Industrial Applications of Thermal Devices With Meso-Scale Features

Two commercial applications are presented that are based on heat transfer augmentation through the use of micro scale geometries. First, we present a micro-channel cross flow heat exchanger, manufactured by a derivative of the LIGA micromachining process. Both the in-plane and cross-flow passages have characteristic widths which can be as low as 250 micrometers. The manufacturing process of the heat exchanger is described, and the scaling laws capturing various design parameters are discussed. Experimental results which validate these scaling laws are presented. A second product, the Micro Jet Cooling Array (MJCA), consists of an array of small diameter impinging microjets with jet diameters as low as 300 micrometers, and provides extremely high heat transfer coefficients over relatively large target areas. The return flow in the MJCA is based on a patent-pending process that essentially isolates the jets from each other. In this manner a large number of small diameter jets can be placed next to each other without the deleterious effect of (a) cross-washing of neighboring jets, and (b) jet-to-jet flow variations due to variations in the discharge pressure over the target. The manufacturing of the MJCA, the scaling laws, and related experimental results are presented.