The production of artificial cold is based on simple physical processes: condensation, compression and expansion of working substances. The working substances used in refrigeration units are called refrigerants.

Refrigeration machines differ:

• by design (absorption, with a built-in or remote condenser - condenser and non-condenser);
• type of condenser cooling (air or water);
• connection diagrams;
• presence of a heat pump.

Advantages

• Ease of use – the set parameters in each room are automatically maintained year-round in accordance with sanitary and hygienic standards;
• Flexibility of the system - the distance between the chiller and fan coil units is limited only by the pump power and can reach hundreds of meters;
• Economic advantage – operating costs are reduced;
• Environmental advantage - harmless coolant;
• Construction advantage - flexibility of layout, minimal cost of usable space for placing a refrigeration machine, since it can be installed on the roof, technical floor of buildings, or in the yard;
• Acoustic advantage – low noise design of the units;
• Safety – the risk of flooding is limited due to the use of shut-off valves.

Types of chillers

The working substance is a solution of two, sometimes three components. The most common binary solutions of an absorber (absorbent) and a refrigerant meet two main requirements for them: high solubility of the refrigerant in the absorbent and a significantly higher boiling point of the absorbent compared to the refrigerant. Solutions of water-ammonia (water-ammonia refrigeration machines) and lithium bromide-water (lithium bromide machines) are widely used, in which, respectively, water and lithium bromide are absorbents, and ammonia and water are refrigerants. The operating cycle in absorption chillers (see the figure below) is as follows: in the generator, to which waste heat is supplied, the working substance boils, as a result of which almost pure refrigerant boils away, because its boiling point is much lower than that of the absorbent.

The refrigerant vapor enters the condenser, where it cools and condenses, giving off its heat to the environment. Next, the resulting liquid is throttled, as a result of which it cools during expansion) and is sent to the evaporator, where, evaporating, it gives up its cold to the consumer and goes to the absorber. The absorbent, from which the refrigerant boiled off at the very beginning, is supplied here through the throttle and absorbs the vapors, because we outlined above the requirement for their good solubility. Finally, the absorbent saturated with refrigerant is pumped to the generator, where it boils off again.

The main advantages of absorption chillers:

1. The ideal solution for creating trigeneration in an enterprise. The trigeneration complex is a complex that allows today to minimize the cost of electricity, hot water supply, heating and cooling for an enterprise through the use of its own cogeneration power plant in conjunction with an absorption chiller;
2. Long service life - within 20 years, until the first major overhaul;
3. low cost of produced cold, cold is produced almost free of charge, because absorption chillers simply utilize excess heat;
4. Reduced noise and vibration levels, as a result of the absence of compressors with electric motors, as a result - quiet operation and high reliability;
5. The use of refrigeration/heating units with a direct-acting flame gas generator makes it possible to eliminate the need for boilers, which must be used in conventional installations. This reduces the initial cost of the system and makes absorption chillers competitive with conventional systems that use boilers and chillers;
6. Ensuring maximum energy savings during peak load periods. In other words, without consuming electricity to produce cold/heat, absorption chillers do not overload the enterprise’s power grid even during peak loads;
7. It is possible to combine into steam district systems with an efficient double-effect refrigeration unit;
8. It is possible to distribute the load under conditions of maximum performance in cooling mode. The device copes with a critical load in cooling mode with minimal power consumption due to the use of coolers with a direct-acting flame gas generator or a steam-heated generator;
9. Allows the use of emergency electric generators of lower power, since the energy consumption of absorption refrigeration units is minimal when compared with electric refrigeration units;
10. Safe for the ozone layer, does not contain ozone-depleting refrigerants. Cooling is carried out without the use of substances containing chlorine;
11. The overall impact on the environment is reduced to a minimum, as the consumption of electricity and gas, which causes the greenhouse effect and, as a consequence, global warming, is reduced.

An absorption chiller is a machine that produces chilled water using residual heat from sources such as steam, hot water or hot gas. Chilled water is produced using the principle of refrigeration: a liquid (refrigerant) that evaporates at a low temperature absorbs heat from its environment as it evaporates. Pure water is usually used as the refrigerant, while lithium bromide (LiBr) solution is used as the absorbent.

How absorption refrigeration systems work

In absorption refrigeration units, the absorbent, generator, pump and heat exchanger replace the compressor of steam compressor (mechanical refrigeration) refrigeration systems. The remaining three (3) components also found in mechanical refrigeration systems, i.e. expansion valve, evaporator and condenser, are also used in absorption refrigeration systems.

