Chemical Thermodynamics

2. Water initially at 155°C is contained in a piston- cylinder assembly. The water undergoes a process to the corresponding saturated vapor state, during which the piston moves freely in the cylinder. There is no heat transfer with the surroundings. If the change of state is brought about by the action of a paddle wheel, determine the net work per unit mass in kJ/kg and the amount of entropy produced per unit mass in kJ/kg. [MO2]

4. For an exact differential, the second derivative of the function (P in this case) is independent of the order of differentiation. Is the proposed function for an equation of state possible? That is, is P an exact differential? Note: Parameters a, b, and c are non-zero constants. Explain.

5. Water at 140°C and 10.0 bar expands through a throttle to 1.0 bar. What is the outlet temperature and how many phase(s) are in the effluent? Explain your answer.

7. Nitrogen in laboratory settings can be supplied from liquid nitrogen tanks. These tanks contain mostly liquid N₂ by mass, but one of the ports on the tank is connected to the "headspace", i.e. the region above the liquid. When the port to the headspace is opened, cold nitrogen vapor flows out of the tank. a. If the tank is well-insulated, how will the pressure and temperature inside the tank change as the nitrogen is used up? (It would commonly take days or weeks to use all the nitrogen.) Explain. b. How will they change if the tank is very poorly insulated? Explain.

8. Plot the phase envelope for propane on a P-V diagram by using the equation of state (EOS) spreadsheet to determine saturation pressures.

A pump brings in 20.0 kg/s of liquid water feed at 1.92 bar and 50 °C. The exit pressure from this pump is 7.05 bar. The pump (being real, not reversible) has an isentropic efficiency of 82%. What is the actual work input (in kW) required to run this pump, assuming the specific volume of the water remains constant at 0.001012 m³/kg?

9. Refrigerant 134a at p₁ = 30 lbf/in², T₁ = 40°F enters a compressor at a steady state with a mass flow rate of 300 lb/h and exits as saturated vapor at p2 = 160 lbf/in². Heat transfer occurs from the compressor to its surroundings, which are at To = 40°F. Changes in kinetic and potential energy can be ignored. The power input to the compressor is 3 hp. Determine the heat transfer rate for the compressor, in Btu/hr, and the entropy production rate for the compressor, in Btu/hr.°R. [MO3, MO7]

2. Which fluid will have a more negative internal energy departure function: water at 375°C and 2.3 bar or water at 100°C and 1.6 bar? Explain.

4.13 Refrigerant 134a enters the evaporator of a refrigeration system operating at steady state at -4°C and quality of 20% at a velocity of 7 m/s. At the exit, the refrigerant is a saturated vapor at a temperature of -4°C. The evaporator flow channel has constant diameter. If the mass flow rate of the entering refrigerant is 0.1 kg/s, determine a. the diameter of the evaporator flow channel, in cm. b. the velocity at the exit, in m/s.

1. Water, initially a saturated liquid at 160°C, is contained in a pistol-cylinder assembly. The water undergoes a process to the corresponding saturated vapor state, during which the piston moves freely in the cylinder. If the change of state is brought about by heating the water as it undergoes an internally reversible process at constant pressure and temperature, determine the work and heat transfer per unit mass in kJ/kg. [MO1]