Entropy Equation for a Control Volume May 15
- Slides: 26
Entropy Equation for a Control Volume May 15, 2012 Prof. Sanghee Kim 1 Sonntag & Borgnakke / Fundamentals of Thermodynamics, 7 th Edition
9. 1 the second law of thermodynamics for a control volume 2 Sonntag & Borgnakke / Fundamentals of Thermodynamics, 7 th Edition
Rate of change = +in – out + generation 개별적 내부비가역에 의한 양의 생성항 반드시 양수(or 0)이 됨 등호: 내적 가역 부등호: 내적 비가역 If the heat transfer is distributed over the CS, then an integral has to be done over the total surface area using the local temperature and rate of heat transfer per unit area 3 Sonntag & Borgnakke / Fundamentals of Thermodynamics, 7 th Edition
9. 2 The steady state process and the transient process (a) Steady-State Process 정상상태 단위질량당 엔트로피가 시간에 따라 변하지 않음 If 입출구가 하나라면 항상 0보다 크거나 같음 4 Sonntag & Borgnakke / Fundamentals of Thermodynamics, 7 th Edition
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(b) Transient Process 질량은 시간에 대한 변화가 없으므로 전체를 더하면 됨 In case when the temperature is uniform throughout the CV at any instant of time 과도과정의 2 법칙 14 Sonntag & Borgnakke / Fundamentals of Thermodynamics, 7 th Edition
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9. 3 The Steady-State Single-Flow Process 1 st law 2 nd law 실제과정을 거치는 단일유동에 대한 축일 17 Sonntag & Borgnakke / Fundamentals of Thermodynamics, 7 th Edition
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9. 4 Engineering Applications; Efficiency Heat engine (thermal efficiency) Actual machine efficiency = Ideal Actual 20 Actual ------Ideal Processes <-> related to 2 nd Law Sonntag & Borgnakke / Fundamentals of Thermodynamics, 7 th Edition 모든 장치는 비가역이지만 이를 가역화하여 최대효율을 알수 있으므로, 이를 기반으로 설계한다
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