Acoustic calculation of fan coil unit program. The operating principle of a fan coil unit. How to choose a fan coil. Where and how to use them. Indoor units can be
What is the chiller-fan coil system used for and where is it used?
The modern chiller-fan coil system occupies a special place among the wide variety of equipment for air conditioning. The main purpose of the system is to create an optimal indoor microclimate and year-round, uninterrupted maintenance of the specified temperature indicators.
The operation of the chiller-fan coil system can provide simultaneous and independent stabilization of the temperature regime in several rooms of the same building at once, even large area or number of storeys.
That is why it is advisable to install a chiller-fan coil air conditioning system at the following facilities:
- production sites and warehouses;
- multi-storey administrative buildings, business centers, offices;
- hotel and shopping and entertainment complexes, concert halls;
- large stores, super- and hypermarkets;
- objects of social purpose with a large number premises (clinics, medical complexes).
Chiller-fan coil system
Chiller-fan coil system: operating principle and features
The operating diagram of the chiller-fan coil system is capable of providing air conditioning for all year round. One of the features is that it is not limited by temperature, unlike systems running on freon. The latter are characterized by operation only in the off-season - when the temperature drops to 0°C, freon systems become insufficiently effective, and at -10°C they simply cannot function safely and require shutdown.
The second feature of the chiller-fan coil system is the operating principle: air flow conditioning occurs thanks to a non-standard refrigerant.Instead of standard refrigerant, water or antifreeze is used as a coolant.
And most importantly, thanks to the chiller fan coil split system, you can simultaneously organize different temperature modes in each of the rooms of the same building. And you can achieve increased operating efficiency by integrating it with a central air conditioner. Thus, each user will be able to independently regulate comfortable temperature premises, regardless of others.
To understand the principle of operation, you need to understand what the components of the system are. The chiller is an external cooling unit that is installed in technical floors, basements (models high power) or on the roofs of buildings. Fan coil units are indoor units installed directly inside the building.
The operating principle is quite elementary. After the chiller has cooled the water/antifreeze liquid to the required temperature, it is supplied using pumps through thermally insulated pipelines to another element of the air conditioning system - the fan coil. They are mounted indoors and act as a closer air conditioner.At its core, a fan coil is similar to the standard indoor unit of any split system, only it operates on liquid, which is heated by the thermal energy of air masses taken from the room and then returned back to the cooler.
How the chiller-fan coil system works
The main components of the chiller-fan coil system, which make zonal ventilation and air conditioning possible, include the following elements:
- a refrigeration unit, also known as a chiller, which provides cooling or heating of liquid in the chiller-fan coil system;
- fan coil (closer air conditioner), which is a local heat exchanger through which a flow of cooled or heated air passes;
- main wiring of device connections;
- a pumping station that transfers coolant through the main line;
- expansion and storage tanks;
- control unit;
- actually, non-freezing liquid or water.
Chiller-fan coil elements
Let's take a closer look at the design of the main elements of the system - the chiller and fan coil.
The chiller is a powerful refrigeration device that contains a compressor, an evaporator and a condenser. Unlike a standard air conditioner, an evaporative heat exchanger does not release the accumulated cold into the atmosphere, but directly into the liquid. After cooling, it flows through the pipes to the fan coil units.
Chillers come in two types:
- absorption;
- vapor compression.
Absorption chiller Compression chiller
The former have a fairly high cost, large dimensions and a fairly narrow specialization.
The most popular today are vapor compression models, which are divided into 3 types:
- outdoor installation with air cooling;
The heat exchanger-condenser is cooled by axial fans
- indoor air-cooled installation;
Air is taken in for cooling and hot air is discharged through air ducts. The movement is facilitated by a centrifugal fan.
- reversible.
They work in two directions: for heating and cooling air and can be installed in air conditioning systems without additional water heating equipment.
The air conditioner-closer (fan coil) is a very efficient heat exchanger, which is simultaneously connected to the cold and hot pipelines. To enhance heat exchange, use a fan installed immediately behind the heat exchanger. The peculiarity of such devices is to create air flows of the required temperature without the influx of air masses from the outside. This is what allows you to achieve maximum effective use thermal energy produced by the chiller. 
The fan coil consists of the following elements:
- heat exchanger-radiator, where the coolant flows;
- fan with motor that regulates cooling performance;
- condensate tray;
- quick-release filter;
- electric heater;
- control unit.
Fan coil selection
Fan coil units come in several types and each modification has its own specifics. When calculating a chiller-fan coil system and selecting fan coil equipment, take into account, first of all, the area of the room, the thermal power, the required performance and the length of the air stream.
