100 kg/s of nitrogen enters a steady-state counter-current heat exchanger at T = 150 K and P = 10 MPa. The nitrogen is cooled in the heat exchanger and then enters an adiabatic flash chamber. The outlet pressure of the flash chamber is P = 0.8 MPa. The liquid leaving the flash chamber is removed as product. The vapor leaving the flash chamber is returned to the counter-current heat exchanger, in which it is heated to a temperature of 135 K. What is the flow rate of liquid product? Use Figure 2-3 for data.

Question

A. 100 kg/s
B. 60 kg/s
C. 25 kg/s
D. 40 kg/s
E. Insufficient information to solve

Answer 1

A. Incorrect. There is one stream entering the process, but two leaving, so neither has a flow rate equal to that of the entering stream.
B. Incorrect. You have likely mixed up the liquid and vapor streams.
C. Incorrect. The vapor exiting the process is not saturated because it has been heated.
D. Correct. This is similar to Example 5-9 and describes a classic Linde process.
E. Incorrect. All the required information is there. You are likely trying to write a balance around either the heat exchanger or the flash chamber; try drawing the system boundaries around the entire process.