Question

4) An ideal-gas mixture of helium and nitrogen with a nitrogen mass fraction of 35 percent is contained in a piston-cylinder device arranged to maintain a fixed pressure of 700 kPa. The mixture is heated from 300 K to 500 K a. Determine the molar mass and gas constant for the mixture. b. Determine the work produced, in kJ/kg. (Hint: Try finding the specific c. Determine the constant-volume and constant-pressure specific heats (Answer: 5.72 kg/kmol, 1.45 kJ/kg K) volumes at the initial and final states. Answer: 291 kJ/kg) for the mixture. Assume constant specific heats for helium and nitrogen, and use values at 300 K. (Answer: 2.285 kJ/kgK, 3.739 kJ/kgK) d. Determine the heat transferred to the device in kJ/kg. (Answer: 747.9 kJlkg) e. Determine the exergy destroyed per unit mass of the mixture, in kJ/kg. The temperature of the heat source is 600 K and ambient temperature is 300 K. (Hint: Write the entropy balance equation for the process. Answer: 199.2 kJ/kg) 0 35% N, 65% He (by mass)

Answer 1