According to the principle of operation and obtaining cold, chillers can be divided into two types: vapor compression and absorption. The scope of both types of refrigeration machines is similar. Both types are mainly used for the production of coolant (coolant) for the needs of air conditioning, industrial refrigeration, ventilation or technology. In addition, chillers can also be used to heat the coolant for heating and ventilation needs. At the same time, steam-compression-type units are used for heating much less frequently than absorption ones due to their low efficiency at negative ambient temperatures. In this article, vapor compression type chillers will be considered.
Principle of operation.
The main elements of a vapor compression chiller are a compressor, an evaporator, a condenser, and a throttling device. The removal of heat energy in a vapor-compression refrigeration machine occurs due to a change in the state of aggregation of the substance (refrigerant). As a rule, refrigerants are fluorine- and chlorine-containing derivatives of saturated hydrocarbons (mainly methane and ethane). The refrigeration machine works according to the following principle: the compressor pumps the gaseous refrigerant into the condenser (see diagram in Fig. 1), where as a result high pressure and heat removal, freon gas is condensed. Further, when the liquid refrigerant passes through the throttling device, its pressure drops, while part of the liquid is converted into vapor. This process is accompanied by a decrease in its temperature. Then the vapor-liquid mixture enters the evaporator, where it boils and finally turns into steam. The evaporator is an intermediate freon/water heat exchanger in which heat is transferred from the refrigerant to the liquid to be cooled. Then the liquid of the required temperature is supplied through the hydraulic circuit to consumers - fan coil units, ventilation installations etc.
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Chiller classification.
Vapor compression chillers can be classified:
- by type of condenser cooling;
- with air-cooled condenser;
- water-cooled condenser;
- for installation outside buildings;
- for installation inside buildings;
- with free cooling system (freecooling);
- with centrifugal fan condenser cooling;
- by type of compressor, etc.
Condenser cooling method:
- air cooled chillers;
- water-cooled chillers (water-cooled).
To chillers outdoor installation include air-cooled monoblock chillers, which are usually installed on the roof of buildings or on special sites next to the buildings served. Also, chillers with a remote evaporator can be attributed to outdoor chillers.
To chillers indoor installation relate:
- chillers with remote condenser(capacitorless);
- water-cooled chillers (water-to-water chillers);
- air-cooled chillers with centrifugal fan.
Chillers of internal installation are located in special rooms - machine rooms. Due to the ease of installation, ease of use and price, air-cooled monoblock chillers are most widely used.
Monobloc air-cooled chillers
Monoblock chillers with are widely used in central air conditioning systems with supply units and in chiller-fan coil systems. Monoblocks have two modifications:
- with axial fans;
- with centrifugal fans (for installation inside buildings).
Chillers with axial fans(Fig. 2) are units mounted on a frame in a single housing and installed on the roof of buildings or nearby on a prepared site. The heat is released in environment.
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Water or aqueous glycol solutions are used as a heat carrier for operation. refrigeration machine during the cold season. If the requirements of the project do not allow the use of glycols, then an intermediate heat exchanger is built into the system (Fig. 3). With this scheme, the temperature parameters of the glycol solution in the chiller must be 2ºС lower than the calculated temperature in the consumer circuit. For example, in order to ensure the temperature parameters of water in the intermediate heat exchanger outlet / inlet: 7/12ºC, it is necessary to obtain a glycol solution at the outlet of the chiller with a temperature of 5ºC.
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In addition, when using an intermediate heat exchanger, it is possible to operate the chiller at negative ambient temperatures. The main advantages of air-cooled monoblock chillers are ease of installation, ease of maintenance, complete readiness of the units for operation (charged with refrigerant and oil), relatively low price. To the number additional benefits monoblocks can be attributed wide opportunities when placed due to the unlimited length of the coolant routes and the height difference between the chiller and consumers. Chillers modular design also have undeniable advantages:
- minimum delivery time due to stock availability;
- cost savings - the system is put into operation in parts as needed;
- variability - by combining modules of different capacities, we obtain a refrigerating machine of the required power (diagram Fig. 4);
- energy savings - the system operates at the same power level, which in this moment required by consumers by enabling/disabling individual modules.
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Chillers with centrifugal fans(Fig. 5) are intended for installation in premises: basements, attics, office special premises. The main difference from chillers with axial fans is the presence of high pressure centrifugal fan/s. Through a network of air ducts, the fan blows air, which cools the condenser and then is removed outside, and the heat is discharged into the environment.
