Air-cooled chillers: their advantages and types. Chiller - principle of operation, principle of operation What is a chiller and how does it work
Chillers are becoming increasingly popular in various fields of human activity. They are widely used not only in industrial areas, but also as household home or office equipment.
Let's consider the principle of operation of the chiller, what it is and how this unit works.
Application areas of chillers
First, let's figure out what a chiller is.
Chiller is a powerful unit designed for cooling liquid used as a coolant in central air conditioning systems, such as air handling units and fan coil units. It is needed for the circulation of liquid substances, for example, water, antifreeze.
The main parameter of a chiller refrigeration machine is power, or cooling capacity. In the climate control equipment market, all devices have a power from 5 to 9 thousand kW. Depending on this parameter, as well as the equipment installed and the area of the premises, chillers find their scope of application.
Thus, low-power systems are used for centralized air conditioning in apartments, houses, offices and other establishments. A unit with a high heat absorption capacity is used in the metalworking industry, mechanical engineering, and medicine. 
Chillers are also needed to perform the following tasks:
- cooling of alcoholic beverages, juices, syrups during production;
- lowering the temperature of drinking and process water in food industry equipment;
- maintaining temperature conditions in swimming pools;
- the formation of ice skating rinks on sports grounds;
- cooling of special medical installations;
- release of medicines at low temperatures;
- cooling of laser machines;
- production of plastic and rubber products;
- equipment for the chemical industry.
Types of chillers
The following types of chillers are available for sale:
- Absorption. During the production process, water or 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:
- External. 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 remaining parts are installed indoors.
Based on the type of condenser, chillers are:
Based on the type of hydraulic module, cooling units are divided into the following types:
- with built-in installation;
- with remote installation.
Based on the type of compressor, chillers can be:
- screw;
- rotary;
- piston;
- spiral
The types of refrigeration equipment also depend on the type of fans. Chillers are equipped with the following fans:
- axial;
- centrifugal.
The classification of units is shown in the photo.
Chiller device
Let's look at how this climate control equipment works and what it consists of.
Vapor compression chiller
The design of a vapor compression refrigeration unit may vary depending on the modification and type of chiller, but the main elements of the system are:
- evaporator;
- capacitor;
- compressor
The operating principle 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 outside. The condenser is the only mechanism in which the refrigerant is in contact with the air. Outside air blows on the mixture, which changes its state of aggregation and turns into liquid. At the same time, the hot freon cools down and releases its energy, the air heats up.
- The working fluid then passes through the control valve and expands. The pressure drops. The temperature drops sharply. The refrigerant boils and, after passing through the chiller’s evaporator, goes into a gaseous state, absorbs the energy of the coolant and cools it. Then the substance again enters the compressor. The cycle repeats.
The chiller circuit and its design are based on this principle. Many units operate on a reverse refrigeration cycle - instead of cooling, they produce heat.
It is better to show how a chiller works on a circuit diagram or in the form of a drawing of 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 of heating systems, reduction in the number of batteries.
- Reduced operating costs.
- Environmental friendliness.
- Minimizing usable area.
- Quiet operation.
- Safety.
Disadvantages of chillers:
- Large dimensions of internal blocks.
- Heavy weight.
- Complex installation, installation depends on modification of units.
- Increased energy consumption.
- High price.
When choosing a refrigeration machine, you should pay attention to all these indicators. If there are few rooms in the room and there are no large rooms, you can buy other climate control equipment, smaller and more efficient.
This is a unit designed to cool liquid, which is used as a coolant in air conditioning systems. Today, the most common type of such units are vapor compression refrigeration machines. The circuit of such a chiller always includes such basic elements as a compressor, evaporator, condenser and expansion device.
The operating principle of such a system is based on the absorption and release of thermal energy due to changes in the state of aggregation of the refrigerant depending on the pressure acting on it. The most important element on which the operation of the chiller primarily depends is the compressor, of which there are several types today:
- rotary;
- spiral;
- screw;
- piston;
- centrifugal;
The above diagram of the chiller operation does not change depending on its design, of which there are several options:
- monoblock outdoor installation;
- monoblock with centrifugal fans;
- with remote condenser;
- with a liquid-cooled condenser.
