Calculation of fan coil units. Operating principle of fan coil

What is the chiller-fan coil system used for and where is it used?

A modern chiller-fan coil system takes special place among a wide variety of room conditioning equipment. 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 social purpose With big amount 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 the comfortable room temperature, 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 installed indoors and act as an 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 instrument connections;
a pumping station that transfers coolant through the main line;
expansion and storage tanks;
Control block;
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 coils.

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 unit 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 block.

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 the 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 the components of the structure 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 a large building, one efficient chiller will be enough, which will in no 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, the transfer of cooled liquid does not use copper connections (as is the case with freon systems), which are quite expensive, but standard water pipes 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 located outdoors or in the 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.

The modern climate control equipment market today is overflowing 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 efficient and safe operation of the 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 the best option to solve your specific 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, the coolant is 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 blocks 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 source of cooling for all types of consumers: from low-power fan coils in small rooms to water coolers for supply air 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 heat generation 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 economically advantageous: 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 big square and the availability of additional technical premises for the placement of pumping stations, tanks, intermediate heat exchangers, etc.

They are not required for multi-zone VRF systems.

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 we take into account the number of additional elements in the first case, the cost will be approximately the same.

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 the 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 well with their tasks, are more profitable in terms of energy costs and have a simpler and more efficient control system.

In large rooms filled with many heat sources, installing air conditioners is irrational. The use of fan coil units allows you to achieve comfortable conditions with less energy consumption. These are heat exchange devices consisting of a fan and a radiator, inside of which water circulates. Before purchasing equipment, its power is calculated. Depending on the level of preparedness of the consumer, calculations are carried out in an academic or simple approximate way.

How to choose the right fan coil power

The total capacity of fan coil units should not exceed the capacity of the chiller

The chiller-fan coil system is one of the options for climate control equipment for creating a comfortable microclimate in office, commercial, industrial and domestic premises. The equipment is designed for two modes: cooling in the warm season and heating in cold period. For multi-zone air conditioning systems, a combined option is recommended: the heat and humidity load falls on fan coil units, and ventilation ensures air purity.

The main elements of the system: chiller - a machine for generating cold; and fan coil units - air conditioners or fan coils, which are a heat exchange device. The coolant is water or an ethylene glycol mixture. The hydraulic unit ensures fluid circulation in the pipeline. The purpose of fan coil units is to bring the air temperature in the room to the specified parameters.

The principle of operation of the device: a fan blows air through the heat exchanger. A cold coil lowers the flow temperature. The cooled air is returned to the room. The process is accompanied by the formation of condensate, which is discharged into the drainage.

Fan coil selection

The air conditioner is selected according to its full cooling capacity. Cooling costs exceed the power spent on heating, so the calculation is based on maximum values. Calculations require taking into account many parameters that affect the amount of heat and moisture released in the room:

Sensible heat entering the room:
- a) the location of the room and windows relative to the cardinal directions;
- b) number of people (with average physical activity an adult generates 130-150 watts of heat);
- c) material, thickness and quality of thermal insulation of walls and ceilings;
- d) power of lighting fixtures;
- e) heat generated during operation household appliances, computers.
Climatic conditions are typical for this region in terms of temperature and humidity.
Coolant temperature in the chiller-fan coil system.
The presence of ventilation, the amount of fresh air flow.
Functional purpose of the room.

Methods for calculating fan coil units

Heat loss at home

Having determined the total heat load in the room, the calculation of the fan coil power begins. Three calculation methods are used. They differ in the complexity of implementation and the accuracy of the results.

Academic

The most accurate calculation option, taking into account all possible parameters. The academic method involves a long and complex calculation process; a beginner will need 8-10 hours to select a fan coil unit for a room of 25-30 square meters. m. The calculations carried out are similar to the studies carried out for the heat exchange processes of the air conditioning system. To work you will need:

thermal conductivity coefficients of fencing materials;
indicators of heat transfer of structural materials to the external environment;
moisture content and enthalpy (components of the id diagram).

When calculating air humidity and its processing, an id diagram is used. It contains several parameters:

relative humidity;
temperature;
moisture content (the amount of steam in 1 kg of air);
enthalpy (the amount of heat in 1 kg of air).

By connecting all available indicators with lines, a diagram of the air condition is obtained. It is used by specialists to calculate air heating and fan coils.

Refined

Technicians involved in the design of air conditioning systems carry out calculations based on the average values of reference values. The method is less accurate than the academic one, but gives a fairly reliable result. The calculation is carried out taking into account the effect of humidity on the power of fan coil units. Manufacturers indicate two performance levels in the specifications: explicit and full. These parameters require explanation:

Explicit performance of the device - takes into account all heat gains in the room without adjusting for humidity.
The total performance of a fan coil is the cooling power spent to compensate for sensible and latent heat. The second parameter is the heat of condensation of steam into liquid. It is calculated using an id chart or special tables.

With low air humidity, latent heat is up to 20%. Add this number to the apparent performance to get the total. With an increase in humidity, the share of latent heat increases to 50-60%.

