An orifice of 20 mm diameter provided in a bottom most side of tank of...
Volume of liquid leaving the tank = Volume of liquid flowing through orifice in time dt
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An orifice of 20 mm diameter provided in a bottom most side of tank of...
Given Information:
- Diameter of the orifice = 20 mm
- Cross-sectional area of the tank = 0.25 m^2
- Initial liquid level in the tank = 1.5 m
- Final liquid level in the tank = 0.5 m
- Coefficient of discharge = 0.6
To find:
Time taken for the liquid surface in the tank to fall from 1.5 m to 0.5 m.
Assumptions:
- The orifice is a small orifice, so the velocity of the liquid flow through the orifice can be considered constant.
- The head loss due to friction in the orifice is neglected.
- The flow through the orifice is steady and incompressible.
Solution:
Step 1: Calculate the velocity of the liquid flow through the orifice.
- The cross-sectional area of the orifice can be calculated using the formula:
A = πr^2, where r is the radius of the orifice.
- Given that the diameter of the orifice is 20 mm, the radius can be calculated as:
r = 20 mm / 2 = 10 mm = 0.01 m
- Substituting the value of r in the formula, we get:
A = π(0.01)^2 = 0.000314 m^2
- The velocity of the liquid flow through the orifice can be calculated using the formula:
Q = Av, where Q is the flow rate, A is the cross-sectional area, and v is the velocity.
- Rearranging the formula, we get:
v = Q / A
- The flow rate Q can be calculated using the formula:
Q = CdA√(2gh), where Cd is the coefficient of discharge, A is the cross-sectional area, g is the acceleration due to gravity, and h is the head.
- Given that Cd = 0.6, A = 0.000314 m^2, g = 9.81 m/s^2, and h = 1.5 m, the flow rate Q can be calculated as:
Q = 0.6 * 0.000314 * √(2 * 9.81 * 1.5) = 0.00682 m^3/s
- Substituting the values of Q and A in the formula for velocity, we get:
v = 0.00682 / 0.000314 = 21.74 m/s
Step 2: Calculate the time taken for the liquid surface to fall from 1.5 m to 0.5 m.
- The distance traveled by the liquid surface can be calculated as the difference between the initial and final liquid levels:
Distance = 1.5 m - 0.5 m = 1 m
- The time taken can be calculated using the formula:
Time = Distance / Velocity
- Substituting the values of Distance and Velocity, we get:
Time = 1 m / 21.74 m/s = 0.0459 s
- Converting the time from seconds to minutes, we get:
Time = 0.0459 s * 60 = 2.754 min