Question

QUESTION 3 Water at a temperature of 60°C flows through a pipe of diameter 90 mm at a rate of 40 L/s. a) b) Determine the Reynolds number for this flow rate. What is the maximum flow rate at which laminar flow would be ensured?

Answer 1

Reynolds number is the ratio between the inertial forces in the fluid and the viscous forces. for water in a pipe it can be reduced to -

r Duct a pipe eymold Numbe for ud Re a vebutg d diameler of pipe mêtre). v nemaie vescosty here Q= Aale of fow (m/s) putfug (8) u (A) Pe = d v Q=flow ralefu m/s) 40 K 10 m/s d 0.090 m we know at vis cosiy Ps a of emperature, at 40c fuu diau of V waler O-662 x10 /s at 60c O475 X10 V of waler

Now, using this in equation c we can calculate-

R_e = $\frac{4\times 0.040 \times 10^{6}}{3.14\times 0.09\times 0.475 }$

= 1.194 X 10⁶

^(b) flow in the pipe is laminar when Reynolds value is less than 2100.

so, using this value in equation (c) we can find out the rate flow at which flow is leminar

2100 = 4 X Q / 3.14 x 0.09 x 0.475 x 10^-6

Q = 2100 x 3.14 x 0.09 x 0.475 x 10^-6 / 4

      = 70.4 x 10^-6 m³/s