An fcc iron-carbon alloy initially containing 0.55 wt% c is exposed to an oxygen-rich and virtually carbon-free atmosphere at 1325 k (1052 c). under these circumstances the carbon diffuses from the alloy and reacts at the surface with the oxygen in the atmosphere-that is, the carbon concentration at the surface position is maintained essentially at 0 wt% c. mis process of carbon depletion is termed decarburization.) at what position will the carborn concentration be 025 wt% after a 10-hours treatment? the value of d at 1325 k is 3.3x 10^-11 m^2/s. (you may need to use some properties of error function attached)

The temperature of air decreases as it is compressed by an adiabatic compressor. a)- true b)- false

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?

Aplate clutch has a single pair of mating friction surfaces 250-mm od by 175-mm id. the mean value of the coefficient of friction is 0.30, and the actuating force is 4 kn. a) find the maximum pressure and the torque capacity using the uniform-wear model. b) find the maximum pressure and the torque capacity using the uniform-pressure model.