This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.On the effect of surface roughness and material on the subcooled flow boiling of water: Experimental study and global correlation. AbstractIn this paper, a new correlation based on experimental results for subcooled flow boiling of water at low pressure is proposed, preceded by a brief review on how the solid-fluid interaction has been dealt with in past correlations. The experimental sample comprises seven heating surfaces of different material (copper, aluminium and stainless steel) and roughness. The experimental facility is presented in detail and the surface morphology of each test specimen is analysed by means of an optical interferometer. The correlation is based on the assumption that the effect of material and roughness can be captured by means of modifiers of a general expression. The surfaces chosen in this work were selected to capture a broad range of industrial applications, and, though the correlation found fits well in the range of commercial and relatively high values of R a (up to 7 µm in the case of copper), further study is needed for larger values, as a discontinuity in the effect was observed, which has been previously determined by some authors. Thus, the proposed global correlation permits the calculation of the boiling heat flux taking into account, in addition to the more classical parameters such as pressure and bulk temperature, the effect of both the roughness and material of the wall heater, allowing its general use in low pressure applications such as those commonly found in the automotive industry.

In this article, a boiling model for "Fluent 6" fluid flow simulation software, for its use in gas-liquid heat exchangers, is presented. After a thorough study of existing bibliographies, a physical model has been compiled, which has been incorporated into the eulerian multiphase model, the most suitable of those available in Fluent for the resolution of these kinds of multiphase flows. Also discussed are some of the aspects of the implementation, which basically consist of the modeling of the interactions between phases as source terms in the governing equations solved by Fluent. Finally, the implementation of the model has been validated against experimental tests from the available literature, achieving a satisfactory degree of concordance.

A numerical simulation procedure was developed in FLUENT code in order to study particle deposition in diluted turbulent gas flows in ducts. A hybrid Eulerian-Lagrangian model was used to evaluate the gas flow and temperature profile as well as particle dispersion and deposition. The mean flow velocity and temperature fields were generated by a Reynolds Average Navier Stokes (RANS) method, using the Reynolds Stress Model (RSM) available in FLUENT. The instantaneous turbulent velocity fluctuation and Brownian force were simulated by a continuous Gaussian random field as a white-noise process respectively. In the particle equation of motion, Brownian diffusion, Saffman lift, Stokes drag and gravity were included. In order to evaluate the deposition model, particles with diameter ranges from 1nm to 50 µm, and different velocity fields were studied. The numerical results obtained under isothermal conditions were compared with the available experimental data, with empirical correlations, and earlier published simulation results. In all cases, an acceptable agreement was observed. The importance of each of the deposition forces included is discussed in this work.The reasonable computational cost of this methodology enables us to study particle deposition in complex geometries, different from smooth surfaces. The results presented provide guidelines to develop an extended computational fouling model in heat exchange surfaces.