How does a cooker hood work?

The air in the kitchen is the most polluted in the entire apartment. When cooking, various combustion products are released, which not only do not have the best effect on human health, but also, precipitating on kitchen surfaces, spoil their appearance. The hood is designed to eliminate air pollution. To do this, there are several important components in its arsenal. In the material, we will analyze which ones.

Cooker hood operating modes
There are two fundamentally different operating modes for a cooker hood : air extraction and recirculation. When the device is operating in air extraction mode, all dirty air is removed from the kitchen through a stationary ventilation duct.

The air extraction mode is considered the most efficient, since the hood shows its maximum performance in it, providing almost 100% removal of combustion products and cooking odors.

Inclined hood BOSCH Serie 4 DWK065G60R blackIn stores: in 6 stores
In recirculation mode, dirty air is not removed from the room, since the hood is not connected to the ventilation duct, but is cleaned in a charcoal filter and returns back to the kitchen volume.Inclined hood Akpo WK-4 Optima eco 60 whiteIn stores: in 27 stores
How the hood works
The principle of operation of the device is quite simple. Let’s consider it on the example of a hood operating in recirculation mode. The suction fan (also called a turbine for its high performance) draws contaminated air into the inner cavity of the hood. The first obstacle in its path is a mesh filter. It cleans the air masses from fatty vapors and dust. The so-called rough cleaning takes place, the main purpose of which is to protect the internal components from fatty deposits. Then the air is passed through a charcoal filter, where it is cleaned of odors (gases containing microscopic particles of food) and soot, and then returns back to the room.

In systems connected to stationary ventilation, the carbon filter is not installed, since there is no need for it. Air masses are immediately removed outside the room.

The hood, not connected to ventilation, is less efficient, since an additional obstacle in the form of a charcoal filter appears in the air path.

Exhaust device
There are not so many components in the composition of the hood, and this is how the kitchen hood is correctly called. The general device of the device is shown in the figure.

Next, we will consider the purpose and principle of operation of each of them.

Fan
The fan, otherwise called the turbine, is the main element of any hood, one might say its “heart”. It consists of an electric motor with an impeller on its axis. The blades of the latter provide forced air circulation in the room. According to their design, turbines are axial:

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The main difference between the types of fans is the location of the motor axis relative to the air flow vector. For axial turbines, they coincide, for tangential ones, they are located perpendicular to each other. The essence of the device’s operation does not change from this, since, both in one and in the second case, the fan provides forced air circulation. The use of turbines of different structures is rather a question of the layout of the hood and the rational use of its internal space.

Some models have in their design two fans connected in parallel.

This technical solution is used to reduce the noise load, since two low-power turbines produce less noise than one powerful one.

To minimize the vibrations arising during the operation of the electric motor, the fan is attached to the casing through rubber damping inserts.

The main parameter of a turbine is its performance. Those. the volume of air that it passes through itself in an hour. The fan performance can vary from 250 to 1000 m 3 / h. This parameter is important when choosing a device, since large rooms require high performance. Otherwise, the air will circulate poorly, and also poorly cleaned. This must be clearly understood when choosing an exhaust hood for indoor air recirculation. In the case of operation in recirculation mode – productivity is decisive! The air is cleaned faster and more efficiently.

With models that are supposed to work in the exhaust mode, things are different. When choosing such a model, one should take into account the throughput of a stationary ventilation duct, which depends on its section and length. It may turn out that the capacity of the hood will be excessive, but the fan will still not be able to pump the estimated volume of air through the small ventilation duct.

Proceeding from this, when using a hood connected to stationary ventilation, you should not “chase” a high performance value.
In stores: in 10 stores
Control Panel
The panel controls the device: changing the fan speed, turning on additional lighting and other functions. For the convenience of the user, it is always located in a conspicuous place, contains simple and understandable symbols that allow you to change the operating modes of the hood.

There are the following types of control panels:

You can understand the controls without even referring to the operating instructions.

Some models with an electronic or touch control panel have a timer function. It allows the user to do other things after finishing cooking while the cooker hood continues to purify the air in the room. The device will turn off automatically after the set time. You do not need to control it.

The main element of the system is a strainer mounted on the inlet of the device. Its task is to protect the internal elements from grease and dust. Physically, the filter is a plate made of anodized aluminum or stainless steel with a mesh structure.

When dirty air passes through the filter, oil vapors and dust are retained by the mesh cells.

In the hoods that return air back to the room, a carbon filter is additionally installed, which can be called a fine filter. Its main purpose is to remove combustion products and odors from air masses.

The filter is based on activated carbon – a special sorbent (a substance that selectively absorbs pollution from the environment) with a developed porous structure. Activated carbon is a gas-permeable material. It is thanks to this feature that the air is purified. Airborne pollutants are trapped in the pores of coal due to chemical reactions called chemisorption in scientific parlance.

These reactions are irreversible, so sooner or later all the pores of the carbon filter are filled with contaminants and the filter stops performing its functions.

The filter can hold in its pores as much contaminant as five times the weight of the carbon used in the filter element.

Typically, the carbon filter is installed at the end of the fan.

The hood filtration system is its Achilles’ heel, since dirty filters are a rather difficult obstacle to the passage of air masses. The strainer must be cleaned regularly and the charcoal filter must be replaced with a new one. To learn how to take care of the hood, covered in material DNS blog.

Lighting
All models of hoods have additional functionality, namely illumination of the working area of ​​the stove, which significantly increases the user’s comfort when cooking. For this, several lamps are mounted in the hood body.

Additional light is switched on from the device control panel.

Incandescent lamps, halogen or LED lamps can be used as light sources.

The quality of lighting of the hob and the frequency of lamp replacement depend on their type . LED lamps last many times longer.

Frame
All of the above components are contained in the hood housing. It is the basis for their fastening. The heaviest element is the fan, so the chassis must be sufficiently rigid. For these reasons, hoods are made of sheet steel or durable plastic.

As for the shape of the hood, the following types of housing are most common:

flat;
dome or fireplace;
island.
Flat and domed hoods can be manufactured to be built into furniture or to be mounted on the wall. The type of material used for the manufacture of external panels depends on the type of execution. Built-in models are usually made of painted sheet steel. Aesthetics is not important here, since the hood body is hidden behind furniture elements.

Exterior hoods are another matter. They are always in sight and the aesthetic component is as important as their functionality. Such hoods are always in sight, therefore, with their appearance, they should complement the interior of the kitchen and decorate it. For these purposes, tempered glass or stainless steel is used in the manufacture of facade surfaces. Both coatings have an excellent appearance and are quite easy to care for.

Models of the lower price segment, as a rule, are made of enamel-painted steel. Such a coating, with proper care, can last just as long, but still, it is more susceptible to damage, manifested in the appearance of scratches and chips, and therefore less durable.

Outcomes
As you can see, the device of the cooker hood is quite simple, but this does not detract from its merits. The presence of an effective hood in the kitchen will not only rid the room of extraneous odors and provide households with clean air, but also give the kitchen working area a finished look.