What is a chiller? The principle of the "Chiller-fan coil" system

It's not easy to understand everything in the world. And it's almost impossible to be a professional in all areas of science and technology. However, in the service of duty, for educational purposes, or simply to raise one's own awareness, we need to quickly get maximum information about a device or process, in an easy and accessible way for non-professionals. For these purposes, there are so-called "manuals for teapots," that is, for those who need to quickly understand what is at stake and how it works. We will analyze this instruction and consider the principle of the chiller (for dummies).

What it is

The chiller (or the refrigerating machine in another way) is an aggregate for creating artificial cold and transferring it to a suitable coolant. In the role of such, as a rule, serves ordinary water, at least - brines (solutions of salts in water). The etymology of the word relates it to the English language, to the verb to chill (English) - to cool, and the chiller (n) formed from it. The refrigerating machine can be of two different types. There is a vapor compression and absorption chiller. The principle of operation of each of them is significantly different.

Always cool

The main task of any refrigeration unit is getting cold in artificial conditions, that is, where it is impossible to do it due to nature (freecooling). It is clear that cooling the water in the winter, with a deep minus in the street, will not be difficult. But what to do in the summer, when the temperature of the surrounding air is much higher than what we need? Here the chiller comes to the rescue. The principle of its operation is based on the use of special media created by certain substances (refrigerants). They have the ability to take heat from another medium (that is, to cool it) by boiling, transferring and releasing it to another medium during condensation. During the operation of the refrigeration cycle, such refrigerants change their phase (aggregate) state from liquid to gaseous and vice versa.

Heat Exchangers

Any refrigerating machine can be conditionally divided into two zones: low and high pressure. Regardless of the type, in each chiller there will always be two heat exchangers: the evaporator in the low pressure zone and the condenser in the high pressure zone. Without these two components of the system, the chiller can not operate. The principle of operation of such heat exchangers is based on thermal conductivity (conduction), that is, the transfer of heat from one medium to another through the wall separating these two media. The evaporator of the refrigerating machine gives the generated cold to the system to the consumer, and the condenser either resets the heat to the environment, or sends it to the recovery (heating of the first stage of DHW, warm floors, etc.).

How does it work

Consider a standard vapor compression chiller. The operating principle of such a refrigerating machine is theoretically based on the Carnot cycle. The compressor increases the gas pressure, simultaneously raising its temperature. Hot gas under high pressure is fed into the condenser, where it participates in the process of heat exchange with another medium of lower temperature. As a rule, it is either water (brine) or air. Here, the gas condenses into the liquid, during which excess heat is released to the coolant and thus removed from the consumer. Then the liquid enters the throttling device, where the pressure in the system decreases with a corresponding drop in temperature. After this, the partially boiled liquid in the TRV (thermostatic valve) flows directly into the evaporator, which is also an important part of the "chiller-fan coil" system. The principle of operation of the evaporator is similar to a condenser. Here there is a heat exchange between the cooling medium (which takes the cold out to the fan coil) and a coolant that starts to boil and at the same time takes away heat from another medium. After the evaporator, the gas enters the compressor and the cycle repeats.

Absorption chiller

Operation of the compressor in the vapor compression cycle requires considerable energy consumption. However, already now there is equipment to avoid these wastes. Consider the principle of the absorption chiller. Instead of a compressor, a pressure boost system based on an absorbent material is used here, using a heat source supplied from the outside. Such source can be hot steam, hot water, or thermal energy from burning gas or other fuel. This energy goes to the rectification or evaporation of the absorbent, during which the pressure of the refrigerant rises and it is fed into the condenser. Then the cycle works similarly to the vapor compression, and after the evaporator the gaseous refrigerant is fed to the heat exchanger-absorber, where it is mixed with the absorbent. As an absorbent, ammonia (in water-ammonia chillers) or lithium bromide (bromistolithium ABCM) is used.

System "chiller-fan coil"

The principle of operation is based on the preparation of air in special heat exchangers-closers, fan coils (from the words fan (fan) and coil- coil ), which are installed in the air ducts before it is directly distributed to the room served. Advantages of such systems before central air conditioning is that in each room it is possible to maintain different air parameters (temperature, humidity, mobility), depending on the purpose of the room and the calculation of the heat balance. And although the air from the supply unit is sometimes passed through the door closers for its final processing, that is, the same as in the "chiller-fan coil" system, the principle of operation of the described systems is significantly different.