FIGURE 4 shows the measured temperature rise profiles for the baseline case at the
three flow rates. In all of the results, the temperature rise based on the inlet temperature
from TABLE 3 is used. It is interesting to see that the tube wall temperature distribution
decreases along the tube axis at the low flow condition. The returning liquid nitrogen in the
annulus is always at a higher temperature than the tube wall for this case. As the flow is
increased, the tube wall temperature distribution changes slope and the tube becomes
warmer than the flow leaving the end. This is due to the axial heat conduction in the tube
transferring energy from the warm annular stream along the tube wall for the two higher
flow rates. At the lowest flow rate, there is not enough heat transfer from the annular
stream to the tube to produce this effect.