Methanol is contained in a large tank under a pressure of 3.1bar absolute. When a valve on the bottom of the tank is opened, the methanol drains freely though a 1-cm ID tube whose outlet is 7.00 m below the surface of the methanol. The pressure at the outlet of the discharge pipe is 1 atm.

(a) Use the Bernoulli equation to estimate the methanol discharge velocity and flow rate in L/min when the discharge valve is fully opened. Neglect the rate of fall of the methanol level in the tank.

(b) When the discharge valve is partially closed, the flow rate decreases, which means that ?u²/2 changes. However, the other two terms in the Bernoulli equation (?p/p and g ?z) remain the same. How do you account for this apparently contradictory result?

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3.5 bar CH₂OH m 7 m