- 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 operating mode 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.
To create comfortable conditions in our home in the summer, we strive to cool the air in our home by installing air conditioners. When we need to reduce the temperature in 2 or 3 rooms, we install the same number of coolers or split systems. But what to do if you need to maintain coolness in a large private house, and even with two or three floors? For such purposes, instead of air conditioners, a chiller-fan coil climate system is used. What it is and how it works will be discussed in this material.
A modern chiller-fan coil system is designed to maintain the temperature inside the entire building year-round. That is, the system can provide both cooling and heating of the air environment. In this case, the temperature in the rooms can be adjusted in accordance with the wishes of the homeowner. In the summer, the main role here is played by a cooling device - a chiller. Its task is to generate cold and supply it inside the building using pipelines with coolant, which plays the role of a coolant in winter.
As a rule, the coolant is ordinary purified water, and less often - an antifreeze substance - ethylene glycol. The latter is not inferior to water in its heat capacity, which is why it is successfully used instead of it both in cooling and heating systems. Next, low-temperature water is supplied through pipes to another heat exchange unit - a fan coil unit installed in each room. In its heat exchanger, the water heats up, transferring its cold to the air in the room, after which it returns back to the chiller.
In fact, the main elements of the chiller-fan coil system resemble the parts of an air conditioner - the outdoor unit (chiller), the indoor unit (fan coil) and the refrigerant pipelines connecting them. Only instead of freon, water flows through the pipes, and there can be as many internal units as you like, it depends on the cooling capacity of the chiller.
Since the operation of the chiller depends on the need for cold, and it is not constant, the intermediate hydraulic module of the circuit has a capacity - an accumulator for the coolant, and to compensate for the thermal expansion of water, an expansion tank is connected to the supply pipeline. The need for a pump to pump coolant is obvious, as shown in the diagram.
Connection of chiller and fan coil units via hydraulic module
As mentioned above, this climate system is an air-based one and in winter can work to heat rooms; only the refrigerant that cools the air becomes a coolant and is heated by the boiler unit. Thanks to this, such schemes are used to maintain the microclimate in the buildings of large shopping centers, cinemas and other buildings with large dimensions.
Types of chillers
It must be said that freon is still present in the system and it is located inside the refrigeration machine. That is, the principle of operation of a chiller, like an air conditioner, is to transfer heat by the working fluid (freon) from one environment to another. In our case, heat is taken by the chiller evaporator from the water heated in the fan coil and transferred to the surrounding air or water again, which serves as a kind of intermediary - the cooler of the condensing unit.
Let us recall that freon is a gas that, under standard conditions, transforms into a liquid state of aggregation. This property is used by the chiller device, where freon evaporates in a heat exchanger - evaporator. This happens due to the extraction of energy for steam formation from water heated in fan coils. As a result, the latter again goes into the building to cool the air, and the freon, pumped by the compressor, enters the second heat exchanger - the condenser, where it cools and returns to a liquid state again.
The condensation process in the second heat exchanger most often occurs under the influence of the external environment; this principle is used by an air-cooled chiller. To achieve high efficiency of the process, air is forced through several radiators at once using axial fans that provide the required flow rate.
The climate systems of large buildings often use water-cooled chillers, whose operating principle is not much different from an air unit. Only here, to condense freon, a different type of heat exchanger is installed, in which water circulates, it serves as a cooler instead of air.
Operating principle of a water-cooled unit
The result is a more expensive and complex circuit with an additional water cooling circuit, but the cooling capacity of such a system is higher than that of an air system. The complexity and high cost arise due to the fact that the water cooling the condenser also needs to be cooled, but now with the help of air, and this requires an additional installation - a cooling tower (dry cooler). It functions simply: water passes through several radiators, each of which has a high-capacity axial fan installed, driving a powerful air flow through it.
Operating principle of fan coil
Having understood the operation of the chiller, let’s move on to consider what a fan coil is. This is a device that ensures the heat exchange process inside each room. Its task is to maintain the air temperature at a given level; for this purpose, the unit is equipped with the necessary instruments and automation equipment.
It operates according to the same scheme as a dry cooler: through an aluminum radiator, inside of which water circulates, an air flow is driven by an axial fan. Having passed through the fins of the heat exchanger, it gives off thermal energy to the water, and itself cools and returns to the room. The working diagram of the fan coil unit is shown in the figure below.
1 – panel for connecting electrical equipment; 2 – unit body in ceiling design; 3 – fan; 4 – heat exchanger made of aluminum or copper; 5 – condensate tray; 6 – air valve with filter; connecting the tube and condensate pump.
