A pressurized water tank is used as a source of water for a fire hose. The pressure of the air in the top of the tank is 20 atm gauge. To be effective, the minimum exit velocity of the water from the hose has to be at least 20 m/s. The water supply pipe and hose consist of 10 metres of 50 mm inside-diameter pipe and hose. The average roughness height inside the pipe and hose is 0.05 mm. The system contains one 90° elbow and one flow control valve. The valve's K vs Closure % calibration curve is provided in Figure.
(a) State any assumptions related with this problem.
(b) Evaluate the valve closure (in %) to achieve a water exit velocity of 20 m/s.
(c) Evaluate the exit velocity when the valve is fully open.
The properties of water are: ρ = 1000 kg/m3 and µ = 1.00 x 10-3 N.s/m2.
