Çengel & Boles, 7th Ed. ME 305 Thermodynamics II. Woodbury. July 11, 2013.
Homework #3. Summer 2013. These problems are due Monday, July 15. 1.
Name:_______________________________ Çengel & Boles, 7th Ed. July 11, 2013
ME 305 Thermodynamics II Homework #3
Woodbury Summer 2013
These problems are due Monday, July 15. 1.
An air standard Otto cycle has V1=400cm3, T1 = 290K, and P1=100kPa. The maxiumum temperature in the cycle is 2200K and the compression ratio is 8. Assume variable specific heats. a) What is the heat added per cycle? b) What is the net work for the cycle? c) What is the cycle thermal efficiency? Compare this to the ideal formula based on the compression ratio for constant specific heats. 2. Repeat problem 3-1 assuming constant specific heats at 300K, but the compression has only 80% isentropic efficiency and the expansion only 85% isentropic efficiency. 3. An air standard Diesel cycle has pressure 95 kPa and temperature 300K at the initial state and P = 7.2 MPa and T = 2150K at the end of the heat addition process. Assume variable specific heats. a) what is the compression ratio? b) what is the cutoff ratio? c) what is the cycle thermal efficiency? 4. An air standard dual cycle has a compression ratio of 9 and the cycle begins with T1=300K, P1=100kPa, and V1=14L=0.014m3. The heat addition is 22.7kJ, with one-half of the heat added during the constant volume portion of the process and the remainder during the constant pressure portion. Assume variable specific heats. a) find the temperatures at the end of each heat addition process. b) find the net work for the cycle (kJ). c) what is the cycle thermal efficiency? 5.