Figure 1. Schematic diagram of a chiller with an air-cooled condenser. 1- compressor, 2-high pressure switch, 3-stop valve, 4-differential valve, 5-condensation pressure regulator, 6-air cooling condenser, 7-line receiver, 8-stop valve, 9-filter drier, 10- sight glass, 11-solenoid valve, 12-coil for solenoid valve, 13-thermostatic valve, 14-brazed plate evaporator, 15-filter drier, 16-low pressure switch, 17-stop valve, 18-temperature sensor, 19- fluid flow relay, 20-electric switchboard.
Whatever design you choose, the principle of operation of the chiller always remains the same. The fundamental point in the design of equipment of this type is compliance with the manufacturer’s recommendations for installation, which clearly indicate the required coolant flow (cooled liquid), permissible outside temperature and the amount of thermal energy that must be removed.
Types of liquid cooling installations (chillers)
In order to choose the right one, you should always contact specialists who have a good idea of what kind of design scheme to propose for each specific case, because despite the general principle of operation, each element of the installation plays a very important role in the functionality of the system as a whole.
What's happened ? A chiller is a refrigeration unit used for cooling and heating liquid coolants in central air conditioning systems, which can be air-conditioning units or fan coil units. Basically, a chiller is used to cool water in production - it cools various equipment. Water has better properties than a glycol mixture, so working with water is more efficient.
A wide power range makes it possible to use the chiller for cooling in rooms of various sizes: from apartments and private houses to offices and hypermarkets. In addition, it is used in the food and beverage industry, in the sports and recreational field - for cooling skating rinks and ice rinks, in pharmaceuticals - for cooling medicines.
The following main types of chillers exist:
- monoblock, air condenser, hydraulic module and compressor are located in one housing;
- chiller with a remote condenser outside (the refrigeration module is located indoors, and the condenser is taken outside);
- chiller with a water condenser (used when the minimum dimensions of the refrigeration module in the room are required and it is not possible to use a remote condenser);
- heat pump, with the ability to heat or cool the coolant.
Chiller operating principle
The theoretical basis on which the operating principle of refrigerators, air conditioners, and refrigeration units is built is the second law of thermodynamics. Cooling gas (freon) in refrigeration units undergoes the so-called reverse Rankine cycle- a type of reverse Carnot cycle. In this case, the main heat transfer is based not on compression or expansion of the Carnot cycle, but on phase transitions - and condensation.An industrial chiller consists of three main elements: a compressor, a condenser and an evaporator. The main task of the evaporator is to remove heat from the object being cooled. For this purpose, water and refrigerant are passed through it. As the refrigerant boils, it takes energy away from the liquid. As a result, water or any other coolant is cooled, and the refrigerant is heated and goes into a gaseous state. After this, the gaseous refrigerant enters the compressor, where it acts on the compressor motor windings, helping to cool them. There, the hot steam is compressed, again heating up to a temperature of 80-90 ºС. Here it is mixed with oil from the compressor.
In the heated state, freon enters the condenser, where the heated refrigerant is cooled by a flow of cold air. Then the final cycle of work begins: the refrigerant from the heat exchanger enters the subcooler, where its temperature decreases, as a result of which the freon turns into a liquid state and is supplied to the filter drier. There it gets rid of moisture. The next point on the path of refrigerant movement is the thermal expansion valve, in which the freon pressure decreases. After leaving the thermal expander, the refrigerant is low pressure steam combined with liquid. This mixture is fed to the evaporator, where the refrigerant boils again, turning into steam and superheating. The superheated steam leaves the evaporator, which is the beginning of a new cycle.
