Download Thermodynamics Review: Ideal Gas Properties, Heat Transfer, and Compressor Performance - P and more Exams Thermodynamics in PDF only on Docsity! ENGR 210 – Introduction to Thermodynamics Review Problems Problem 1 Two kg of nitrogen at 40°C and 200 kPa are contained in a frictionless piston-cylinder device. The nitrogen is compressed to ½ of the initial volume in a process such that pV1.4 = constant. Treat nitrogen as an ideal gas. Calculate the initial volume, VI 0.929 m3 Calculate the value of the constant 181 kPa m4.2 Calculate the work of the compression 149 kJ Calculate the final temperature, TF 413 K Calculate the heat transfer for the process, assuming variable specific heats 0.719 kJ Problem 2 A rigid tank is divided into two compartments each 0.75 m3 separated by a barrier. Compartment I contains 5 kg of H2O at 50°C. Compartment II contains 2 kg of H2O at a pressure of 1 MPa. The barrier is broken and heat is transferred until the system reaches equilibrium with the surroundings at 100C as a saturated mixture. Calculate the initial pressure in I 12.3 kPa Initially, in I (circle): Comp liq – Sat liq – Sat mix – Sat vap – Superheated vapor Calculate the initia temperature in II 544 C Initially, in II (circle): Comp liq – Sat liq – Sat mix – Sat vap – Superheated vapor Calculate the quality of the final saturated mixture 0.128 Calculate the heat transfer for the process - 2450 kJ Problem 3 Air at 80 kPa, 300 K, and 250 m/s enters a diffuser at a rate of 2.5 kg/s and leaves at 315 K. The exit area of the diffuser is 400 cm2. As it passes through the diffuser, the air loses heat at a rate of 12 kJ/s. Calculate the exit velocity 151 m/s Calculate the exit pressure 37.2 kPa Problem 4 You are to design an air compressor with an inlet pressure of 100 kPa, an inlet temperature of 300 K, and an exit pressure of 2 MPa. Calculate the the work per unit mass by incorporating an Ideal (polytropic, n=1.35) two stage compression process 315 kJ/kg Calculate the work per unit mass with isentropic, single stage compression 408 kJ/kg Problem 5 Air flows through an adiabatic, internally reversible compressor at a rate of 0.04 kg/s. At the inlet, the pressure is 200 kPa and the temperature is 17°C. The air is compressed to a pressure of 4 MPa.. Calculate the exit temperature, using variable specific heat 420°C Find the power input to the compressor 16.2 kW Suppose on an actual compressor the exit temperature is found to be 447C. Find the adiabatic efficiency of this compressor 0.933 Problem 6 A 2 m3 insulated rigid tank initially contains air at 100 kPa and 22°C. The tank is connected to a supply line through a valve. Air is flowing in the supply line at 400 kPa and 22°C. The valve is opened. 3kg of air enters the tank. The valve is then closed. Find the initial mass of air in the tank 2.36 kg Find the initial internal energy of air in the tank 497 kJ Find the final internal energy of air in the tank 1382 kJ Find the final temperature of air in the tank 87.1°C Find the final pressure of air in the tank 277 kPa
