An evasé (eee-va-say) is a critical component in industrial fan systems that significantly enhances performance and efficiency. Installed on the fan outlet, it helps improve airflow by providing a natural path for the gas to expand. The evasé connects to the fan outlet at the smaller flange side and gradually expands outward. While the outer edge of the evasé expands at a consistent rate, the inner edge expands more significantly, resulting in a much larger flange at the opposite end.
The Purpose of an Evasé
The natural path of gas as it exits the fan is high velocity at the outer edge of the outlet. This creates a high-velocity vector near the outer housing, while at the bottom of the outlet (assuming a top horizontal outlet), the gas naturally curls. This curling occurs because the airflow follows the direction of the fan wheel’s rotation as it exits. Without an evasé , the flat bottom of the outlet disrupts the natural curling motion, reducing efficiency.
An evasé allows the gas to curl and expand smoothly, stabilizing the flow and improving performance. It is categorized as a static pressure regain device, which helps recover efficiency that would otherwise be lost due to abrupt velocity changes at the fan outlet.
Three Primary Benefits of Using an Evasé
- Reduced Gas Velocity – By lowering the outlet velocity, an evasé enables the gas to achieve a more stable flow pattern. This improves downstream performance and reduces turbulence, resulting in overall system efficiency gains.
- Horsepower Optimization – In applications with limited horsepower capacity, an evasé can be the key to meeting those constraints. For example, if the best efficiency achievable without an evasé requires 153 horsepower, but the system is limited to 150 horsepower, the evasé can regain enough efficiency to bring the horsepower requirement below 150.
- Energy Savings – By improving the overall efficiency of the fan, an evasé reduces the energy consumption required to achieve the same performance. Over time, this translates to lower electricity costs, making it a cost-effective addition to the system when space allows.
When properly integrated, an evasé offers significant performance and efficiency improvements for fan systems. Whether the goal is to reduce outlet velocity, meet horsepower limitations, or lower energy consumption, incorporating an evasé can provide measurable benefits.
For systems requiring optimized performance and efficiency, evaluating the potential of adding an evasé is essential. When designed correctly, it can help meet application requirements while reducing operating costs.
Our application engineers have extensive experience with a wide range of industrial applications. Contact our team today to discuss your project. We can help you select the best fan for your application.