Scheme of operation of an industrial chiller
#1 Compressor
The compressor has two functions in the refrigeration cycle. It compresses and moves refrigerant vapor in the chiller. When vapor is compressed, pressure and temperature increase. Next, the compressed gas enters where it cools and turns into a liquid, then the liquid enters the evaporator (at the same time its pressure and temperature decrease), where it boils, turns into a gas, thereby taking heat from the water or liquid that passes through the evaporator chiller. After this, the refrigerant vapor enters the compressor again to repeat the cycle.
#2 Air-Cooled Condenser
An air-cooled condenser is a heat exchanger where the heat absorbed by the refrigerant is released into the surrounding space. The condenser usually receives compressed gas - freon, which is cooled and, condensing, passes into the liquid phase. A centrifugal or axial fan forces air flow through the condenser.
#3 High Pressure Limit
Protects the system from excess pressure in the refrigerant circuit.
#4 High Pressure Pressure Gauge
Provides a visual indication of refrigerant condensation pressure.
#5 Liquid Receiver
Used to store freon in the system.
#6 Filter Drier
The filter removes moisture, dirt, and other foreign materials from the refrigerant that will damage the refrigeration system and reduce efficiency.
#7 Liquid Line Solenoid
A solenoid valve is simply an electrically controlled shut-off valve. It controls the flow of refrigerant, which is closed when the compressor stops. This prevents liquid refrigerant from entering the evaporator, which could cause water hammer. Water hammer can cause serious damage to the compressor. The valve opens when the compressor is turned on.
#8 Refrigerant Sight Glass
The sight glass helps to observe the flow of liquid refrigerant. Bubbles in the fluid flow indicate a lack of refrigerant. The moisture indicator provides a warning if moisture enters the system, indicating that maintenance is required. The green indicator does not indicate any moisture content. And yellow indicator signals indicate that the system is contaminated with moisture and requires maintenance.
#9 Expansion Valve
A thermostatic expansion valve or expansion valve is a regulator whose position of the regulating body (needle) is determined by the temperature in the evaporator and whose task is to regulate the amount of refrigerant supplied to the evaporator, depending on the superheat of the refrigerant vapor at the outlet of the evaporator. Therefore, at any given time, it must supply only such an amount of refrigerant to the evaporator that, taking into account the current operating conditions, can completely evaporate.
#10 Hot Gas Bypass Valve
Hot Gas Bypass Valve (capacity regulators) are used to match the compressor capacity to the actual evaporator load (installed in the bypass line between the low and high pressure sides of the refrigeration system). The hot gas bypass valve (not included as standard on chillers) prevents compressor short cycling by modulating compressor output. When activated, the valve opens and diverts hot refrigerant gas from the discharge into the liquid refrigerant stream entering the evaporator. This reduces the effective throughput of the system.
#11 Evaporator
An evaporator is a device in which a liquid refrigerant boils, absorbing heat as it evaporates, from the coolant passing through it.
#12 Low Pressure Refrigerant Gauge
Provides a visual indication of refrigerant evaporation pressure.
#13 Low Refrigerant Pressure Limit
Protects the system from low pressure in the refrigerant circuit to prevent water from freezing in the evaporator.
#14 Coolant Pump
Pump for circulating water through a refrigerated circuit
#15 Freezestat Limit
Prevents liquid freezing in the evaporator
#16 Temperature sensor
Sensor that shows the water temperature in the cooling circuit
#17 Coolant Pressure Gauge
Provides a visual indication of the coolant pressure supplied to the equipment.
#18 Automatic topping up (Water Make-Up Solenoid)
It turns on when the water in the tank drops below the permissible limit. The solenoid valve opens and the tank is filled from the water supply to the desired level. The valve then closes.
#19 Reservoir Level Float Switch
Float switch. Opens when the water level in the tank decreases.
#20 Temperature Sensor 2 (From Process Sensor Probe)
A temperature sensor that shows the temperature of the heated water that returns from the equipment.
#21 Evaporator Flow Switch
Protects the evaporator from freezing of water in it (when the water flow is too low). Protects the pump from dry running. Indicates that there is no water flow in the chiller.
