# Thermodynamics Ultimate Trivia Quiz!

15 Questions | Total Attempts: 231  Settings  .

• 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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