Heat Transfer

Efficient heat transfer technologies are essential for magnetically confined fusion reactors; this applies to both the current generation of experimental reactors as well as future power plants. A number of High Heat Flux devices have therefore been developed specifically for this application. One of the most promising candidates is the HyperVapotron, a water cooled device which relies on internal fins and boiling heat transfer to maximise the heat transfer capability (see figure below [1]).

Examination of a single cavity within a Hypervapotron (dimensions in mm)

Over the past 30 years, numerous variations of the HyperVapotron have been built and tested at fusion research centres around the globe resulting in devices that can now sustain heat fluxes in the region of 2030 MW/m2 in steady state. Until recently, there had been few attempts to model or understand the internal heat transfer mechanisms responsible for this exceptional performance with the result that design improvements have been traditionally sought experimentally which is both inefficient and costly. We have developed an engineering model of the HyperVapotron device aiming to establish the most appropriate modelling choices, in-depth studies were performed examining the turbulence models (within the Reynolds Averaged Navier Stokes framework), near wall methods, grid resolution and boiling submodels. It is expected that the methodologies and tools developed will enable designers of future High Heat Flux devices to perform significant virtual prototyping before embarking on the more costly build and test programmes.

HyperVapotron cavities, RANS vs. ILES (snapshot) [1]
Large Eddy Simulation of Hypervapotron Flow

Currently, we are also working on micro and nano heat transfer using multi-scale methods and molecular dynamics. We try to understand the effects of fluid and materials on micro/nano heat transfer and create molecular machines that will result in significant enhancements of thermal management [5-7]

References

  • J. Milnes, A. Burns, D. Drikakis, Computational modelling of the HyperVapotron cooling technique, Fusion Engineering and Design, 87(9), 1647-1661, 2012.
  • V. A. Titarev, E. Romenski, D. Drikakis, E. Surrey, Computational modelling of the IFMIF lithium target, Fusion Engineering and Design, Vol. 84, 1, 49-56, 2009.
  • J. Milnes, D. Drikakis, Qualitative assessment of RANS models for Hypervapotron flow and heat transfer, Fusion Engineering and Design, Vol. 84, 1305-1312, 2009.
  • D. Drikakis, N. Asproulis, Multiscale Computational Modelling of Flow and Heat Transfer, International Journal for Numerical Methods for Heat and Fluid Flow, 5(20), 2010
  • M. Frank, N. Asproulis, D. Drikakis, Crystal-like heat transfer of liquids in nanochannels, Physical Review Letters, under review, 2014.
  • M. Frank, N. Asproulis, D. Drikakis, Density effects on the ballistic heat transfer of confined liquids, Physical Review E, under review, 2014.
  • N. Asproulis, M. Kalweit, E. Shapiro, D. Drikakis, Mesoscale flow and heat transfer modelling and its application to liquid and gas flows, Journal of Nanophotonics, 3(01), 031960-031975, 2009.