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# Cairo 2nd Petrol Lecture 7

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• 1. Mechanical Engineering Thermodynamics 2nd year Petrol dept. 2011-2012 Lecture (7) Gas Power Cycles Lecturer : Dr. Esmail Bialy
• 2. Background&#xF097; 1- Ideal Gas Relation&#xF097; 2- 1st Law of Thermodynamics (Closed Systems)
• 3. Ideal Gas Relation
• 4. Forms&#xF097; 1- PV=mRTPressure Volume mass Gas Const. Temperature(kPa) (m3) (kg) (kJ/kg.K) (K)
• 5. Forms&#xF097; 2- Pv=RTPressure Specific Volume Gas Const. Temperature(kPa) (m3/kg) (kJ/kg.K) (K)
• 6. Forms&#xF097; 3- PV=nRuTPressure Volume no. of Universal Temperature kmoles Gas Const.(kPa) (m3) (kmole) (kJ/kmole.K) (K)
• 7. Specific Heats
• 8. Specific Heats
• 9. Specific Heats &#x3B3; &#x3B3;
• 10. Specific Heats&#xF097; From the last two relations, we can drive another two relations&#xF097; Cp=&#x3B3;R/(&#x3B3;-1) For Air= 1.0035 kJ/kg.K&#xF097; Cv=R/(&#x3B3;-1) For Air= 0.716 kJ/kg.K
• 11. Note:1-For Ideal Gases&#xF097; &#x394; h= Cp&#x394;T&#xF097; &#x394;u = Cv &#x394;T2- For Steam&#xF097; &#x394; h= h2-h1&#xF097; &#x394;u = u2-u1 from steam tables
• 12. 1st Law of Thermodynamics (Closed Systems) (Revision)
• 13. Note!!!rp, r, rcrp: Pressure ratio (Brayton Cycle)r: Compression ratio (Otto &amp; Diesel Cycles)rc: Cutoff ratio ( Diesel Cycle)
• 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.