Thermodynamics Ultimate Trivia Quiz!

15 Questions | Total Attempts: 231

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Thermodynamics Ultimate Trivia Quiz! - Quiz

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Questions and Answers
  • 1. 
    A Diesel engine has a compression ratio of 15. If the air drawn into the engine is at 300 K and 100 kPa, what will be the pressure during combustion?
    • A. 

      4400 kPa

    • B. 

      290 kPa

    • C. 

      13,000 kPa

    • D. 

      None of these answers are close (within 100 kPa).

  • 2. 
    A Diesel engine has a compression ratio of 15. If the air drawn into the engine is at 300 K and 100 kPa, what will be the temperature before combustion starts? 
    • A. 

      6050 K

    • B. 

      880 K

    • C. 

      1360 K

    • D. 

      None of these answers are close (within 100 K).

  • 3. 
    In a Diesel engine, the temperature after compression is 1200 K. We then add 800 kJ/kg of energy to the flow during combustion. What is the temperature after combustion?
    • A. 

      The temperature doesn't change during combustion in a diesel engine.

    • B. 

      1800 K

    • C. 

      2300 K

    • D. 

      2000 K

  • 4. 
    In a normal combustion engine (based on an Otto cycle) the temperature after compression is 1200 K. We then add 800 kJ/kg of energy to the flow during combustion. What is the temperature after combustion?
    • A. 

      The temperature doesn't change during combustion in an Otto cycle.

    • B. 

      1800 K

    • C. 

      2300 K

    • D. 

      2000 K

  • 5. 
    What are the SI units of the Universal Gas constant R?
    • A. 

      J / K

    • B. 

      J / kg. K

    • C. 

      J / mol. K

    • D. 

      None of these options is correct.

  • 6. 
    An ideal gas with a density of 3 kg/m3 at 300 K has a pressure of 250 kPa. What is the molar mass (grams / mol) of this gas?
    • A. 

      30 grams / mol

    • B. 

      25 grams / mol

    • C. 

      35 grams / mol

    • D. 

      None of these options is close to the correct answer.

  • 7. 
    Consider the nozzle shown here. Which of the equations below is most correct if the velocity of the flow at 2 is much higher than the velocity at 1?
    • A. 

      This equation

    • B. 

      This equation

    • C. 

      This equation

    • D. 

      This equation

  • 8. 
    Consider the flow mixer as shown, which mixes water of different temperatures. The inflow at A is 10 kg/s at 50 C. The inflow at B is 5 kg/s at 100 C, and the inflow at C is 2 kg/s at 200 C. Compute the exit temperature at D, assuming the flow is completely mixed. Choose the closest answer from the list below.
    • A. 

      82 C

    • B. 

      75 C

    • C. 

      96 C

    • D. 

      115 C

  • 9. 
    Consider the flow mixer as shown, which mixes water of different temperatures. The inflow at A is 10 kg/s at 50 C. The inflow at B is 5 kg/s at 100 C, and the inflow at C is 2 kg/s at 200 C. Assuming the flow is completely mixed, compute the irreversibility. Choose the closest answer from those shown below.
    • A. 

      160 kW

    • B. 

      175 kW

    • C. 

      190 kW

    • D. 

      None of these answers are within 10 kW of the correct solution.

  • 10. 
    For the Rankine cycle shown here, the boiler operates at a pressure of 3 MPa with a maximum temperature of 450 C. The temperature in the condenser is 60 C. Compute the Carnot cycle efficiency.
    • A. 

      0.55 (55%)

    • B. 

      0.5 (50%)

    • C. 

      0.6 (60%)

    • D. 

      0.45 (45%)

  • 11. 
    For the Rankine cycle shown here, the boiler operates at a pressure of 3 MPa with a maximum temperature of 450 C. The temperature in the condenser is 60 C. Compute the thermal efficiency of this Rankine cycle. 
    • A. 

      0.54 (54%)

    • B. 

      0.42 (42 %)

    • C. 

      0.26 (26 %)

    • D. 

      0.32 (32 %)

  • 12. 
    A refrigerator using R-134a as the working fluid has a minimum temperature of -10 C and a maximum pressure of 2 MPa. Assuming an ideal refrigeration cycle as shown in this figure, compute the Coefficient of Performance (COP). (Hint: Compute QL and QH first)
    • A. 

      1.9

    • B. 

      2.0

    • C. 

      1.8

    • D. 

      0.9

  • 13. 
    The back work ratio is the ratio of the power required by the pump (WP) divided by the power created by the turbine (WT). This is much higher for a Brayton cycle than for a Rankine cycle. Select the reasons for this from the list shown below.
    • A. 

      Liquids are easier to pump than gases are to compress.

    • B. 

      Because steam contains more energy than air for any given temperature and pressure.

    • C. 

      Because the specific heat capacity of water is higher than that of air.

    • D. 

      The difference between the specific volume of the working fluid in the turbine and pump is much greater for a Rankine cycle. For a Brayton cycle, the difference is much smaller.

  • 14. 
    Consider the T-s diagram shown for a power producing cycle. Which type of power cycle is this?
    • A. 

      Brayton Cycle

    • B. 

      Otto Cycle

    • C. 

      Air Propulsion Cycle

    • D. 

      There is not enough information to choose one option.

  • 15. 
    Consider the standard (ideal air) jet propulsion device shown. The pressure and temperature entering the jet are 90 kPa, 290 K. The compression ratio is 14 to 1 (i.e. 14:1) and the temperature after combustion is 1500 K. Compute the velocity of the air leaving the nozzle assuming that the pressure at the nozzle exit is 90 kPa.
    • A. 

      970 m/s

    • B. 

      340 m/s (the speed of sound at 290 K, 90 kPa)

    • C. 

      680 m/s

    • D. 

      There is not enough information to solve this problem.

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