In order to reduce building energy consumption and improve the air quality inside buildings, ventilation engineering must be done well. Some ventilation strategies and construction requirements are listed below, which can provide reference for similar projects. First, let's look at the ventilation mode.
1、 Ventilation mode
1. Enhanced ventilation based on wind pressure
Although this ventilation strategy can not reduce the indoor temperature below the outdoor temperature, it can also be classified as a cooling strategy because it can take away the indoor heat load to cool the human body, thus making the indoor thermal environment meet the requirements of human thermal comfort. Enhanced ventilation can be realized based on wind pressure, heat pressure and temperature difference in the morning and evening. It is mainly applicable to severe cold areas, cold areas in summer and transitional seasons.
(1) Architectural form design strategy
For wind pressure ventilation, generally speaking, the larger the shape coefficient is, the better the ventilation effect is, and the better the cooling effect is in summer. However, the larger the shape coefficient is, the greater the heat loss is, which is adverse to the thermal insulation in winter. Therefore, the shape coefficient of buildings should be determined according to the climate characteristics of different regions.
(2) Design strategy of building air outlet
In order to obtain good ventilation, the air inlet should be set within the range of 0.5~1.5m above the indoor floor. Because the hot air density is small, it is easy to gather in the indoor high altitude, so the air inlet should be low and high. It is verified by experiments that when the window wall ratio reaches 40%, increasing the window area has little effect on the wind speed, and small air inlets with large air outlets are conducive to improving the wind speed.
(3) Design strategy of building wind guidance measures
For example, the misplaced wall, funnel shaped entrance and other reasonable architectural design can play a good role in wind guidance. If the building itself cannot do BIM to wind guidance, the wind deflector can be used to change the air flow at the entrance, and the wind can be introduced into the room to enhance the wind pressure and ventilation effect. In addition, reasonable installation and layout of sun visors, louvers and outdoor plants can play a good role in wind guidance.
2. Pre cooled ventilation
When the temperature rises in summer, even the wind from the electric fan is hot in some areas. This strategy can reduce the ventilation temperature below the outdoor temperature. Pre cooling ventilation can be realized based on cooling storage cavity ventilation, underground cavity ventilation and evaporative cooling ventilation, and is mainly applicable to summer and transition seasons in hot summer and cold winter areas and hot summer and warm winter areas.
(1) Cooling storage chamber ventilation
In order to realize the ventilation and cooling of the cold storage chamber, there are three necessary conditions: ventilation chamber, cold storage chamber and night ventilation. The ventilation chamber can be a double roof, a double skin, a closed concave balcony or a patio or an external room. The low sky temperature at night is a natural cold source, which can cool and store the cold storage body. The cold storage body can provide a cold wind environment for the room during the day. In addition, if the ventilation chamber is fully in contact with the soil, the heat storage of the soil can also play a cooling role, such as patios and cold lanes.
(2) Underground cavity ventilation
The temperature of the soil fluctuates slightly, and the temperature is basically constant below 9m underground. The soil can also be used as a natural cold source. When the air inlet pipe is buried to a certain depth underground, the cooling of the pipe wall through which outdoor hot air can pass is introduced indoors, which can have the effect of ventilation and cooling. Generally, the air inlet is set on the windward side to obtain positive pressure, and the air outlet is set on the leeward side to obtain negative pressure. It should be noted that the air flow speed should be controlled for tunnel ventilation. If the wind speed is too fast, it can not achieve good cooling effect. Moreover, tunnel ventilation will be limited by land, with large investment, and mechanical equipment is required for auxiliary ventilation.
(3) Evaporation cooling ventilation
Water evaporation can take away a lot of heat, and this principle can be used to achieve the purpose of cooling. According to the data, the temperature is 25 ℃, the air pressure is 100kPa, the heat required for each 1 ℃ increase in water temperature is 4MJ/kg, and the latent heat of evaporation can reach 2200MJ/kg. Evaporating 1L of water can reduce the temperature of a medium-sized apartment by 10 ℃. The pond in the courtyard and the water curtain on the facade all use evaporative cooling ventilation.
2、 Key points of ventilation construction
1. Installation of refrigeration equipment and auxiliary refrigeration equipment
(1) The models, specifications and technical parameters of refrigeration equipment and auxiliary refrigeration equipment must meet the design requirements, and have product quality certificates and product performance test reports; The installation shall refer to the relevant installation data and drawings provided by the supplier.
(2) The concrete foundation of equipment must be subject to quality handover and acceptance, and can be installed only after it is qualified.