Evaporation stage of absorption coolers

Refer to Figure-2 for a schematic explanation of the absorption cooling process. Similar to mechanical refrigeration, the cycle "begins" when the high pressure liquid refrigerant from the condenser passes through the expansion valve (1, in Fig. 2) into the low pressure evaporator (2, in Fig. 2) and collects in the evaporator Settlement.

At this low pressure, a small amount of freon begins to evaporate. This evaporation process cools the remaining liquid refrigerant. Likewise, the transfer of heat from the relatively warm process water to the currently cooled refrigerant causes the latter to evaporate (2, in Fig. 2), and the resulting steam is supplied to the lower pressure absorber (3, in Fig. 2). As the process water loses heat to the refrigerant, it can be cooled to significantly lower temperatures. At this stage, chilled water is actually obtained by evaporating freon.

Absorption stage of absorption chillers

Absorption of refrigerant vapor in lithium bromide is an exothermic process. In the absorber, the refrigerant is “sucked” into an absorbent lithium bromide (LiBr) solution. This process not only creates an area of ​​low pressure that draws a continuous flow of refrigerant vapor from the evaporator into the absorber, but also causes the vapor to condense (3, in FIG. 2) as it releases the heat of vaporization provided in the evaporator. This heat, together with the heat of dilution generated by mixing the refrigerant condensate with the absorbent, is transferred to the cooling water and released in the cooling tower. Cooling water is the utility in this cooling stage.

Regeneration of lithium bromide solution

As the lithium bromide absorbent absorbs refrigerant, it becomes more and more dilute, reducing its ability to absorb more refrigerant. To continue the cycle, the absorbent must be reconcentrated. This is achieved by continuously pumping the dilute solution from the absorber to a low temperature generator (5 in Figure 2), where the addition of residual heat (hot water, steam or natural gas) boils (4, in Figure 2) the refrigerant from the absorbent. Often this generator is used to recover waste heat from a plant. Once the refrigerant is removed, the reconcentrated lithium bromide solution is returned to the absorber, ready to resume the absorption process, and the free freon is sent to the condenser (6, in Fig. 2). At this stage of regeneration, the waste heat from steam or hot water is useful.

Condensation

The refrigerant vapor welded in the generator (5, in Figure 2) is returned to the condenser (6), where it returns to its liquid state when the cooling water raises the heat of evaporation. It then returns to the expansion valve where the full cycle is completed. During the condensation stage, the cooling water becomes useful again.

Various technologies for absorption chillers

Absorption chillers can be single-shot, double-sided or the latest, which is a triple effect. Single effect machines have a single oscillator (see diagram above, Figure 2) and have a COP value of less than 1.0. Double effect machines have two generators and two capacitors and are more efficient (typical COP values ​​> 1.0). Triple effect machines add a third oscillator and capacitor and are the most efficient, with a typical COP value of >1.5.

Pros and cons of absorption chiller systems

The main advantage of absorption chillers is lower energy costs. Costs can be further reduced if natural gas is available at a low cost or if we can use a low-grade heat source that is otherwise lost in the plant.

The two main disadvantages of absorption systems are their size-weight, and their need for larger cooling towers. Absorption chillers are larger and heavier compared to electric chillers of the same capacity.

Next, the freon flows into the condenser, where it is cooled (usually due to the environment) to a temperature T3 (~45C), while the pressure ideally remains unchanged, but in reality it drops by tenths of an atm. During the cooling process, freon condenses and the resulting liquid enters the throttle (an element with high hydrodynamic resistance), where it expands very quickly. The output is a vapor-liquid mixture with parameters P4 (~7 atm) and T4 (~0C), which enters the evaporator. Here the freon gives up its cold to the coolant flowing around the evaporator, heating up and evaporating at constant pressure (in reality, it will drop to tenths of an atmosphere). The resulting cooled coolant (Tx~7C) is the final product. And at the exit from the evaporator it has parameters P1 and T1, with which it enters the compressor. The cycle is completed. The driving force is the compressor.

Refrigerant and coolant

Classification of vapor compression chillers

Outdoor installation (built-in condenser)

Indoor installation (remote condenser)

By type of capacitor:

Water cooling

Traditionally, cooling towers are used to cool the condenser of refrigeration machines, in which water heated in the condenser is sprayed through nozzles in a stream of moving outside air, and in direct contact with the air is cooled to the wet bulb temperature of the outside air, then entering the condenser. This is a rather bulky device that requires special maintenance, installation of a pump and other auxiliary equipment. Recently, so-called “dry” cooling towers or condenser coolers have been used, which represent a surface water-to-air heat exchanger with axial fans, in which the heat of the water heated in the condenser is transferred to the air, which is circulated through the heat exchanger by axial fans.

