How do crossflow fans prevent airflow short-circuiting and truly promote air circulation?
Publish Time: 2025-12-15
In modern elevator design, the elevator car, as a confined and narrow vertical transportation space, is prone to causing discomfort such as stuffiness and dizziness for passengers when fully loaded due to air stagnation and increased carbon dioxide concentration. To ensure passenger comfort and health safety, crossflow fans are widely installed on the top of the car to continuously introduce fresh outside air and promote internal airflow. However, if poorly designed, the fresh air drawn in by the fan may escape directly from the exhaust vent without sufficient mixing, creating an "airflow short-circuit" and resulting in low ventilation efficiency.1. Causes of Airflow Short-Circuiting: Shortest Path ≠ Best EffectAirflow short-circuiting refers to the rapid exhaust of fresh air along the path of least resistance before it has fully diffused throughout the entire car space. In the enclosed environment of an elevator car with a large height-to-width ratio and few internal obstacles, if the air inlet and outlet are too close together, or if the fan's airflow direction is directly opposite the exhaust vent, a "through-draft" short-circuit can easily form. At this time, although the fan continues to operate, the air in most areas remains stagnant, unable to effectively dilute pollutants or regulate temperature and humidity.2. Unique Advantages of Crossflow Fans: Wide and Uniform AirflowThe core feature of crossflow fans lies in their elongated impeller structure and horizontal airflow pattern. When installed at the front or rear edge of the car's top, it delivers a thin, uniform airflow curtain along the width of the car, covering the entire length of the car wall. This "area-like airflow," compared to the "point jet" of axial flow fans, is more likely to adhere to the ceiling, creating a wall-attaching effect and guiding the airflow to slowly diffuse downwards along the ceiling, rather than directly impacting the opposite exhaust vent. Simultaneously, crossflow fans have lower outlet air velocity and lower noise, avoiding the discomfort caused by strong airflow in certain areas, making them more suitable for densely populated public spaces.3. Scientific Layout: Separate Inlet and Exhaust Vents + Optimized Airflow Guiding StructureTo prevent short-circuiting, the system design must adhere to the principle of "separate inlet and exhaust, extended path":The air inlet is located on one side of the car top; the exhaust vents are arranged at the bottom or far end of the top on the opposite side, forcing airflow through the entire car space; a guide plate or rectifier grille is installed on the inner side of the car top to further disperse the concentrated airflow and promote lateral diffusion; some high-end elevators also have micro-perforated return air channels in the car walls, forming a three-dimensional circulation path of "top supply and bottom return" or "side supply and side return." This layout significantly extends the residence time of air in the car and improves ventilation efficiency. Actual measurements show that a well-designed crossflow ventilation system can reduce the CO₂ concentration in a fully loaded car to a comfortable level within 3–5 minutes.4. Intelligent Control: On-Demand Adjustment, Dynamically Matching LoadThe crossflow fan also integrates a CO₂ sensor or a passenger recognition module to achieve intelligent start/stop and airflow adjustment. For example, it operates at low speed to maintain basic ventilation when unloaded; automatically increases airflow after multiple people are detected entering; and enhances ventilation during long stops. This on-demand air supply strategy avoids unnecessary energy consumption while ensuring air quality during peak hours.The value of crossflow fans in elevator ventilation lies not only in providing airflow, but also in ensuring that the airflow is directed correctly. Through its wide-range airflow characteristics, scientific intake and exhaust layout, and intelligent control logic, it effectively avoids airflow short-circuiting, creating a gentle and uniform air circulation system covering the entire cabin. In today's world, where people are increasingly concerned about indoor air quality, this "invisible breathing system" is silently safeguarding every safe and comfortable elevator ride.
