Calculation of performance and selection of air curtains

Advantages of water-type thermal curtains

• Firstly, such curtains consume a minimum of energy, "feeding" from the heating circuit of the warehouse heating system.
• Secondly, such curtains stabilize the temperature in the protected room, creating ideal conditions for storing the most "capricious" inventory items.
• Thirdly, water curtains not only protect, but also heat the entrance to the warehouse.
• Fourthly, thermal curtains neutralize the appearance of drafts, improving the working conditions of warehouse personnel.
• Fifth, such curtains can be modified by turning them from a heater into an air conditioner. Moreover, such a transformation is carried out by disconnecting the curtain circuit from the coolant circulation system in the heating system. After that, the curtain starts to work like a huge fan, air conditioning both the warehouse entrance and the storage itself.

That is why the scope of application of water curtains can be the widest, extending from thermal shielding of the thresholds of large warehouse openings to protecting the interior of a store or cafe from dust and insects.

Ways to improve efficiency when using air curtains

First of all, the heat curtain should be selected in such a way that its technical parameters correspond as much as possible to the conditions in which it will be operated (height or width of the doorway, air performance and direction of its jet, thermal power, in the case of air heating, etc.). etc.).

A correct assessment of the paths of air intake into the room makes it possible to see ways to increase the efficiency of the operation of air-thermal curtains. This process must be agreed between the manufacturer (designer, installer) of the air curtains and the consumer. Indeed, in some cases, for the most correct operation of the device, it is required to make changes to the existing building structures.

So, firstly, the adjustment of the heat curtain should be provided:

• the temperature of the air flow out of the curtain should vary depending on the temperature in the doorway;
• the directional angle of the air flow must be changed in order to be able to adjust it to a specific object (height of doors, gates).

If unregulated thermal curtains are used, then during their selection it is necessary to give preference to the following types of them (in order of decreasing their efficiency):

• thermal curtains with vertical supply (bottom);
• lateral, located on both sides of the opening;
• upper curtains (above the opening);
• one-sided, lateral.

The angle of direction of the air stream coming from the curtain is regulated in each case separately, depending on the air intake from the street.

In cases where the object is equipped with a gate with sliding leaves, it is advisable to install side two-sided or one-sided curtains (to use the effect of the overlapping stream). In this case, the placement of a thermal curtain over the opening is not so effective, since during the opening process of the gate, the curtain runs "idle" for some time.

The thermal curtain must not work with the door closed. In this case, the probability of heating the doors themselves and heat losses through them is created.

It is advisable to provide for the presence of stationary or articulated vestibules. Energy losses in this case are significantly reduced.

If the height of the door is equal to the height of the ceiling, then flexible ceiling screens are desirable. A ceiling with "pockets" is preferred. To allow warm air to circulate and return to the working area.

Particularly noteworthy are two-jet (combined) air curtains with good damper properties and low energy losses caused by the release of heated air from the room (Fig. 3). Such a curtain is a structure that has two vertically installed transfer boxes with power units (or one power unit for two boxes) that supply warm air. Two boxes located closer to the opening provide unheated air supply. The efficiency of thermal curtains increases when they are installed in a vestibule with a special wall configuration, thus providing counter currents that prevent air from entering from the outside.

Fig. 3. Working diagram of a two-jet thermal curtain with a vestibule:1 - power unit (heater and fan); 2 - box supplying heated air; 3 -box supplying cold air; 4 - vestibule

In preparing the article, materials from books were used: V. Karadzhi, Yu. Moskovko “Ventilation equipment. Technical recommendations for designers and installers ", V. Ananiev, L. Balueva, A. Galperin and others." Ventilation and air conditioning systems. Theory and practice".

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Air heating is used to maintain a comfortable temperature inside residential, public or industrial buildings in cold weather. The principle of operation is as follows: a heating element is inserted into the ventilation system, which heats the passing air. There are three main types of space heating systems:

• infrared;
• conventional;
• air.

The latter type includes thermal curtains.

The main structural element of this heating equipment is an air duct that ensures a uniform flow of flows. The guide plates attached to the duct can change the direction of the jet at an angle to the plane of the opening. The heat curtain also has other required elements:

• a heating element;
• fan or fan system;
• air filters.

