Precision cooling for C02 reduction
Local boiling can be an efficient way to implement precision cooling. The heat transfer involving nucleating and collapsing vapor bubbles near the surface of a hot metal is known as nucleate boiling. This phenomenon can positively impact cooling, as a significant amount of heat is extracted from the hot metal for the evaporation of the coolant to its vapor phase. Thus, heat is efficiently transferred locally near the hot spot through the vapor bubbles. However, excessive boiling could be counter productive and can lead to formation of a thin vapor film with low thermal conductivity on the metal surface. This film reduces heat transfer, prevents cooling and can eventually lead to material breakdown. Hence, it is extremely important to use nucleate boiling without the risk of having film boiling. Therefore, accurate estimation of boiling heat flux is the first step towards utilizing the potential of nucleate boiling. The main focus of this work is on numerical models to estimate the wall boiling heat flux. Such numerical models can be used in conjunction with Computational Fluid Dynamics (CFD) to analyse the heat transfer inside an ICE coolant jacket. A semi-mechanistic boiling model, based on established existing models in literature, has been proposed. Experiments performed on simplified geometries, representative of the areas in the ICE where boiling can be encountered, are used for validating the new model. The results from the validation study show that boiling is affected by properties of the flow, fluid and the solid. In addition to an improvement in accuracy of predicting the boiling heat flux, the model also provides a conservative measure to limit boiling and ensure the adverse effects of excessive boiling are not encountered. Finally, the limitations in the current model are discussed along with a possible solution for improvement.
semi- mechanistic models
internal combustion engine
active nucleation site density
subcooled flow boiling
Chalmers, Mekanik och maritima vetenskaper, Strömningslära
Improved estimation of subcooled flow boiling heat flux for automotive engine cooling applications
ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019,; Vol. 3A-2019(2019)
Paper i proceeding
Vasudevan S., Etemad S., Davidson L., and Villar G.M. “A blended model to compute heat transfer in subcooled flow boiling”. Technical report
Precisionskylning för CO2-minskning
Energimyndigheten (44065-1), 2017-03-01 -- 2022-03-31.
Thesis for the degree of Licentiate – Department of Mechanics and Maritime Sciences: 2019:16
EB lecture hall, E-building, Chalmers-Johanneberg
Opponent: Associate Professor Zan Wu, Division of Heat Transfer, Lund Institute of Technology, Sweden