In this part we will calculate Reynolds number for the pipe sizing calculation example. Refer Part-1 for understanding the problem statement and the solution steps.

From the concept of Reynolds number, it can be written that

**Reynolds number (Re) = ρ*s*L/μ ………………………eq.1**

Where,

**ρ – **Density of the fluid

s – Velocity of the fluid

L – Characteristic length

μ – Dynamic viscosity

For our water pipe sizing calculation example, we have the following inputs (refer Part-1):

Fluid used = water

So, density of fluid (**ρ**) = 1000 kg/m^{3}

Dynamic viscosity of fluid (μ) = 0.000894 Pa-S

Assumed flow rate = 0.5 Liter/sec = 0.0005 cubic-meter/sec

Assumed pipe diameter = 20 mm = 0.02 m

So, velocity of the fluid (s) = 0.0005/(π*0.25*0.02*0.02) = 1.591 m/sec

Characteristic length (L) = 0.02 m

By putting all the input values in the **eq.1,** we get

**Re = 35592.84**

**As, the Reynolds number is greater than 4000, so, the flow in our case is of turbulent type.**

The next part (Part-7) will deal with the selection of correct moody friction factor.