Advantage of chillers with centrifugal fans:
- long service life due to the location in a heated room.
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Air is taken from the room, blowing can be organized through air ducts in one of three directions (Fig. 6)
Hydromodule. The circulation of the coolant (water, glycol solution) between the chiller and consumers (fan coil units) is provided by a hydronic module ( pumping station) (Fig. 7, a), Hydromodule includes circulation pump, expansion tank, stop valves, storage tank (buffer tank), control and protection system.
The storage tank (Fig. 4, b) is necessary to increase the capacity of the coolant in the system. The buffer tank reduces the number of compressor starts and pumping equipment thereby extending the life of the chiller. The buffer tank may not be part of the hydronic module and may be supplied separately.
Chillers with a remote condenser (condenserless) (Fig. 8)
A chiller with a remote condenser is a unit in which all the main elements: a compressor, an evaporator, a throttling device are installed on the same frame in a single housing. At the same time, the chiller itself is designed for indoor installation, and the air-cooled condenser is designed for outdoor use and is installed outside.
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The main advantages of chillers with a remote condenser:
- the possibility of year-round operation using water;
- ease of maintenance at any time of the year;
- high efficiency, due to the absence of a glycol circuit and intermediate heat exchangers;
- long service life due to location in a heated room;
- the possibility of using a capacitor in a low-noise or explosion-proof version.
No air conditioning system has such a variety of connection schemes, like chillers. This is because cooling with a chiller is perhaps one of the oldest and most common methods, which is used not only in air conditioning, but also in the medium and low cold segment.
The chiller includes a refrigeration machine with all the main elements: a compressor, a condenser, a throttling device and an evaporator. Depending on the cooling capacity and type, the chiller can be equipped with various additional auxiliary elements. The other main element of the chiller is the hydronic module. It is he who circulates cold / heated liquid through fan coil units or any other devices. Also, depending on the requirements of the user, the hydronic module can have additional elements. It must necessarily contain: an expansion tank, a circulation pump, strainer, vibration dampers and shut-off and control valves. It includes shut-off, solenoid valves, air, safety valves- i.e. elements responsible for the efficiency and safety of the hydraulic module. In case of insufficient volume of liquid in the hydraulic circuit, it is necessary to use an accumulation tank, which can be built into the hydronic module.
The most common and best-selling type of chillers for liquid cooling are monobloc chillers with an air-cooled condenser with axial fan, and water is used as a cold/heat carrier. The location of the chiller must be outdoors- the roof of buildings or a place next to a building on the ground. In this case, the chiller with the hydronic module can be located either in different buildings or in one building. Such a chiller connection scheme successfully works for cooling in the summer. However, on winter period water must be drained, and refilled in the summer. It is this procedure that is the main drawback of this connection scheme, since such work requires highly qualified specialists and responsibility during the work.
If there is a need to operate the chiller in winter for heat, and in summer for cold and water must circulate in the hydraulic circuit, then a connection scheme for a chiller with an air condenser is possible. The condenser must be remote, installed outdoors. All other parts of the chiller are located in a warm room. With this scheme, all positive points the previous scheme, and the negative point that is associated with draining water for the winter is eliminated. Yet there are shortcomings. Since the condenser is remote, the part of the refrigeration circuit that goes from the chiller to the condenser has restrictions on the length of the route and the height difference.
A more universal chiller installation scheme, capable of operating both in winter and summer with water charging, is a chiller scheme with a water-cooled condenser. With this scheme, the chiller itself and the hydronic module are located in a warm room, and its operation is not affected by the outdoor temperature. This is very important factor in the operation of the chiller, since the freezing of water in the hydraulic circuit is excluded, and there is no need to drain the water in the winter. But in order to cool the water, which ensures the operation and condensation of the refrigerant in the condenser, an additional water circuit is needed from the condenser to the “dry cooler”. Such a circuit is more complex, cumbersome, and all this increases its cost relative to the circuit with an air-cooled condenser.
The chiller scheme with air condenser and centrifugal fan allows to bypass all the restrictions associated with the extension of pipelines for the refrigeration and hydraulic circuits, the need for draining, etc. The installation of the chiller and the hydronic module is possible in a warm room. But since the condenser is air-cooled, it needs outside air. Air has to be supplied to blow the condenser through air ducts and also removed through air ducts. In winter, in order to maintain a constant air temperature in the room, an automation system should be provided to regulate the supply of cold outside air or its overlap. The scheme is rarely used, mainly due to the high cost and complexity of supplying and regulating outdoor air through ducts.