In the first case, the water circuit is open, in the second case it is closed, in which it is necessary to install all the necessary equipment: circulation pump, expansion tank, safety valve, shut-off valves. To prevent water from freezing when the chiller operates in cooling mode at subzero outside temperatures, the closed circuit is filled with an aqueous solution of antifreeze liquid. When the condenser is cooled with water, the heat of condensation is also uselessly lost and contributes to thermal pollution of the environment. If there is a heat source, such as a hot water system or process line, it may be useful to use the heat of condensation during the cold production period.

By type of hydraulic module:

With remote hydraulic module

Body pump- this is the “heating” operating mode of the chiller. The vapor compression cycle operates in a slightly different sequence, the evaporator and condenser change their roles and the coolant is not cooled, but heated. By the way, we note that although the chiller is a refrigeration machine, producing three times more cold than it consumes, it is even more effective as a heater - it will provide four times more heat than it consumes electricity. The heat pump mode is most common in public and administrative buildings, sometimes used for warehouses, etc.

Compressor soft start- an option that allows you to get rid of high starting currents that exceed operating currents by 2-3 times.

Chiller typology

The range of manufactured chillers has been significantly updated in recent years due to the widespread use of new, more efficient types of compressors: scroll, single-screw, twin-screw, which are gradually replacing piston compressors in the range of small, medium and large capacities. The range of chillers with a built-in hydraulic module has expanded, including those with a storage tank.

Plate and surface heat exchangers are more often used as evaporators, which has made it possible to reduce the dimensions of the units and their weight. Recently, manufacturers have begun to produce chillers using environmentally friendly freons R407° C, . Depending on the method of cooling the condenser, refrigeration units are divided into chillers with air-cooled condenser and water-cooled condenser. The greatest use is found in chillers with air-cooled condenser, when heat is removed from the condenser by air, often external air.

This method of heat removal requires installation outside the building or the use of special measures to ensure this method of cooling. Chillers with air-cooled condenser are available in a monoblock design, when all elements of the chiller are located in one block, and chillers with a remote condenser, when the main unit can be installed indoors, and the condenser, cooled by outside air, is located outside the building, for example on the roof or in the yard . The main unit is connected to an air condenser installed outside the building using copper freon pipes.

Monoblock chillers

Chillers with axial fans

It is possible to design the chiller with an additional method of regulating the cooling capacity. With chiller versions 1 and 3, the heat of condensation is transferred to the outside air and is irretrievably lost. For chiller options 2 and 4, additional shell-and-tube heat exchangers are installed, duplicating the condenser completely in option R (using 100% of the condensation heat to heat water) or partially (using 15% of the condensation heat to heat water).

In option 4, an additional shell-and-tube condenser is installed on the discharge line after the compressor before the main air condenser. The chiller configuration can be: ST-standard; LN - with a reduced noise level, which is achieved by installing a sound-absorbing casing for the compressor and reducing the rotation speed of the axial condenser fan compared to the standard configuration; EN - with a significant reduction in noise level, which is achieved by installing a sound-absorbing casing for the compressor, increasing the open cross-sectional area of ​​the condenser for air passage and reducing the rotation speed of the axial fan, as well as installing the compressor on spring anti-vibration supports, using flexible inserts on the discharge and suction pipelines of the refrigeration contour.

The sound power level requirements of an operating axial fan chiller when installed outside a building may not be very high unless there are specific noise level requirements in the development where the building is located. If such limitations apply, it is necessary to calculate the room sound pressure level emitted by the chiller and, if necessary, use specially configured chillers.

Chillers with centrifugal fans

When choosing this type of chiller and its placement, it is necessary to ensure a free supply of cooling air to the chiller and removal of air heated in the condenser. This is done with the help of suction and discharge air ducts, and a ventilation network is formed, consisting of a centrifugal fan, an air heater (chiller condenser), air ducts, intake and exhaust ventilation louvres. The dimensions of the latter are selected based on the recommended air speeds in the cross section of the grilles and air ducts.

