(4.10) 50,000 lb/h of a fluid having a density of 53 lbm/ft' and a viscosity of 1.5 cp will flow in the annulus of a double-pipe heat exchanger. The hairpins are 30 ft long with 3-in. schedule 40 outer pipe, 1.5-in. schedule 40 inner pipe, internal return bends
and 1.5-in. schedule 40 nozzles. A total of six hairpins will be used, and the maximum allowable pressure drop for the
stream is 12 psi. Determine which of the following configurations should be used in connecting the annuli of the hairpins:
• Six hairpins in series
. Two parallel banks of three hairpins each
• Three parallel banks of two hairpins each

If you were designing a bumper for a car, would you prefer it to exhibit elastic or plastic deformation? why? consider the functions of a bumper in both a minor "fender-bender" and a major collision.

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?

Afluid flows with a velocity field given by v=(x/t)i.. determine the local and convective accelerations when x=3 and t=1.