Chemical Engineering License Review, Second Edition
This text contains 146 problems with detailed step-by-step solutions, and is an ideal study guide and the first truly practical, no-nonsense review for the difficult PE Exam.
TABLE OF CONTENTS Chemical Engineering License Review, Second Edition
Bernoulli's Theorem
Applying the principle of conservation of energy (first law of thermodynamics) to a flowing fluid (Fig. 2-4), the following Bernoulli equation is obtained for the steady flow of a fluid:
| where u A, u B | = velocities of fluid, ft/s, at A and B, respectively |
| Z A, Z B | = liquid heights at A and B with respect to a datum plane, ft |
| P A, P B | = pressures at A and B, lbf/ft 2 |
| ? A, ? B | = densities of fluids at A and B, lb/ft 3 |
| u 2/2 g c | = kinetic head, ft lbf/lb |
| F | = energy loss due to friction, ft lbf/lb |
| W | = work done by the pump on the fluid ft lbf/lb |
Figure 2-4: Illustration for the Bernoulli equation.
The various terms in the Bernoulli equation must be expressed in the same units as energy (ft lbf/lb). Normally g/ g c ? 1, and therefore g/ g c can be dropped from the terms containing Z.
Example 2-1
A shown in Fig. 2-5, water flows through the pipe. If the contraction loss is half a velocity head based on the velocity at B, calculate the velocity in feet per second and diameter in inches at B. Neglect the pressure drop due to friction.
Figure 2-5: Data illustration for Example 2-1.
Solution. Apply the Bernoulli equation between the...
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