Calculation of the heating power of the thermal curtain

• Strictly speaking, the curtain is not a heater. The curtain is an energy-saving device that "seals" the doorway with an air curtain and prevents heat loss. Therefore, the heating power is determined rather subjectively.
• The technical characteristics of the air curtain usually indicate "increase in air temperature" - the temperature difference between the intake and exhaust air.
• For the majority of curtains, the optimal heating power has already been selected - in each of the models, the optimal heater in terms of power has already been installed
• Some manufacturers (Olefini, for example) produce different modifications of the same air curtain model - with different heating capacities (for example, 12 kW and 15 kW).
• See also:
• Calculation of the efficiency of OLEFINI air curtains

How to calculate the structure

Outside cold air enters the building due to different pressures inside and outside the building. The volume of air supplied by the curtain must completely exclude the penetration of cold air inside. For correct calculations, you need to know the following: the size of the gate, the amount of outside air that enters through the opening without a curtain, the temperature inside and outside the room.

Dimensional drawing of the heating unit

There are several formulas for this calculation. Here are the ones that, according to experts, are the most accurate:

1. With the formula VHB = L, you can find out the air flow that enters the room (L), if you multiply the speed of the air mass (V), the height (H) and the width (B) of the gate.
2. The following formula calculates the air flow required to completely block and prevent the passage of cold air masses through the gate or opening: L / J (B / b + 1) = Z.
3. L-flow rate of air that enters the room.
4. J-coefficient (0.45) of the air curtain range.
5. B is the width of the gate.
6. b - width of the slot for air supply to the curtain.

Types of air curtains

How to choose the right thermal curtain? All existing models can be classified according to the installation method and the type of coolant.

By installation type

Today there are three types of air-thermal curtains:

1. Horizontal. Classic performance. Installed directly above door (window) openings. As a rule, these are small economy class models with a capacity of up to 5-6 kW;
2. Vertical. Install only vertically to the side of the opening. This installation method is chosen when, due to one reason or another, horizontal installation is impossible or inconvenient. Today on the market of climatic equipment there are design models of vertical mounting, issued in the form of columns;
3. Embedded. They are characterized by the fact that the body of the device is completely hidden under the false ceiling. A directed air stream exits from a nozzle hidden behind a decorative grille.

Horizontal and vertical installation
Recently, on the Russian market of climatic technology, one can find universal thermal curtains that can be installed both horizontally above the opening and vertically to the side of the opening.

By type of coolant

Depending on the method of air heating, all air curtains are divided into three groups:

1. Gas;
2. Aquatic;
3. Electrical.

Gas air curtains heat the air by burning propane. This is a rather specific equipment that is installed in large enterprises with a huge traffic during peak hours. Such systems are not used in rooms with an area of ​​less than 60 m2. They are characterized by high efficiency, cost, operating costs.

Air-heating curtains are chosen when there is good access to the hot water or heating system. The principle of operation of the equipment is as follows: hot water from the system passes through a heat exchanger, which is blown by a turbine. Due to the difficulties with the supply and availability of the coolant, there are no budget class models among the water curtains, up to 1 m long.

The main advantages of such models:

• minimum power consumption;
• low noise level during operation;
• affordable price;
• long service life;
• high technical characteristics.

Electric air curtains are very popular among our compatriots. The equipment can be used in almost any environment: from small windows and doors (models up to 2.5 kW) to industrial doors. Main advantages:

• the availability of the coolant;
• simple control.

The disadvantage is the significant consumption of electricity during operation.

How to choose a thermal curtain. How to choose the right thermal curtain

Selection and calculation of a thermal curtain

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The main factor when choosing is the width of the doorway, the air flow rate and the height of the installation itself. If the opening is high, then the speed of the outgoing air must be high. The heat curtain should be located as close as possible to the doorway and completely cover it. If the opening is very large, then several curtains can be installed close to each other. They will create a continuous air flow. If the room is very large and has several entrances and exits, it is necessary to calculate the wind forces in the drafts entering the room before installing the equipment. When there is insufficient power, it will not block the opening to its full height; if the air flow is too strong, warm air may escape.

