Ventilation in the room, especially in residential or industrial, should function 100%. Of course, many may say that you can simply open a window or door to ventilate. But this option can only work in the summer or spring. And what to do in the winter when it is cold outside?
Need for ventilation
Firstly, it is immediately worth noting that without fresh air, the human lungs begin to function worse. It is also possible the emergence of a wide variety of diseases, which with a high percentage of probability will develop into chronic. Secondly, if the building is a residential building in which children are located, then the need for ventilation increases even more, as some ailments that can infect a child are likely to remain with him for life. In order to avoid such problems, it is best to do the arrangement of ventilation. It is worth considering several options. For example, you can do the calculation of the supply ventilation system and its installation. It is also worth adding that diseases are far from all problems.
In a room or building where there is no constant exchange of air, all furniture and walls will be covered with plaque from any substance that is sprayed in the air. Suppose, if this is a kitchen, then everything that is fried, cooked, etc., will give a precipitate. In addition, dust is a terrible enemy. Even cleaning products that are designed to clean will still leave their residue, which will negatively affect residents.
Type of ventilation system
Of course, before proceeding with the design, calculation of the ventilation system or its installation, it is necessary to determine the type of network that is best suited. Currently, there are three fundamentally different types, the main difference between which is in their functioning.
The first category is called the supply. The bottom line is that such a system will constantly draw fresh air into the building.
The second group is the exhaust. In other words, this is an ordinary range hood, which is most often installed in the kitchen premises of a building. The main task of ventilation is to extract air from the room to the outside.
Recirculation. Such a system is perhaps the most effective, since it simultaneously pumps air from the room, and at the same time delivers fresh from the street.
The only question that arises for all further is how does the ventilation system work, why does the air move in one direction or another? For this, two types of air mass awakening source are used. They can be natural or mechanical, that is, artificial. To ensure their normal operation, it is necessary to carry out the correct calculation of the ventilation system.
General network calculation
As mentioned above, just selecting and installing a particular type will not be enough. It is necessary to clearly determine exactly how much air needs to be removed from the room and how much needs to be pumped back. Specialists call this the air exchange that needs to be calculated. Depending on the data obtained, when calculating the ventilation system, it is necessary to repel when choosing the type of device.
To date, a large number of various calculation methods are known. They are aimed at determining various parameters. For some systems, calculations are carried out to find out how much warm air or fumes should be removed. Some are carried out in order to find out how much air is needed to dilute pollution, if it is an industrial building. However, the minus of all these methods is the requirement of professional knowledge and skills.
What to do if it is necessary to calculate the ventilation system, but there is no such experience? The very first thing that is recommended to be done is to familiarize yourself with the various regulatory documents available to each state or even region (GOST, SNiP, etc.) These papers contain all the indications that any type of system must comply with.
Multiple calculation
One example of calculating a ventilation system can be a multiplicity calculation. This method is quite complicated. However, it is quite feasible and will give good results.
The first thing to understand is what multiplicity is. A similar term describes how many times the air in the room changed to fresh in 1 hour. This parameter depends on two components - this is the specificity of the structure and its area. For a visual demonstration, the calculation according to the formula for a building with a single air exchange will be shown. This suggests that a certain amount of air was removed from the room and at the same time fresh air was introduced in such a quantity that corresponded to the volume of the same building.
The formula for calculation is as follows: L = n * V.
Measurement is carried out in cubic meters / hour. V is the volume of the room, and n is the value of the multiplicity, which is taken from the table.
If you are calculating the ventilation system of a room with several rooms, then in the formula you need to take into account the volume of the entire building without walls. In other words, you must first calculate the volume of each room, then add up all the available results, and substitute the final value in the formula.
Mechanical ventilation
The calculation of the mechanical ventilation system, and its installation should take place according to a certain plan.
The first stage is the determination of the numerical value of air exchange. It is necessary to determine the amount of substance that must enter the building in order to meet the requirements.
The second stage is the determination of the minimum dimensions of the air duct. It is very important to choose the correct cross-section of the device, since such things as the purity and freshness of the incoming air depend on it.
The third stage is the choice of the type of system for installation. This is an important point.
The fourth stage is the calculation and design of the ventilation system. It is important to clearly draw up a plan diagram according to which the installation will be carried out.
The need for mechanical ventilation arises only if the natural flow can not cope. Any of the networks is calculated on such parameters as its air volume and the speed of this flow. For mechanical systems, this figure can reach 5 m 3 / h.
For example, if it is necessary to provide natural ventilation with an area of 300 m 3 / h, then a ventilation duct with a caliber of 350 mm will be needed. If a mechanical system is mounted, then the volume can be reduced by 1.5-2 times.