(3) The equipment installation position, elevation and nozzle direction must meet the design requirements. For refrigeration equipment or auxiliary refrigeration equipment fixed with anchor bolts, the sizing block shall be placed correctly and contacted closely; The bolts must be tightened and prevented from loosening.
(4) The allowable deviation of the longitudinal and transverse levelness of the overall installed refrigeration unit is 1/1000, and shall comply with the provisions of the equipment technical documents.
(5) The allowable deviation of levelness or perpendicularity for the installation of auxiliary refrigeration equipment shall be 1/1000, and shall comply with the provisions of equipment technical documents.
(6) For refrigeration equipment or refrigeration auxiliary equipment with vibration isolation measures, the installation position of vibration isolator shall be correct, the compression amount of each vibration isolator shall be uniform, and the deviation shall not be greater than 2mm.
2. Fan installation
(1) When fixing the fan foundation, the elevation and levelness of the foundation shall be corrected first to ensure that the compression amount of each group of vibration isolators bearing the load is uniform. After the vibration isolator is installed, protective measures such as displacement and overload prevention shall be taken, and the dimensions of each part shall meet the design requirements.
(2) The inlet and outlet pipes of the fan shall be equipped with 150~250mm long flexible joints, which shall be connected with the air duct by flange.
(3) When the fan is suspended and installed, the vibration isolation support and hanger used must be firmly installed. Knots of vibration isolation supports and hangers? The structural form and overall dimensions shall comply with the design requirements or the provisions of the equipment technical documents. The welding of vibration isolation supports and hangers shall be carried out in accordance with the relevant provisions of the current national standards, and the rectification shall be completed after welding.
(4) The installation direction and impeller rotation direction must be correct when installing the fan. The levelness, elevation and coupling concentricity of the installation meet the specification requirements.
(5) The fan installed in the middle of the pipe must be equipped with special supports and hangers, and the reducing duct connected to the fan shall be installed after the fan is in place and leveled.
3. Air duct installation
(1) When installing air ducts and components, such as through walls, floors and roofs, holes shall be reserved. The size and position shall meet the design requirements, and the flange shall not be set in the wall opening.
(2) When connecting the air duct flange, appropriate flange gasket shall be applied: the sealing gasket between air duct and air duct, and between air duct and fan of general air system shall be asbestos free environmental friendly gasket; The air duct of smoke exhaust system shall be temperature resistant? 280 ℃/h asbestos free environment-friendly gaskets, with a thickness of 3~5mm. The padding shall be flush with the flange and shall not protrude into the pipe.
(3) The connecting bolts of the air duct flange shall be tightened evenly to prevent air leakage caused by unevenness. Screws and nuts connecting flanges shall be on the same side (refer to the whole air duct). The flange of the air duct riser shall be threaded from top to bottom with the screw facing down to protect the thread from being damaged by cement mortar.
(4) After the air duct elevation is determined, the support, hanger and other forms shall be determined according to the space location of the air duct system. The fabrication of air duct supports and hangers shall be strictly in accordance with the national standard 03K132 material BIM building specifications and practices.
(5) Fabrication, setting and spacing of supports and hangers.
4. Muffler installation
(1) Installation of tubular muffler and muffler elbow: support and hanger shall be set separately, and its weight shall not be borne by air duct; Before installation, the quality of the muffler should be spot checked, with a sampling rate of 10%. The installation position and direction should be correct, and the connection between the muffler and the air duct should be closely connected.
(2) Installation of sheet muffler with metal shell: check the flatness of the wall plate of the metal shell before installation, and correct if there is any deformation. Prepare the process card, and determine the assembly sequence as follows: first connect the four wall panels, then install the silencer. The installation sequence of the silencer is to install the walls on both sides first, and then install one by one from one end. Heat resistant rubber plate shall be laid at the connection between the silencing plate and the upper and lower wall plates of the metal shell, and the distance between the silencing plates shall meet the requirements.
5. Installation of combined air valve
The structure of the combined air valve is mainly composed of single air valve, bottom frame, transmission mechanism, actuator, electric cabinet and other components. When the combined air valve is used, due to the large size of the equipment, if the site hoisting and transportation conditions may not be met, it needs to be disassembled and shipped after the equipment supplier's factory assembly and testing. Each combined air valve is disassembled into a row or rows of frame units, single air valve, actuator, connecting transmission parts, control box and other parts. The splicing and installation of arrived bulk parts shall be completed by the electromechanical contractor, and the equipment supplier shall be responsible for on-site guidance.
