5 lbm of saturated water vapor is to be condensed at a constant-pressure of 20 psia in a piston-cylinder device until all the water is a saturated liquid. Determine the work and heat transfer for the process.
Given: Water; m = 5 lbm; P = 20 psia; x1 = 1,0; x2 = 0.0
Assume: ?KE = ?PE = 0
What will be an ideal response?
Solution: The First Law for closed systems reduces to
Q – W = m (u2 – u1)
For a constant pressure process, the moving boundary work is W = P (V2 – V1) = mP(v2 – v1)
For water at 20 psia:
v1 = 20.09 ft3/lbm
u1 = 1082 Btu/lbm
v2 = 0.01683 ft3/lbm
u2 = 196.19 Btu/lbm
So, W = (5 lbm) (20 psia)(144 in2/ft2)(0.01683 - 20.09) ft3/lbm = -289,050 ft-lbf = -371 Btu
Q = -4800 Btu
You might also like to view...
Explain passive and active fire protection.
What will be an ideal response?
Which of the following statements is LEAST-Likely true?
A. Ethylene glycol coolant is mixed with purified water until its concentration is correct. B. When coolant strength has been allowed to become weak or additives are depleted, a coolant flush and change is recommended. C. Draining off a quart of coolant and adding straight coolant can weaken a slightly weak concentration. D. Coolant in too high a concentration can be further diluted with purified water.
What is a vent connector?
A) Vent connector is simply another name for vent. B) The vent connector is the collar on the gas appliance where the vent pipe connects. C) The vent connector is the pipe running from the furnace to the vent. D) A vent connector is used to join two pieces of vent pipe.
How must ammeters be connected in a circuit when used to measure current?
A) Varies with circuit construction B) In series with the component being measured C) Varies with the component being measured D) Directly across the component