It is necessary to determine the pressure loss in the ventilation network based on an aerodynamic calculation. The pressure loss in the ventilation network must correspond to the pressure developed by the centrifugal fan at the air flow rate cooling the condenser. If the pressure of the centrifugal fan is less than the pressure loss in the ventilation network, it is possible to use a more powerful electric motor for the centrifugal fan upon special order. Air ducts must be connected to the chiller using flexible inserts so that vibration is not transmitted to the ventilation network.

Chiller performance

Chiller diagram with built-in hydraulic module

Energy-saving technologies in chillers

At the same time, the daily graph of heat excess is also uneven with a clearly defined maximum. Traditionally, in chillers with a capacity of 20–80 kW, two identical compressors are installed and two independent refrigeration circuits are made. As a result, the unit is capable of operating in two modes at 50% and 100% of its rated power. The new generation of chillers with cooling capacities from 20 to 80 kW allows three-stage capacity control. In this case, the total refrigeration capacity is distributed between the compressors in a ratio of 63% and 37%.

In new generation chillers, both compressors are connected in parallel and operate on the same refrigeration circuit, that is, they have a common condenser and evaporator. This design significantly increases the energy conversion efficiency (ECE) of the refrigeration circuit when operating at part load. For such chillers, at 100% load and an outside air temperature of 25°C, KPI = 4, and when operating at 37%, KPI = 5. Considering that 50% of the time the chiller operates at a load of 37%, this provides significant energy savings.

• control all operating parameters of the equipment;
• regulate the set value of the water temperature at the outlet of the chiller in accordance with the parameters of the outside air, technological processes or commands from a centralized control system (dispatch);
• select the optimal power control step;
• in case of real need, quickly and efficiently perform a defrosting cycle (for models with a heat pump).

As a result, short-term compressor starts are automatically minimized, compressor operating time is optimized, and water parameters at the outlet of chillers are adjusted in accordance with real needs. As tests have shown, on average, only 22 compressor starts are turned on during the day, while the compressors of conventional chillers are turned on 72 times.

The average annual chiller KPI reaches 6, and energy savings when using modern chillers instead of conventional ones is 7.5 kWh per 1 m2 of serviced facility area per season, or 35%. Another important advantage that the use of new chillers provides is that the need to install bulky storage tanks disappears, and the circulation pump built into the chiller body allows you to do without an additional pumping station.

Servicing such compressors is labor-intensive and requires highly qualified personnel. In recent years, new SCROLL compressors have appeared on the market, which do not have the characteristic disadvantages of piston and screw compressors. Scroll compressors have high energy efficiency, low noise and vibration levels and do not require maintenance. This type of compressor is simple in design, very reliable and, at the same time, inexpensive. However, the productivity of Scroll compressors, as a rule, does not exceed 40 kW.

The use in modern chillers of many small but very reliable Scroll-type compressors, as well as several refrigeration circuits, has made it possible to obtain a very “maneuverable” chiller that is capable of delivering the required refrigerating power with high accuracy. Obviously, the use of such a chiller makes the installation of a pumping station unnecessary, and a wide selection of pumps of different capacities built into the chiller body solves all issues related to the circulation of chilled water. Particular attention should be paid to the very small inrush currents of new equipment. After all, the start-up of small Scroll compressors, which have low power consumption, occurs alternately, in accordance with the increasing load on the unit.

All chillers of the latest generations have a modern microprocessor control system that allows you to adjust the set value of the water temperature at the outlet of the chiller in accordance with the parameters of the outside air, technological processes or commands from a centralized control system (dispatching). From an economic point of view, using a large number of scroll compressors and installing a built-in circulation pump instead of a separate pumping station turns out to be a more profitable option than using expensive, powerful and complex semi-hermetic compressors.

Advantages and disadvantages of chillers

Advantages

• Scalability. The number of fan coil units (loads) on the central refrigeration machine (chiller) is practically limited only by its productivity.
• Minimum volume and area. The air conditioning system of a large building may contain a single chiller, occupying a minimum volume and area; the appearance of the facade is preserved due to the absence of external air conditioning units.
• Virtually unlimited distance between the chiller and fan coils. The length of the routes can reach hundreds of meters, since with a high heat capacity of the liquid coolant, the specific losses per linear meter of the route are much lower than in systems with a gas refrigerant.
• Wiring cost. To connect chillers and fan coils, ordinary water pipes, shut-off valves, etc. are used. Balancing water pipes, that is, equalizing the pressure and flow rate of water between individual fan coils, is much simpler and cheaper than in gas-filled systems.
• Safety. Potentially volatile gases (gas refrigerant) are concentrated in the chiller, which is usually installed in air (on the roof or directly on the ground). Piping failures within a building are limited by the risk of flooding, which can be reduced by automatic shut-off valves.

