29. One kg of air, initially at a temperature at 127C, expands reversibly at a constant pressure until the volume is doubled. If the gas constant of air is 287 J/kg.K, the magnitude of work transfer is kJ (round off to 2 decimal places). 30. Air (ideal gas) enters a perfectly insulated compressor at a temperature of 310K. The pressure ratio of the compressor is 6. Specific heat at constant pressure for air is 1005 J/kg.K and ratio of specific heats at constant pressure and constant volume is 1.4. Assume that specific heats of air are constant. If the isentropic efficiency of the compressor is 85 percent, the difference in enthalpies of air between the exit and the inlet of the compressor is kJ/kg (round off to nearest integer).