As you know, standard chillers are designed to operate with a very limited temperature range of the cold / heat carrier at the inlet and outlet of the evaporator heat exchanger. Not always such temperature indicators suit consumers. In this case, an intermediate heat exchanger is used, in which the temperature of the cold / heat carrier is brought to the factory standard values, and only then it goes directly to the chiller. The connection scheme of a chiller with an intermediate heat exchanger is most often used for industrial purposes, where there is a need to cool a very hot medium to specified temperatures. There are also disadvantages of such a scheme. A second hydraulic circuit appears, an additional circulation pump. Chillers operating according to this scheme are manufactured by the manufacturer to order, and are much more expensive. Basically, the consumer himself makes the calculations and selection of the intermediate heat exchanger. Often such calculations are quite approximate and may give deviations. temperature regime operation of the chiller itself, and this, in turn, can lead to various malfunctions. 
Chiller cooling capacities vary widely - from 16 kW to 7000 kW. The higher the performance, the more complex and expensive the chiller is equipped with a compressor. Very often, the selection of equipment is made in such a way that the required total cooling capacity is divided into several parts, which allows to reduce the minimum required load on each chiller, and thus more complex scheme parallel connection of chillers. Parallel connection is also used if there is a need to provide redundancy or rotation of chillers. The ideal option is an parallel connection chillers of the same capacity. In the case of their different performance, it becomes necessary to balance the operation of the chillers, based on the required flow rates of the cold/heat carrier. Such a scheme is complicated in that it is always necessary to ensure a uniform supply of cold / heat carrier for both chillers, in case of their simultaneous operation, automatic backup or rotation.
Chillers are gaining more and more popularity in various fields of human activity. They are widely distributed not only in industrial areas, but also as household home or office equipment.
Consider the principle of operation of the chiller, what it is and how this unit works.
Chiller Applications
First, let's figure out what a chiller is.
Chiller - powerful unit, designed to cool the liquid used as a coolant in central systems conditioning such as air handling units, fancoils. It is needed for the circulation of a liquid substance, for example, water, antifreeze.
The main parameter of a refrigeration chiller is power, or cooling capacity. In the climate technology market, all devices have a capacity of 5 to 9 thousand kW. Depending on this parameter, as well as the installed equipment and the area of \u200b\u200bthe premises, chillers find their scope.
So, for centralized air conditioning in apartments, houses, offices and other institutions, systems are used low power. Unit with high ability heat absorption is used in the metalworking industry, mechanical engineering, medicine. 
Chillers are also needed to perform such tasks:
- cooling alcoholic beverages, juices, syrups in the production of products;
- lowering the temperature of drinking and process water in the equipment Food Industry;
- maintaining the temperature regime in the pools;
- education ice rinks on sports grounds;
- cooling of special medical installations;
- release medicines at low temperatures;
- cooling of laser machines;
- production of plastic and rubber products;
- equipment for the chemical industry.
Types of chillers
On sale are such types of chillers as:
- Absorption. In the production process, water or an absorbent is used instead of freon.
- Vapor compression. Cooling occurs as a result of a vapor compression cycle consisting of evaporation or throttling.
According to the installation method, refrigeration machines are divided into the following types:
- Outdoor . Installed in the form of a monoblock on the street.
- Internal . The equipment consists of two parts. The condenser is mounted outside the building, the rest of the parts - inside the room.
By type of condenser, chillers are:
According to the type of hydraulic module, cooling units are divided into the following types:
- with built-in installation;
- with remote installation.
By type of compressor, chillers can be:
- screw;
- rotary;
- piston;
- spiral .
Kinds refrigeration equipment also depend on the type of fans. Chillers are equipped with such fans:
- axial;
- centrifugal.
The classification of units is shown in the photo.
Chiller device
We will analyze how this climate technology works and what it consists of.
Vapor compression chiller
The design of the vapor compressor refrigeration unit may vary depending on the modification and type of chiller, but the main elements of the system are:
- evaporator ;
- condenser;
- compressor .
The principle of operation of a vapor compression chiller is as follows.
- When the compressor compresses the vapors of the working substance, or refrigerant, the pressure reaches 30 atm, the temperature rises to 70 ° C. The condensation process begins.
- The condenser releases heat to the outside. The condenser is the only mechanism in which the refrigerant comes into contact with air environment. outside air blows the mixture, which changes the state of aggregation and turns into a liquid. At the same time, the hot freon cools down and gives off its energy, the air heats up.
