Ventilation duct It is an important part of the ventilation system. The purpose of the ventilation duct system design is to reasonably organize the air flow, reasonably determine the structure, layout and size of the air duct on the premise of ensuring the use effect, so that the initial investment and operation cost of the system are very low.

Shenyang Ventilation Engineering It is the general name of air supply, exhaust, dust removal and smoke exhaust system engineering.

1、 Ventilation system design problems

1.1 Air distribution:

Ventilation engineering The basic principle of air flow organization is that the exhaust outlet should be as close as possible to the source of harmful substances or heat dissipation equipment, and the air supply outlet should be as close as possible to the operation site or the place where people often stay.

1.2 System resistance:

The ventilation duct is an important part of the ventilation system. The purpose of the ventilation duct system design is to reasonably organize the air flow, reasonably determine the structure, layout and size of the air duct on the premise of ensuring the use effect, so that the initial investment and operation cost of the system are very low. Theoretically, the difference of resistance coefficient between the place where the air supply and exhaust pipes enter the civil engineering shaft with and without laminar flow plate can reach 10 times. From the actual inspection of a project, it is found that the air pipe and air outlet of the same model of fan are similar, and the air volume when used for air supply is 9780m3/h, and when used for air exhaust is 6560m3/h, the difference is 22.7%. The smaller air outlet selection is also a factor for the increase of system resistance and the decrease of air volume.

1.3 Fan selection:

According to the characteristic curve of the fan, it can be seen that the fan can work under various air volumes. At a certain working point of the characteristic curve, the air pressure of the fan is balanced with the pressure in the system, and the air volume of the system is determined.

one point four Fire damper set up:

The main purpose of setting fire damper is to prevent fire spreading through air duct. The author advocates the "backflow prevention" measure of connecting the toilet exhaust branch pipe to the exhaust shaft for 60mm rise, which has the characteristics of simple structure, low cost and reliable operation. Since the elbow is used to enter the shaft, the branch pipe and the main pipe have the same airflow direction, and this part has small local resistance, the total resistance of the shaft exhaust is not necessarily increased due to the reduction of the shaft area.

2、 Coordination with construction specifications:

The current Code for Construction and Acceptance of Ventilation and Air Conditioning Engineering (GB50243-97) (hereinafter referred to as the Construction Code) was issued on October 20, 1997 and started construction on May 1, 1998, which is a mandatory national standard.

Article 8.2.4 of the construction specification stipulates that the exposed part of the driving device of the fan is provided with a protective cover. Century Star introduces that when the air inlet or air inlet pipe of the fan is directly connected to the atmosphere, a protective net or other safety measures should be installed. Some design drawings have not installed protective nets at the air inlets of fans such as positive pressure smoke prevention fans or have not specified what kind of protective nets to install.

3、 Cooperation among disciplines:

(1) The size of the holes that need to be reserved at the places where the ventilation pipe passes through the concrete wall, floor slab, etc. was not provided to the civil engineering discipline in detail and was implemented in the civil engineering drawings, which caused the holes to be drilled during construction, increased unnecessary expenses, and even affected the strength of the civil engineering, especially the embedded work of the ventilation pipe, piezometer pipe, etc. of the civil air defense project will be difficult to remedy if it is not done well;

(2) There are no specific construction requirements for civil air duct. For example, the civil engineering specialty requires that the mortar should be full when laying bricks in the ventilation shaft, and several internal walls of civil engineering should be plastered with cement mortar to ensure that the internal wall of civil air duct is smooth and air tight.

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