Chapter 6, Problem 6.85P

P

Refrigerant 134a is compressed with no heat transfer in a piston–cylinder assembly from 30 lbf/in.2, 20°F to 160 lbf/in.2 The mass of refrigerant is 0.04 lb. For the refrigerant as the system, W = 0.56 Btu. Kinetic and potential energy effects are negligible. Determine the final temperature, in °F.

During a polytropic process, 10 lb of an ideal gas, whose R = 40 ft.lb/lb.R and cp = 0.25 Btu/lb.R, changes state from 20 psia and 40°F to 120 psia and 340°F. Determine (a)n, (b) U and H, (c) S, (d)Q, (e)∫ , (f)- ∫...... (g)If the process is steady flow during which K = 0, what is Ws?. What is K if Ws = 0? (h)What is the work for a nonflow process?

Carbon dioxide (CO2) contained in a piston-cylinder arrangement, initially at 6 bar and 400 K, undergoes an expansion to a final temperature of 260 K, during which the pressure-volume relationship is pV1.25 = constant. Assuming the ideal gas model for the CO2, determine the final pressure, in bar, and the work and heat transfer, each in k.J/kg.

3 pounds of an ideal gas undergoes an isentropic process from 93.6 psig and a volume of 0.8 ft3 to a final volume of 3.7 ft3. If cp = 0.129 and cv - 0.098 Btu/lb.R, what are (a) t₂ (b) p₂, (c) AH and (d) W.

Air expands adiabatically in a piston–cylinder assembly from an initial state where p1 = 100 lbf/in.2, v1 = 3.704 ft3/lb, and T1 = 1000 °R, to a final state where p2 = 20 lbf/in.2 The process is polytropic with n = 1.4. The change in specific internal energy, in Btu/lb, can be expressed in terms of temperature change as Δu=(0.171)(T2 - T1).Determine the final temperature, in °R.Kinetic and potential energy effects can be neglected.

3. Air in a piston-cylinder assembly expands isentropically from state 1 where T1 = 40 °C to state 2, where the specific volume is twice that of state 1. Using the ideal gas model with k = 1.1, determine: a. T2 (°C) b. Work per unit mass (kJ/kg)

Five lbs of propane is contained in a closed, rigid tank initially at 80 lbf/in.2, 50°F. Heat transfer occurs until the final temperature in the tank is 0°F. Kinetic and potential energy effects are negligible. Determine the amount of energy transfer by heat, in Btu. Q= i Btu

Ammonia contained in a piston–cylinder assembly, initially saturated vapor at T1 = 6°F, undergoes an isothermal process to a final specific volume v2 = 3.2 ft3/lb. Determine the final pressure, in lbf/in2, and the final quality, x2.