India is fast becoming a data-centre hub. The Indian market, estimated at 700 MW, is expected to grow to 1.5 GW in the next 3-4 years. Data centres are big energy guzzlers. The International Energy Agency (IEA) estimates that in 2022, data centres around the world consumed 240-340 terawatt hour (TWh) of electricity, roughly 1-1.3 per cent of global final electricity demand.

Why do they need consume this much? Because energy is needed to cool the servers at the data centres. There are three ways of cooling the servers — room level, rack level and chip level. Of the three, chip-level is said to be the most energy efficient.

Chip-level cooling is done by phase-change materials (like ice) or by ‘heat pipes’. Most heat pipes feature a porous wick which moves the working fluid to the evaporator from the condenser. But the wicks are costly.

Then there are these heat pipes called thermosyphons. They simply siphon out the heat — a liquid moves through it, picking up heat from the hot regions and dumping the heat into the atmosphere. Thermosyphons are gravity-assisted wickless heat pipes that utilise gravitational force to transport the working fluid from the condenser section to the evaporator section.

A group of scientists led by Prof Pallab Sinha Mahapatra and Prof Arvind Pattamatta from the Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, have developed an ‘Integrated Flat Thermosyphon Heat Sink (IFTHS)’ with enhanced performance. The IFTHS has a condenser with integrated hollow fins, the inner surface of which is used for condensation and the outer surface is used for air-side convective cooling.

In their paper published in Applied Thermal Engineering, the researchers have said that a super-hydrophobic (water-repelling) condenser and a mini-channel used in the device gave superior cooling performance. “The lifespan of electronic components can be increased by 3.73–17.75 times and the room air cooling load can be reduced by 8.04–25.12 kJ/kg when the IFTHS configurations are used for cooling electronic chips in data centre servers instead of the baseline configuration. The novel IFTHS configurations developed in the present study can contribute to energy-efficient chip-level thermal management in energy-intensive data centers,” the paper noted.

The conventional air-cooled heat sinks used for cooling CPUs in rack servers can be replaced by the IFTHS without any additional modifications, it says.

Prof Marco Marengo, Professor of Thermal Sciences, from the Department of Civil Engineering and Architecture, University of Pavia, Pavia, Italy, has reviewed this work. In his comments, published in IIT-Madras Tech Talk, Prof Marengo noted that by using both inner and outer surfaces for condensation and air-side convective cooling, the IFTHS outperforms (the conventional) flat thermosyphon.

“This technology has the potential to enhance the cooling effectiveness of these systems in energy-intensive sectors and for data centres,” he says.