Cryogenic Single-Phase Heat Transfer in a Microscale Pin Fin Heat Sink

A combined experimental and computational fluid dynamics (CFD) study of single-phase liquid nitrogen flow through a microscale pin-fin heat sink is presented. Such cryogenic heat sinks could find use in applications such as high performance computing, spacecraft thermal management, and hydrogen storage thermal management. A circular pin fin heat sink in diameter 5cm and 250 micrometers in depth was studied herein. Unique features of the heat sink included its variable cross sectional area in the flow direction, variable pin diameters, as well as a circumferential distribution of fluid into the pin fin region. The stainless steel heat sink was fabricated using chemical etching and diffusion bonding. Experimental results indicate that the heat transfer coefficients were relatively unchanged around 2600 W/m² Kfor flow rates ranging from 2 – 4 g/s while the pressure drop increased monotonically with the flow rate. None of the existing correlations in literature on cross flow over a tube bank or micro pin fin heat sinks were able to predict the experimental pressure drop and heat transfer characteristics. CFD was used to solved for the momentum and energy equations for a laminar flow, steady-state, with initial and boundary conditions. Commercial code, developed by ANSYS Fluent, was used to\ud perform the simulations. The three dimensional model showed reasonable ( ~7 percent difference) agreement in the average heat transfer coefficients between experiments and CFD simulations