Flaws

• Chiller-fan coil systems, in the strict sense, are not ventilation systems - they cool the air in each air-conditioned room, but do not affect air circulation in any way. Therefore, to ensure air exchange, chiller-fan coil systems are combined with air (roof) air conditioning systems, the refrigeration machines of which cool the outside air and supply it to the premises through a parallel forced ventilation system.
• Being more economical than rooftop systems, chiller-fan coil systems are certainly inferior in efficiency to VRV and VRF systems. However, the cost of VRV systems remains significantly higher, and their maximum productivity (volumes of cooled rooms) is limited (up to several thousand cubic meters).
• Some aspects of refrigeration design
• A refrigeration machine is a large (all three dimensions significantly exceed a meter, and the length can exceed 10 m) and heavy (up to 15 tons) equipment. In practice, this means an almost unconditional need to use unloading frames to distribute the mass of the chiller over a large area with a choice of acceptable support points. Standard frames are not always suitable for each specific case, therefore, most often, special design is required.
• The VMT-Xiron chiller consists of 1-4 compressors, 1-12 fans, 1-2 pumps, which causes a whole range of negative vibrations, therefore, the chiller must be installed on vibration supports of the appropriate load-bearing capacity, and all pipelines are connected through vibration inserts of the appropriate diameter .
• As a rule, the connecting diameters of the chiller's pipelines are smaller than the main pipe (usually by one, sometimes by two standard sizes), so a transition is required. It is recommended to install a vibration insert directly at the chiller, followed immediately by a transition. Due to significant hydraulic losses, it is not recommended to remove the transition from the unit.
• To avoid clogging of the evaporator on the coolant side, it is mandatory to install a filter at the inlet to the chiller.
• In the case of a built-in hydraulic module, there must be a check valve at the outlet of the chiller to avoid water movement against the design one.
• To regulate the forward and reverse flows, a jumper between them with a differential pressure regulator is recommended.
• Finally, in the documentation you should always pay attention to which coolant the data is given for. The use of non-freezing coolant reduces the efficiency of the refrigeration system by an average of 15-20%.

Diagram of the operation of a chiller with an air condenser and a winter start-up system (monoblock design, without a hydraulic module)

Specification

1. Danfoss compressor
2. High pressure switch KR
3. Rotolock shut-off valve
4. Differential valve NRD
5. Linear receiver
6. Rotolock shut-off valve
7. Filter drier DML
8. Sight glass SG
9. Solenoid valve EVR
10. Thermostatic valve TE
11. Filter drier DAS/DCR
12. Low pressure switch KR
13. Rotolock shut-off valve
14. Temperature sensor AKS
15. Fluid flow switch FQS
16. Electrical panel

Diagram of operation of a chiller with a remote air condenser and a winter start-up system (without a hydraulic module)

Specification

1. Danfoss compressor
2. High pressure switch KR
3. Rotolock shut-off valve
4. Oil separator OUB
5. Check valve NRV
6. Differential valve NRD
7. Condensing pressure regulator KVR
8. Ball valve GBC
9. Air Cooled Condenser
10. Ball valveGBC
11. Check valve NRV
12. Linear receiver
13. Rotolock shut-off valve
14. Filter drier DML
15. Sight glass SG
16. Solenoid valve EVR
17. Coil for Danfoss solenoid valve
18. Thermostatic valve TE
19. Brazed plate evaporator type B (Danfoss)
20. Filter drier DAS/DCR
21. Low pressure switch KR
22. Rotolock shut-off valve
23. Temperature sensor AKS
24. Fluid flow switch FQS
25. Electrical panel

Scheme of operation of a chiller with a water-cooled condenser and condensation pressure control

Specification

1. Danfoss compressor
2. High pressure switch KP
3. Rotolock shut-off valve
4. Brazed plate water cooling condenser type B (Danfoss)
5. Water control valve WVFX
6. Filter drier DML
7. Sight glass SG
8. Solenoid valve EVR
9. Coil for Danfoss solenoid valve
10. Thermostatic valve TE
11. Brazed plate evaporator type B (Danfoss)
12. Filter drier DAS/DCR
13. Low pressure switch KP
14. Rotolock shut-off valve
15. Temperature sensor AKS
16. Fluid flow switch FQS
17. Electrical panel