Since the operation of fan coil units in the summer is associated with a large flow of cooled air masses, the design of the unit includes a special container for accumulating condensate and a small pump that pumps it into the sewer. In addition to the ceiling version of the fan coil shown in the diagram, there are duct and wall models of the devices.
Unlike the heating system, the chiller is connected to the fan coils through pipelines covered with thermal insulation, otherwise the efficiency of the entire system will significantly decrease.
The area of any home or public building is divided into climatic zones with different temperature conditions. For this reason, each zone must be served by one or a group of fan coils with the same automation settings. The total number of fan coil units is determined by calculation at the stage of design development.
It should be noted that it is impossible to do without correct calculation and design of the system, since all of the equipment listed has a very decent cost. The cost of a mistake is too high, since an incorrectly selected chiller for cooling water or a fan coil for a particular room will not be able to provide the required microclimate, and redoing everything anew will be very expensive.
Conclusion
Chiller-fan coil systems are characterized by efficient operation and energy saving; to produce 3 kW of cold, approximately 1 kW of electricity is needed. But designing, purchasing equipment, as well as installing and maintaining fan coils and chillers require considerable investment.
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Chillers are gaining more and more popularity. Today they can be seen in various fields: pharmaceuticals, health and sports fields, food industry, shopping centers, residential buildings and apartments, offices and many other establishments. Chillers are installed in rooms of different sizes. All thanks to the solid power range. What is the demand for this equipment? What is a chiller, what is its structure and how does it work?
Important equipment features
The refrigeration unit, which is designed to heat and cool liquid coolants in the main air conditioning system, is called a chiller. The coolants can be fan coil units or supply-type mechanisms.
The service life of the chiller largely depends on the technical characteristics of the product. It is also of great importance whether the operating rules for this equipment are followed.
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.
- Thanks to this equipment you will be able to save money.
- The equipment can be used at any time of the year.
- It is possible to automatically maintain the set parameters in each room.
- Due to the use of shut-off valves, the risk of flooding is minimized.
- During operation, the equipment makes virtually no noise.
- The coolant is safe and environmentally friendly.
- Construction advantages - flexibility of layout, low cost of usable space for equipment placement.
The choice of chiller should be approached with all responsibility. In order not to make a mistake, it is important to know what types of chillers exist, as well as what the structure and basic principles of operation of such installations are.
The design of a chiller is somewhat different from that 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 cold. This equipment can cool, for example, a glycol solution or water. Next, the liquid gets to 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 pressure gauges;
- filter drier;
- thermostatic valve;
- flow switch;
- pump;
- receiver.
The exact set of components depends on the modification of the equipment.
On what principle does the chiller operate?
Hitachi centrifugal chiller operation diagram
The principle of operation of the chiller has its own characteristics. If you need this equipment, then you should definitely familiarize yourself with it. 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 penetrates through the radiator of the indoor unit, which is cooled. Air blows over the radiator. As a result, the freon warms up and the air temperature drops. Freon enters the compressor. In a chiller, the role of freon is played by cold water that flows through the radiator. The radiator is blown with warm air from the room. The water heats up and the air cools down. Water again enters the chiller.
The heat exchanger intended for the chiller has two circuits:
- liquid circulates along one of the circuits;
- freon moves along another circuit.
These two circuits touch each other. However, water and freon do not mix. In order to increase the efficiency of the system, these environments move towards each other.
Such processes occur in the heat exchanger.
- Through the thermostatic 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, the freon heats up and the walls cool.
- Water flows along 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
There are various types of chillers on sale:
- absorption - energy is extracted mainly from waste heat, which arises during the production process and is simply released into the environment (for example, hot water cooled by air);
- vapor compression - cold is generated in the vapor compression cycle, which consists of procedures such as evaporation, throttling, etc.
According to the installation method, chillers are divided into:
- external - a single monoblock that is mounted outdoors;
- internal - equipment that consists of two parts. The condenser is installed outside the building, all other parts are installed inside.
Based on the type of condenser, chillers are divided into the following subtypes:
- with water type cooling. A system with such cooling is relatively expensive, but it is highly reliable;
- with air cooling. The simplest and most inexpensive option.
Based on 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 pump 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 of 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 extremely important that no obstacles are created to the air entering the condenser and to being exhausted by the fans;
- centrifugal. Equipment with such a fan is recommended for installation inside a building. It is characterized by its small dimensions and low noise level.
Important aspects of chiller installation
To experience all the benefits of operating a device such as a chiller unit, its installation must be carried out strictly in compliance with certain rules. Here are the main ones.
- This equipment should only be installed by qualified technicians.
- The chiller must fully meet the design criteria of the utility network in terms of installation location, design and power.
