Precision Cooling in engines

Force balance at a vapor bubble at the instant of departure from its nucleation site. Fd -- Quasi-steady drag force, Fdu -- Unsteady drag force, Fsl -- Shear lift force and Fbcy -- Force due to buoyancy

PhD student:	Sudharsan Vasudevan sudvas@chalmers.se
Supervisor:	Sassan Etemad sassan.etemad@chalmers.se
Co-supervisor:	Lars Davidson lada@chalmers.se
Cooperation:	AB Volvo, Volvo Cars
Sponsors:	The Swedish Energy Agency, FFI
Publications: 1	-
Start of project:	September 2017
End of project:	-

BACKGROUND
Excessive cooling is loss of energy. The motive is to understand the potential of nucleate boiling in local cooling. The project involves two main objectives. First, a numerical method is to be developed aiming at improved accuracy in prediction of heat transfer due to nucleate boiling. Further, the effect of surface structure modification on enhancement of the heat transfer is to be explored and accounted for in the method. The method is to be implemented in simulations involving coolant jacket models of internal combustion engines.

The analysis of bubble behaviour in forced convection boiling will form the basis for the numerical method. Forces acting on individual bubbles and interaction between the bubbles will be explored. The Boiling Departure Lift-off (BDL) model for estimating wall heat flux at subcooled flow boiling conditions, proposed by Steiner et al. (2005) is being evaluated. The force balance on an individual bubble (see figure above) is used to estimate the bubble radii at the point when it slides from the nucleation site in the horizontal direction (departure) and at the point when it lifts perpendicular to the heated surface (lift-off). Also, the focus will be to predict the onset of film boiling in order to avoid getting into that regime. The method will be tested on simple geometries and validated with results from experiments present in literature. From there on, it can be extended to applications like internal combustion engines, batteries and electric motors.

RERERENCE
Steiner, H., Kobor, A. and Gebhard, L. (2005)(. A wall heat transfer model for subcooled boiling flow. International Journal of Heat and Mass Transfer, 48(19-20), pp.4161-4173.

REFERENCES

S. Vasudevan, S. Etemad and L. Davidson
"Improved Estimation of Subcooled Flow Boiling Heat Flux for Automotive Engine Cooling Applications." Proceedings of the ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. Volume 3A: Fluid Applications and Systems. San Francisco, California, USA. July 28 -- August 1, 2019. V03AT03A001. ASME.
PDF file
S. Vasudevan, S. Etemad, L. Davidson and G. Montero Villara
"Numerical model to estimate subcooled flow boiling heat flux and to indicate vapor bubble interaction", International Journal of Heat and Mass Transfer, Volume 170, May 2021, 121038.
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S. Vasudevan, S. Etemad, L. Davidson and M. Bovo
"Comparative analysis of single and multiphase numerical frameworks for subcooled boiling flow in an internal combustion engine coolant jacket", IApplied Thermal Engineering, No. 119435, 2022.
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