Benzene at atmospheric pressure and 41°C is in a tank with a fluid level of 15 ft above a pump. The pump provides a pressure increase of 50 psi to a destination 25 ft above the tank fluid level. The suction line to the pump has a length of 20 ft and is 2-in, schedule-40. The discharge line has a length of 40 ft to the destination and is 1.5-in, schedule-40. The flowrate of benzene is 9.9 lb/sec.

Derive an expression for the NPSH in head units (ft of liquid) vs. flowrate in ft /s.

Derive an expression for the system curve in head units (ft of liquid) vs. flowrate in ft /s.

Locate the operating point on both plots on Figure P19.70.

What is the maximum flowrate before cavitation becomes a problem?

What is the pressure drop across the valve at the operating point?

What is the maximum flowrate possible with one pump, two pumps in series, and two pumps in parallel?

Data:

Transcribed Image Text:

Pressure head across pump, ft of liquid NPSH R, ft of liquid 1600 1400 1200 1000 800 600 400 200 0 50 40 30 20 10 0 0.0 0.0 0.1 0.1 0.2 0.3 Flow of Benzene (at 41°C), ft³/s 0.2 0.3 Flow of Benzene (at 41°C), ft³/s 0.4 0.4 0.5 0.5 0.6