- It is prohibited to install equipment that has a defect.
- The equipment can only be moved to the place where it will be installed using a crane.
- It is allowed to fill only with water, as well as a solution of ethylene or propylene glycol, which has a concentration of up to 50 percent.
- Commissioning tests must be carried out without fail.
- There must be space around the chiller to allow unobstructed access for the service technician.
- Safety precautions and manufacturer's recommendations must be strictly followed.
By purchasing and installing a chiller, you can be sure that you will receive a modern and reliable system.
Chillers are used in a wide variety of human activities. Their main purpose is rapid cooling of liquids, which makes them indispensable in centralized air conditioning systems and maintaining the required temperature in industrial installations.
Chiller purpose
The term “Chiller” comes from the English word “Chiller” - cooling heat exchanger. This equipment is widely used in the metalworking, chemical, food industries, mechanical engineering, metallurgy, and plastic molding industries to reduce the temperature of the liquid circulating in the jackets of the cooling circuit and ensure that the equipment reaches a given temperature. The coolant (usually water) circulates through the process equipment, cools it, accumulating thermal energy, and is sent to the chiller, where it transfers heat to the refrigerant and is sent back to the process equipment. This repeats cycle after cycle.
Central air conditioning systems use a chiller-fan coil system to quickly achieve and maintain the desired room temperature. The device is indispensable when it is necessary to stabilize the temperature in the premises. By choosing the right performance, chillers can lower the temperature of both small rooms and multi-story buildings. The maximum power of such installations is 9000 kW.
Chiller operating principle
The operating principle of the chiller is based on the physical processes of heat transfer. The temperature of any liquid increases with compression and decreases with expansion. In a chiller, heat from the coolant is transferred to the refrigerant used in the device, which in turn is heated during the intake of high temperature.
In other words, the chiller is a powerful refrigeration unit, which is located in a chain of various air conditioning systems. The principle of operation of the chiller is based on the fastest cooling of any coolant through the physical properties of the working substance and the return of low-temperature liquid back to the air conditioning system.
The main components of chillers:
1. An evaporator is a heat exchange device that is designed to accumulate heat from the cooled coolant substance.
2. Compressor – a device that circulates refrigerant in the chiller with a maximum temperature of up to +70 degrees Celsius and a pressure of up to 3 MPa. Depending on the area of use, there can be several types: piston, screw, spiral, centrifugal, rotary.
3. Condenser - a mechanism for cooling refrigerant vapors.
4. Throttle is a special device that is designed to reduce pressure and transfer the refrigerant into the liquid phase.
Any type of coolant can circulate in the chiller as a refrigerant - water, ethylene glycol, antifreeze, freon. The coolant in cooling units is water. In this case, the heated coolant to a temperature of +12-15 degrees Celsius comes from the cooled equipment directly to the evaporator, where the refrigerant takes up heat and heats up from indirect contact. As a result, the refrigerant boils relatively quickly, while expanding and evaporating, passing into the gaseous phase state. The coolant is cooled to a temperature of +7-10 degrees Celsius.
To reduce the temperature, the refrigerant in the gaseous phase enters the compressor, which increases its pressure and, accordingly, the temperature from 80 to 90 degrees Celsius. After compression, the vapors flow directly into the condenser, where the refrigerant temperature is rapidly reduced by blowing air from the atmosphere. The heat is released outside and, if necessary, can be used in fan coil units for subsequent heating of indoor air. Next, the refrigerant is filtered through a specialized dryer, which removes excess moisture from it and goes directly to the throttle. The latter reduces the pressure of the substance and transfers it to the liquid phase immediately before feeding it back into the evaporator to start the next cooling cycle of the coolant.
Chiller classification
Depending on various parameters, chillers are classified:
1. According to the condensate cooling method:
- monoblock without capacitors;
- monoblock with water type of cooling;
- vapor compression chillers – with air type of cooling.
2. By configuration:
- absorption chillers;
- with remote type condenser;
- monoblock with built-in capacitor type.
3. According to heating ability:
- with heat pump;
- without heat pump.
4. According to the design of the fan used:
- with a centrifugal fan;
- with an axial fan.
Chiller selection
When selecting a chiller for a specific task, the fundamental characteristics for calculation are maximum power and cooling capacity. The main factors that influence the choice of a particular model are:
- overall dimensions of the room, area, volume;
- location of the object;
- type of planned installation - in a separate room or outdoors;
- the need to clean the coolant (water);
- the type of refrigerant used, as well as its displacement volume, speed and temperature schedule;
- total duration of highways;
- other characteristics.
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 operation diagram of the chiller 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.