# Hydraulic Diameter

1.
General formula

2. Formula for rectangular duct

3. Formula for annular flow

## 1. Calculation of hydraulic diameter

Hydraulic diameter is used for non-circular flow

D_{H}=Hydraulic Diameter

## 2. Hydraulic diameter for rectangular duct

Hydraulic Diameter in rectangular
pipe

e=Height of the flow section (m)

l=Width of the flow section (m)

## 3. Hydraulic diameter for annular flow

Hydraulic Diameter in annular flow

R=Outside diameter of the tube (m)

K=R_{inside}/R

R_{inside}=Inside diameter of the tube (m)

**Source**
Mecanique et Rheologie des fluides en genie chimique, Noel Midoux,
Lavoisier Tec et Doc, page 197