• The heat curtain is selected in such a way that the width of the air nozzle covers the entire width of the door opening. These data can be found in the tables of technical characteristics presented on our website. \
• The jet of the thermal curtain should "pierce" the entire opening in height. This data is also found in the tables provided by the manufacturers. However, it should be remembered that the effective length of the jet can serve as an estimate of the permissible installation height of the upper curtain or the width (half-width) of the side curtain opening only for “soft” outdoor conditions (tn = 0С, wind 1 m / s) and balanced supply and exhaust ventilation. Any tightening of conditions will reduce the effective throw.
• And finally, the heat curtain can be selected according to the indicated volume of air consumption - from 250 m3 / h to 400 m3 / h per 1 m2 of the opening area for openings up to 3 meters high and from 400 m3 / h to 600 m3 / h per 1 m2 of the opening area for openings with a height of more than 3 meters.
• Power is a secondary parameter selected by the manufacturer, as a rule, in such a way as to provide heating of the blown air by 25 degrees.

Air curtain classification

Depending on the design, all air curtains can be subdivided into

• Water curtains. Only hot air is supplied, for which the system uses a two-way heat exchanger to heat it. This main part is made of copper pipes with aluminum fins. Of the undoubted advantages of water curtains, one can note the super-economical consumption of electricity, which is consumed only for the operation of the fan blades. Most often they are produced in a ceiling side version, but you can find a more complex configuration (in the form of a column or an ellipsoid), they are controlled remotely using a remote control. They can be used in openings of doors and gates, which remain open for a considerable amount of time. Special series allow them to be used for openings with a height of 3-5 meters. Among the disadvantages of water air curtains, it is necessary to note the complexity of installation and the potential danger of freezing of the heat exchanger. Air curtains are produced by such well-known manufacturers of climatic equipment as the international holding Ballu Industrial Group and the Russian research and production association Teplomash;
• Electric curtains. They have a wider range of possibilities, since they can supply not only hot, but also cooled air. Models with a heater have a tubular heating element, a spiral heating element or a STITCH needle heater in the design. Tubular heating elements (which are a hollow steel rod with quartz sand, inside which there is a spiral with a high ohmic resistance) are safer, and are also able to painlessly tolerate power surges. Most modern air curtains use ceramic heating elements (RTC thermistors), which are much more durable and more economical than their predecessors. In addition, a thermostat is necessarily provided in the design, which allows the device to be turned off when a predetermined temperature is reached, which makes it possible to somewhat reduce energy consumption.

Air curtain selection criteria

When choosing a thermal curtain, it is necessary to build on the specific conditions, taking into account the following parameters. Curtain size

Curtain size

It is selected based on the size of the opening on which the equipment will be installed, taking into account the fact that the air flow must block it with a certain margin. One should not save on the size of the curtain, since otherwise the formed cracks will enhance the unwanted air exchange.It should be borne in mind that the maximum allowable area of ​​the opening covered by one curtain is 12 m2, so sometimes you have to install several devices close to each other.

Air performance

It is this indicator (the volume of air pumped by the unit in 1 hour) that is fundamental for all air curtains. Measured in m3 / hour or m3 / s. The higher it is, the denser the created air gap and, accordingly, the more efficient the operation of the device. Experts recommend in standard situations to use equipment with a capacity of 700 m3 / s to cover an opening of 2.5 meters in height. In all complex and non-standard cases, such calculations should be entrusted to professionals.

Power

When making rough calculations, the following nuances must be taken into account:

• whether the curtain will work additionally to heat the room or its task is only to cut off external air flows. It should be noted that the electric heat curtain should not be considered as a full-fledged heating device. In this case, the excess thermal power of the structure will not only lead to significant material costs, but can also become a source of unwanted drafts;
• it is planned to occasionally turn on the curtain, or its operation with a constantly open opening. In the latter case, up to 70% of the power will be lost;
• the presence in the room of a protective vestibule, automatically swinging doors, several entrances.

In the general case, in a capital structure, it is roughly based on the calculations of the need for 1 kW of power for every 10m2 of the room. When installing air curtains in refrigerators and freezers, models without a heating function are used.

Heat curtains electric and water KEV (Teplomash)

Air curtains KEV of the 300 E series, in particular, the KEV-12P304E model, ideally solve the problem of neutralizing cold air flows. They can be mounted both horizontally, at the height of standard doorways (2.5 - 3 meters), and from the side (vertically). The power of these devices varies from 12 to 24 kW. Most of them are used in everyday life, therefore, a lot of attention has been paid to ease of use. There is even a fully functional remote control system. If we consider the water thermal curtains Teplomash KEV-60P314W and others, then they are somewhat different, the power of the devices can reach 60 or even 98 kW. By the method of installation and the effectiveness of protection of any kind of room, they are similar to models that use electrical energy as a heat carrier.