According to installation method, air conditioners are divided into:
- wall;
- floor;
- ceiling fan coil units;
- universal (wall-ceiling).
Indoor units can be:
Cassette
Their purpose is to uniformly distribute, heat or cool air flows in rooms where suspended ceiling units are provided, where the equipment is built. This installation allows you to hide constituent elements structures and minimize noise. Air flow distribution is possible in 2 or 4 directions.
Duct
Channel type models are built directly into the ventilation duct. The air mass is taken in through separate air ducts, and its output is through air ducts located behind the suspended ceiling units. Models of such air conditioners show excellent performance and are used, for the most part, for rooms with large areas, trading floors, storage areas, etc. 
Duct fan coils
Advantages of the chiller-fan coil air conditioning system
The modern chiller-fan coil system has proven itself to be excellent and is becoming one of the most popular solutions for organizing effective ventilation and air conditioning of buildings and premises.It is not surprising, because the advantages of the system compared to other options are very convincing and here are some of them:
Unlimited piping length, determined solely by chiller capacity
By installing a high-power pumping station, it is possible to install chillers and fan coil units at a sufficiently large distance from each other (the length of the line can reach several hundred meters), without loss of efficiency and service performance.
Minimum space for installation of units
Even for big building One efficient chiller will be enough, which will not in any way affect the aesthetics appearance building and will eliminate the need to install a large number of external units.
Budget cost of wiring
In the chiller-fan coil system, no copper connections(as is the case with freon systems), which are quite expensive, and standard water pipelines and shut-off valves.
Safety in everyday use
A big plus for safety is that all volatile gases are inside the chiller, and it, in turn, is most often placed on outdoors or in basement. The risk of leakage is minimal, which allows us to talk about almost complete safety of people.
Excellent adaptability
Each user of the room can set individual temperature settings and adjust them at their own discretion. In addition, installation of the units can be done without stopping the entire system, unlike standard freon systems.
Modern market climate control technology Today it is filled with a huge number of offers, however, it is not recommended to select equipment for the chiller-fan coil system and install it yourself. Only professional specialists with practical knowledge and experience in this field will help organize effective and safe work equipment.
Comparative analysis of the pros and cons of the chiller-fan coil system and the VRF air conditioning system.
Before carrying out the analysis, it is necessary to define what a multizone VRF system is. In essence, this is a large multi-split air conditioning system, with many indoor units connected to the outdoor unit. Thanks to this, you can simultaneously configure and support different temperature regime in different rooms.At first glance, it may seem that they have minor differences from each other, but each of them has its own design features, disadvantages and advantages, by comparing which you can choose best option to solve exactly your problems.
The key difference between a chiller-fan coil system and a VRF air conditioning system
Basic design feature, which distinguishes these two systems, is that in the chiller-fan coil system, ice water (or non-freezing aqueous solutions, such as ethylene glycol), while only freon circulates in the VRF air conditioning system.
Power comparison
The record power of the most productive chiller is 20 megawatts. In practice, models of much lower power are used (up to 1.4 megawatts). If there is a need for a more powerful and productive unit, the system is combined from several refrigeration units.
VRF air conditioning systems have a maximum possible power of 140 kilowatts. Basically, the system is assembled from outdoor units with a capacity of 12 to 28 kilowatts. To increase productivity, VRFs are also assembled from multiple units.
Comparison by route length
The undoubted advantage is that the route in the chiller-fan coil system has an unlimited length. The issue of extending it without loss of performance is solved by purchasing and installing water pumps of higher power.
The weak point of the VRF system is the inability to extend the route from the outdoor to the indoor unit more than 150 m. The total length of pipelines is a maximum of 300 m. In addition, you need to take into account the difference in height difference between the indoor and outdoor units - it should not exceed 50 m .
It is with this factor that the need to evenly space and distribute the external units of the VRF system throughout the roof is associated. Today there are advanced modifications with a cooling tower and water cooling, which can be used even in very large buildings. But at the same time, they lose their advantage in the form of efficiency and ease of maintenance.
Comparison of cooling capacity in supply systems
The big advantage of the chiller-fan coil system over VRF is the ability to use just one chiller unit as a cooling source for all types of consumers: starting from fan coils low power V small rooms, ending with water coolers of supply ventilation units used in huge retail areas.
VRF systems, for the most part, cannot be connected to coolers in supply-type installations, so in order to cool air masses in supply ventilation units, you will need to use additional. devices (the same chillers, compressor units with freon, etc.).
