Anovel tested technology for cooling electronic circuitry is also useful in many other industries. The method is called “Thin Cavity Fluidic Heat Exchanger”(TCFHE). Technology details can be viewed at the U.S. Patent and Trademark Web site, at application 20100078155.

Figure 1. Basic TCFHE cross-section
The TCFHE is a simply constructed, small-volume, high-performance, and effective method for cooling critical electronic devices at the chip, board, module, and system levels. Its high thermal performance originates from a very-high-velocity air flow, a very thin boundary layer, and high air utilization. It can efficiently and reliably cool critical regions in electronics at very low cost, in a small space, with high design flexibility, and with no concern for air leakage causing damage. The TCFHE resolves the conflict in high-speed electronics to completely seal a compact enclosure for shielding and packaging purposes while also removing high heat loads. It is technically positioned between fan and heat sink cooling methods and water cooling methods. When fan and heat sink methods or packaging constraints cannot obtain the needed thermal performance, the TCFHE is the next best choice over water cooling.

Figure 2. Top view of TCFHE prototype
Figure 1 shows the cross-section of a basic TCFHE for a simple planar structure. It consists of a thermal load, heat transfer plate, a cavity spacer, a cover plate, a gas inlet, and a gas outlet. The cavity spacer can be a feature of the heat transfer plate or the cover plate instead of a separate item. Heat produced by the thermal load is conducted to a heat transfer plate, which can be planar, tubular, or another shape. Compressed air or other gas passes by the plate through a thin gap (<1-10 mils) at high speed and carries the heat away. At the expense of higher inlet pressure, a thinner gap provides better cooling, which is not casually obvious. Although heat sink fins or channels could be used in the gap, they are less efficient, less reliable, and more costly than a thin-gap spaced surface. The TCFHE structure can be embedded within a printed circuit board or IC package as well.

Figure 3. Exploded top view of prototype
Test data for a prototype TCFHE was taken using cavity gap thicknesses of 3, 5, 10, and 20 mils (using paper). The prototype is shown in Figure 2 through Figure 4, consisting of three main pieces. A set of graphs was produced to measure cooling performance using a load power of 3.6 Watts and an ordinary shop compressor for an air source. The cooling area was 1 inch long by 1.25 inches wide and air inlet temperature was about 29°C. The prototype was thermally insulated for worsecase test purposes using bubble wrap. Electronic pressure gauges (plenum located), flow meter, and temperature sensors (not shown) were used for air measurements.