Approximate or approximate

The simplest calculation option is offered by employees at points of sale of air conditioning systems using fan coils, who do not have professional selection skills. Calculations occur quickly with a minimum set of parameters used. Generalized preliminary calculations in premises for various purposes provide the following data:

for offices with office equipment and computers, you will need a closer air conditioner with a power of 150 watts per 1 sq. m;
a living space with a ceiling height of 2.7-3 m needs a fan coil unit with a cooling capacity of 100 watts per 1 sq. m area.

For example: the area of a room in an apartment is 20 square meters. m – Q = 100 X 20 = 2000 W or 2 kW.

The final power is determined without taking into account latent heat. In regions with a dry climate, the error is up to 20%, and when high humidity(80-90%) error within 50%.

Possible difficulties

Some manufacturers of climate control equipment indicate the cooling power of a fan coil not in the usual kW, but in BTU. British Thermal Unit means British Thermal Unit. The unit ratio is 1 kW = 3412 BTU/h.

For ease of customer orientation, the power of the devices is indicated in rounded figures. For example: 7000 BTU/h = 2100 W.

Features of fan coil calculations

Manufacturers' data on cold production by a closer air conditioner are tied to standard temperature indicators:

dry bulb 27°;
wet thermometer 19°;
water entering the fan coil is 7°.

Variable factors include fan speed; the specifications indicate high. There is also medium and low. Among the factors whose changes affect the performance of the fan coil:

inlet water temperature;
air flow (fan speed);
the amount of water passing through the fan coil;
room air temperature.

Self-calculation electrical power fan coil units for an office or production workshop can cause serious difficulties. This kind of work is entrusted to specialists. Helps with accurate calculations online calculator on sites related to climate control technology. For domestic use of the device, an approximate calculation is suitable.

Installation of a chiller-fan coil system requires high design skills and accurate calculations. Without them, the parameters of the climate control equipment will be incorrect, there will be insufficient or reduced energy supply, the service life will be reduced, and the likelihood of breakdowns of functional units will increase.

You can learn about power calculation methods that allow our company’s engineers to accurately determine the performance of an industrial air conditioning system in this article.

How to choose a fan coil? Factors influencing equipment parameters

When calculating the functional characteristics of fan coil units, a number of indicators are taken into account. Based on them, a professional will accurately determine the required system parameters. This will allow you to install optimal equipment that is balanced in cost, performance and resource consumption. The following is taken into account:

Dimensions of the room and purpose of its use;
The number of openings in the walls and orientation relative to the cardinal points;
Climatic indicators of the region, average temperature and humidity of outside air;
Material of floors and wall cladding of the building;
The number and power of devices in the room that produce heat;
Installation of ventilation system;
Average number of people inside.

Each of these parameters individually affects the performance of the fan coil, decreasing or increasing it. The combination of these indicators can significantly change the power of the equipment necessary for the comfort of people in the room.

Methods for determining fan coil power

There are three main methods. Each of them requires a different amount of time for calculations and gives a certain percentage of accuracy.

Depending on the situation, one of the following methods is used:

Academic - long, but as accurate as possible;
Refined - a balanced solution between the accuracy of calculations and the time spent;
Estimated - allows you to quickly determine the approximate performance of equipment, but does not take into account the parameters of the room and building. It has a high error.

The academic method takes into account all factors that influence heat exchange processes in the room. Accurate reference values and coefficients of thermal conductivity and heat transfer are used.

The high duration of the technique justifies itself when installing fan coil units in research laboratories, pharmaceutical or medical production, and at facilities where the maximum possible precise definition parameters.

Our company’s technical specialists most often use a refined method to calculate equipment power. Calculations are based on average values of indicators from reference books and give results of high accuracy. When determining indicators, it is important to take into account air humidity. For this reason there are the following types fan coil performance:

Direct - all heat inflows in the room are taken into account without air humidity being included in the calculations;
Indirect - calculated based on all incoming thermal energy inflows, taking into account air humidity;
Complete - determined on the basis of two types.

Calculations are based on I-d readings diagrams humid air, which allows you to take into account many characteristics of the room and increases the accuracy of the result.

The approximate method can be carried out independently and does not require special knowledge, but it does not take into account the mass of parameters. The average value is obtained by selecting a 1000 W fan coil for every 10 m2 of a room, the height of which is 2.7-3 m. Approximate parameters affect the operation of the entire air conditioning system, so it is not recommended to rely on it. The climate control equipment will not operate properly and will quickly fail.

To get the most accurate calculations, you need to seek help from professionals. The Smart Climate company provides the services of qualified specialists who, within a limited time, will make calculations and help you select the optimal power of the fan coil in accordance with the operating parameters.

Source: http://mir-klimata.apic.ru/

Article from the magazine "Climate World", number 11. 2001

Dear readers!

The editors of the magazine continue to publish individual chapters of the book “Ventilation and air conditioning systems. Theory and Practice", prepared by specialists of the Euroclimate company.

Initial data:

Office premises (7 rooms) with total area 150 m2, room height h = 3 m, false ceiling of the “Armstrong” type - 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 central 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. The chiller (refrigeration machine) is installed on the roof of the building, fan coil units (closers) are installed under the ceiling of each room.

To provide the system with hot water (45–40°C) not only in summer, but also in transition period time when the heating system is not yet functioning, we will opt for a chiller with a “heat pump” type WRAN from CLIVET. This “hot-cold” operating mode is possible through the use of a reversible refrigeration circuit ( heat pump) with high energy efficiency.