Which of the following is NOT one of these assumptions?
19. The equation:
is frequently applied to a valve. Several assumptions are incorporated into the derivation of this equation. Which of the following is NOT one of these assumptions?
A. The system is operating at steady state.
B. The system is adiabatic.
C. The potential energies of the entering and exiting streams are equal to each other.
D. The system is at constant, uniform pressure throughout.
E. All of the above are necessary assumptions for the derivation of this equation.
A. Incorrect. This is assumed resulting in removal of the time dependent or time derivative terms.
B. Incorrect. The equation would contain a Q term if the valve wasn’t assumed adiabatic. Valves are not used to add or remove heat. When there is a significant temperature difference between the fluid and the surroundings, the pipes and valves can be insulated to for safety and to prevent process interference.
C. Incorrect. No height terms are present. Additionally, the valve would have to be extremely large to justify including potential energy terms.
D. Correct. Pressures can be—and probably are—different for the fluid entering the valve than for the fluid leaving. Remember that enthalpy includes pressure in its definition (U + PV)
E. Incorrect. One of these assumptions is not incorporated into the equation.
?
You might also like to view...
Which of the following improper operation is least likely cause exposure to toxic fumes?
A) Flare pilot or burner not lit B) Failure to line up purge gas to flare stack C) Refrigerant leak D) Loss of lubrication on equipment
ASTM specifications classify masonry mortar into Type M, Type S, Type N, and Type O. Which of these types is recommended for use in masonry foundation walls?
What will be an ideal response?
Why is cooperation and coordination so important between the various contractors on a project?
What will be an ideal response?
The term prime mover refers to:
a. the starter used on a diesel engine b. the primary power source for a heavy-duty machine c. the primary piston stroke in a two-stroke engine d. the first component the crankshaft turns