Comparison by ability to work in the cold season
The operation of many buildings, offices, shopping and entertainment centers requires high-quality air conditioning to cool the premises even in winter period. This is due to the significant release of heat in modern buildings from intense lighting, permanent job equipment (commercial, industrial, office), etc. Chiller-fan coil systems cope excellently with this task even in severe frosts, thanks to the ethylene glycol (or other non-freezing liquid) circulating inside the system.
Modern VRF systems, as a result of improvements and design modifications, are also able to function even at low temperatures.
Comparison by energy consumption
Chiller-fan coil systems are quite energy-intensive: for 1 kW of cold you need to spend 0.5 kW of electricity.
VRF air conditioning systems are much more profitable in economic aspect: 1 kW of cold requires only 350 W
Comparison of required area for installation and placement and availability of technical premises
To organize and install a chiller-fan coil system, you need large area and availability of additional technical premises for placement of pumping stations, tanks, intermediate heat exchangers, etc.
For multizone VRF systems they are not required.
Comparison by operating features
On this point, the VRF system definitely wins. It does not require maintenance personnel, and the operating mode is determined individually.
To maintain a chiller-fan coil system, the presence of qualified personnel is required who will regularly monitor the condition and correct operation of the equipment, control the tight seal of the elements, the operation of pumps, chiller, glycol circuits, etc.
Comparison by cost
The price of chiller-fan coil systems is lower than that of equipment for VRF systems. However, if you consider the number additional elements in the first case, the cost will be approximately at the same level.
After analyzing the advantages and disadvantages of each system, we can conclude that systems with a chiller have a wider scope of application, moreover, they can cool the air in air supply units without the use of additional devices.However, if there is a limitation on energy consumption, or there is no opportunity to maintain your own service department, it is better to give preference to multi-zone VRF air conditioning systems. They cope perfectly with the tasks, are more profitable in terms of energy costs and have a simpler and effective system management.
To calculate it yourself required parameters cooling capacity of the chiller-fan coil system and select the optimal fan coil, you need to sum up all heat inputs into the room, take into account many factors and circumstances, such as:
- How many people will be in the room on average;
- What is the room functionally intended for?
- Parameters of windows and walls (dimensions window openings, orientation to the cardinal points);
- Climatic characteristics of the region where the building is located, values of temperature and humidity of outside air, solar radiation etc.;
- Design, thickness, thermal conductivity of external enclosing structures;
- The total approximate amount of heat that can potentially be emitted by devices and equipment located in the room or planned to be placed in the room (all computers, lighting fixtures, etc. must also be taken into account);
- Presence and parameters of the ventilation system;
- Coolant temperature graph (with a graph of +10, +15 0 C, the cooling capacity of the fan cooler is lower than at +7, +12 0 C).
Fan coil calculation methods
Academic
This calculation principle gives the most accurate results, but at the same time it takes the most time and effort. As a rule, this method is used more for research than for practical purposes: to study the processes of heat exchange, heating and cooling of indoor air at different conditions using ventilation, air conditioning and heating systems. It is also applicable for calculating the main indicators of the chiller-fan coil system. All the factors described above in the article are taken into account, and some more nuances, less significant factors, are added to them. The calculation is made using exact reference values of thermal conductivity and heat transfer coefficients, with an i-d diagram, etc. Since this method takes quite a lot of time, especially without experience and special training, it is used only in cases where it is really justified.
Refined
This calculation is less accurate than the previous one, but is much faster. For it, the average values of the quantities involved in the calculation are taken. This calculation method is usually used by company technical specialists when selling and installing fan coil units. It is possible to determine performance by three types:
- Explicit performance (all heat gains without taking into account air humidity);
- Hidden (all sources of heat influx, taking into account air humidity);
- Full (both explicit and hidden performance are taken into account).
To determine latent heat, they are used i-d charts or corresponding tables. At low air humidity values, it is permissible to determine the total heat simply by increasing the calculated sensible heat by 20%. Where humidity is high, latent heat calculations must be carried out separately - otherwise the calculation error can reach 50-60%.
Estimated
This calculation is based on the area of the room. Meaning required power is taken as 1 kW of cold per 10 m 2 of room. Latent heat is usually not taken into account. However, at an air humidity of 40%, latent heat can account for more than 30% in addition to sensible heat. Therefore, such a calculation will not give reliable results and in worst cases may even lead to a malfunction of the chiller-fan coil system. However, this method is, in principle, acceptable for calculating the system, for example, for residential premises. In office and residential premises with windows facing south or east, or with a large number of equipment that generates heat, it is better to increase the calculated cooling capacity, calculated in this way, by 25-50%, that is, take the specific heat release equal to 125-150 W/m2 .
