Proper ventilation engineering is essential to reduce building energy consumption and improve indoor air quality. Below, we outline several ventilation strategies and construction guidelines that can serve as a reference for similar projects. Let’s first explore the different ventilation methods.
1. Ventilation Methods
1.1 Enhanced Ventilation Based on Wind Pressure
This strategy, while not capable of lowering indoor temperatures below outdoor levels, is still considered a cooling method. It helps remove indoor heat loads and cools occupants, ensuring thermal comfort. Enhanced ventilation can be driven by wind pressure, thermal pressure, and temperature differences between morning and evening. It is primarily suitable for cold regions, including summer and transitional seasons in these areas.
(1) Architectural Form Design Strategy
Generally, a larger building shape coefficient results in better ventilation and improved summer cooling. However, increased shape coefficients also lead to greater heat loss, which is unfavorable for winter insulation. Therefore, building shape coefficients should be designed according to the climate characteristics of each region.
(2) Design Strategy for Building Air Vents
For optimal ventilation, air inlets should be positioned 0.5 to 1.5 meters above the indoor floor. Since hot air is less dense and tends to accumulate at higher indoor levels, air outlets should be placed high to allow hot air to escape effectively. Experiments show that when the window-to-wall ratio reaches 40%, increasing window area has minimal impact on wind speed. Moreover, smaller air inlets paired with larger air outlets help increase airflow velocity.
(3) Design Strategy for Ventilation Features
Architectural elements such as staggered walls and funnel-shaped entrances can effectively guide airflow. If the building design itself cannot optimize airflow using BIM, air guide plates can be installed at entrances to redirect air indoors, enhancing wind pressure and ventilation. Additionally, proper placement of sun visors, blinds, and outdoor plants can further aid in directing airflow.
1.2 Pre-Cooled Ventilation
During hot summers in certain regions, even the breeze from electric fans can feel warm. Pre-cooled ventilation lowers ventilation temperature below the outdoor air temperature. It can be achieved through cold storage chamber ventilation, underground chamber ventilation, and evaporative cooling ventilation, and is mainly suited for summer and transitional seasons in hot summer/cold winter and hot summer/warm winter zones.
(1) Cold Storage Chamber Ventilation
This method requires three key elements: a ventilation chamber, a cold storage body, and nighttime ventilation. The ventilation chamber can be formed by a double-layered roof or facade, a closed concave balcony, a courtyard, or an external room. The naturally low nighttime sky temperature acts as a cold source, cooling the cold storage body, which then supplies cool air indoors during the day. If the ventilation chamber is in full contact with soil, the soil’s heat storage properties can also aid cooling, as seen in courtyards and shaded alleys.
(2) Underground Cavity Ventilation
Soil temperature fluctuations are minimal below a depth of 9 meters, making it a stable natural cold source. By burying air inlet pipelines underground at this depth, the cooler pipeline walls help reduce the temperature of incoming outdoor air, cooling the indoor environment. Typically, air inlets are placed on the windward side to create positive pressure, while outlets are on the leeward side to generate negative pressure. Airflow speed must be controlled, as high speeds reduce cooling effectiveness. Note that underground ventilation requires significant land and investment, and often mechanical assistance.
(3) Evaporative Cooling and Ventilation
Evaporation absorbs significant heat, making it a useful cooling method. Data shows that at 25°C and 100 kPa pressure, heating water by 1°C requires 4 MJ/kg, while latent heat of evaporation is 2200 MJ/kg. Evaporating just 1 liter of water can reduce the temperature of a medium-sized apartment by 10°C. Features such as courtyard ponds and facade water curtains utilize evaporative cooling ventilation.
2. Key Points for Ventilation System Construction
2.1 Installation of Refrigeration Equipment and Accessories
(1) Refrigeration equipment models, specifications, and technical parameters must meet design requirements and have quality certificates and performance reports. Installation should follow supplier guidelines and drawings.
(2) Equipment foundations must pass quality inspection and acceptance before installation.
(3) Equipment placement, elevation, and pipe orientation must adhere to design standards. Shims used for fixing equipment with anchor bolts should be correctly positioned and tightly secured to prevent loosening.
(4) The allowable tolerance for overall refrigeration unit levelness is 1/1000, complying with equipment technical specifications.
(5) For refrigeration auxiliary equipment, allowable deviations for levelness or verticality are also 1/1000, as per technical documents.
(6) Vibration isolation components must be installed accurately, with uniform compression capacity across isolators, with deviations not exceeding 2 mm.
2.2 Fan Installation
(1) When fixing the fan foundation, calibrate elevation and levelness first to ensure even load distribution across isolators. After installation, apply protective measures to prevent displacement and overload. All dimensions must meet design specifications.
(2) Install soft joints of 150-250 mm length on fan inlet and outlet pipes, using flange connections to the air duct.
(3) Vibration isolation supports and hangers must be securely installed, conforming to design or equipment specifications. Welding must follow national standards, with corrections made post-welding.
(4) Ensure correct fan installation direction and impeller rotation. Coupling levelness, elevation, and concentricity must meet specifications.
(5) Fans installed mid-pipeline require dedicated support hangers. Reducing air ducts connected to fans should be installed after proper positioning and leveling.
2.3 Air Duct Installation
(1) Reserve properly sized and located openings for air ducts passing through walls, floors, or roofs. Flanges should not be placed within wall openings.
(2) Use appropriate flange gaskets: asbestos-free, environmentally friendly gaskets for ordinary air systems; and asbestos-free gaskets rated for 280°C/hour with 3-5 mm thickness for smoke exhaust systems. Gaskets must be flush with flanges and not protrude into ducts.
(3) Tighten flange bolts evenly to prevent air leaks. Bolts and nuts should be placed on the same side along the entire duct. For duct risers, bolts should be threaded top-down to protect threads from damage.
(4) After setting duct elevation, determine support and hanger types based on spatial constraints. Support production must comply with national standard 03K132 and BIM building specifications.
(5) Follow guidelines for the production, installation, and spacing of supports and hangers.
2.4 Muffler Installation
(1) For tube-type mufflers and muffler elbows, install separate supports and hangers; their weight should not be borne by air ducts. Perform random quality inspections on 10% of mufflers before installation. Ensure correct position and direction, and secure connections to air ducts.
(2) For metal shell mufflers, check and correct wall panel flatness before installation. Develop a process card and follow assembly sequence: connect four wall panels first, then install sound-absorbing panels starting with the two side walls, followed by the others sequentially. Place heat-resistant rubber plates at joints between sound-absorbing panels and metal shell walls, marking and positioning them to maintain required spacing.
2.5 Installation of Combination Air Valves
Combination air valves consist of individual air valves, bottom frames, transmission mechanisms, actuators, and electrical control boxes. Due to their size, if on-site lifting and transport are limited, these valves must be disassembled after factory assembly and testing. Components are shipped as frame units, individual valves, actuators, transmission parts, and control boxes. Mechanical and electrical contractors complete assembly on-site, with supplier guidance provided.
Article source: Architectural Technology Magazine
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