A zero-dimensional dryout heat flux model based on mechanistic interfacial friction models for two-phase flow regimes with channel flow in a packed bed

• Published in: International journal of heat and mass transfer 2019-10, Vol.141, p.554-568
• Main Authors: Yeo, D.Y., NO, H.C.
• Format: Article
• Language: English
• Subjects: Annular flow; Channel flow; Dryout heat flux; Flooding; Flow mapping; Friction; Heat flux; Heat transfer; Interfacial friction; Packed beds; Particle size; Porous media; Pressure drop; Root-mean-square errors; Slug flow; Two phase flow; Void fraction
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2019.06.096

•Transition criterion for channel flow was developed in terms of void fraction and particle diameter.•Mechanistic interfacial friction models were suggested based on two-phase flow regimes of a packed bed.•A zero-dimensional dryout heat flux model was suggested using the suggested interfacial friction models.•Predictions of the pressure drop and dryout heat flux were improved using the suggested models. In this paper, two-phase drag models for a packed bed of uniform-size particles were suggested, and they were applied to the calculation of pressure drop and dryout heat flux. We provided physical basis for the two-phase flow regime model through the analysis of the interfacial friction (Fi). The suggested model provides flow patterns representing bubbly, slug, and channel flow and considering three criteria including d2Fi/dα2 = 0, Fi = maximum, and Fi = 0. The results obtained from the three criteria were drawn with several observation-based experimental ones to generate the flow regime map (void fraction vs. particle diameter). Through the current flow regime map, we clearly saw the existence of channel flow in a packed bed with particles smaller than around 3.5 mm. Then, mechanistic interfacial friction models were developed on basis of the current two-phase flow map of bubbly flow, slug flow, channel flow and annular flow. The suggested interfacial friction models were validated with top- and bottom-flooding air-water experiments and boiling experiments. We found out that the capability of pressure drop estimation by the current model were significantly improved for a bed with small particles. Finally, a zero-dimensional dryout heat flux (DHF) model was derived using the suggested interfacial friction models, and validated against DHF experimental data for beds with 1-D configuration. The root-mean-square error (RMSE) of the suggested DHF model was 35%, which was the smallest among the RMSEs of the previous DHF models.