Local Heat Transfer Coefficients Measurement Under Micro Jet Impinging Using Nitrogen Gas (N2)

Abstract

Experimental and simulation studies were performed to reveal local heat transfer coefficients under jet impinging in micro domain with Nitrogen gas. The experimental device was made of a 500 μm thick Pyrex and 400 μm thick silicon wafers. On the Pyrex wafer, four 100 nm thick resistance temperature detector (RTD) thermistors and a heater were fabricated from titanium. Jet orifices were etched by deep reactive ion etching (DRIE) on a silicon wafer, which was attached to the Pyrex wafer through a vinyl sticker (250 μm thick). A 1.9 mm × 14.8 mm × 250 μm micro channel was formed by laser drilling into the sticker. Varying flow rates of Nitrogen gas and heat fluxes of the heater, temperatures of the four thermistors were collected and local heat transfer coefficients were inferred enabling to divulge the jet impinging cooling characteristics. Initial simulations were used to complement experiments and to obtain detailed flow patterns of the jet, temperature distribution on the heater area, and fluid temperature distribution.

Analysis of transient temperature response under micro jet impinging using nitrogen (N2)

“…The time constant of this multifaceted heat transfer process is determined by the heat transfer mode that responds the slowest -either conduction or convection. The time constant, τ, was defined for heating as follows [24]:…”