Christopher is a 17-year-old high school senior who is constantly getting into arguments with his mother. she believes he should have a 9 p. m. curfew and that he should not hang out with certain people in certain neighborhoods. she is fearful he will become a victim of crime. christopher believes he is a strong man who should not have a curfew and that he can protect himself. according to the lifestyles theory, christopher should associate with in order to lower his chances of victimization.

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?