On the hydrodynamic characterization of a passive shape memory alloy valve

An attractive approach to the thermal management of next generation photonics devices (heat fluxes > 10² W/cm²) is micro-channel cooling, and micro-valves will be required for refined flow control in the supporting micro-fluidic systems. In this paper, a NiTi Shape Memory Alloy (SMA) micro-valve design for passive flow control and thermal management was prototyped at the macro scale and hydrodynamically characterized. The dynamic behavior of the valve was observed and the loss coefficient (ζ_ν) derived from pressure-flow measurements. The hydrodynamic characterization study is important because ζ_ν is sensitive to Re and geometry in the flow regime of the micro-fluidic system. Static replicas of the SMA valve geometry were tested for low Re (110-220) and a range of opening ratios (β) in a ø1 mm miniature channel. The loss coef ficients were found to be sensitive to flow rate and decreased rapidly with an increase in Re. A correlation was developed to interpolate ζ_ν from a given Re and β. The valve loss coefficients obtained in this work are important parameters in the modeling and design of future microfluidic cooling systems.