Ventilation and exhaust systems in cafes and restaurants

Recommendation points

• What are the standards
• Dining room ventilation
• Kitchen and hot shop
• Service premises
• If the establishment is in a residential building
• Industrial ventilation equipment

We bring to your attention a small overview where we considered the basic issues in the construction of ventilation systems for catering establishments. You will learn what standards are in force in this regard, what equipment is provided for solving such problems and what parts the system consists of.

What are the standards

The main goals of the project for the ventilation system of the restaurant and cafe are two: for the construction object to pass acceptance, and for the system parameters to correspond to real requirements. In the first relation, one should rely on SNiP 41-01-2033 and the set of rules to it 60.13330 with all nested references. These documents describe the basic requirements for air exchange and climate control in public and industrial premises..

In fact, the indicated air exchange rates turn out to be significantly overestimated, which translates into a noticeable overspending of electricity for the operation of air pumps, heating and cooling the air. It can be argued that the values ​​taken as the norm are not substantiated by the real needs of people. Therefore, specialists introduce the concept of the efficiency of air distribution, which takes as a basis air exchange directly in the respiratory zone..

With the right distribution system and automatic control, the system can potentially operate at peak performance to meet regulatory requirements. At the same time, the normal mode will provide a sufficient, reasonable level of air exchange, saving tens and hundreds of kilowatts of energy.

To draw up the project of ventilation of the restaurant “according to the mind” it will be useful to familiarize yourself with the textbook “Ventilation of public buildings” by MP Kalashnikov. This manual not only highlights the main stages of designing ventilation systems, but also, which is much more important for the developer, describes the elements of the system and the basic principles of operation of forced air exchange devices. After such an educational program, it will be much easier to communicate with designers and contractors..

To determine the reasonable standards for the preparation of the internal climate of public buildings, the foreign standard ASHARAE 62.1-2004 is recommended, which is based not on the concepts of oversupply, but on real clinical studies and the introduction of energy-saving technologies. Unfortunately, the Russian-language version of this standard does not yet exist, but the main provisions are easy to learn even through machine translation..

Dining room ventilation

The first part of the catering ventilation system is the dining room, where an arbitrary number of visitors can be. The two main criteria for assessing the operation of the ventilation system are the total rate of air exchange and the rate of air consumption, expressed in m³/ person or m³/ h / m² taking into account the provision of space per person (from 1.4 m²/ person) in catering establishments. The average figure for dining rooms can be taken as 10 m³/ h / m², which is slightly more than a reasonable value, but is quite consistent with the traditional adoption of a safety factor in the event of a hall overflow.

The technical implementation of the distribution system is extremely important: the location of the exhaust and supply channels, the direction of the flow. The coefficient of efficiency of air distribution depends on them. Its highest value is achieved with displacement ventilation: this is a quick exchange of air in the breathing zone and a mediocre exchange in the area under the ceiling and directly above the floor. In this version, the supply ducts exit at the bottom of the room, the exhaust ducts are located at the top. The least efficient is the standard ventilation scheme with the placement of both supply and exhaust under the ceiling, the average efficiency values ​​correspond to forced-extract ventilation with an air flow from top to bottom.

In addition to air exchange, the air flow rate, humidity and temperature are normalized. The quality of the microclimate is ensured by an automatic air conditioning system, but even here there are pitfalls. The fact is that the operation of the ventilation system must be coordinated with the heating, it must also take into account the peculiarities of natural ventilation. It is important to understand that in different areas of the room, the supply of air of the same quality can lead to a pronounced difference in the final microclimate. To eliminate such phenomena, calibration regulation units or normalizers (fan + heater) are installed in the main ducts supplying air to different parts of the dining room, and air distribution is performed through adjustable anemostats.

The efficiency of the inflow placement on the ceiling is due to the more free placement of the air ducts. Behind the suspended ceiling structure, you can hide communications of almost any complexity, masking the outputs of anemostats is also not a problem. It is much more difficult to correctly position the exhaust / supply openings of the lower zone. They should be located at an even and maximum distance from the return flow channels. It usually makes sense to lay exhaust ventilation ducts along the outer walls of the room, and in spacious halls, descend from the ceiling under the cladding of the supporting columns. A slightly different approach is to force supply air under high pressure from the ceiling in habitable areas. However, in this case, it is rather difficult to regulate the speed of the mixing flows, it is optimal if the jet reaches a level of 1.2–1.4 meters above the floor at a speed of 0.7–0.8 m / s.

Kitchen and hot shop

For the kitchen, the same basic principles apply, but a number of special requirements are also taken into account. The general rate of air exchange is higher here and can reach 20-30 m³/ h / m². And since the volume of the kitchen room is significantly lower than that of the dining room, the air exchange rate reaches such values ​​at which it makes no sense to assess the efficiency of air distribution.