#22 Capacity (Reservoir)
To avoid frequent starts of compressors, use a container of increased volume.
A chiller with a water-cooled condenser differs from an air-cooled one in the type of heat exchanger (instead of a tube-fin heat exchanger with a fan, a shell-and-tube or plate heat exchanger is used, which is cooled by water). Water cooling of the condenser is carried out with recycled water from a dry cooler (drycooler) or cooling tower. In order to save water, the preferred option is to install a dry cooling tower with a closed water circuit. The main advantages of a chiller with a water condenser: compactness; Possibility of indoor placement in a small room.
Questions and answers
Question:Is it possible to use a chiller to cool liquid per flow by more than 5 degrees?
The chiller can be used in a closed system and maintain a set water temperature, for example, 10 degrees, even if the return temperature is 40 degrees.
There are chillers that cool water through flow. It is mainly used for cooling and carbonating drinks, lemonades.
What is better: chiller or dry cooler?
The temperature when using a dry cooler depends on the ambient temperature. If, for example, it is +30 outside, then the coolant will be at a temperature of +35...+40C. Drycoolers are used mainly in the cold season to save energy. The chiller can achieve the desired temperature at any time of the year. It is possible to manufacture low-temperature chillers to obtain liquid temperatures with negative temperatures down to minus 70 C (the coolant at this temperature is mainly alcohol).
Which chiller is better - with a water or air condenser?
The water-cooled chiller is compact in size, so it can be placed indoors and does not generate heat. But cold water is required to cool the condenser.
A chiller with a water condenser has a lower cost, but may additionally require a dry cooling tower if there is no water source - a water supply or a well.
What is the difference between chillers with and without a heat pump?
A chiller with a heat pump can operate for heating, that is, not only cool the coolant, but also heat it. It must be taken into account that as the temperature decreases, heating worsens. Heating is most effective when the temperature drops at least minus 5.
How far can an air condenser be moved?
Typically the capacitor can be carried up to a distance of 15 meters. When installing an oil separation system, the height of the condenser is possible up to 50 meters, provided that the diameter of the copper lines between the chiller and the remote condenser is correctly selected.
To what minimum temperature does the chiller operate?
When installing a winter start-up system, the chiller can operate up to an ambient temperature of minus 30...-40. And when installing arctic fans - down to minus 55.
Types and types of liquid cooling installations (chillers)
It is used if the temperature difference ∆T l = (T L - T Kl) ≤ 7ºС (cooling of technical and mineral water)
2. Scheme of liquid cooling using an intermediate coolant and a secondary heat exchanger.
It is used if the temperature difference ∆T l = (T L - T Kl) > 7ºС or for cooling food products, i.e. cooling in a secondary gasket heat exchanger.
For this scheme, it is necessary to correctly determine the flow rate of the intermediate coolant:
G x = G f · n
G x – mass flow rate of intermediate coolant kg/h
Gf – mass flow rate of cooled liquid kg/h
n – circulation rate of the intermediate coolant
n =
where: C Рж – heat capacity of the cooled liquid, kJ/(kg´ K)
C Рх – heat capacity of the intermediate coolant, kJ/(kg´ K)
∆T x = (T Nx – T Kx)– temperature difference of the intermediate coolant in the evaporator
The operating principle of the chiller-fan coil system is somewhat different from other climate control equipment. It has its own characteristics that make chillers indispensable in many areas. They may have some competition, but they have a different purpose.
The operation scheme of the chiller-fan coil system is based on the transfer of thermal energy, as in air conditioners and heat pumps. But it has a number of design features and a wide range of applications. It is already possible to install a chiller-fan coil for your home, although several years ago such equipment was considered industrial.
Chiller fan coil - what is it?
From English, the terms “chiller” and “fan coil” are translated as “refrigerator, cooler” and “fan with heat exchanger, coil.”
The components of the system are:
- Chiller;
- Pumping station;
- Main distribution (pipelines);
- Refrigerant;
- Coolant;
- Automatic regulation system;
- Fan coil units (fan coil).
