IMPROVEMENT OF A MINI ANNULUS-CHANNEL BY TWISTING TUBE WALL FOR SUPERCRITICAL CO2 FLOW
Keywords:
Mini-channel, supercritical CO2, pseudo-critical temperatureAbstract
A mini annulus-channel with a hydraulic diameter of 1.65 mm was improved by twisting the inner tube wall with the twisted ratio of 9.13 for enhancing heat transfer coefficients and reducing pressure losses of supercritical CO2 flowing turbulently with the mass flux of 450 kg/m2-s. The experimented heat transfer coefficients of the supercritical CO2 flow in both channels (before and after improvement) were figured out by a modified Wilson plot method in various conditions. It can be shown that heat transfer coefficients of the improved channel are higher evidently than that of the former channel at and near the pseudo-critical temperatures of supercritical CO2 while heat transfer coefficients in both channels are not different when the CO2 temperatures are far away from the pseudo-critical temperature. The apparent advantage of the improved flow channel is that it can reduce pressure losses due to the supercritical CO2 flow by approximately 4 times of the original flow channel. In addition, a heat transfer correlation multiplied with a correction factor is suggested for this flow channel based on experimental data.
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