Thermodynamics Flashcards
(20 cards)
A gas turbine cycle consisting of two adiabatic steps and two isobaric steps.
A. Brayton cycle B. Sterling cycle C. Rankine cycle D. Otto cycle
A. Brayton cycle
For any closed system formed initially from given masses of prescribed chemical species, the equilibrium state is completely determined
by any two properties of the system, provided only that these two properties are independently variable at the equilibrium state.
A. Phase rule B. Lewis-Randall rule C. Duhem’s Theorem D. Henry’s Law
C. Duhem’s Theorem
A device substantially without moving parts, in which a fuel, such as hydrogen, natural gas, methanol, propane, can be converted directly
into twice the quantity of electrical energy that would result from the usual boiler-turbine-generator combination.
A. fuel cell B. steam power plant C. geothermal plant D. heat engine
A. fuel cell
The dew point of air indicates
A. the actual temperature of air
B. the temperature at which its volume per unit weight of dry air is calculate
C. the temperature at which its enthalpy is calculated
D. the temperature at which its water content will start to condense
D. the temperature at which its water content will start to condense
One ton of refrigeration capacity is equivalent to
A. 50 k cal/hr B. 200 BTU/hr C. 200 BTU/minute D. 200 BTU/day
C. 200 BTU/minute
At the exit of a nozzle:
A. pressure is high and velocity is low
B. both pressure and velocity are high
C. pressure is low and velocity is high
D. both pressure and velocity are low
C. pressure is low and velocity is high
The entropy change of any system and its surroundings, considered together, resulting from any real process is positive and approaches
a limiting value ___ for any process that approaches reversibility.
A. unity B. zero C. infinity D. less than 1
B. zero
The Buckingham Pi-theorem is applied to
A. pressure-velocity relationship in compressible fluid flow
B. heat transfer by natural convection
C. dimensional analysis of a physical system
D. the stability of a control system
C. dimensional analysis of a physical system
The temperature at which the moisture in humid air exerts a partial pressure equal to its vapor pressure is the
A. dry bulb temperature B. ambient temperature C. critical temperature D. dew point
D. dew point
For a monoatomic ideal gas, calculate the difference in entropy change at constant pressure and constant volume suffered by 3 moles of
the gas on being heated from 300 K to 600 K.
A. 4.13 eu B. 6.20 eu C. 10.33 eu D. 12.02 eu
B. 6.20 eu
Assuming CO2 to be an ideal gas, calculate the work done by 10 grams of the gas in expanding isothermally and reversibly from a volume
of 5 L to 10 L at 27oC.
A. 26.4 cal B. 38.1 cal C. 49.7 cal D. 93.9 cal
D. 93.9 cal
Ten lb. of water at 14.7 psia is heated at constant pressure from 40o
F to saturated vapor. Compute the entropy change.
A. 16.4 Btu/R B. 17.4 Btu/R C. 18.0 Btu/R D. 18.4 Btu/R
B. 17.4 Btu/R
A turbine uses 100,000 lbm/hr of steam that enters with an enthalpy of 1400 BTU/lbm and essentially zero entrance velocity 10,000 hp
developed. The exit velocity of the steam is 500 ft/sec. expansion is adiabatic. What is the exit enthalpy?
A. 1100.2 BTU/lb B. 1110.0 BTU/lb C. 1140.5 BTU/lb D. 1160.4 BTU/lb
C. 1140.5 BTU/lb
A 10% NaOH solution at 70o
F is mixed with a 70 NaOH solution at 200o
F to form a solution containing 40% NaOH. If the mixing is done
adiabatically, what will be the final temperature of the solution?
A. 180 oF
B. 200 oF
C. 220 oF
D. 240 oF
C. 220 oF
A refrigerator is rated at COP of 4. The refrigerated space that it cools requires a peak cooling rate of 30,000 kJ/hr. what size electrical
motor (rated in horsepower) is required for the refrigerator.
A. 3.45 Hp B. 1.67 Hp C. 2.79 Hp D. 3.90 Hp
C. 2.79 Hp
A Carnot engine operates between two temperature reservoirs maintained at 200oC and 20oC, respectively. If the desired output of the
engine is 15 Kw, determine the heat transfer from the high
A. 39.42 kW B. 24.42 kW C. 29.21 kW D. 33.50 kW
A. 39.42 kW
What is the efficiency of an Otto cycle with a compression ratio 6:1. The gas used is air.
A. 0.167 B. 0.191 C. 0.488 D. 0.512
D. 0.512
Superheated steam at 200 psia and 50o
F superheat expands adiabatically and reversibly to 14.7 psia. Calculate the final enthalpy.
A. 1032 Btu/lb B. 1120 Btu/lb C. 1250 Btu/lb D. 1305 Btu/lb
A. 1032 Btu/lb
An air-lift pump is used for raising 0.8 L/s of a liquid of density 1200 kg/m3
to a height of 20 m. air is available at 450 kPa. If the efficiency
of the pump is 30%, calculate the power requirement, assuming isentropic compression of the air.
A. 792 W B. 1400 W C. 2345 W D. 3210 W
A. 792 W
Calculate the ideal available energy produced by the discharge to atmosphere through a nozzle of air stored in a cylinder of capacity 0.1
m3 at a pressure of 5 MN/m2
. The initial temperature of the air is 290K and the ratio of the specific heats is 1:4.
A. 840 kJ B. 1050 kJ C. 1200 kJ D. 740 kJ
A. 840 k
