A compound gear train is composed of five gears: A, B, C, D and E. Gear A has 12 teeth and is meshed with gear B. Gear B has 36 teeth and shares a shaft with gear C, which has 16 teeth. Gear C is meshed with gear D which has 48 teeth. Gear D is meshed with gear E, the output gear. Power is supplied at gear A with 100 ft•lb of torque and is traveling at 1,600 rpm. The necessary torque output for the system is 450 ft•lb. What should the gear ratio of the system be?

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?