An existing steady state liquefaction process has been taking in 10 kg/s of nitrogen at P = 0.1 MPa and T = 298.15 K, and producing 10 kg/s of saturated liquid nitrogen. Due to a process upset, the temperature of the nitrogen entering the process increases to T = 300 K. Which of the following is a likely consequence?

Question

A. The quality of the liquid nitrogen will decrease.
B. The energy load on the heat exchanger(s) in the system will rise.
C. The flowrate in will fall below 10 kg/s.
D. The process will explode.
E. The nitrogen will begin to react with itself, forming diatomic molecules.

Answer 1

A. Incorrect. Quality of a liquid is 0 by definition, so it cannot decrease.
B. Correct. The amount of energy required to reduce the temperature will increase to make up for the temperature difference.
C. Incorrect. The inlet flowrate is not likely to change because of the temperature excursion.
D. Incorrect. This is not a “likely” consequence. Processes are routinely designed in a way that ensures they are safe from small process upsets.
E. Incorrect. Gaseous nitrogen is already diatomic.