The ventilation of the kitchen as a whole must take into account the requirements of industrial sanitation, which regulate temperature, humidity and air flow rate directly in the area where workers are located. It is not easy to achieve an acceptable air flow speed with such a rate of air exchange, but this can be achieved by multiple intersections of the supply ventilation air flows and the general direction of air movement from top to bottom, that is, the opposite of the path of natural convection.

Such high rates of air exchange are explained by the fact that in addition to replenishing the natural needs of a person for air for breathing, one should seek to dissolve harmful secretions, which are much more in the kitchen. For the same reason, exhaust systems from the kitchen and dining room must be implemented according to individual schemes and not intersect. The inflow is often made common on the condition that the supply air pumps are located directly at the points of air discharge into the premises, that is, in front of the diffusers, grilles and heat curtains. It is also normal practice to separate about 20-30% of the inflow volume directly from the hall, which is associated with the difficulty of placing numerous supply channels and the need to avoid the spread of the smell of cooking food into the hall.

For a hot kitchen workshop, there is an additional requirement to compensate for the release of thermal energy. According to industrial sanitation standards and depending on the parameters of kitchen equipment, the limitation can be about 15-20 W / m³. It is clear that this issue cannot be solved by general ventilation: with such an air exchange, the air flow rate will exceed all conceivable and inconceivable limits. Therefore, local high-efficiency ventilation should be organized, usually over hobs by means of hoods and in places where excess heat is concentrated in refrigerators, laundry, washing and drying equipment. These exhaust systems do not communicate with the general ventilation system in any way; here it is necessary to arrange a third individual exhaust channel. But the required volume of supply air is added to the total value of the kitchen inflow.

Service premises

Among other premises, the provision of a microclimate is carried out mainly only for administrative offices. There are general office air exchange rates of 30 m³/ h / m² and limitation in air speed up to 1 m / s. The same applies to staff rest rooms and individual workplaces..

Corridors, stairs, storerooms and other utility rooms do not need ventilation. However, there is an important digression here: in large multi-storey buildings, an emergency ventilation device may be required here, directed against the evacuation route..

It will also be useful to place some of the supply ducts in such a way that in rooms without ventilation, a minimum air exchange is maintained. This will help to exclude the formation of excessive humidity and stuffiness in the air, relieve the passage areas from an unpleasant musty smell. Implementation will require a system of internal ducts connecting the rooms with the inflow, as well as a slight redundancy of the exhaust system in comparison with the supply.

If the establishment is in a residential building

The most difficult engineering task is considered to be the organization of ventilation of public institutions located on the first or in the basement floors of residential buildings. The main difficulties come down to the technical implementation of air ducts that communicate the system with the street atmosphere. No one will allow using the engineering systems of the building for this, and the laying of our own canals in a common technical well, although possible, is difficult to implement.

The simplest way out of the situation is the installation of vertical air ducts along the outer wall of the building. This mainly concerns exhaust flows saturated with carbon dioxide and vapors. They can be discharged only above residential floors, otherwise there is a high risk of contaminated air entering the living quarters of neighboring buildings. It is not recommended to take intake ventilation from the ground floor level: usually the ducts lead to a cleaner area 7-10 meters from the ground, avoiding the capture of car smog and street odors.

The artistic and architectural value of the facades can hinder the installation of external air ducts. This is solved by enclosing channels in a common well, limited by a decorative casing. If, according to the conclusion of the city architectural department, this option is not acceptable, then ventilation channels are laid on the back of the building. The location of external communications is almost always the starting point in the development of ventilation systems.

Industrial ventilation equipment

The main technical complex of equipment for ventilation is usually located in the room immediately before the outlet of the supply and exhaust air ducts outside. This is due to the need to locate at least three exhaust air pumps at the point of the system closest to the outlet. A kind of limitation is the permissible noise level: it is much easier to place the entire set of units in one specially equipped and isolated room than to distribute them throughout the system.

Along with the supply and exhaust air pumps, recuperators can be located in the ventilation room, which carry out heat exchange between the exhaust and supply air streams, thereby saving costs for fresh air conditioning. Other elements of the system are also located in combination: normalizers of humidity and temperature, automation, emergency equipment, recirculation devices. It is highly recommended to use power regulators that regulate air exchange in accordance with the data of gas analyzers and the current capacity of the hot shop.

The rest of the communications network, distributed throughout the premises, includes rigid insulated ventilation ducts, slide dampers and local air quality calibrators. Also, an integral part of the ventilation system of this level of complexity is a system of sensors that control not only the temperature and air exchange of the supplied air, but also communication with the automation of the heating system and air conditioners.