A steel ball of 20 mm diameter (k = 60 W/m·ºC, α = 177×10-6 m2/s, rho = 7854 kg/m3) is dropped in a large tank of water. The sphere ball is initially isothermal at 360 K and drops until the center temperature is 320 K, and the temperature of the water is 280 K. The sphere ball may be assumed to quickly reach the terminal velocity of 1.3 m/s in the water. Determine the height of the water tank required to cool the sphere ball to 320 K. Use analytical one-term approximation method for the conduction heat transfer.

On a average work day more than work place firs are reorted

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?

Draw the engineering stress-strain curve for (a) bcc; (b) fcc metals and mark important points.