Refrigerants and Its Classification : Identification : Properties .

A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to a gas and back again. Many working fluids have been used for such purposes. Fluorocarbons, especially chlorofluorocarbons, became commonplace in the 20th century, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in various applications are ammonia, sulfur dioxide, and non-halogenated hydrocarbons such as propane.

Classification of refrigerants:-
There are four classification of refrigerants based on the chemical composition, as listed below:-
1. Chlorofluorocarbons (CFCs).
2. Hydro chlorofluorocarbons (HCFCs).
3. Hydro fluorocarbons (HFCs).
4. Refrigerant blends (azeotropic and zeotropic).

Chlorofluorocarbons (CFCs) are the First refrigerants to be developed. They are composed of chlorine, fluorine, and carbon. They Low in toxicity and noncorrosive. And even they are Nonflammable and nonexplosive (but should not be released where flame or electric heating element is present). Heat causes CFCs to break down into their elements, releasing compounds such as phosgene gas (extremely harmful to the respiratory system). The Common CFCs include R-11, R-12, R-113, R-114, R-115, R-500, R-502, and R-503. Chlorofluorocarbons (CFCs) are Believed to be major cause of ozone depletion. By international agreement, not manufactured since 1995.

2. Hydrochlorofluorocarbons (HCFCs):-
Hydrochlorofluorocarbons (HCFCs) are molecules composed of methane or ethane in combination with a halogen. This makes up a new molecule that is considered to be partially halogenated.
The HCFCs have shorter lives and cause less ozone depletion than the fully halogenated CFCs. Therefore, they have reduced potential for global warming. HCFCs such as R-22 and R-123 are considered to be interim refrigerants. They will be used until suitable replacements are available, the EPA requires the phase-out of HCFCs by the year 2030.

3. Hydrofluorocarbons (HFCs):-
Hydrofluorocarbons (HFCs) include such refrigerants as R-134a and R-23. They are different from chlorofluorocarbons—they contain one or more hydrogen atoms and no chlorine atoms. HFCs are considered to have zero potential for ozone depletion. They have only a slight effect on global warming.

4. Refrigerant blends (azeotropic and zeotropic) :-
Another more recent category is that of refrigerant blends, commonly referred to as "azeotropic" and "zeotropic." The use of refrigerant blends is increasing. Azeotropic blends do not change or separate in composition when used in refrigeration systems. Zeotropic refrigerants are also blends comprised of various refrigerants. When used in a refrigeration system, their volumetric composition and saturation temperature do change.

Identification of refrigerants:-
By number system following the letter R (for refrigerant) & by color code (on cylinder).
Some of the refrigerants commonly used in Refrigeration & air Conditioning field:-

Properties of refrigerants:-
• Nontoxic and nonpoisonous.
• Nonexplosive.
• Noncorrosive.
• Nonflammable.
• Make leaks easy to detect.
• Operate under low pressure (have a low boiling point).
• Must follow standards set by EPA (Environmental Protection Agency).
• Stable as a gas.
• Permit refrigerator or compressor parts moving in the fluid to be easily lubricated.
• Have a high liquid volume per pound.
• Have low vapor volume per pound.
• Have as little pressure difference as possible between evaporating pressure and condensing pressure.

Post a Comment