It's pretty hard to understand everything in the world. And to be a professional in all areas of science and technology is almost impossible. However, on duty, for educational purposes, or simply to increase our own awareness, we need to quickly get the maximum information about some device or process, in an easy and accessible form for non-professionals. For these purposes, there are so-called "dummies manuals", that is, for those who need to quickly understand what is at stake and how it works. Let's analyze a similar instruction and consider the principle of operation of a chiller (for dummies).
What is this
A chiller (or a refrigerating machine in another way) is a unit for creating artificial cold and transferring it to the appropriate coolant. As such, as a rule, ordinary water acts, less often - brines (solutionss alts in water). The etymology of the word refers it to the English language, to the verb to chill (English) - to cool, and the noun formed from it chiller (English) - cooler. The chiller 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 to obtain cold in artificial conditions, that is, where it cannot be done due to nature (free-cooling). It is clear that it will not be difficult to cool the water in winter, with a deep minus on the street. But what to do in the summer, when the ambient temperature is much higher than we need? This is where a chiller comes in. Its principle of 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, cool it) during boiling, transfer and release it into 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 refrigeration machine can be conditionally divided into two zones: low and high pressure. Regardless of the type, any chiller will always have two heat exchangers: an evaporator in the low pressure zone and a condenser in the high pressure zone. Without these two components of the system, the chiller will not be able to operate. PrincipleThe operation of such heat exchangers is based on thermal conductivity (conduction), that is, the transfer of heat from one medium to another through a wall separating these two media. The evaporator of the refrigeration machine returns the generated cold to the system to the consumer, and the condenser either dumps the removed heat into the environment or sends it to recovery (heating the first stage of hot water supply, underfloor heating, etc.).
How it works
Consider a standard vapor compression chiller. The principle of operation of such a refrigeration machine is theoretically based on the Carnot cycle. The compressor pressurizes the gas while simultaneously raising its temperature. Hot gas under high pressure is supplied to the condenser, where it participates in the process of heat exchange with another medium at a lower temperature. As a rule, it is either water (brine) or air. Here, the gas condenses into a liquid, during which excess heat is released, given to the coolant and thus removed from the consumer. Further, the liquid enters the throttling device, where the pressure in the system decreases with a corresponding temperature drop. After that, the liquid partially boiled in the expansion valve (thermal expansion valve) enters directly into the evaporator, which is also an important part of the chiller-fan coil system. The principle of operation of an evaporator is similar to that of a condenser. Here, heat exchange takes place between the coolant (which carries the cold into the fan coil unit) and the refrigerant, which begins to boil and at the same time takes heat from another medium. Afterevaporator gas enters the compressor, and the cycle repeats.
Absorption chiller
The operation of a compressor in a vapor compression cycle requires a significant amount of electricity. However, there is already equipment available to avoid these expenses. Consider the principle of operation of an absorption chiller. Instead of a compressor, an absorbent-based pressurization system using an external heat source is used. Such a source can be hot steam, hot water, or thermal energy from burning gas or other fuel. This energy is used to rectify or evaporate the absorbent, during which the pressure of the refrigerant rises and it is fed into the condenser. Further, the cycle works similarly to the vapor compression cycle, and after the evaporator, the gaseous refrigerant is fed to the heat exchanger-absorber, where it is mixed with the absorbent. The absorbent used is ammonia (in water-ammonia chillers) or lithium bromide (lithium bromide ABCM).
Chiller-Fan Coil System
The principle of operation is based on the preparation of air in special heat exchangers, closers, fan coil units (from the words fan (English) - fan and coil - coil), which are installed in air ducts before its direct distribution to the serviced premises. The advantages of such systems over central air conditioning is that different air parameters can be maintained in each room.(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 closers for its final processing, that is, just like in the "chiller-fan coil" system, the principle of operation of the described systems is noticeably different.