Diagram of a hydraulic module for a chiller with one pump

Specification:

1. Thermally insulated open container
2. Pump
3. Ball valve
4. Separable connection
5. Pressure gauge
6. Reaching the consumer
7. Water inlet
8. Bypass valve
9. Coarse filter
10. Flow control relay
11. Visual control of liquid level

According to the principle of operation, a fan coil unit is very similar to the internal unit of a split system. The main difference is the coolant: instead of refrigerant, the fan coil uses ordinary water or an antifreeze solution. The liquid cools or heats the incoming air, which is brought to the desired temperature and returned to the room. The resulting condensate is discharged to the street or to the sewer using a pump.

As is the case with heating radiators, several fan coil units are often installed in one room at once - the required number depends on the power of the devices and the area of ​​the room. In addition, they can be connected to supply ventilation, which allows the devices to be used in mixed mode (mixing air received from inside with fresh air).

Temperature regulation is carried out using an electronic system control unit, temperature sensors and various valves. Complex air conditioning systems also use central air conditioners, which are responsible for cleaning and humidifying the incoming air.

Types of chiller-fan coil systems

• Single zone system. It is used primarily for servicing large premises with uniform heat distribution, since all single-circuit fan coil units connected to it are heated and cooled simultaneously.
• Multi-zone system. Uses fan coil units with double-circuit heat exchangers, which allows you to separate the supply of cold and hot water. Devices in such a system can simultaneously provide different air temperatures in different rooms.

Types of fan coil units

• Cassette;
• Floor-standing;
• Wall-mounted;
• Duct.

• Single-flow (air is discharged from the device in one direction);
• Double-flow (two air flows come out of the device in different directions);
• Four-flow (models of this type produce four air flows, which makes them the best choice for air conditioning large areas).

How to choose a fan coil

• Type (cassette, floor, wall or duct);
• Power (the minimum value in watts can be obtained by multiplying the area of ​​the air-conditioned room by 100);
• Energy efficiency (relevant only for large air conditioning systems, since fan coil units consume quite little electricity);
• Noise level (it is recommended to use devices with quiet fans, the noise level of which does not exceed 60 decibels).

• Scalability. The distance between units in split systems does not exceed 15 meters due to the refrigerant used in them. At the same time, the distance between the chiller and the fan coil can exceed hundreds of meters, which makes it easy to expand the system if necessary.
• Versatility. Unlike air conditioners in standard split systems, fan coil units can operate without stopping all year round.
• Safety. Fan coil coolants are much safer compared to gas refrigerant used in split systems.

• Large system sizes. Due to the impressive dimensions of the chiller-fan coil system, its installation is only advisable in spacious buildings.
• Poor filtration quality. The air purification filters built into fan coil units cope with their task much worse than their analogues in split systems.
• High installation complexity. Due to the large size and weight of chiller-fan coil systems, their installation takes a lot of effort and time.

Operating principle of the dry cooler

• Plate heat exchanger. Can be V-shaped, horizontal or vertical. Most often made from aluminum or copper. Efficient heat transfer is ensured by the high number of fins and, as a result, the large surface area of ​​the heat exchanger.
• One or more fans. Most dry coolers are equipped with axial cooling impellers with a radius of 200 to 350 mm. In large devices with V-shaped heat exchangers, fans with a diameter of up to 1000 mm are allowed. In addition, high-performance industrial cooling systems can use centrifugal fans.
• Protective and regulating automatic equipment responsible for maintaining the required coolant temperature and changing the fan speed.
• The heated coolant (ordinary water or anti-freezing solution) is supplied to the dry cooler inlet, where its temperature is reduced to the temperature of the street air. The cooling level can be adjusted by changing the fan speed. The liquid is supplied using a circulation pump. After this, the cold coolant is supplied back to the cooled equipment, and then the cycle is repeated.

Advantages and disadvantages of dry cooling towers

• High energy efficiency;
• Environmental safety (the energy carrier circulates in a closed circuit, and, as a result, does not evaporate, keeping the air humidity level at the same level);
• Ease of installation, operation and maintenance;
• Low cost of equipment;
• Easy scaling (new units can be easily added to the existing cooling system);
• When working with dry coolers, you can use any non-freezing solutions.

• The performance of the devices depends on the outside air temperature (problems are possible during periods of peak temperatures in winter and summer);
• Dry coolers use more electricity than standard evaporative cooling towers.

