Question

4. Application of the Second Law Vapor (700 C and 10 MPa) is expanded through a turbine with isentropic efficiency of 95% to 1 MPa at a mass flow rate of 18 kg/s. Assuming an adiabatic process, (a) Find actual work of turbine (5 points). (b) Find quality of the mixture at the exit of the turbine [10 points) (c) How much the entropy increases through this process [10 points)

Answer 1

T a Assume alimpa Givens Ri= lompa, Ti = 700€ 1. Mist = 95% Po= impa t ↑ m = 18 kg/s from Superhealed , Steam table at P = lampa &T=700°C hi= 3862-69 kJ/kg 81 = 7.1603 kJ/kgk at P= impa from Sahurated pressure Table, - hf = 762-23 kJ/kg , hsq=2014.05 kilig 8f=2-1367 kJ/kgk, Sky = 4.4462 kJ/kg ke Si=52= Sft asta 7-1603 = 2-1367 + 2x4-4402 = »7 l ing superheated o h at P= 1 MPa and S=7:1603 from super heated table, I ha=3073.48 kJ/kg - nis = hi-hal = 0.45=3862-69 - ha S hi-ha 386269-307345 .: =) har = 31/2-94 kJlky (a) Actual work = m Chithel) = 1863862-69-3112-94) = $13.4955 MWI O quality & mixhre at exit is Superbeared

Tds = dh-vd P ds= dk - hi-h2 = 3862.69-3112194 1 Tsat Sat (273 +179-87) cs = 16555 KJ/KgK As = nix ds = 18x1-655 05 - 29.8 kJ/k7