Chapter 6, Problem 6.8CU

1. thermodynamics

answer 99 and 100

2. An ideal gas undergoes a process from state 1 ( T1= 300 K, P1= 100 kPa) to state 2 ( T2= 600 K, P2 500 kPa). The specific heats of the ideal gas are : c, = 1 kJ/kg-K and c, = 0.7 kJ/kg-K. The change in specific entropy of the ideal gas from state 1 to state 2 (in kJ/kg-K) is (correct to two decimal places).

The entropy of an ideal gas depends on both T and P. The function s° represents only the temperature-dependent part of entropy.

Answer 94 and 95

Argon gas flows through a well-insulated nozzle at steady state. The temperature and velocity at the inlet are 550°R and 150 ft/s, respectively. At the exit, the temperature is 480°R and the pressure is 40 lb/in?. The area of the exit is 0.0085 ft². Use the ideal gas model with k-1.67, and neglect potential energy effects. Determine the velocity at the exit, in ft/s, and the mass flow rate, in lb/s. Step 1 Your answer is correct Determine the velocity at the exit, in ft/s. V₂- 677.088 Hint Step 2 ft/s Determine the mass flow rate, in lb/s, through the nozzle. m = i lb/s Attempts: 2 of 4 used

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). Sketch the process on a Temperature-specific entropy plot, showing the lines of constant pressure which pass through steps 1 and 2.

ANS COMPLETELY AND SURE

Q.6.A. Oxygen enters a nozzle with a negligible velocity at 440 K and 12 bar, and leaves at 1.9 bar. Determine the volumetric flow rate of the oxygen at the nozzle entrance if the nozzle exit area is 2.5 cm2 and the ratio of inlet temperature to the outlet equal 1.69. (Cy = 718 J/kg K and Cp = 1005 J/kg K)