A planar source at the center of an infinite slab of graphite 2 meters thick emits 108 thermal neutrons per cm2/sec. Given that the system is at room temperature, calculate the: (a) total number of thermal neutrons in the slab per cm2 at any time; (b) number of thermal neutrons absorbed per cm2/sec of the slab; (c) neutron current as a function of position in the slab; (d) total number of neutrons leaking per cm2/sec from the two surfaces of the slab; (e) probability that a source neutron does not leak from the slab.

Amass of 1.5 kg of air at 120 kpa and 24°c is contained in a gas-tight, frictionless piston-cylinder device. the air is now compressed to a final pressure of 720 kpa. during the process, heat is transferred from the air such that the temperature inside the cylinder remains constant. calculate the boundary work input during this process.

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

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?