If the air has to flow from station P to station Q, the maximum possible value of pressure in kPa at station Q is

Question

Common Data for Question 01 & 02

In an experimental set-up, air flows between two stations P and Q adiabatically. The direction of flow depends on the pressure and temperature conditions maintained at P and Q. The conditions at station P are 150 kPa and 350 K. The following are the properties and relations pertaining to air:

Specific heat at constant pressure,

      C_p = 1.005 kJ/kg K;

Specific heat at constant volume,

      C­_V = 0.718 kJ/kgK;

Characteristic gas constant, R = 0.287 kJ/kgK.

Enthalpy h = c_pT,

Internal energy, u = C_v T.

 

1. If the air has to flow from station P to station Q, the maximum possible value of pressure in kPa at station Q is close to                                                                                                                                                                                     

      (a) 50                                                                  (b) 87

      (c) 128                                                                (d) 150

 

       2 .  If the pressure at station Q is 50 kPa, the change in entropy (S_Q – S_P) in kJ/kgK   is                                                                                

      (a) –0.155                                                           (b) 0

      (c) 0.160                                                             (d) 0.355