The heat transfer coefficient for hydrogen flowing over a sphere is to be determined by observing the temperature-time history of a sphere fabricated from pure copper. The sphere, which is 20 mm in diameter, is at 75°C before it is inserted into the gas stream having a temperature of 27°C. A thermocouple on the outer surface of the sphere indicates 55 C 97 s after the sphere is inserted into the hydrogen. Assume and then justify that the sphere behaves as a spacewise isothermal object and calculate the heat transfer coefficient.

The y form of iron is known as: a) ferrite b) cementite c) perlite d) austenite

If a particle moves along a path such that r : (3 sin t) m and ? : 2t rad, where t is in seconds. what is the particle's acceleration in m/s in 4 seconds? a)- 16.43 b)- 16.29 c)- 15.21 d)- 13.79

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?