Chill out: Embedded thermoelectric devices; two-phase cooling; mini membrane fan.
Researchers from the University of Pittsburgh and Carnegie Mellon University propose using locally embedded thermoelectric devices (TEDs) to perform active cooling inside circuits.
“Circuits like clock generators and arithmetic and logic units (ALU) create high-frequency heat fluxes with their peak hot spots occurring on the microprocessor,” said Feng Xiong, associate professor of electrical and computer engineering at Pitt’s Swanson School of Engineering, in a press release. “Cooling systems at the chip size are over designed and a more targeted strategy is necessary to dissipate heat in these hot spots.”
The TED eliminates high frequency temperature variation, removing heat from hot spots inside circuits to colder regions throughout the device using thermoelectric effects at the same frequency. The team used materials with high thermal conductivity, theoretically improving the cooling efficiency by a factor of 100 compared to conventional thermoelectric materials.
“We demonstrated a practical method to actively cancel the transient temperature variations on circuit elements with TEDs,” Feng continued. “This result opens a new path to optimize the design of cooling systems for transient localized hot spots in integrated circuits.” [1]
Researchers from the University of Missouri are developing a two-phase cooling system designed to efficiently dissipate heat from server chips through phase change. The system can operate passively without consuming any energy when less cooling is needed.
“The liquid goes in different directions and evaporates on a thin metal surface,” said Chanwoo Park, a professor of mechanical and aerospace engineering in the Mizzou College of Engineering, in a statement. “Using this boiling surface, we’re able to achieve very efficient heat transfer with low thermal resistance.”
The cooling system dissipates heat from server chips through phase change, such as boiling a liquid into vapor in a thin, porous layer. (Credit: Mary Dillion/University of Missouri)
When more heat removal is needed, a mechanical pump can be activated, which still only uses a small amount of energy. The cooling system is designed to easily connect and disconnect within server racks. [2]
Researchers at the University of Stuttgart developed a mini membrane fan that uses targeted airflow to cool devices such as power electronics. The fan’s energy consumption ranges from 25 to 75 mW.
The membrane fan comprises a permanent magnet, two elastic membranes, and two opposing excitation coils attached to the membranes. The thickness of the excitation coil is less than 180 µm. When a sinusoidal current flows through the coils, the membranes are alternately pulled downwards and upwards, causing the membrane opening to open and close, resulting in a forward airflow with an air velocity of over 2.5 m/s while producing minimal noise of less than 30 dBA. The high airflow enables effective cooling even at distances from the fan, making it suitable for hotspot cooling in hard-to-reach areas of a device.
[1] Liu, Y., Cheng, HY., Malen, J.A. et al. Thermoelectric active cooling for transient hot spots in microprocessors. Nat Commun 15, 4275 (2024). https://doi.org/10.1038/s41467-024-48583-9
[2] Rohan Kokate, Chanwoo Park. Experimental analysis of subcooled flow boiling in a microchannel evaporator of a pumped two-phase loop. Applied Thermal Engineering, 2024; 249: 123154 http://dx.doi.org/10.1016/j.applthermaleng.2024.123154
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