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# Cairo 2nd Petrol Lecture 7

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### Cairo 2nd Petrol Lecture 7

1. 1. Mechanical Engineering Thermodynamics 2nd year Petrol dept. 2011-2012 Lecture (7) Gas Power Cycles Lecturer : Dr. Esmail Bialy
2. 2. Background 1- Ideal Gas Relation 2- 1st Law of Thermodynamics (Closed Systems)
3. 3. Ideal Gas Relation
4. 4. Forms 1- PV=mRTPressure Volume mass Gas Const. Temperature(kPa) (m3) (kg) (kJ/kg.K) (K)
5. 5. Forms 2- Pv=RTPressure Specific Volume Gas Const. Temperature(kPa) (m3/kg) (kJ/kg.K) (K)
6. 6. Forms 3- PV=nRuTPressure Volume no. of Universal Temperature kmoles Gas Const.(kPa) (m3) (kmole) (kJ/kmole.K) (K)
7. 7. Specific Heats
8. 8. Specific Heats
9. 9. Specific Heats γ γ
10. 10. Specific Heats From the last two relations, we can drive another two relations Cp=γR/(γ-1) For Air= 1.0035 kJ/kg.K Cv=R/(γ-1) For Air= 0.716 kJ/kg.K
11. 11. Note:1-For Ideal Gases Δ h= CpΔT Δu = Cv ΔT2- For Steam Δ h= h2-h1 Δu = u2-u1 from steam tables
12. 12. 1st Law of Thermodynamics (Closed Systems) (Revision)
13. 13. Note!!!rp, r, rcrp: Pressure ratio (Brayton Cycle)r: Compression ratio (Otto & Diesel Cycles)rc: Cutoff ratio ( Diesel Cycle)
14. 14. Example (5-10): A Diesel engine has a compression ratio of 20:1 with an inletstate of 95 kPa, 290 K, and volume 0.5 L. The maximum cycletemperature is 1800 K. find the maximum pressure, the netspecific work, and the thermal efficiency.