The Douglas DC-3 ( Fig. 6.84 ) has a maximum velocity of 229 mi/h at an altitude of 7500 ft. Each of its two engines provides a maximum of 1200 hp. Its weight is 25,000 lb, aspect ratio is 9.14, and wing area is 987 ft 2 . Assume that the propeller effi ciency is 0.8, and the Oswald effi ciency factor is 0.7. Calculate the zero-lift drag coeffi cient for the DC-3.

Refrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 mpa and -10°c at a rate of 0.05 ka/s and leaves at 0.8 mpa and 50°c. the refrigerant is cooied in the condenser to 0.72 mpa and 26'c. it is then throttled to 0.15 mpa. sketch the t-s diagram for the system and evaluate: 6) the rate of heat removai from the refrigerated space (kw), it) the power input to the compressor (kw), ii) the isentropic efficiency of the compressor (%), and iv) the cop of the refrigerator.