Why did Frederick Scott Archer develop something entirely new called the collodion process?
He wanted something that was different from everyone else's style.
He was unhappy with the uneven texture of the print negative in the calotype
process.
He found the elaborate steps involved in the calotype process to be too difficult.
He couldn't afford the expense of all of the tools needed for the calotype
process.

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?