While the pressure remains constant at 100 psia the volume of a system of air changes from 20 ft3 to 10 ft3 . What are (a) ∆U in Btu, (b) Q in Btu, (c) Wn, Btu
1.) While the pressure remains constant at 100 psia the volume of a system of air changes from
20 ft3
to 10 ft3
. What are (a) ∆U in Btu, (b) Q in Btu, (c) Wn, Btu
2.) Four pounds of air gain 0.491 Btu/R of entropy during a nonflow isothermal process. If p1
= 120 psia and V2 = 42.5 ft3
find (a) V1 and T1 (b) Q, and (c) Ws with υ1 = 100 ft/sec and υ2 =
500 ft/sec.
3.) A 1 hp stirring motor is supplied to a tank containing 22.7 kg of air. The stirring action is
applied for 2 hours and the tank losses 850 kJ/hr of heat. Calculate (a) the paddle work in
kJ, (b) change of internal in kJ, and (c) the change in temperature of air after 2 hours,
assuming that the process occurs at constant volume.
4.) A gas with cp = 5.2 kJ/kg.K and R = 2.056 kJ/kg.K initially at 2000 kPa, 3m3
and 115oC
undergoes an isentropic process to 105 kPa. Find (a) V2 and T2. What is the work (b) if the
process is nonflow, (c) if the process is steady flow with ΔKE = 10 kJ?
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