ALBERT

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Heat and Mass Transfer, Volume 141〈/p〉 〈p〉Author(s): D.Y. Yeo, H.C. NO〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉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 (〈em〉F〈sub〉i〈/sub〉〈/em〉). The suggested model provides flow patterns representing bubbly, slug, and channel flow and considering three criteria including d〈sup〉2〈/sup〉〈em〉F〈sub〉i〈/sub〉〈/em〉/d〈em〉α〈/em〉〈sup〉2〈/sup〉 = 0, 〈em〉F〈sub〉i〈/sub〉〈/em〉 = maximum, and 〈em〉F〈sub〉i〈/sub〉〈/em〉 = 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.〈/p〉〈/div〉 〈/div〉