Ionic wind pump with air being deflected toward critical heat zones. | Source: USPTO
Apple's U.S. Patent No. 8,305,728 for "Methods and apparatus for cooling electronic devices," describes a system in which the direction of ionized air moving through a computing device is deflected by either an electric or magnetic field. Currently, mechanical fans pull in air and push it through predetermined physical paths within a computer, usually over passive heat exchangers, and out through an exhaust port.
Driving the air in Apple's system is the ionic wind generator, basically a solid-state air mover based on "corona discharge--an electrical discharge near a charged conductor caused by the ionization of the surrounding air." The system is comprised of a corona electrode, a collector electrode and a high voltage power supply. When voltage is applied to electrodes, an electric field is created and causes particles in the surrounding air to take on a charge, or become ionized. An electric field propels the charged particles toward the collector electrode, which collide with other neutral particles as they move to create to generate "bulk air movement."
As the ionized air moves through the device, it can be deflected or redirected by a "deflection field generator," which can be a magnet or electromagnet. The magnitude of deflection is governed by the Lorentz force, or force on a charged particle from an electromagnetic field, which can be varied by the deflection field generator.
Illustration of charged particles (110) colliding with neutral particles (108) as they are moved
from the corona electrode (102) to the collector electrode (104) in an ionic wind generator.
By employing standard issue heat sensors, the ion wind pump and deflection field generator system can direct cooling air to high temperature areas like the CPU or GPU.
The system also solves another problem associated with always-on mechanical fans, the so-called "no slip" condition at the "surface and the mean free stream velocity at the outer reaches from the surface" of a component. When such a condition arises, it creates a boundary layer of air over a component, making heat transfer more difficult. By modulating the rate of deflection, or time in which air flow passes over a component, the system creates eddy currents and turbulent flows to disturb the boundary layer.
Finally, the ionized air exits the device through a vent that is in the path of the ionic pump's normal air flow.
Illustration of air being directed via deflection field generators.
Interestingly, the invention notes that the system is not limited to large desktops and laptops, but in mobile devices such as cell phones and media players as well.
Although such ion wind pump technologies are used in specialized industrial and laboratory settings, a solution has not yet been presented in a consumer device. Apple has shown that it is actively looking to solve issues related to cooling internal components, including noise reduction as seen with the asymmetrical fans in both MacBook Pro with Retina display models (1, 2), however it is unknown if the company will implement the solid state generator any time soon.