A fundamental study on the heat transport characteristics in a pulsating heat pipe by using a forced oscillation system (Measurement of effective thermal conductivity)
Recently, highly efficient small heat transport devices have been required. In particular, pulsating heat pipes (PHP) have come to draw a lot of attention. The contribution of sensible heat transport and latent heat transport in oscillating working fluid, which plays an important role in heat transport performance of PHP, has not been clarified enough experimentally yet. The purpose of this study is to evaluate the contribution of sensible heat transport and latent heat transport experimentally by making liquid column oscillate sinusoidally in the channel. The channel was initially evacuated, and ethanol was charged to form a liquid column, which is called single component system. In addition, the ethanol was charged in the channel with air in the gas phase at atmospheric pressure, which is called two components system. The effective thermal conductivity of latent heat transport is determined by the difference between the effective thermal conductivity in single component system and that in two component system. In two components system, that is sensible heat transport, the effective thermal conductivity decreases monotonically as oscillation center moves to cooling section under the same amplitude, because residence time of liquid column at heating section decreases. On the other hand, in latent heat transport, the effective thermal conductivity increases as oscillation center moves to cooling section under the same amplitude, because liquid film at cooling section becomes longer. In addition, numerical analysis was conducted for sensible heat transport in oscillating working fluid. The comparison of the numerical results with the experimental results indicates that liquid film at the tip of liquid column would enhance sensible heat transport.
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