The device of thermal curtains of this brand is reliable and durable. The body is made of steel and covered with a high quality polymer coating. The housing includes a heating element, a fan and nozzles for supplying a stream of heated air. The principle of operation is quite simple, the air sucked in by the fan heats up and through the nozzle, already heated, is fed into the opening.

The marking on Teplomash devices is deciphered as follows: the first three letters of the KEV indicate the manufacturer (Teplomash), the next two digits are the power in W, the letter is the functional purpose (P-curtain), then three digits are the series number, the supply voltage (1-220V , 3-380V), modification number. The letter W is a water source of heat, E is an electrical source.

Horizontal or vertical

Horizontal curtains are more traditional, they are installed at the top of the opening, while the air flow is directed downward. Their use is limited, since at present standard models are capable of overlapping the opening height of 2-2.5 meters, and non-standard equipment is too expensive.

Vertical curtains provide more room for maneuver. Industrial air-heating curtains for a warehouse most often have a vertical structure.In this case, the curtain is installed on the side of the door or gate so that the air flows intersect with each other, providing the desired result

Considering the model range, it is necessary to pay attention that horizontal and vertical modifications are not interchangeable for all manufacturers, having significant differences in the layout

Sizes and prices

The price of an air curtain most globally depends on the size of the installation. Air openings are subdivided into several subtypes according to their dimensions:

Let's consider some of the most popular models from different manufacturers:

The principle of operation of the thermal curtain

This device is also called a heat separator for its work. The heat inside the building is stored by means of a vertical air flow. In this case, air acts as a heat insulator and performs this quite effectively, given its low ability to transfer heat.

The thermal insulation properties of air are widely used - most heaters are either foam materials, inside the bubbles of which there is air or an inert gas, or a fibrous material that holds air with a pile. Clothes that block the flow of air with the fibers of the fabric or wool in the fur work in a similar way.

In a thermal curtain, air prevents heat loss by protecting it from horizontal air currents. The room is separated from the outer space by a wall of heated air. The vertical movement of the air is provided by a powerful fan. The heat curtain is placed above the door, and the heated air from it enters the floor and further spreads inside the room.

Due to the temperature difference, cold air cannot enter the room, which protects the internal atmosphere from such unfavorable influences:

• Insects;
• Dust and other air pollutants;
• Traffic fumes;
• Smoke;
• Unpleasant odors.

To effectively protect the room from external influences, it is necessary to heat the air.The effectiveness of this protection will be significantly reduced if the air in the heat curtain is at or colder than the room temperature. Also, additional circulation of cold air will only lead to discomfort. Therefore, the device producing the heat curtain is provided with a heating element.

Heat curtains are divided into electric and water curtains according to the method of air heating.

Principle of operation

Air curtains work according to a fairly simple principle. There is a very powerful fan inside the unit that generates a high-speed air flow. The warm air flow forms a barrier that prevents cold air from entering the room. In turn, warm air remains in the room due to this obstacle.

Most often, the advisability of installing such a device is achieved when the curtain is installed above the door, directing the air flow downward. Given the principle of operation, the scheme of such equipment is quite simple, and anyone can figure it out. Very often, thermal curtains are installed in warehouses, shops and other establishments where doors need to be opened frequently.

Among other things, the installation of this device will allow you to keep the door open all the time, even in winter. At the same time, energy savings will be achieved, since the microclimate of the room will remain at its previous level. Another plus is that the curtain can be used in the summer. When the air conditioner is turned on in the house, you can open the doors, turn on the curtain and not worry about the cool air leaving the room. Moreover, the curtain also performs an additional function, protecting the house from dust, insects, etc.

The fan of the air curtain generates a high-speed air flow that reflects the air from inside and outside the room

In order for the device to work effectively, it is necessary to select it correctly. And for the right choice, you need to make a calculation. This process consists of several stages, including:

• calculation of the curtain length;
• calculation of the required heating power of the device;
• determination of the air flow rate;
• organization of management;
• selection of the type of installation;
• selection of a heat source.

Curtain length and heating power

The efficiency of its operation will depend on how correctly the heat curtain is selected. For calculating the device, the decisive indicator will be the air flow rate, the width of the doorway, as well as the height of the installation.

