Oxygen is compressed from an initial state of p1 = 1 bar, T1 = 25◦ C to a final state of p2 = 650 kPa, T2 = 270◦C in a compressor operating at steady state. Model the oxygen as a perfect gas with γ = 1.4 and cp = 0.92 kJ/kg·K. Neglecting stray heat transfer and kinetic and potential energy effects, determine: (a) the work, in kJ per kg of oxygen flowing through the compressor. (b) the isentropic efficiency η for the compressor.

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?

For the closed feedwater heater below, feedwater enters state 3 at a pressure of 2000 psia and temperature of 420 °f at a rate of ix10 ibhr. the feedwat extracted steam enters state 1 at a pressure of 1000 psia and enthalpy of 1500 btu/lbm. the extracted er leaves at an enthalpy of 528.7 btu/lbm steam leaves as a saturated liquid. (16) a) determine the mass flow rate of the extraction steam used to heat the feedwater (10) b) determine the terminal temperature difference of the closed feedwater heater

How to increase the thermal officiency of an ideal simple rankino cycle? among these methods, which one is the best and why?