Two-phase flow instability in a liquid nitrogen heat exchanger. (3rd Report. Improved, horizontally installed heat exchanger without a spiral tube).

概要

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Experimental and analytical investigation are conducted on flow instability in a horizontally installed liquid nitrogen shell and tube-type heat exchanger. The experiments are carried out by making use of water steam as a secondary fluid, and it is observed that flow instability occures in the range of large inlet flow rate. An anemometer using a hot film as a sensor is used to measure inlet velocity perturbation of liquid nitrogen. Mode analysis of the inlet velocity perturbation reveals that there exists a fundamental mode and its higher harmonics up to the third. As the period of the fundamental mode is nearly equal to the transit time for a fluid particle to travel through the heated tube, which is obtained by a static analysis, it is suggested that flow instability is of the density wave type. Moreover, static instability that is accompanied with a fall of the pressure drop is also observed in the vicinity of the stability boundary. The analysis of the static heat transfer and pressure-drop characteristics can simulate the experimental data.
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