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Smart thermal management of high-power microprocessors using phase-change

Periodic Reporting for period 1 - ThermaSMART (Smart thermal management of high-power microprocessors using phase-change)

Reporting period: 2017-12-01 to 2019-11-30

Developments in modern high-speed microprocessors enhance communication, computing and electronics, play a profound role in our societies and industries. Increased use of supercomputers, power devices, electric vehicles, photovoltaics, avionics and radar devices, miniature fuel cells and gas-liquid reactors, operating at high power densities have brought about a dramatic demand for thermal management. Sustaining long-term high speeds and reliable operation requires efficient heat dissipation.

Conventional air cooling is highly inefficient with only around fraction of the air injected contributing towards cooling. Phase-change based cooling offers a promising alternative to conventional air cooling in both earth and space environments, given high phase-change heat transfer coefficients. We are building on our previous FP7 IRSES THERMAPOWER project which led to major advancements in the fundamental understanding of phase change phenomena. We aim to achieve this by building new collaborations of top researchers from 15 world-class universities across 5 continents from EU, Asia, Africa, North America and South America, and 3 European SMEs with expertise in precision experiments, micro-fabrication, theoretical modelling, numerical simulation and engineering design. This collaboration will enable knowledge transfer and access to unique international facilities at Maryland, Stanford, Rio de Janeiro, Dalian, Tianjin, Bangalore, Toronto, Kyushu, Kobe and Pretoria complementing EU know-how based at Edinburgh, Nottingham, Paris, Warsaw and Dublin.

The project will train over 40 early stage researchers in latest experimental and modelling techniques. The research programme planned addresses key fundamental and practical questions in complexities of scale hitherto unstudied, including contact line interactions amongst evaporating bubbles or droplet populations on patterned substrates. Expertise is being transferred through planned secondments and exposure of secondees to different research environments, regular meetings, technical workshops and training schools. This will consolidate the EU’s position at the forefront of cutting-edge research in this area and will promote long lasting collaboration between Academia and Industry.
ThermaSMART is at the forefront of scientific discovery and technological innovation in the area of cooling technologies for microelectronic chips. Cooling is vital to protect the vast amounts of data generated and to sustain the processing speed of computer chips, which are always at risk of damage due to overheating whether on ground applications or space applications. This is a problem as the amount of energy generated on a modern fast processor can heat it up by 80 degrees, which causes localised over-heating and failure. ThermaSMART focusses on phase-change cooling, where coolants evaporate to cool down the processor. The ensuing vapour is condensed before circulating back to the device. These coolants are pumped through systems with microchannels the width of human hair, and the system size is slightly smaller than a typical nanoSIM card.
Through a series of international secondments, the consortium is studying both the fundamental behaviour of coolants as they evaporate or boil, and the design implications.
New phenomena were discovered regarding how the coolants leave patterns as they evaporate, their effect on soft surfaces and their behaviour as droplets move or get stuck on the device surface. The consortium also revealed for the first time that particles in vapour clouds move chaotically, impacting condensation behaviour.
These results will be important in the development of phase-change cooling devices that can be used by the thermal management industry in the micro-electronics sector, including for products such as electric vehicles, miniature fuel cells and gas-liquid reactors. There will be a positive environmental impact, as more efficient cooling will increase the lifespan of such high-power devices.
Key results were disseminated in papers in journals of the highest repute, Youtube, at conferences and workshops aimed at academic and industry, via the social media of ThermaSMART and its partners, and online.
From the engineering design of these microchannels, the consortium revealed the importance of gravitational orientation of microchannels during flow boiling. Gravity was previously considered too insignificant to be a key factor and the work done in ThermaSMART disproves this. This result lays the foundation for improved cooling in space, where heat dissipation is a critical limiting factor.
These results were achieved through a series of secondments that helped develop novel numerical, theoretical and experimental methods. Exploitation and dissemination events were held where ECRs, ERs, guests from the community and industry discussed the way forward.
ThermaSMART demonstrated a strong track record of skill-development through schools and workshops. Our seconded researchers, both ECRs and ERs from academia and industry, participated in modelling schools and annual workshops where latest experimental and modelling methods were discussed. Our ECRs were strategically seconded (from EU to our non-EU partners and from South African partner to EU beneficiaries), such that complementary skills were learnt at the host institute. This played an important role in improving their career prospects. Many of our ECRs graduated with a Doctorate degree due to the work done during their secondments and the innovation this instigated. Some were recruited by major companies in senior roles, either in development or innovation.
Our collaborators incorporated ThermaSMART research in their products, which extend beyond microprocessor cooling, and in preliminary demonstrators, which were exhibited in international fora.
Based on results gained while on secondment ThermaSMART partner Elvesys improved its droplet generation pack, and is developing a new microdroplet generation platform. With conventional techniques it is difficult to control droplet size – a particular problem in the pharmaceutical industry, where this can cause an irregular burst of drug release, leading to cytotoxic effects. The platform under development will be able to maintain high levels of droplet uniformity, at a high production rate.
Elvesys and sister company Cherry Biotech designed a preliminary platform for a microprocessor phase-change microfluidic cooling system. which incorporates knowledge gained on secondment to increase the efficiency of thermal transfer using a microchannel. This has applications in other Cherry Biotech projects, such as ultra-fast polymerase chain reaction for fast disease diagnosis.
FlowCapture made advances in using micro-focused X-ray systems to visualize flows in microchannels, and in collaboration with the University of Edinburgh applied machine-learning techniques to flow regime identifications in gas-liquid two-phase flows. As part of the programme, Flow Capture launched a new product, a multiphase flow measurement system targeted at academia and industry.
ThermaSMART continues to enhance EU’s industrial and academic competitiveness in the field of phase-change cooling. This includes not only the development of new experimental and modelling methods but also includes generating new fundamental insights that helps our industry partners to gain an edge over their competitors.