Chapter 6, Problem 6.36CU

A 300-lb iron casting, initially at 1050°F, is quenched in a tank filled with 2121 lb of oil, initially at 80°F. The iron casting and oil can be modeled as incompressible with specific heats 0.10 Btu/lb · °R, and 0.45 Btu/lb · °R, respectively. (a) For the iron casting and oil as the system,determine the final equilibrium temperature, in °F. Ignore heat transfer between the system and its surroundings. Tf = i °F (b) For the iron casting and oil as the system,determine the amount of entropy produced within the tank, in Btu/°R. Ignore heat transfer between the system and its surroundings. O = i Btu/°R Touthoolk ond Medie

Water initially a saturated liquid at 110°C is contained within 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 amount of entropy produced per unit mass, in kJ/kg K. Select one: a. 5.8202 O b. 2.1968 С. 3.7721 d. 4.9961

Define the entropy of a pure substance is determined from the tables (like other properties).

C6 1.

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

Thermodynamics

for steam, the specific ideal gas constant = 461.5 J/kg K A closed system is comprised of pure water substance initially at a temperature of 500 oC and a pressure of 20 MPa (state 1). The system undergoes an isochoric process whereby its pressure drops to 0.1 Mpa (state 2). Evaluate the specific entropy, specific volume and temperature of the system at state 2.

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.

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.