Calculate rectangular opening dimensions, flow rate, average velocity, circular baffle cut geometry, and sump over–under–over heights. These are geometric calculations, not complete thermal, hydraulic or flood-safety designs.

Size a rectangular opening using a specified average velocity. This is a continuity calculation, not a pressure-drop design.

Use a velocity appropriate to your application; no universal design value is assumed.

Related Calculators

Baffle Opening Area & Flow Formula

The following formulas relate baffle opening size (cross-sectional area) to flow rate using a chosen (or specified) design velocity.

A & = W × H\ Q & = A × v = W × H × v

Variables:

  • Q is the volumetric flow rate (m³/s)
  • A is the opening cross-sectional area (m²)
  • W is the baffle opening width (m)
  • H is the baffle opening height (m)
  • v is the average/design velocity through the opening (m/s)

To calculate the opening area, multiply the baffle width by the baffle height (A = W · H). To estimate flow rate through that opening at a given design velocity, use Q = A · v. To solve for W, H, or v, rearrange Q = W · H · v.

What is a Baffle?

A baffle is a flow-directing or obstructing panel used in various engineering applications, such as tanks, reactors, ducts, and heat exchangers. Baffles are used to control flow patterns to promote mixing, heat transfer, or separation. Depending on the application, they can reduce unwanted swirling/vortexing (for example, in tanks) or increase turbulence (for example, in shell-and-tube heat exchangers) to improve performance.

How to Calculate Baffle Size?

The following steps outline how to calculate the Baffle Size.

  1. First, select the opening quantity to solve for: width, height, flow rate or average velocity.
  2. Enter the three displayed known quantities and select their units. Use an appropriate specified average velocity when sizing an opening.
  3. Choose the output unit, then select Calculate.
  4. For circular cut geometry or a sump layout, select that task and enter its displayed dimensions instead.
  5. The opening calculation uses Q = W · H · v and A = W · H. It does not predict pressure drop.
  6. Review the result and calculation details. Sump heights do not include water above the weirs or power-off drain-back; the middle baffle clearance is not its panel height.

Example Problem : 

Use the following variables as an example problem to test your knowledge. Check: Q = W · H · v = 2 · 5 · 1 = 10 m³/s.

Flow Rate (Q) = 10 m³/s

Baffle Width (W) = 2 m

Baffle Height (H) = 5 m
Design Velocity (v) = 1 m/s