That is why, when choosing equipment, it is necessary to take into account some features. So, the higher the curtain is installed, the higher the air flow rate it should have.

Such a curtain should completely overlap the doorway and be as close to it as possible. In the case of a very wide opening, it is better to install several small thermal curtains that will create a continuous barrier. For this, the device must be installed side-by-side. If the building has several entrances, it is necessary to take into account the presence of drafts, which should be blocked by a more powerful model. When a horizontal curtain cannot be installed directly above the opening, it is worth looking at the possibility of installing a vertical curtain.

The main indicator of air curtains is the air flow rate

As for the selection of the power of the thermal curtain, there are also some selection features. The point is that the device is powered by an ordinary heater, so its power is calculated subjectively. The curtain acts as a door, eliminating heat loss. This is what you need to pay attention to when choosing. The difference between the temperature of the intake and exhaust air makes it possible to determine the temperature rise.

Some curtains come with a matched rated power, which is achieved by introducing a heater with the most suitable performance into the design. You also need to pay attention to the fact that sometimes manufacturers produce the same model, but in different modifications with different power ratings.

Air velocity calculation

On their own, most likely, it will not be possible to manage this issue. The optimal speed for efficient operation of the heat curtain must be calculated by a specialist. Otherwise, it can lead to a decrease in the efficiency of equipment operation. The flow rate calculations of air-heating curtains are based on the air curtain outlet speed.

For efficient operation of the air curtain, the optimal speed must be calculated by a specialist.

This indicator directly depends on the size of the rotor, as well as on the rotation speed. In the selection process, it is worth taking into account the recommended height indicated in the characteristics of the curtain, but at the same time, it is always necessary to take into account the correction for wind and draft. This is especially true when it comes to fairly large rooms that have several entrances. If you do not make an amendment to the calculations, then the efficiency of the equipment will be in great doubt.

For most models, a diagram of the separation of air flow velocities at different distances from the curtain is indicated in the instructions. It is not necessary to mount an overly powerful curtain, because this will create additional losses of warm air. But there is also one prerequisite for the correct functioning of the veil. The thing is that the device will perform its functions only if the flow rate near the flooring is not below the 2.7 meters per second mark.

Important characteristics of all types of curtains

All of these types of curtains are classified according to characteristics such as:

Power.

The calculation of power indicators when choosing thermal curtains is calculated according to the following algorithm: with a ceiling height ranging from 280 to 300 cm, 1 kW of power should fall on 10m2 of the room. This is a simplified technique, but for a more accurate calculation of air conditioning equipment, you need to use the help of qualified specialists from companies that sell / install air curtains.

• Household curtains can be installed not only on the openings of residential buildings. They are used for installation above checkout windows in kiosks and other MAFs. Such equipment reduces the likelihood of drafts and performs the functions of additional heating equipment for small rooms.
• Medium curtains are designed for openings with a height of 250 to 300 cm. They provide a reduction in heat loss with frequent opening of the entrance doors and prevent drafts in large rooms.
• Large and heavy-duty devices are designed for industrial facilities with an opening height of more than 700 cm. They are installed on the openings of warehouse gates or hangars, at the entrance groups of supermarkets and shopping centers.

Mode of operation.

• permanent equipment;
• systems of variable action.

• Horizontal air curtains are installed above the openings of windows or doors. In this case, the climatic equipment is mounted over the entire width of the opening, in order to prevent the flow of outside air along the edges. This type of air curtain is the most popular, but in cases of the year there is no structural possibility of such installation, or for large openings, vertical devices with side placement are used. The installation technology of these types of curtains has minor differences.
• Vertical devices are installed on the sides of the openings so as to ensure the horizontal direction of the produced air flow.To improve the efficiency of the climatic equipment, vertical air curtains are installed on both sides of the opening. In the catalogs of manufacturers, there are universal curtains that can be mounted in a vertical and horizontal position.

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Vertical (industrial) air curtains Frico

Vertical air curtains from the most famous world manufacturer are less common, but, nevertheless, they are present on the domestic market. They are used where the doorways are wide enough, which means that the volume of the room is larger. These are production, industrial, trade and warehouse premises. These devices are larger, more efficient, although the principle of operation is similar to horizontal models using hot water from centralized heating systems. Naturally, performance and reliability are paramount for industrial devices, with original design being the second most important consideration.