The role of refrigerants in air conditioning and refrigeration systems

Air-conditioning maintenance company tells you the role of refrigerants in air-conditioning refrigeration systems

The refrigeration technology for air-conditioning belongs to the range of ordinary refrigeration, mainly using liquid vaporization refrigeration. (The main reason is that the liquid vaporization process needs to absorb the specific latent heat, and the liquid pressure is different, the boiling point is also different, the lower the pressure, the lower the boiling point.)

In addition, according to the different ways of heat transfer from low-temperature objects to high-temperature objects, it can be divided into: vapor compression refrigeration and absorption refrigeration.

For vapor compression refrigeration, the working principle is to make the refrigerant perform four main thermal processes of compression, heat release, flow connection and heat absorption in thermal equipment such as compressors, condensers, expansion valves and evaporators to complete the refrigeration. cycle.

There are three types of refrigerants:

1) The refrigerant is the working substance of the refrigeration cycle in the refrigeration device. Its working principle is that the refrigerant absorbs the heat of the cooled substance in the evaporator and evaporates, and transfers the absorbed heat to the surrounding air or water in the condenser , And is cooled into a liquid, reciprocating cycle, with the help of state changes to achieve the role of refrigeration.

2) Commonly used refrigerants

A. Ammonia (NH3 R717)

The advantage of larger ammonia is its large refrigeration capacity per unit volume, moderate evaporating pressure and condensing pressure, and it is cheap and easy to buy, especially for large refrigeration equipment such as cold storage and cold storage. c

However, the large amount of ammonia is determined to have a strong stimulating effect and is harmful to the human body. At present, it is stipulated that the concentration of ammonia in the air should not be greater than 20mg/m3. Ammonia is a combustible substance. When the volume percentage of ammonia in the air reaches 16-25%, there is a danger of explosion when it encounters a flame.

Freon

Most Freon itself is non-toxic, odorless, and non-flammable, and is suitable for air conditioning and refrigeration equipment in engineering buildings or laboratories. Especially Freon R22 has been widely used in my country's air conditioning and refrigeration equipment. Its thermodynamic performance is comparable to ammonia, and it is safe and reliable. It is a good refrigerant, but the current price is relatively high, which affects large-scale popularization and use.

Fatal shortcomings: greenhouse effect gas, its greenhouse effect value is 1700 times larger than carbon dioxide, and more dangerous is that it will destroy the ozone layer in the atmosphere.

According to the international "Montreal Protocol", R22 will be banned in 2020, and developing countries can appropriately extend the ban on production until 2040.

At present, the internationally optimistic alternatives to R22 are R407C and R410A. In addition, R12, which is commonly used in automobile refrigeration, is replaced by R134A. At present, the owners of some large and medium-sized projects in China clearly require the use of environmentally friendly refrigerants such as R407C.

Refrigerant

Shanghai Decoration Design Company tells you that the refrigerant is an intermediate substance, such as commonly used air conditioning chilled water, which is cooled in the evaporator and then transported over a long distance to cool the object that needs to be cooled. At present, the commonly used refrigerant is water, which can only be used in conditions higher than 0 ℃, when it is required to be lower than 0 ℃. Salt water is generally used, such as: sodium chloride or calcium chloride aqueous solution, or an aqueous solution of organic compounds such as ethylene glycol and propylene glycol.