Energy, Entropy and Engines An Introduction to Thermodynamics

90 SOLVED PROBLEMS

Question: 7.13

Problem: Calculate the pressure of nitrogen that has a specific volume v = 0.025 m³ / kg and a temperature of 252 K using (a) the ideal gas equation and (b) the van der Waals equation of state. Find: Pressure of nitrogen P. Known: Specific volume ν = 0.025 m³ / kg, temperature T = 252 K. ...

The molar specific volume of nitrogen is \b...
Question: 10.1

Problem: An engine operating on a cold air standard Otto cycle takes air at 100 kPa and 25 °C and compresses it isentropically to 2.2 MPa. The work output from the cycle is 200 kJ / kg of air. Find the efficiency of the cycle, and the maximum temperature reached in the cycle. Find: Efficiency ...

The compression ratio of the cycle can be found, s...
Question: 4.13

Problem: Oxygen contained in a cylinder is compressed adiabatically by a piston from an initial state with V1 = 0.2  m³ , P1 = 200  kPa  and T1 = 25 ° C  to a final temperature T2 = 200 ° C . Find the work done during this process. Find: Work W done during compression. Known: Initial volume V1 = ...

The mass of oxygen is  m=\frac{P_1V_1}{RT_1...
Question: 6.17

Problem: Atmospheric air at 100 kPa and 300 K is compressed in a reversible, adiabatic process to 800 kPa. Determine the exergy of the compressed air. The air at 800 kPa is allowed to cool to 300 K. Determine the exergy destroyed during the cooling process. Find: Exergy of the air at the ...

The exit temperature is  T_2 =T_1\left\lgro...
Question: 6.16

Problem: Air enters a gas turbine at 1100 K and 800 kPa with a velocity of 80 m / s. Determine the exergy of the air at the inlet to the turbine. Assume the atmosphere is at 300 K and 100 kPa. Find: Flow exergy ψ of the air at the turbine inlet. Known: Air pressure P = 800 kPa, air temperature T ...

Specific enthalpy contribution:  h-h_o =h(1...
Question: 6.15

Problem: A compressed air tank contains 500 kg of air at 800 kPa and 400 K. How much work can be obtained from this if the atmosphere is at 100 kPa and 300 K? Find: Maximum work Wu that can be obtained from the compressed air. Known: Mass of air m = 500 kg, air pressure P = 800 kPa, air ...

Specific internal energy contribution:  u -...
Question: 6.13

Problem: Argon enters an adiabatic nozzle at 4 bar and 850 °C and exits at 1 bar. If the isentropic efficiency of the nozzle is 90%, find the exit velocity and temperature of the gas. Find: Exit velocity V2 and temperature T2 of argon. Known: Inlet temperature T1 = 850 °C = 1123.15 K, inlet ...

Assuming isentropic flow, the exit temperature is ...
Question: 6.6

Problem: Air at 100 kPa and 20 °C is compressed in a continuous process in an adiabatic compressor to a pressure of 400 kPa. Determine the exit temperature and the work required per kilogram of air. Find: Exit temperature T2 and work required per kilogram of air w12 for compression. Known: Initial ...

The exit temperature is T_2=T_1\left\lgroup...
Question: 6.5

Problem: An insulated cylinder fitted with a piston contains 5 kg of air at 500 kPa and 1000 K. The air expands in an adiabatic process until its volume doubles. Calculate the work done by the air. Find: Work W done by air during expansion. Known: Mass of air m = 5 kg, initial pressure P1 = 500 ...

Solving for the final temperature, T_2=T_1\...