DESIGN OF NATURAL VENTILATION SYSTEM TO ENSURE STANDARD AIR CONSUMPTION

Abstract

Total losses of aerodynamic pressure in an exhaust ventilation system have been determined in two ways: by calculation of the air regime of the building as a whole, together with the ventilation systems serving the building, and the aerodynamic calculation of a system isolated from the building. The calculation of the building air mode has been carried out by the iterative method of solving the system of equations of air balances of all premises of the building and units of all ventilation systems. Ventilation systems that provide standard air consumption for all systems on all floors of the building have been subject to an analysis. The found relations between aerodynamic resistances of the floor branch of such an exhaust ventilation system from the exhaust grate to the common trunk and the trunk itself from the floor branch to the mouth of the exhaust shaft allowed us to assert that an increase in the air rate to the upper normative permissible air boundaries is possible, since despite the increased aerodynamic resistance in the trunk of the system, pressure losses in the floor branches of the upper floors are reduced due to ejection. The article provides an analysis of the natural ventilation system with the external air inflow through the swing-flap window and the supply valves. The calculations have shown the feasibility of using a supply opening, the aerodynamic resistance of which is close to zero in the calculated external ventilation conditions. In addition, the supply device must be adjustable, so that when the outside air temperature lowers and, consequently, the available pressure of the ventilation system increases, its cross-section may be reduced to avoid an unnecessarily big flow of the supply air. An example of such a supply device can be a swivel-flap window with adjustable opening. Aerodynamic calculations of natural ventilation systems, which are isolated from the building, may be provided only at an almost zero inflow aerodynamic resistance to the sufficient air flow in the ventilation design external conditions.