Thermofluid modeling of an oscillating heat pipe

Transient complex thermofluid systems are widely applied in fields such as aerospace engineering and electronics cooling. Oscillating heat pipes (OHPs) are examples of such systems. They consist of serpentine channels containing trains of liquid slugs and vapor bubbles, in which the vapor bubbles thermally expand and compress, moving the train and thereby delivering heat from hot regions to cold condensers. The modeling approach reported here aims to capture the essential physics of OHPs with minimal complexity. It contains two modules. The first module solves the two-dimensional heat equation in the embedding solid structure. The second module uses first principles to solve the one-dimensional fluid motion and heat transfer equations within the fluid-filled OHP channels, including simple models for the phenomena of liquid film deposition and dynamics, nucleate boiling, and bubble dry-out, while conserving mass, momentum, and energy. These two modules are weakly coupled by the immersed boundary method (IBM), which enables flexibility in OHP channel configuration and plate shape. In contrast to previous approaches that rely on empirical correlations for model parameters, our approach treats parameters as uncertain values to be estimated by data assimilation. We compare pointwise temperature measurements with published experimental OHP studies and show good agreement. In particular, the model captures critical changes in performance due to dry-out.