An ideal otto cycle has a compression ratio of 9 and uses air as the working fluid. at the beginning of the compression process, air is at 100 kpa and 27 °c. the pressure is doubled during the heat-addition process. ting forte nia (a) the amount of heat transferred to the air; (b)the net work output (c) the thermal efficiency; (d) the mean effective pressure for the cycle.

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?