In the chiller, heat exchange occurs between the refrigerant and the surrounding air. Depending on the operating mode, it can give or receive thermal energy. The refrigerant cools or heats the coolant.
Various brands of freons are used as a refrigerant in chillers. They are not interchangeable; each model and brand has its own freon.
The coolant is water or antifreeze - a mixture of water with ethylene glycol or propylene glycol. Less commonly used as additives are sodium chloride (table salt) and calcium chloride. Depending on their concentration, the freezing point of the mixture changes.
Cassette type fan coil installed in production. Chiller-fan coil operation diagrams
In this section we will look at connection diagrams for a chiller with a remote and built-in condenser. On them you will see the ability to connect additional systems.
Since the chiller is a universal refrigeration machine, it can be used for different purposes. For example, connect heated floors to it or.
The circuit for a chiller with a built-in capacitor looked exactly the same, but points 1 and 2 would be combined. Sometimes a cooling tower is included in the system for greater energy efficiency.
Chiller fan coil or air conditioners?
Split and multi-split are traditional air conditioning systems for small rooms and buildings. There are small capacity chiller-fan coil systems that can replace an 18,000 BTU air conditioner. More information about chiller models and prices can be found in this online store. What are their differences and advantages?
Any number of fan coil units corresponding to its capacity can be connected to the chiller. An analogue of such a system are multi-zone (multi-split) air conditioners.
The main chiller unit can be placed on the roof or in the basement, where it is easily accessible for maintenance and repair and hidden from public view. The outdoor unit of the air conditioner is installed on the facade of the building, access to it is difficult.
Air conditioners require frequent diagnostics, prevention and repair. They fail more often, are less wear-resistant and have lower energy efficiency.
The temperature range of air conditioners is lower, which affects energy consumption when operating for heating in winter and cooling in summer.
To operate a chiller-fan coil system, longer lines are required than for air conditioners. The cost of installation work is increasing.
If one outdoor air conditioner unit breaks down, one or more rooms will be left without cooling or heating, and not the entire building.
For the operation of air conditioners, a freon line is laid between the outdoor and indoor units. If it breaks, the refrigerant evaporates and requires refilling. If the pipelines leading to the fan coil units are damaged, it is enough to replenish the water supply in the storage tank.
- The vapor-liquid mixture is supplied to the evaporator after passing through the expansion valve
- Heat exchange of freon and coolant in the evaporator
- The compressor sucks refrigerant vapor from the evaporator
- The compressor serves to compress the 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 passes into the liquid phase due to heat removal
- 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 the hydraulic module. It can be either built-in - that is, located on the same frame with the refrigeration circuit, or located on a separate frame. The hydraulic module usually includes:
- pump
- battery tank
- set of plumbing and shut-off 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 as much as possible with coolant to achieve highly efficient heat exchange. Sometimes double-pump schemes are used, when the functions of circulating coolant inside the chiller and supplying already cooled liquid are separated. This is necessary, for example, in cases where it is necessary to supply liquid to a greater height, since when passing through the heat exchanger, the pressure decreases, therefore, in order to be as efficient as possible, it is necessary to supply the cooled coolant directly from the tank to the consumer without loss of pressure. The feed pump is selected according to the supply requirements:
- pole height (m)
- pressure (bar)
- required flow rate (m3/hour).
The battery tank serves to store cooled liquid and reduce the number of starts and stops of the compressor, thus operating in optimal mode. If the accumulator tank is too small for the power of the water cooler, then the chiller, programmed for a certain differential, will cool this volume too quickly and stop at the set degree, then, under the influence of the consumer load, 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 circuit
With competent engineering calculations, design and high-quality assembly, it will be durable and trouble-free. Specialists from CenterProm-Holod, a Russian manufacturer of chillers, will be happy to help you with this. Buy a chiller to suit your requirements using the website form or select a chiller with the help of a technical specialist by phone - quickly, optimally, inexpensively at CenterProm-Holod.