Abstract

There are numerous technical applications where hot components, with uneven temperature distribution, require cooling. In such applications, it is desired to provide efficient local cooling of the hot spots, while avoiding unnecessary over-cooling of the other regions. Such an approach, known as precision cooling, has several advantages. In addition to the fact that it reduces the effort for cooling, it limits the unintended heat lost to the cooling medium. In liquid cooled systems, such as Internal Combustion Engines (ICE), subcooled flow boiling offers immense potential for precision cooling. The primary challenges in extracting this potential are understanding the complexities in the subcooled flow boiling phenomenon and estimating the risk of encountering film boiling. The present study introduces a numerical model to estimate the wall heat flux in subcooled flow boiling and the model includes a mechanistic formulation to account for vapor bubble interaction. The formulation for vapor bubble interaction serves two purposes: (a) blends two well-established models in the literature, one in the isolated bubbles regime and other in the fully developed boiling regime, to estimate the wall heat flux; and (b) provides information to limit boiling in order to not encounter film boiling. The results from the new model are validated with two different experiments in the literature and the wall heat flux estimated by the model is in agreement with experimental results and responsive to different input parameters, such as bulk velocity, operating pressure and inlet subcooling. The new model requires only input of local flow quantities and hence implementation in Computational Fluid Dynamics (CFD) is straightforward.

Highlights

  • Technical applications involving hot components often require cooling for maintaining structural integrity and for optimum performance

  • One of the technical applications, which might benefit from subcooled boiling for precision cooling purpose, can be found in the coolant jacket of the internal combustion engine (ICE)

  • A modification is suggested to the Boiling Departure Lift-off (BDL) model that improves the accuracy of the predicted results

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Summary

Introduction

Technical applications involving hot components often require cooling for maintaining structural integrity and for optimum performance. Such components could experience uneven distribution of temperature. The subcooled flow of a liquid coolant could result in occurrence of local boiling on the hot spots, which in turn would remove a substantial amount of heat. Such local boiling needs to be controlled and limited in order to avoid film boiling which might cease the heat transfer process and result in undesired consequences. One of the technical applications, which might benefit from subcooled boiling for precision cooling purpose, can be found in the coolant jacket of the internal combustion engine (ICE)

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