20 Due 4/12

1. You want to cool your cryogenics experiment by pumping pressurized liquid nitrogen through it. What is the power needed for a reversible pump that pressurizes 20 g/s of liquid nitrogen at 77.3 K from 200 kPa to 1MPa? Make appropriate approximations.

2. A typical specific heat ratio for the hot combustion gases entering the turbine of a jet engine is 1.25. For the gas constant, just use the one for air. Assume that the gases enter the turbine at 640 kPa and 927$^\circ$C, and exit at the ambient pressure of 100 kPa at a rate of 2 kg/s. Also assume that the specific heat ratio is constant going through the turbine, and that the turbine is adiabatic and reversible. Find the exit temperature, power, and heat flow. Do not compute any volumes, specific or not, when solving this question.

3. An reversible isobaric heat exchanger heats a stream of carbon dioxide at 100 kPa from 300 to 500 K. It takes in heat from a 600 K reservoir. Find the work required, the heat taken from the reservoir, and the overall entropy generation.

4. Do 9.62 in the hardcover, 9.69 in the softcover. Use constant specific heats. You can write a separate first law for each stream, and then apply that the heat coming out of the nitrogen is the heat entering the oxygen. But it is simpler to write one first law for the entire thing.