Exhaust ventilation
The calculation of the exhaust ventilation system, like any other, should begin with the fact that productivity is determined. The units of this parameter for the network are m 3 / h.
To make an effective calculation, you need to know three things: the height and area of the rooms, the main purpose of each room, the average number of people who will simultaneously be in each room.
In order to start calculating the ventilation and air conditioning systems of this type, it is necessary to determine the multiplicity. The numerical value of this parameter is set by SNiP. It is important to know that the parameter for a residential, commercial or industrial premises will be different.
If the calculations are carried out for a residential building, then the multiplicity is 1. If we are talking about installing ventilation in the administrative building, then the indicator is 2-3. It depends on some other conditions. To successfully carry out the calculation, you need to know the magnitude of the exchange in multiplicity, as well as in the number of people. The highest flow rate must be taken to determine the required system power.
To find out the multiplicity of air exchange, it is necessary to multiply the area of the room by its height, and then by the value of the multiplicity (1 for household, 2-3 for others).
In order to calculate the ventilation and air conditioning system per person, you need to know the amount of air consumed by one person and multiply this value by the number of people. On average, with minimal activity, one person consumes about 20 m 3 / h, with average activity, the indicator increases to 40 m 3 / h, with intense physical exertion, the volume increases to 60 m 3 / h.
Acoustic calculation of the ventilation system
Acoustic calculation is a compulsory operation that is attached to the calculation of any room ventilation system. A similar operation is carried out in order to perform several specific tasks:
- determine the octave spectrum of air and structural ventilation noise at design points;
- compare the existing noise with the permissible noise according to hygiene standards;
- identify a way to reduce noise.
All calculations must be carried out at strictly established design points.
After all measures have been selected for building-acoustic standards, which are designed to eliminate excessive noise in the room, a verification calculation of the entire system is carried out at the same points that were previously determined. However, the effective values obtained during this noise reduction measure should also be added here.
To carry out the calculations, certain initial data are needed. They became the noise characteristics of the equipment, which are called sound power levels (USM). Geometrical mean frequencies in Hz are used for calculation. If an approximate calculation is carried out, then corrective noise levels in dBA can be used.
If we talk about design points, then they are located in human habitats, as well as in places where the fan is installed.
Aerodynamic calculation of the ventilation system
Such a calculation process is carried out only after the calculation of air exchange for the building has already been carried out, and it was also decided to trace the ducts and channels. In order to successfully carry out these calculations, it is necessary to draw up an axonometric diagram of the ventilation system, in which it is necessary to distinguish parts such as fittings of all air ducts.
Using information and plans, it is necessary to determine the length of individual branches of the ventilation network. It is important to understand here that the calculation of such a system can be carried out in order to solve two different problems - direct or inverse. The purpose of the calculations depends on the type of task:
- direct - it is necessary to determine the dimensions of the cross sections for all sections of the system, while setting a certain level of air flow that will pass through them;
- the reverse is to determine the air flow by setting a certain section for all ventilation areas.
In order to carry out calculations of this type, it is necessary to divide the entire system into several separate sections. The main characteristic of each selected fragment is a constant air flow.
Calculation Programs
Since making calculations and constructing a ventilation scheme manually is a very time-consuming and lengthy process, simple programs have been developed that can do all the actions on their own. Consider a few. One such ventilation system calculation program is Vent-Clac. Why is she so good?
Such a program for the calculation and design of networks is considered one of the most convenient and efficient. The algorithm of this application is based on the use of the Altshul formula. The peculiarity of the program is that it copes well both with the calculation of ventilation of a natural type and of a mechanical type.
Since the software is constantly updated, it is worth noting that the latest version of the application is able to carry out such work as aerodynamic calculations of the resistance of the entire ventilation system. It can also effectively calculate other additional parameters that will help in the selection of preliminary equipment. In order to carry out these calculations, the program will need data such as air flow at the beginning and at the end of the system, as well as the length of the main air duct of the room.
Since manually calculating all this for a long time and you have to break the calculations into stages, this application will provide significant support and save a lot of time.
Sanitary standards
Another option for calculating ventilation is according to sanitary standards. Similar calculations are carried out for public and administrative facilities. To make the correct calculations, you need to know the average number of people who will constantly be inside the building. If we talk about regular consumers of air inside, then they need about 60 cubic meters per hour per one. But since temporary facilities also visit public facilities, they also need to be taken into account. The amount of air consumed per person is about 20 cubic meters per hour.
If we carry out all the calculations based on the initial data from the tables, then when we get the final results, it will become clear that the amount of air coming from the street is much larger than that consumed inside the building. In such situations, they most often resort to the simplest solution - installing a ventilation hood at about 195 cubic meters per hour. In most cases, the addition of such a network will create an acceptable balance for the existence of the entire ventilation system.