What are the key points in the design of VAV variable air volume systems for hotel public areas? Terminal unit selection and noise control
I am an HVAC expert. The design of VAV variable air volume systems in hotel public areas is a key part of ensuring indoor comfort and energy efficiency. Especially for high-end hotels, the precision of air volume regulation, noise control, and coordination with interior finishes directly affect the guest experience. The following analysis combines standards and engineering practice and covers three aspects: design key points, terminal unit selection, and noise control.
I. Design Key Points
1. System zoning and load matching
According to Article 7.3.2 of the Code for Design of Heating Ventilation and Air Conditioning of Civil Buildings (GB 50736-2012), VAV systems should reasonably divide air-conditioning zones to avoid terminal regulation failure caused by excessive load differences. In hotel public areas (such as the lobby, restaurant, and ballroom), occupant density and sensible/latent load variations are significant. An "interior/exterior zoning" strategy is recommended: interior zones (such as corridors and atriums) are dominated by sensible load, while exterior zones (near windows) need to account for envelope heat transfer.
*Practical case*: In the lobby of a five-star hotel, because interior and exterior zones were not separated, the terminal dampers near the windows frequently adjusted in summer due to solar radiation, causing excessive noise. This was later solved by adding an independent supply air branch.
2. Minimum outdoor air assurance
According to Article 3.0.6 of GB 50736-2012, VAV systems need a separate outdoor air handling unit (PAU) to ensure that the outdoor air volume in transitional seasons or at low load is not lower than hygiene requirements (generally 30 m³/h per person). Outdoor air should preferably use constant air volume or two-speed control to avoid negative pressure caused by closing the return air damper.
*Engineering experience*: It is recommended to install a CO₂ concentration sensor at the PAU outlet and link it to adjust the outdoor air damper opening, balancing energy savings and air quality.
3. Duct design
The main duct air velocity should preferably be 6-8 m/s (refer to Article 6.3.1 of the Code for Acceptance of Construction Quality of Ventilation and Air Conditioning Works GB 50243-2016), and branch ducts should be reduced to 4-5 m/s to reduce resistance and noise. Terminal branch ducts need a static pressure box with a length of not less than 1.5 m, and acoustic elbows should be used.
II. Terminal Unit Selection
1. Type selection
- Single-duct type (S-VAV) : Suitable for areas with stable loads (such as meeting rooms), with high cost-effectiveness.
- Series fan-powered box (FPB) : Suitable for large spaces such as lobbies and ballrooms. The built-in fan ensures supply air volume at low load, but attention should be paid to its energy consumption (refer to Article 4.2.8 of the Design Standard for Energy Efficiency of Public Buildings GB 50189-2015).
2. Selection parameters
- Air volume range: Select according to 80% of the maximum load, reserving 10% margin.
- Pressure drop control: When the terminal unit is fully open, the pressure drop should be ≤50 Pa to avoid excessive system energy consumption.
- Material: The casing should use galvanized steel sheet (thickness ≥1.2 mm), lined with 25 mm thick centrifugal glass wool (density ≥32 kg/m³), balancing insulation and sound absorption.
III. Noise Control
1. Code requirements
According to Article 6.2.1 of the Code for Sound Insulation Design of Civil Buildings (GB 50118-2010), the noise limits for hotel guest rooms, restaurants, and other areas are: ≤35 dB(A) at night and ≤40 dB(A) during the day. The noise of the terminal unit itself should be ≤25 dB(A) (at 1 m from the air outlet).
2. Noise reduction measures
- Terminal selection: Give priority to low-noise models (such as FPBs with silencers), and the fan speed should preferably be <800 rpm.
- Airflow organization: Air outlet velocity should be controlled at 2-3 m/s (diffusers), and side supply outlets ≤2.5 m/s.
- Duct silencing: Install silencers every 15 m on main ducts, and use acoustic flexible ducts (length ≥1 m) for terminal branch ducts.
Summary
The design of VAV systems in hotel public areas needs to focus on zoning rationality, terminal selection matching, and noise limit control. Terminal selection should choose FPB or S-VAV based on load characteristics and ensure that pressure drop and noise parameters meet requirements. Noise control needs to address both the source (fans, dampers) and the transmission path (silencers, air velocity). The above are reference opinions. The actual project situation still needs further comprehensive evaluation and implementation in combination with specific operating conditions, site conditions, and other factors.