A turbine operates at a pressure ratio of 12, expanding air (assumed as ideal gas). The inlet conditions at the turbine are T1 = 1227oC and p1=12bar. Assume constant values of cp=1.005kJ/kgK, cv=0.719kJ/kgK. Omit the changes of kinetic/potential energies. Find: - The outlet temperature assuming reversible and adiabatic process. (741K) - If the isentropic efficiency of the turbine is 75%, find the outlet temperature of the real process. (930.8K) - Find the work produced per kg of air driving the turbine in the case of ideal and real processes. What do you observe?

The temperature of air decreases as it is compressed by an adiabatic compressor. a)- true b)- false

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?

The process in which the system pressure remain constant is called a)-isobaric b)-isochoric c)-isolated d)-isothermal