Scope of application of dry coolers

• In industries requiring large volumes of coolant;
• In industry, for cooling coolants in refrigeration and injection molding equipment, as well as heat removal from extruder engines, machine tools and generators;
• In construction to reduce the temperature of refrigeration units and electric generators;
• For free cooling of air in public and industrial buildings (free cooling).
• A wide range of models and configurations of dry coolers allows you to choose a unit with suitable characteristics for any operating conditions, so their popularity is only increasing every year.

Based on the principle of operation and the production of cold, chillers can be divided into two types: vapor compression and absorption. The scope of application of both types of refrigeration machines is similar. Both types are primarily used for the production of coolant (coolant) for air conditioning, industrial refrigeration, ventilation or technology needs. In addition, chillers can also be used to heat coolant for heating and ventilation needs. Moreover, steam-compression units are used for heating much less frequently than absorption units due to their low efficiency at negative ambient temperatures. This article will discuss vapor compression type chillers.

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 thermal energy in a vapor-compression refrigeration machine occurs due to a change in the state of aggregation of the substance (refrigerant). As a rule, the refrigerant is freons - fluorine- and chlorine-containing derivatives of saturated hydrocarbons (mainly methane and ethane). The refrigeration machine operates on the following principle: the compressor pumps gaseous refrigerant into the condenser (see diagram in Fig. 1), where, as a result of high pressure and heat removal, gaseous freon condenses. Further, when the liquid refrigerant passes through the throttling device, its pressure drops, and 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 refrigerant/water heat exchanger in which heat is transferred from the refrigerant to the cooled liquid. Then the liquid of the required temperature is supplied through a hydraulic circuit to consumers - fan coil units, ventilation units, etc.

Rice. 1

Classification of chillers.

Vapor compression chillers can be classified:

1. by type of condenser cooling;

• with air-cooled condenser;
• with water cooled condenser;

• for installation outside buildings;
• for installation inside buildings;

• with a free cooling system (free cooling);
• with a centrifugal condenser cooling fan;
• by compressor type, etc.

According to the method of cooling the condenser:

• air cooled chillers;
• water-cooled chillers (water-cooled).

Outdoor chillers include monoblock chillers with air-cooled condenser, which are usually installed on the roof of buildings or on special sites near the buildings they serve. Chillers with a remote evaporator can also be classified as outdoor chillers.

Indoor chillers include:

• chillers with a remote condenser (condenserless);
• water-cooled chillers (water-to-water chillers);
• air-cooled chillers with a centrifugal fan.

Indoor chillers are located in special rooms - machine rooms. Due to ease of installation, ease of operation and price, monoblock chillers with air-cooled condenser are most widely used.

Monoblock chillers with air cooled condenser

Monoblock chillers are widely used in central air conditioning systems with air 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. Heat is released into the environment.

Rice. 2

Water or aqueous glycol solutions are used as a coolant to operate the refrigeration machine during the cold season. If the project requirements 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 should be 2ºC lower than the design temperature in the consumer circuit. For example, in order to ensure the temperature parameters of water in the intermediate heat exchanger output/input: 7/12ºC, it is necessary to obtain a glycol solution at the outlet of the chiller with a temperature of 5ºC.

Rice. 3

In addition, when using an intermediate heat exchanger, it is possible to operate the refrigeration machine at negative ambient temperatures. The main advantages of monoblock air-cooled chillers are ease of installation, ease of maintenance, complete readiness of the units for operation (filled with refrigerant and oil), and relatively low price. Additional advantages of monoblocks include wide placement possibilities due to the unlimited length of coolant routes and the height difference between the chiller and consumers. Modular design chillers also have undeniable advantages:

• minimum delivery time due to availability in warehouse;
• cost savings - the system is put into operation in parts as needed;
• variability - by combining modules of different capacities we obtain a refrigeration machine of the required power (diagram Fig. 4);
• energy saving - the system operates at the power level that is currently needed by consumers by turning on/off individual modules.

Rice. 4

Chillers with centrifugal fans(Fig. 5) are intended for installation in premises: basements, attics, special service premises. The main difference from chillers with axial fans is the presence of a high-pressure centrifugal fan/s. Through a network of air ducts, the fan forces air, which cools the condenser and is then removed outside, and the heat is discharged into the environment.

Advantages of chillers with centrifugal fans:

• long service life due to location in a heated room.

