Research round-up: cooling systems, batteries and bioplastics

In our research round-up we showcase recently published work by four different research groups. Keep reading to find out more about what our researchers are currently working on.

Numerical study of the impact of the channel shape on microchannel boiling heat transfer

International Journal of Heat and Mass Transfer Volume 150 (April 2020)

M.Magnini, O.K.Matar

Research by Matar Fluids and the University of Nottingham examines cooling systems in high-performance electronics, and attempts to answer an important, industrially-relevant question: what is the impact channel cross-sectional shapes on boiling heat transfer performance with applications to cooling in microelectronics systems?

Building on the work of previous researchers, the team used a customised version of OpenFOAM and the Volume-Of-Fluid method to carry out simulations of a single isolated bubble transported through the cooling system. Their results demonstrate definitively that the shape of a channel impacts the efficiency of its performance in cooling, and that high aspect-ratio rectangular channels may be beneficial at larger flow rates, while square channels are most efficient for low flow rates. These results will have a profound effect on the design of thermal management systems for the cooling of microelectronics chips.

Read ‘Numerical study of the impact of the channel shape on microchannel boiling heat transfer’ in full


Experimental investigation of an ammonia-water-hydrogen diffusion absorption refrigerator

Applied Energy Volume 256 (December 2019)

Ahmad Najjaran, James Freeman, Alba Ramos, Christos N.Markides

Alternative cooling technologies are of increasing interest in the context of achieving a reduction in primary energy use from fossil fuels through the utilisation of renewable energy sources or heat wasted from a multitude of processes, and mitigating the harmful emissions associated with conventional systems. Diffusion absorption refrigeration (DAR) technology is a type of sorption-based cooling option that can be driven purely by thermal energy without the need for electrical or mechanical energy inputs.

In this work, a detailed experimental evaluation is conducted of a newly-proposed ammonia-water-hydrogen DAR unit with a nominal cooling capacity of 100 W, explicitly aimed at domestic-scale solar cooling applications. This DAR unit is larger than what has been considered in previous experimental studies, and lends itself more readily to the intended distributed solar-cooling application, both in terms of its integration with solar collectors and the potential to cover the typical cooling demands of domestic users. At this scale, the system also has a strong potential to provide larger cooling loads through modularisation.

Experimental results are complemented by model predictions of this DAR unit in order to obtain an understanding of the operation and performance of such systems, especially at off-design conditions that are of great importance in solar applications, and to explore the predictive power of existing design tools for next-generation variants of this promising technology.

Read ‘Experimental investigation of an ammonia-water-hydrogen diffusion absorption refrigerator’ in full


Environmental life cycle assessment of the production in China of lithium-ion batteries with nickel-cobalt-manganese cathodes utilising novel electrode chemistries

Journal of Cleaner Production, Volume 254 (May 2020)

Evangelos Kallitsis, Anna Korrea, Geoff Kelsall, Magdalena Kupfersberger, Zhenggang Nie

As the world is ramping up battery manufacturing to meet the increasing demand for electric vehicles, ensuring that batteries are produced in a sustainable manner becomes increasingly important. In their recent publication in Journal of Cleaner Production, Evangelos Kallitsis et al. explored how technological modifications towards increasing the energy density of automotive battery cells affect the environmental footprint of producing a battery and assessed the effect of the Chinese domination in the sector. The research demonstrated that increasing the energy density of automotive battery cells was shown to result in less environmentally harmful batteries while the impact of locating the manufacturing chain in China was shown to come at a high environmental cost. The latter is associated with the increased coal intensity of the local electricity mix resulting in high greenhouse gas emissions for the energy-intensive aluminium, electrode and battery production processes. Accurate assessments of the globally distributed battery value chain are crucial in ensuring an effective transition to a sustainable transport future.

Read ‘Environmental life cycle assessment of the production in China of lithium-ion batteries’ in full


Efficient formation of 2,5-diformylfuran (DFF) in ionic liquids at high substrate loadings and low oxygen pressure with separation through sublimation

ACS Sustainable Chemistry and Engineering (January 2020)

Amir Al Ghatta, James D. E. T. Wilton-Ely, Jason P. Hallett

The development of an efficient process focused on the valorisation of bio-monomers for bioplastics from sugars have seen so far a techno-economic barrier due to high costs for separation and purification of the final product. Amir Al Ghatta et. al. have successfully developed an efficient and cost-effective method of production which could pave the way for the widespread use of PEF bioplastics instead of oil-derivative and environmentally unfriendly PET plastics, particularly in the food & beverage packaging sector.

The efficient synthesis of the intermediate molecule 5-HMF from sugars has always been seen as the key point for a successful process for the production of bioplastic, since 5-HMF can be converted in different monomers that can be used as a replacement of the oil derivative ones for plastic synthesis.  In the last 20 years much research have been done to produce 5-HMF in the most efficient way. Ionic liquids proved to be one of the most promising solvents which can remarkably enhance the yield compared other classical organic solvents, which are not environmentally friendly due to their toxicity and flammability. However the separation of 5-HMF from the ionic liquids have proven so far to be unfeasible for the high affinity of the molecule with these solvents, hindering the application in large scale.

Research conducted by Al Ghatta shows that the molecule 2,5 diformylfuran (DFF) that can be used for the synthesis of PEF, derived from the aerobic oxidation of HMF, can be easily separated from the ionic liquids by sublimation at very mild conditions, opening a potential path for the valorisation of sugars in ionic liquids where separation is not anymore a limiting issue.  In the last publication, Al Ghatta et al.  developed a two pot new catalytic system for the conversion of sugars to DFF in the ionic liquid at high substrate loading and mild reaction conditions, as they don’t require high temperatures or high pressure. The result is an economically viable and carbon neutral process, which could enable the production of bioplastics on a much larger scale than is currently available.

Read ‘Efficient formation of 2,5-diformylfuran (DFF) in ionic liquids at high substrate loadings’ in full

 

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