Liquid Cooling For MacBooks Maybe Even iPhones

Apple has filed for patents on two separate liquid cooling technologies, which might be intended for use on future notebooks and possibly even mobile devices like the iPhone.

MacNN reports, on Thanksgiving Day 2008, the US Patent & Trademark Office published Apple’s patent application titled Liquid-cooled portable computer - (patent number 20080291629).

Here’s Apple’s summary of the invention:

“The computational performance of electronic devices has increased significantly in recent years. This increased performance has been accompanied by an increase in power consumption and associated heat generation. Furthermore, this additional heat generation has made it harder to maintain acceptable internal and external operational temperatures in these devices.

“Portable devices, such as laptop computers (notebook PCs), cellular telephones, and personal digital assistants have additional design constraints which make it even harder to manage thermal load. In particular, size and weight limitations in such devices can make it difficult to achieve desired operational temperatures. For example, in many portable devices the size and weight of metal heat sinks may be prohibitive. Furthermore, battery life constraints in such devices may limit the available power for active cooling mechanisms, such as fans.

“Hence what is needed are cooling mechanisms that overcome the problems listed above.

“One embodiment of the present invention provides a computer system that includes a power source that is coupled to a heat pipe, where the power source includes an integrated circuit. This heat pipe may contain a liquid coolant that has a density greater than a first pre-determined value at room temperature. A pump is coupled to the heat pipe is configured to circulate the liquid coolant through the heat pipe. Furthermore, a heat exchanger coupled to the heat pipe is configured to transfer heat from the heat pipe to an environment external to the computer system.

”In some embodiments, the integrated circuit includes a processor. In some embodiments, the liquid coolant includes: water, a coolant in an R133 group of coolants, and/or a coolant in an R134 group of coolants. Furthermore, in some embodiments the liquid coolant includes two phases of matter. For example, the two phases may include a gaseous phase in bubbles, and nucleation of the bubbles may be used to increase the heat-transfer coefficient of the liquid coolant. In another example, latent heat may be used to increase the heat-transfer coefficient of the liquid coolant. And in some embodiments the liquid coolant includes metal particles to increase the heat-transfer coefficient of the liquid coolant.

“In some embodiments, the liquid coolant has a thermal conductivity greater than a second pre-determined value. In some embodiments, the pump includes a mechanical pump and/or an electrostatic pump. Furthermore, in some embodiments the pump is configured to circulate the liquid coolant using mechanical vibration of a membrane.

“In some embodiments, the computer system includes a laptop computer. In some embodiments, the heat exchanger includes a forced-fluid driver and a heat coupling-mechanism coupled to the forced-fluid driver. This forced-fluid driver may be configured to pump heat from inside the computer system to the environment. Furthermore, in some embodiments the heat coupling-mechanism includes convective-cooling fins.

‘In some embodiments, the computer system includes a cold plate coupled to the power source and the heat pipe. This cold plate includes channels which increase a surface area wetted by the liquid coolant, thereby increasing a heat-transfer coefficient of the cold plate.

“Another embodiment provides a method for cooling a portable computer system. During this method, the liquid coolant is circulated in the heat pipe. Then, heat is transferred from the heat pipe to an environment external to the portable computer system using the heat exchanger. Note that the heat is generated by an integrated circuit in the portable computer system.”

According to MacNN Apple’s patent generally relates to heat-transfer techniques and more specifically to the use of liquid coolants to transport heat in future MacBooks. The new cooling systems may eventually, according to Apple, go beyond the laptop and into their other portables such as the iPhone, iPod touch or even a yet unseen gaming console. With Quad-core processors coming to market in the coming year, cooling systems are going to be paramount in keeping desktops, laptops and other devices cool.