Hot combustion gases of a furnace are flowing througha concrete chimney (k =1.4 w/m · °c) of rectangular cross section. the flow section of the chimney is 20 cm ×40 cm, and the thickness of the wall is 10 cm. the average temperatureof the hot gases in the chimney is ti=280°c, and the averageconvection heat transfer coefficient inside the chimney is hi=75 w/m2· °c. the chimney is losing heat from its outer surfaceto the ambient air at to=15°c by convection with a

The mass flow rate of the fluid remains constant in all steady flow process. 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?

Vibration monitoring this technique uses the noise or vibration created by mechanical equipment and in seme cases by plant systems to detemine their actual condtion. a)- true b)- false