Water at 288.7 k flows through a 15.24-cm. diameter horizontal pipe into a 190-l drum. determine the minimum time it will take to fill the drum if the flow remains laminar.

Respuesta :

The flow will be laminar if Reynold's number[tex] N_{R} [/tex] is less than 2000.

Use the Reynold's formula and rearrange to calculate velocity of water in the pipe.

[tex] N_{R} = \frac{v D}{\nu} [/tex]

Where, [tex] v [/tex] is velocity of the fluid, [tex] D [/tex] is the diameter of pipe, and [tex] \nu [/tex] is the kinematic viscosity i.e. [tex] 1.12 \times 10^{-6} m^2/s [/tex] for water at 288.7 K from Appendix.

So, velocity is:

[tex] v = \frac{N_{R} \nu}{D} [/tex]

The flow rate Q:

[tex] Q = vA=v\pi D^2/4=\frac{\frac{N_R \nu}{D} \pi D^2}{4} =[tex] t = \frac{V}{\frac{N_R \nu \pi D}{4}} = \frac{4V}{N_R \nu \pi D} =\frac{4 \times 190 L\frac{10^{-3} m^3}{L}}{2000 \times 1.12\times 10^{-6} m^2/s \pi 15.24 cm\frac{1 m}{100 cm}} = 2226.3 s \frac{1 min}{60 s}= 37.1 min [/tex] [/tex]

Where A is the area of cross section of pipe.

The time taken to fill is:

[tex] t = Q/V [/tex]

Where V is the capacity of the tank.