- Then the working medium passes through the control valve and expands. The pressure drops. The temperature drops sharply. Freon boils and, having passed through the chiller evaporator, passes into a gaseous state, absorbs the energy of the coolant and cools it. Then the substance again enters the compressor. The cycle is repeated.
The chiller circuit and its device are based on this principle. Many units operate on a reverse refrigeration cycle - they produce heat instead of cooling.
How the chiller works, it is better to show on circuit diagram or in the form of a drawing of the cooling equipment. 
absorption chiller
The principle of operation of an absorption chiller is shown in the diagram.
Advantages and disadvantages of chillers
The refrigeration system has a number of advantages:
- Ease of use.
- Possibility of placing the unit at a distance from the refrigerated room.
- Partial replacement heating systems, reducing the number of batteries.
- Reducing operating costs.
- Environmental friendliness.
- minimization usable area.
- Quiet operation.
- Security.
Disadvantages of chillers:
- Large dimensions of indoor units.
- Big weight.
- Difficult installation, installation depends on the modification of the units.
- Increased power consumption.
- High price.
When choosing a refrigeration machine, you should pay attention to all these indicators. If the room has few rooms and no rooms big size you can buy another climatic equipment, smaller and more efficient.
Chillers are gaining more and more popularity. Today they can be seen in various fields: pharmaceuticals, health and sports field, food industry, shopping malls, residential buildings and apartments, offices and many other establishments. Chillers are installed indoors different sizes. All thanks to a solid powerband. What is the demand for this equipment? What is a chiller, what is its device and how does it work?
Important features of the equipment
Refrigeration unit for heating and cooling liquid heat carriers in main system air conditioning, called the chiller. Heat carriers can be fan coil units or supply type mechanisms.
The service life of a chiller depends largely on specifications products. Also great importance whether the rules for the operation of this equipment are observed.
The main features of the chiller include the following.
- This system is flexible. In it, the distance between the fan coil units and the chiller is limited only by the pump power and can be hundreds of meters.
- With this equipment, you can save money.
- The equipment can be used at any time of the year.
- There is a possibility in automatic mode maintain the set parameters in each room.
- Through the use stop valves the risk of flooding is minimized.
- During operation, the equipment practically does not make noise.
- The coolant is safe, environmentally friendly.
- Construction advantages - layout flexibility, low cost of usable area for equipment placement.
The choice of a chiller should be approached with all responsibility. In order not to be mistaken, it is important to know what types of chillers exist, as well as what are the device and the basic principles of operation of such installations.
The device of the chiller is somewhat different from the device of a conventional refrigerator or air conditioning system. The chiller does not lower the air temperature. It lowers the temperature of the substances used to move the cold. This equipment can cool, for example, a glycol solution or water. Further, the liquid enters where the cold is needed.
The chiller has the following functional elements:
- air condenser;
- storage capacity;
- high and low pressure switch;
- compressor mechanism;
- plate heat exchanger;
- liquid manometers;
- filter dryer;
- thermostatic valve;
- flow switch;
- pump;
- receiver.
The exact set of components depends on the hardware modification.
How does a chiller work?
Hitachi Centrifugal Chiller Operation Diagram
The principle of operation of the chiller has its own characteristics. If you needed this equipment then you should definitely check it out. The operation of the chiller is based on an almost non-stop cycle. A lot depends on the consumer here.
For example, freon moves through the air conditioning system. Gas is leaking through the radiator indoor unit which is chilled. Air blows over the radiator. As a result, freon warms up, and the air temperature drops. Freon enters the compressor. In the chiller, the role of freon plays cold water that flows through the radiator. The radiator is blown warm air from the premises. The water heats up and the air cools down. Water enters the chiller again.
The heat exchanger designed for the chiller has two circuits:
- liquid circulates in one of the circuits;
- freon moves along the other circuit.
These two circuits touch each other. However, water and freon do not mix. In order to increase the efficiency of the system, these media move towards each other.
Such processes take place in the heat exchanger.
- Through the expansion valve, liquid freon penetrates into its heat exchanger circuit. This substance expands, which leads to the removal of heat from the walls. Because of this, freon heats up, and the walls cool.
- Water flows through the heat exchanger circuit. Because the walls are cooled, the temperature of the liquid drops.
- Freon enters the compressor, and cold water cools something.
- The cycle repeats.
