make the pressure above atmospheric pressure, prevent the air into the refrigeration system. In addition, the requirements of the refrigerant condensing pressure at ambient temperature and the condensing temperature should be as low critical temperature should be as high. Critical temperature level determines the refrigerant at room temperature or normal temperatures can be liquefied. Solidification temperature is the lower bound of the range refrigerant use, the lower the condensing temperature, the larger the refrigerant in the scope of application.

For large piston-type compressors, refrigerant unit volume cooling capacity requirements should be as large, this can reduce the compressor size and reduce the refrigerant cycle. But for small or micro-compressor unit of volume, the cooling capacity can be smaller.

(2) in the physical and chemical requirements in the physical and chemical requirements including refrigerants of viscosity, thermal conductivity and dissolved, absorbent, chemical stability, etc.

General requirements for refrigerant viscosity should be as small, high thermal conductivity coefficient shall be equal to reduce pipeline enhance the flow resistance and heat transfer equipment for heat intensity, thus increasing the efficiency of heat transfer equipment, reduce the heat transfer area. In addition, the refrigerant should have certain absorption and chemical stability. Of these, chemical stability is not burning, explosion and use no decomposition and eradicating corruption, refrigerant itself or with oil and water mix, there should be no significant metal corrosion, on the seal material swelling effect should be kept to a minimum.

Refrigerant solubility refers to its and the nature of immiscible oil, the properties should be viewed from two areas for analysis:

① If the refrigerant and oil can be arbitrary miscible, its advantages are able to create good conditions for lubrication of the organism, and in the evaporator and condenser heat transfer surface to heat transfer oil film formation hindered; its disadvantage is brought out from the compressor's oil, will make the temperature increase in evaporation.

② part or slightly soluble in oil in the refrigerant, its advantages are from compressor oil with a low volume, the evaporator evaporating temperature more stable; the disadvantage is that in the evaporator and condenser heat transfer surface formation is very difficult to clear film, affecting heat transfer.

(3) in the security requirements owing to refrigerant leak in may, the required refrigerant on personal health no damage, non-toxic and non-stimulating effect.

2. classification of refrigerants?

Classification of refrigerants in the following two ways:

(1) classification according to chemical composition according to the chemical separation of refrigerants can be divided into inorganic compound refrigerant, freon, saturated hydrocarbon refrigerants, unsaturated hydrocarbon refrigerants and azeotropic mixtures of refrigerants, etc.

(2) according to the classification of refrigerants condensing pressure by condensation can be divided into high temperature (low voltage) refrigerants, in temperature (medium pressure) refrigerant and low temperature (pressure) refrigerant.

3. What are the common characteristics of refrigerants?

-In the compresses the refrigerant in the widely-used freon refrigerant is ammonia, and hydrocarbons, the following specific about the characteristics of the ammonia, and freon.

(1) the characteristics of ammonia and ammonia is one of the medium temperature refrigerants, its evaporation temperature-33.4 ℃, the critical temperature is 132 ° c, using range is + 5 ~-70 ℃. Purification of ammonia on steel corrosion-free, and no adverse effects on lubricating oil, water, the lubricating oil to lower freezing.

Ammonia vapour colorless, but there was a strong smell of stimulation. Ammonia on the human body have greater toxicity, when ammonia liquid splash into the skin will cause frostbite. Ammonia at room temperature, not combustion, but when heated up to 350 ° c, the decomposition of nitrogen and hydrogen, hydrogen and oxygen, the mixture will explode.

(2) the freon nature freon is a transparent, odorless, non-toxic, not combustion and explosion and chemical stability of refrigerant. Different chemical composition and structure of freon refrigerant thermodynamic properties differ significantly from each other and can be applied to the high temperature, low temperature refrigeration compressor in moderate to accommodate different refrigeration temperature requirements.

Commonly used freon refrigerants R12, R22, with R502 and R134a. Which, in residential air conditioning R22 is applied more a freon refrigerants, its thermodynamic properties and ammonia are similar, but does not burn, not explosive, use than ammonia more safe and reliable. In addition, the freon R134a is a relatively new type of refrigerant and its evaporation temperature-26.5 ℃. The main thermodynamic properties of R134a and R12, will not damage the ozone layer in the air, but will cause the greenhouse effect.

4, commonly used R-22 refrigerant which characteristics?

Freon is currently widely used refrigerants, it is the totality of saturated hydrocarbons, its characteristics are slightly toxic, no smell, no burning, no explosive risk, chemical stability, does not react with water non-corrosive to metal. Freon variety, to avoid the trouble of writing its molecular formula, also for the convenience of memory, it has developed a set of simplified code to represent various freon refrigerant R12, R22, R502, etc. Following to R22 (CHLF2), for example, describes its characteristics, similar to other refrigerants.

R22 is burning, it is difficult to break. R22 in contact with the flame, factoring out the toxic gases called (CoCl2), maintenance of refrigeration compressor open flame should be sufficient ventilation of the refrigeration system (inflatable), the operation response environment ventilation, R22 in the iron and steel, copper container can be a long time in 135-150 ° c of temperature, over temperature starts to decompose. It and the role of frozen oil, with the exception of acid and water, the carbon in the oil, generate carbon-free, and the coexistence with the iron, the temperature reaches 550 ° c will explode.

R22-standard boiling point40.8 ° c, temperature refrigerant R22 is, when the use of water for cooling medium, the condensing pressure should not exceed 1.53MPa; when using air cooling, condensing pressure should not exceed 2.16MPa (excluding tropical air conditioning).

Water solubility in R22 in than R12 in 10 times above, and the lower the temperature, the higher the proportion of its water content and, therefore, require the moisture R22 does not exceed 40 ~ 60mg/L (ppm).

R22 and oil-soluble, compressor pump housing and condenser in mutually dissolved, and isolation in the evaporator, its solubility with the temperature. R22 penetration, easier than R12, so its leak tightness requirements higher unit volume cooling capacity than R12 big 40%. Good electrical properties of R22, insulation performance is fine, but when the liquid dielectric constant high insulation resistance is low; high dielectric constant, which means that due to impurities and insulation resistance reduced tendency to increase, as lubricants blending,dielectric strength will dramatically, therefore, in a closed system range, the electric insulation materials plant impurities to special attention.