Which of the following statements is true for an adiabatic, reversible, steady-state compressor? Assume “the system” is defined as the fluid inside the compressor.
A. The efficiency of the reversible compressor can be calculated as a function of the inlet temperature (TC) and outlet temperature (TH).
B. The change in entropy for the system, the surroundings, and the universe are all zero.
C. The process described is impossible because heat must be rejected to a TC reservoir, which means the system cannot be adiabatic.
D. The process description results in -1 degrees of freedom, so the system is impossible.
E. None of the above is true.
A. Incorrect. This is true of a Carnot cycle where the temperatures are those of the heat sources and sinks, not material flows.
B. Correct. Because the system is reversible, no entropy is generated. Because the system is adiabatic, the Q/T term is 0. Steady-state means the time differential disappears. The entropy balance simplifies to Sin = Sout.
C. Incorrect. A compressor does not reject or accept heat (you are thinking of a heat engine). It DOES take an inlet stream at a certain temperature and specific entropy and produce an outlet stream with another, possibly different, temperature and specific entropy.
D. Incorrect. Degrees of freedom, as calculated using the Gibbs phase rule, refer to intensive properties. Here no intensive properties are specified, or even named.
E. Incorrect. One of these statements is true.
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You built a rectangular deck 14 ft long and 12 ft wide with a set of steps 48 inches wide. You builta railing on the outside using 2X4s around the top, capped with a 6-in deck board. The spindles were spaced on 4-inch or less centers. You built a rectangular patio 14 feet by 16 feet, using 4 inches of concrete for the floor. For the patio you removed 7 inches of dirt and replaced it with 3 inches of sand. To prevent erosion you constructed a 400-square-foot retaining wall. You used stones 15 inches wide, 6 inches high, and 10 inches deep. You are also a groundskeeper for an 18-hole golf course. The greens average 92 feet in diameter on which you applied 5 pounds per 1,000 square feet of 18-5-12 units of fertilizer. The fertilizer comes in 50-pound bags at $32.98 per bag.
a. How many square feet are in the deck? b. How many deck boards are needed for the floor running the length of the deck? c. How many of what length 2X4s and deck boards are needed for the railing? d. Approximately how many spindles are needed? e. What is the area of the patio? f. How many cubic feet of dirt were removed? g. How many cubic feet of sand are needed? h. How many cubic yards of concrete are needed? i. How many stones are needed for the retaining wall? j. What did it cost to fertilize the greens?
The efficiency of a Carnot cycle operation between the same temperature limits as the diesel cycle above is nearest:
The pressure and temperature at the inlet to an ideal diesel cycle, with P-v diagram shown, are 100 kPa and 10ºC. It has a compression ratio of 18 and a cut-off ratio of 2. The maximum temperature in the cycle is 1400ºC. Assume constant
specific heats from Table below for all calculations.
A) 87%
B) 85%
C) 83%
D) 81%
The main purpose of dairy cattle is to produce _____
a. leather c. milk b. meat d. all answers are correct
Soils that are compacted during construction should be ____ before replanting to provide a better base for new plants, allow for better drainage, and reduce runoff.
A. fertilized B. aerated C. amended D. allowed to revitalize for six months