Rice. 5

Air is taken from the room; blowing can be organized through air ducts in one of three directions (Fig. 6)

Hydromodule. The circulation of coolant (water, glycol solution) between the chiller and consumers (fan coils) is ensured by a hydraulic module (pumping station) (Fig. 7, a). The hydraulic module includes a circulation pump, an expansion tank, shut-off valves, an accumulator tank (buffer tank), control and protection system.

The storage tank (Fig. 4, b) is necessary to increase the coolant capacity in the system. The buffer tank allows you to reduce the number of starts of compressors and pumping equipment, thereby increasing the service life of refrigeration machines. The buffer tank may not be included in the hydraulic 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: compressor, evaporator, throttling device are installed on one frame in a single housing. At the same time, the chiller itself is intended for indoor installation, and the air-cooled condenser is intended for outdoor use and is installed outside.

Rice. 8

The main advantages of chillers with a remote condenser:

• possibility of year-round operation using water;
• ease of service 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 design.

Water chillers

This section of our Internet portal presents models of chillers with water-cooled condenser. Unlike models with an air condenser, which are designed optimally for operation in air conditioning systems of buildings, a water condenser chiller or, as specialized experts call it, a “water water” chiller, its design is fully consistent with its use in production processes. Today it is no longer possible to imagine the production of thermoplastics and dairy products, or the operation of laser machines and the production of food drinks, the production of which involves a natural fermentation process without the use of constant temperature systems. This is where the industrial water cooling chiller became a core element of the production process. A water-cooled chiller system has a number of advantages over models with an air condenser.

Advantages of a water chiller:

1. Minimum overall dimensions for such installations

Due to the fact that heat is removed by liquid, the condenser design has much smaller dimensions than a capacitor in which heat is removed by blowing air. This makes it possible to place the refrigeration machine directly in the workshop, which has a positive effect on the service life of the equipment, and also makes it possible to use them throughout the entire calendar year.

2. Since the principle of operation of a water chiller allows it to be used all year round, models of water-cooled units are equipped with components with increased wear resistance, which has a positive effect on the reliability of chillers.

3. The use of clean running water, which is used in general during production, to remove heat from the condenser has a positive effect on the cooling capacity of the chiller and its service life.

Working principle of water cooled chiller

The main components of the chiller are the refrigeration circuit units: compressor, evaporator, condenser and thermostatic valve.

The external liquid circuit of the cooling system using a chiller takes heat from other equipment involved in the production process and carries it to the heat exchanger (evaporator). This is where the two different temperature circuits of the chiller system intersect. Heat from the external circuit is transferred to the internal circuit of the chiller, then due to the physical properties of the refrigerant and other components of the chiller, heat is transferred to the condenser, where the heat is removed by the flow of running water in the cooling tower or by blowing with an air flow in the dry cooler.

Important to remember

Chillers are equipment that ensures the operation of all production process units that require heat removal. The practice of using refrigeration units (chillers) in production processes proves that it is much more economical to use a water-cooled chiller than an air-cooled one. This is due to the fact that air-cooled chillers are extremely rarely used for all 12 months of the year, therefore the units are designed for fewer machine hours. If we take into account that expensive equipment is almost always used in production, we can draw the following conclusion: the failure of a chiller with remote condenser cooling will entail the breakdown of many installations requiring heat removal. Therefore, do not forget that the price of a water chiller includes not only the cost of the refrigeration machine, but also a certain guarantee of long-term operation of other equipment that cannot be operated without the operation of the chiller.

How to choose the right water chiller and buy suitable model?

First of all, it is necessary to calculate the cold performance of the chiller. Otherwise, the installation will not perform its functions or will wear out. The second step is to pay attention to the possible placement of the condenser (it should be understood that during air cooling a large amount of heat will be released into the air space) or connection to running water. The next question that will confront you is whether a chiller hydraulic module is required and, if necessary, determine its technical characteristics. If your technical specialists know all the selection parameters, then choosing an industrial chiller at the best price in our store will not be difficult for you. A well-thought-out product sorting filter will help you quickly get suitable models. If you have difficulties at any stage of selecting a chiller in Moscow or any other city in the Russian Federation, then immediately contact our engineers for advice. We are always ready to help you in choosing a chiller model that is suitable strictly for your parameters; only from us you can buy equipment from various manufacturers, and the price will be lower than the market average, since our company has signed agreements with official representatives of manufacturing plants in Russia. You can buy a chiller in Moscow using the service of a free visit to the site by an engineer from our company.