Types of chillers
On sale are different kinds chillers:
- absorption - energy is extracted mainly from waste heat, which occurs during the production process and is simply released into the environment (this, for example, hot water, cooled by air);
- vapor compression - cold is generated in a vapor compression cycle, which consists of procedures such as evaporation, throttling, etc.
According to the installation method, chillers are divided into:
- outdoor - a single monoblock, which is mounted on the street;
- internal - equipment that consists of two parts. The condenser is installed outside the building, all other parts - inside.
According to the type of condenser, chillers are divided into the following subspecies:
- with water cooling. A system with such cooling is relatively expensive, but it is characterized by increased reliability;
- with air cooling. The most simple and inexpensive option.
According to the type of hydraulic module, chillers are divided into the following types:
- with built-in installation. Equipment with this hydraulic module is a monoblock, which includes an expansion tank and a pumping group;
- with remote installation. Such a hydraulic module is usually used in cases where the power of the built-in mechanism is insufficient. It is also used in cases where there is a need for redundancy.
The chiller can be equipped with one of the following types compressors:
- screw;
- rotary;
- piston;
- spiral.
Chillers are also classified depending on the type of fan. The equipment can be equipped with the following fans:
- axial. Equipment with such a fan can only be installed outside the building. It is essential that no obstruction be created to the entry of air into the condenser and to its exhaust by the fans;
- centrifugal. Equipment with such a fan is recommended for installation inside the building. It is small in size and low in noise.
Important aspects of chiller installation
In order to feel all the advantages of operating such a device as a chiller plant, its installation must be carried out strictly in compliance with certain rules. Here are the main ones.
- This equipment must only be installed by qualified technicians.
- The chiller must fully meet the criteria of the project engineering network in terms of installation location, design and power.
- It is forbidden to install equipment that has a defect.
- Move the equipment to the place where it will be installed only with a crane.
- It is allowed to fill in only water, as well as a solution of ethylene or propylene glycol, which has a concentration of up to 50 percent.
- AT without fail commissioning tests must be carried out.
- There must be space around the chiller to allow unhindered access for the service technician.
- It is necessary to strictly follow the safety precautions and recommendations of the manufacturer.
By purchasing and installing a chiller, you can be sure that you will receive a modern and reliable system.
- The vapor-liquid mixture is fed into the evaporator after passing through the expansion valve
- Heat exchange of freon and coolant in the evaporator
- The compressor draws refrigerant vapor from the evaporator
- The compressor is used to compress gas and circulate freon through the system by creating a pressure difference
- The compressor pumps compressed gas into the condenser
- In the condenser, the compressed gas, due to the removal of heat, passes into the liquid phase
- Liquid freon enters the expansion valve and the whole cycle is repeated
Chiller operation- this is not only the work of the basic components of the refrigeration circuit.
The second integral part of any chiller is hydromodule. It can be either built-in - that is, located on the same frame with the refrigeration circuit, or located on a separate frame. The structure of the hydromodule, as a rule, includes:
- pump
- battery tank
- set of plumbing and shutoff valves.
The pump serves to circulate the coolant through the heat exchanger and supply it to the consumer. Without a pressure pump, normal operation is impossible, since the evaporator must be filled with coolant to the maximum in order to carry out highly efficient heat exchange. Sometimes two-pump schemes are used, when the functions of the circulation of the coolant inside the chiller and the supply of the already chilled liquid are separated. This is necessary, for example, in cases where it is required to supply liquid to a great height, since the pressure decreases when passing through the heat exchanger, therefore, in order to be as efficient as possible, it is necessary to supply the cooled coolant immediately from the tank to the consumer without pressure loss. The feed pump is selected according to the feed requirements:
- post height (m)
- pressure (bar)
- required flow rate (m3/h).
The accumulator tank serves to store the cooled liquid and reduce the number of starts and stops of the compressor, thus, it occurs in optimal mode. If the accumulator tank is too small for the capacity of the water cooler, then the chiller, programmed for some differential, will cool this volume too quickly and stop at the set degree, then under the influence of the load of the consumer, it will quickly heat up again and will resume again. This mode of operation can lead to damage to the chiller compressor. The battery tank is able to reduce the number of starts and stops to the recommended - no more than 5-7 times per hour.
Chiller scheme
With proper engineering calculation, design and quality assembly, will be durable and uninterrupted. The specialists of CenterProm-Holod, a Russian manufacturer of chillers, will be happy to help you with this. Buy a chiller according to your requirements under the order through the website form or select a chiller with the help of a technical specialist by phone - quickly, optimally, inexpensively at CenterProm-Holod.
