4ft (w) x 3 ft (d) box concrete culverts (n=0.013, entrance has 90° and 15° wingwall flares) carry 150 cfs along a 31-m length of pipe constructed at 1.0 % slope. the tailwater depth is 2 ft.
a) what is the headwater depth?
b) are the culverts flowing under inlet or outlet control conditions?
c) what would the headwater depth and flow regime for a flow rate of 190 cfs

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?