Preferably having done everything necessary calculations according to the cooling capacity of the system, add an additional 10-15% reserve.
Moreover, when choosing a fan coil unit by power, be sure to pay attention to the units of measurement in which the manufacturer indicates the cooling power - it can be indicated in the usual W or BTU/h.
If carrying out calculations causes you difficulty, or you are unsure of the correctness of the calculations, contact qualified specialists. In this case, a mistake can cost large financial losses in the future.
Fan coil is a heat exchange equipment that is included in common system The chiller-fan coil unit is the final element of the entire circuit that serves to cool/heat air in enclosed spaces.
Fan coil selection
Depending on many factors, the fan coil unit is calculated and selected. These factors include:- number of people in the room;
- purpose of the premises;
- area and cardinal orientation of window openings and walls of the room;
- geographical location rooms with temperature and humidity characteristics of outside air;
- material and quality of external walls and ceilings;
- quantity and power lighting fixtures or other devices that are located indoors and may generate heat;
- the presence of a room ventilation system.
Methods for calculating fan coil
There are three ways to calculate a fan coil unit to create the required temperature background in the room. They can be called differently.Academic
This is the most accurate and longest calculation process. Such calculations are made when carrying out scientific developments or studies of heat exchange processes of cooling/heating indoor air using air conditioning systems. The same method is applicable for fan coils. All the factors listed above and several other less significant ones are taken into account in order to provide for all the nuances when operating the fan coil unit to the maximum extent possible. In this case, exact reference values of the coefficients of thermal conductivity, heat transfer of fencing materials, heat transfer coefficients from the walls to the internal and external environment. When making calculations, an i-d diagram must be used humid air. With this calculation, without special preparation, you can spend the whole day selecting fan coil units for a room of 20-30 square meters. m.
Refined
This calculation is made by technical specialists, leading managers of companies that sell fan coil units and chiller-fan coil air conditioning systems. The calculation is not as accurate as in the previous case, but is performed much faster and based on the average values of all reference quantities that may be involved in the calculation. However, with such a calculation it is necessary to calculate productivity taking into account air humidity. Therefore, there are three definitions of productivity:
- sensible productivity, which takes into account sensible heat, i.e. all heat inflows without taking into account air humidity;
- latent productivity, which takes into account latent heat, i.e. all heat inflows taking into account air humidity.
- full performance, which takes into account sensible and latent heat, i.e. all heat inflows taking into account air humidity.
Latent heat is calculated using using i-d charts or special tables.
In regions with low air humidity, you can add 20% to the calculated sensible heat and get the full heat. Thus, 20% should be allocated to latent heat. In regions with high humidity, it is necessary to separately calculate latent heat. Otherwise, you can make a selection with an error of up to 50-60%.
Approximate (urgent, estimated)
This calculation is made by managers who sell fan coils and chiller-fan coil air conditioning systems, but do not have selection skills. It is made based on the area of the room. For every 10 sq.m, a fan coil with a cooling capacity of 1000 W is selected. with ceiling heights up to 2.70 - 3 m.
Latent heat is almost never taken into account in such cases. And in regions with a humidity of 40%, latent heat is approximately 30% of sensible heat, and with a humidity of 80-90% - up to 50% of sensible heat. Such calculations can affect the operation of the entire chiller-fan coil system or lead to its breakdown, therefore such calculations and selection of fan coil units must be trusted by trusted and qualified specialists.
Initial data:
Office premises (7 rooms) with a total area of 150 m2, room height h = 3 m, “Armstrong” false ceiling - only in the corridor. The premises have the possibility of natural ventilation (by opening and closing windows (see the layout of the premises in Fig. 1).
The façade of the building faces the main street, and installation of external units of split systems on the façade is not permitted.
To create comfortable conditions in offices, in this case the most optimal solution air conditioning is a chiller-fan coil system. ( refrigeration machine) is installed on the roof of the building, fan coil units (closers) are installed under the ceiling of each room.
To ensure the system hot water(45-40°C) not only in summer, but also in the transition period, when the heating system is not yet functioning, we will choose a chiller with a “heat pump” type WRAN from CLIVET. This “heat-cold” operating mode is possible through the use of reversible refrigeration circuit (heat pump) with high energy efficiency.
The outer casing of the chiller is made of Peraluman alloy, suitable for outdoor use. The WRAN unit is equipped with a microprocessor control system that allows you to configure, regulate and optimize all functions. Remote controller remote control, connected to a microprocessor, allows you to make all settings and control the functioning of the chiller from a distance.
