Asimply supported beam is to be 18’-0" long, braced only at its ends. select the lightest w-shape of a572 steel (fy = 50 ksi) given the conditions below. check the beam for shear and deflection. if the total load deflection (∆tl) is limited to l/300, would this beam still work? show work to explain your answer.

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?