According to Apple, in one implementation, the cooling system includes a heat spreader that is in thermal contact with a heat generating component in the computer, a frame casting, and a heat pipe to passively dissipate heat generated from the heat generating component in the computer to the frame casting. The heat pipe includes a first portion that is co-planar with and in direct contact with the heat generating component, and a second portion that is in thermal contact with the frame casting.

Here's Apple's background on the invention: "As computer components evolve into more powerful devices, their power requirements consequently increase. With this increase in power consumption, a commensurate increase in power dissipation in the form of heat results. For example, in a laptop computer system, microprocessors, such as a central processing unit (CPU) and a graphical processing unit (GPU), and a chipset are major sources of heat.

"Heat dissipation is an important consideration in the design of modern-day computer systems. If heat is not adequately dissipated from the system, components may fail causing catastrophic damage to the system. To date, cooling systems have utilized finned heat sinks, augmented by axial flow fans mounted on the heat sink and/or air movers in the form of fans within or around the computer system. Nevertheless, as the amount of heat generated by the components increases, the current cooling systems will prove inadequate because larger heat sinks and/or fans will not fit into the already cramped space in and around a computer system."

And here's Apple's summary of the invention: "In general, in one aspect, this specification describes a cooling system for a computer. The cooling system includes a heat spreader that is in thermal contact with a heat generating component in the computer, a frame casting, and a heat pipe to passively dissipate heat generated from the heat generating component in the computer to the frame casting. The heat pipe includes a first portion that is co-planar with and in direct contact with the heat generating component, and a second portion that is in thermal contact with the frame casting.

"Particular implementations can include one or more of the following features. Conductive and convective heat transfer characteristics of the frame casting can be utilized to provide additional passive cooling for the heat generating component. One or more ancillary heat pipes can be embedded in the heat spreader, in which the one or more ancillary heat pipes make thermal contact with the heat generating component. The first portion of the heat pipe can be embedded in the heat spreader and the second portion of the heat pipe can extend from the heat spreader to the frame casting and be in thermal contact with the frame casting along a length of the frame casting. The first portion of the heat pipe can comprise an evaporative portion of the heat pipe. The second portion of the heat pipe can comprise a condensation portion of the heat pipe. Heat generated by the heat generating component can be transferred to coolant within the evaporative portion of the heat pipe to vaporize the coolant. The vaporized coolant can be cooled within the condensation portion of the heat pipe and transfer the heat generated by the heat generating component to the frame casting. The heat pipe can comprise a hollow core that contains the coolant, and a wicking layer surrounding the hollow core for transporting the vaporized coolant from the evaporative portion of the heat pipe to the condensation portion of the heat pipe. The heat pipe can further include a thermal conductive layer surrounding the wicking layer for transferring at least a portion of the heat generated by the heat generating component to the frame casting and the heat spreader.

"Particular implementations can further include one or more of the following features. The heat generating component can comprise a central processing unit (CPU), a graphical processing unit (GPU), or a chipset. The cooling system can further include a radial fan in the computer for blowing air in the computer and exhausting the air from the computer through a vent in the frame casting. The second portion of the heat pipe can be disposed over the vent such that the air exhausted through the vent by the radial fan actively cools both the second portion of the heat pipe and the frame casting. The cooling system can further include a fin stack located at the vent in the frame casting, wherein the second portion of the heat pipe is also in thermal contact with the fin stack. A top surface of the heat spreader can include a plurality of channels for increasing surface area and improving the heat transfer rate between the heat spreader and the air in the computer. The plurality of channels can be formed on the top surface of the heat spreader such that each channel points to a center of the radial fan to direct air flow in the computer to the radial fan. A bottom surface of the heat spreader can include a thermal interface contact for each heat generating component in the computer to reduce thermal resistance between the heat spreader and each heat generating component.

"In general, in another aspect this specification describes a cooling system for a computer including a heat spreader having a top surface and a bottom surface, in which the bottom surface of the heat spreader is in direct contact with a heat generating component in the computer and the top surface of the heat spreader includes a plurality of channels for increasing a surface area of the heat spreader and improving the heat transfer rate between the heat spreader and air in the computer. The cooling system further includes a radial fan in the computer for blowing the air in the computer and exhausting the air through a vent of the computer. The plurality of channels are formed on the top surface of the heat spreader such that each channel points to a center of the radial fan to reduce resistance of air flow in the computer to the radial fan.

"Particular implementations can include one or more of the following features. The cooling system can further include a frame casting, and a heat pipe coupled to the heat spreader and coupled to the frame casting for passively dissipating heat generated from the heat generating component in the computer to the frame casting. The heat pipe can include a first portion that is co-planar with and in direct contact with the heat generating component, and a second portion that is in thermal contact with the frame casting. The first portion of the heat pipe can be embedded in the heat spreader and the second portion of the heat pipe can extend from the heat spreader to the frame casting and be in thermal contact with the frame casting along a length of the frame casting.

"According to the cooling system disclosed, the conductive and convective heat transfer characteristics of the frame casting are utilized to significantly improve heat dissipation. Passive and active cooling mechanisms are integrated into the cooling system and, depending on the temperature of the computer system at any given time, one mechanism or both can be utilized. Thus, the cooling system offers multiple levels of cooling capacity."

The inventor is Ihab Ali. The graphic below is a front top perspective view of a cooling system according to one implementation.