Arigid tank whose volume is 0.5 m , initially containing ammonia at 20°c, 1.5 bar, is connected by a valve to a large supply line carrying ammonia at 12 bar, 60°c. the valve is opened only as long as required to fill the tank with additional ammonia, bringing the total mass of ammonia in the tank to 143.36 kg. finally, the tank holds a two-phase liquid-vapor mixture at 20°c. determine the heat transfer between the tank contents and the surroundings, in kj, ignoring kinetic and potential energy effects.

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?

Inspection for bearing condition will include: (clo4) a)-color b)-smell c)-size d)-none of the above

Asteel wire of 2 mm diameter is fixed between two points located 2 m apart. the tensile force in the wire is 250n, if its density of steel is given by 7830 kg/m3 the fundamental frequency of vibration hz? ?