MAE 204 Lecture Notes - Lecture 19: Max Q, Polytropic Process, Isentropic Process

• School: University at Buffalo
• Department: Mechanical & Aerospace Engr
• Course: MAE 204
• Professor: Salac David

Document Summary

Entropy is a property ds = q/dt for a reversible system. Entropy change for any entropy is sdetermied by the state. S2 -s1 = + minsin - moutsout +sgen ds/dt = 1in to out q/dt + minsin-moutsout +sgen. S2-s1 = c ln (t2/t1) if isentropic then t1 = t2. S2-s1 = cv ln (t2/t1) + r ln (v2/v1) S2 -s1 = cp ln (t2/t1) - r ln (p2/p1) If isentropic then (t2/t1)s = (v1/v2) ^(k-1) (t2/t1)s = (p2/p1)^(k-1/k) (p2/p1)s = (v1/v2)^k. S2- s1 =s. 2 - s. 1 - rln (p2/p1) s. in table. If isentropic (p2/p1)s = pr2/pr1 (v2/v1)s = vr2/vr1. Pr and vr in tables: pr,vr only depend on pressure] This is the work out of an open simple reversible steady -flow system. This is the open system version of wd = pdv. Mass balance: dm/dt = m. in -m. out -----m. in = m. out =m. Energy balance : de/dt = 0 = q. in -w. out + m. inhin + m. hout.