7–115 Air is to be cooled in the evaporator section of a refrig- erator by passing it over a bank of 0.8-cm-outer-diameter and 0.8-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 5 m/s. The tubes are arranged in-line with longitudinal and transverse pitches of S L = S T = 1.5 cm. There are 25 rows in the flow direction with 15 tubes in each row. Determine (a) the refrigeration capac- ity 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?