Indoor units(fan coil units) and outdoor unit(chiller) are connected to each other by steel water-gas pipelines, which must be insulated to avoid condensation on the walls of the pipes when they circulate through them with parameters tsupply. = 7°C, trev. = 12°C (when the system is operating in cooling mode). Each fan coil unit has a collection pan from which a drainage pipeline is discharged. All drainage pipelines are connected by a common collector and connected to existing system sewerage. All communications are laid along the corridor in the area false ceiling. To lay a drainage pipeline, it is necessary to provide a slope of 10 mm per 1 m of length.
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To ensure the circulation of coolant in the system, a pumping station is installed.
CLIVET pumping stations include automation and all necessary technological piping. They are ready for use immediately after connecting them to the electrical and hydraulic systems.
To determine the standard sizes of the equipment included in the air conditioning system, appropriate calculations should be made.
Calculation of excess heat and selection of equipment
The calculation of the heat load of fan coil units is based on the data obtained on the presence of people, office equipment and other sources of heat generation in each room.
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We determine the total amount of excess heat for each room and select fan coil models from the DELONGHI catalog based on cooling capacity. Data for calculation and selection of fan coil units are given in table. 2.
Based on the total cooling capacity of all fan coil units (19.6 kW), we select a chiller from the CLIVET catalog (with the nearest higher cooling capacity) - WRAN 91 (cold = 20.6 kW, heat = 23.1 kW).
Choosing a chiller with a “heat pump” allows you to use the air conditioning system in heating mode during the transition period of the year when the heating system is not yet turned on.
Based on the calculation of excess heat, the following was determined: The heat load of the entire system is 19.6 kW. The coolant is water with parameters 7-12°C. Steel pipes, water and gas pipes.
Chiller WRAN 91 with a cooling capacity of 20.6 kW without built-in pumping circuit. Fan coil units - according to table 1.
Hydraulic calculation of the system
Purpose hydraulic calculation is to determine the diameters of the pipelines of each section of the system and select pumping station for stable operation of the water circuit.
If a chiller with a built-in pumping station (hydraulic circuit) is used, it is necessary to determine whether its pressure is sufficient for normal operation of the system.
If a chiller is used without a built-in pumping station (hydraulic circuit), then the required pumping station is selected based on the hydraulic calculation data.
In accordance with the floor plans, an axonometric diagram of the “chiller-fan coil” system is drawn up, section numbers are designated and their lengths are determined (Fig. 2).
The pressure loss calculation must be made for the most distant fan coil unit. In this case, this is an FC 30 fan coil. Pressure losses are the sum of losses along the length and losses along local resistance. Length losses are determined in accordance with the calculation tables water pipes. Losses due to local resistance can be taken equal to 30% of the value of losses along the length.
Let's consider the hydraulic calculation method using the example of section No. 1 (see Fig. 2).
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Section No. 1 is the section between the chiller and the first fan coil along the water flow. Its load is the total system load:
Q1 = 19.7 kW or
Q2 = 19.7: 1.16 · 1000 = 16,982 kcal/h.
The water temperature difference according to the catalog at the inlet and outlet of the fan coil is Dt = 5°C (from the catalogue). Thus, it is possible to calculate the water consumption in section No. 1:
where Q2 - , kcal/h; C is the heat capacity of water equal to 1 kcal/kg °C.
G1= 16896/1·5=3376 kg/h (0.939 l/s).
Using the water supply system calculation table, for example from the Designer's Handbook, we select a pipeline diameter of 32 mm, based on the condition that the water speed does not exceed 1 m/s.
We determine the specific pressure loss along the length R (see, for example, the “Designer’s Handbook”). It is 77 mm of water. st./m.
a) Knowing R and the length of the section, you can calculate the resistance of the section R_I, equal to 385 mm water column.
c) The hydraulic resistance of the fan coil, equal to 900 mm water column, is determined from catalogs.
d) Knowing the water flow (total) and the selected brand of chiller (), the resistance of the heat exchanger in the chiller itself can be determined using a diagram from the CLIVET catalog.
In this example, the hydraulic resistance of the heat exchanger is 28 kPa or 2800 mm water column.
e) After adding the resistances of all sections, we get total losses system pressure; we add 30% - a reserve for local resistance - and we get the required pressure that the pumping station should develop Drn≥106 kPa.
DP = R1 + 30% (R1) = 8154 + 0.3 · 8154 =10600 mm water. wt = 106 kPa
Using the diagram from the CLIVET catalog, we determine the brand of pumping station M2, which develops a network pressure of 135 kPa, that is, more than 106 kPa.
