Thermal Effects on Micro-Sized Tesla Valves

Abstract

The Tesla valve is a no-moving-parts check valve that may be used in a variety of mini- or micro-fluidic applications for passive flow promotion and/or rectification. Its effectiveness is measured via its diodicity which depends on the Reynolds number and its unique design features. The valve may be aligned in-series to further increase its fluidic diode effect — forming a multi-staged Tesla valve (MSTV). Using Computational Fluid Dynamics (CFD) and high performance computing, the current investigation assesses the effects of heat transfer on the overall MSTV diodicity and the extent to which the MSTV enhances heat transfer. For laminar, single-phase flow, thermal boundary conditions were imposed to include an isothermal MSTV wall at 20 °C and a flow inlet temperature of either: 20 °C, 50 °C or 80 °C. The flow outlet temperature and MSTV diodicity was then determined for the various inlet temperatures, Reynolds numbers, working fluids (i.e. Prandtl number, Pr) and number of Tesla valves in MSTV. Working fluids were varied between: air (Pr ∼ 0.7), water (Pr ∼ 5) and ethylene glycol (Pr ∼ 200). The MSTV channel cross-section was set to 1 mm2 and the valve-to-valve distance was held constant while varying the number of Tesla valves. Results indicate that there is a significant decrease in diodicity for water and ethylene glycol as the inlet temperature increases, suggesting higher performance of the MSTV when there is less heat transfer. For air, MSTV performance was found to actually increase with temperature. Due to mixing effects, the MSTV was demonstrated to function as an efficient heat exchanger relative to an un-valved mini-channel of similar size.