Diverging Section

The diverging section is a component of a Venturi nozzle, positioned downstream of the throat. It features a conical or gradually expanding geometry that increases the cross-sectional area in the direction of flow. Its primary function is to decelerate the fluid that has been accelerated through the converging section and throat, converting kinetic energy back into pressure energy—a process known as pressure recovery. This section is critical for minimizing energy losses and ensuring efficient operation in applications such as flow measurement, mixing, or spray systems.

In flow measurement, the pressure difference between the upstream and throat sections is used to determine flow rate, and the diverging section helps restore pressure to reduce overall system energy loss. In mixing or spray systems, the controlled deceleration can influence droplet size or mixing quality. The design of the diverging section must balance pressure recovery against frictional losses; a larger divergence angle increases losses, while a smaller angle requires a longer section.

Typical parameters for this component include inlet diameter (25–200 mm), outlet diameter (50–400 mm), divergence angle (5–15°), length (100–800 mm), wall thickness (3–20 mm), surface roughness (0.8–3.2 μm Ra), operating pressure (1.0–1.6 MPa), operating temperature (-40–85 °C), material grade (304/316L), and weight (5–50 kg). These values are reference ranges and must be confirmed for the specific model and application. Common materials include stainless steel, carbon steel, aluminum, and plastics such as PVC or PTFE.

Standards such as ISO 5167, ASME B16.34, ISO 1302, and ASTM A240 may be referenced for design, dimensions, surface finish, pressure-temperature ratings, or material specifications. However, listing a standard does not imply certification or compliance; verification with the legal manufacturer or supplier is required.

The diverging section operates on the Bernoulli principle and conservation of mass. As the flow area increases, the fluid velocity decreases. According to Bernoulli's equation, this decrease in velocity results in an increase in static pressure, recovering a portion of the pressure dropped in the converging section and throat. The efficiency of pressure recovery depends on the divergence angle and the length of the section; a gradual expansion minimizes turbulence and energy losses.