Chapter 6, Problem 6.5E

Entropy generation outside system boundaries can be accounted for by writing an entropy balance on an extended system that includes the system and its immediate surroundings.

Carbon dioxide (molar mass 44 kg/kmol) expands reversibly in a perfectly thermally insulated cylinder from 3.7 bar, 220 0C to a volume of 0.085 m3. If the initial volume occupied was 0.02 m3, calculate the gas constant, adiabatic index, final pressure and work input. Assume nitrogen to be a perfect gas and take cv = 0.63 k J / k g K.

Steam undergoes an adiabatic expansion in a piston-cylinder assembly from 100 bar, 360°C to 1 bar, 160°C. What is the work in kJ per kg of steam for the process? Calculate the amount of entropy produced, in kJ/K per kg of steam. What is the maximum work that could be obtained from the given initial state to the same final pressure? Show both processes on a property labeled sketch of the T-s diagram.

A vessel of volume 0.04 m3 contains a mixture of saturated water and steam at a temperatureof 250°C. The mass of the liquid present is 9 kg. Find the pressure, mass, specific volume,enthalpy, entropy and internal energy.

Steam at a pressure of 21 bar and a dryness fraction of 0.9 occupies a volume of 0.427 m' in a cylinder behind a piston is allowed to expand reversibly to a pressure of 7 bar according to the relationship, PV1.25 = Constant. Sketch the process on the p-v diagram and calculate the work and heat transfers in kJ. %3D

a) Explain the argument based on the Carnot cycle for why AS= s must be a state function for every chemical system in the universe. b) Using the Nernst equation, explain how to charge a battery by applying an external voltage. c) Show how the Boltzmann entropy formula can be used to compute the entropy change for one mole of gas doubling its volume.

6. A certain quantity of gas occupies 0.56 m³ at 400° C and 28 bar. Determine the gain in entropy if the gas expands isothermally to a final volume of 2.8 m². R= 287 J/kg K. the following creas Ans. 3.746 kJ/KI

Data are provided for steady-state operation of an electric motor in figure below, where hA = 5 W/K.   Determine for the motor the rate of entropy production, in W/K.

For the entropy balance equation, the mechanism of entropy transfer includes____________     Entropy can be transferred by heat     Entropy can be transferred by work     Entropy can be transferred by mass flow      Entropy cannot be transferred by mass flow