The required production rate for a certain product is 45 units/hr. Its work content time is 71.5 min. The production line for this product includes 5 automated workstations. Because the automated stations are not entirely reliable, the overall line efficiency is expected to be only 88%. All of the other stations will have one worker each. It is anticipated that 6% of each cycle will be lost due to worker repositioning. Balance delay is expected to be 7%.

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?