Chapter 6, Problem 6.33P

Nitrogen is cooled at a constant pressure of 1200 Pa from an initial specific volume of 1.80m³/kg to a final specific volume of 0.75 m³/kg. If the mass of nitrogen (cp=1.0399 kJ/kg-K and k=1.399) undergoing the process is 2.26kg, determine: a. The nonflow work, in kJ b. The change in entropy, in kJ/K C. The change in enthalpy and internal energies, in kJ

A rigid cylindrical tank stores 80 kg of a substance at 400 kPa and 480 K while the outside temperature is 290 K. A paddle wheel stirs the system transferring shaft work at a rate of 0.7 kW. At the same time an internal electrical resistance heater transfers electricity at the rate of 1.6 kW. A. Do an energy analysis to determine the rate of heat transfer for the tank. B. Determine the absolute value of the rate at which entropy leaves the internal system (at a uniform temperature of 480 K). Answer in kW/K C. Determine the rate of entropy increase in the system's surroundings. Answer in kW/K

3. A piston-cylinder assembly initially contains 3 kg of water at 75 kPa and pressure at 50 °C. Then the water is heated at constant pressure and the entropy of the water at the end of the process becomes 7.94 kJ / kgK. The entropy change during the process of water is: a. 24,81 kJ/K b. 21,71 kJ/K c. 14,86 kJ/K d. 16,2 kJ/K e. 7,23 kJ/K

A mass of 3 kg of water contained in a piston–cylinder assembly expand from an initial state where T1 = 551°C, p1 = 700 kPa to a final state where T2 = 224°C, p2 = 300 kPa, with no significant effects of kinetic and potential energy. It is claimed that the water undergoes an adiabatic process between these states, while developing work. Evaluate entropy production in Joules/k.

D2

One-quarter Ibmol of oxygen gas (O₂) undergoes a process from p₁ = 20 lbf/in², T₁ = 500°R to p₂ = 150 lb/in². For the process W = -500 Btu and Q = -202.5 Btu. Assume the oxygen behaves as an ideal gas. Determine T2, in °R, and the change in entropy, in Btu/°R.

4. Nitrogen with a mass of 0.3 lbm undergoes a process from P1 = 20 psi, T1 = 500°R to P2 = 150 psi. The process is found to have work and heat transfer in the amount of W = -500 Btu and Q = -125.9 Btu. Assuming the gas is ideal, determine: a. T2 (°R) b. the change in specific entropy (Btu/lbm°R) C. Is using the ideal gas model appropriate here? Provide justification for your answer.

When two systems are in contact, the entropy transfer from the warmer system is equal to the entropy transfer into the cooler one at the point of contact. That is, no entropy can be created or destroyed at the boundary since the boundary has no thickness and occupies no volume.

1 kg of water, T1 = 300 ° C, P1 = 200 kPa in a piston-cylinder assembly passes a process to its final state at constant pressure T2 = 150 ° C by throwing heat from its initial state to the surrounding environment. At the end of this process, determine(a) Piston boundary work, (b) The amount of heat discharged from the piston to the surrounding environment, (c) The amount of entropy produced by the piston cylinder (d) The amount of entropy produced by the surrounding environment. (Take the piston cylinder surface temperature 150 ° C!)