INVESTIGATION OF INTRINSIC DYNAMIC CHARACTERISTICS IN AN OSCILLATING HEAT PIPE

Abstract

Conjugate heat transfer devices based on oscillating phenomenon allow thermal instability to play a crucial role in thermal management. This study proposed and tested a hollow cylindrical oscillating heat pipe (OHP) for managing waste heat sources. Deionized water was filled as a working medium at ratios of 10%-90%. Experiments were conducted with heat inputs 10-120 W; the performance was dependent on the features of self-sustained oscillations. Dry-out was found only under low filling conditions, and this operating fault can be avoided by increasing the working medium. A medium level of approximately 50% is optimal. The intrinsic thermal instability related to the performance of an oscillating thermal design has attracted considerable academic interest. Simplifications and assumptions of traditional modeling approaches render them unsuitable for probing the dynamic characteristics of such thermal designs. A nonlinear autoregressive exogenous (NARX) modeling based on machine learning techniques was introduced to identify the causality of the heat transfer mechanism of the OHP. The discrete models estimated using the NARX modeling accurately simulated OHP dynamics, which were further revealed through spectrum analysis. Energy excitation, shown as frequency resonances, was distinctly related to OHP performance.