http://hdl.handle.net/10016/964 Fri, 24 May 2013 23:40:10 GMT 2013-05-24T23:40:10Z http://hdl.handle.net/10016/2638 Title: Thermal analysis and optimization of a heat regenerator composed of two coupled moving bed heat exchangers Author(s): Almendros-Ibáñez, José Antonio; Soria-Verdugo, Antonio; Ruiz-Rivas, Ulpiano; Santana Santana, Domingo José Abstract: This work presents a study to optimize the performance of a heat regenerator composed by two coupled moving bed heat exchangers (MBHE). A MBHE is used to recover heat, from a hot gas stream, and the other one is used to preheat an air stream. A direct application might be a gasifier. The heat exchangers performance was studied in two cases, considering or not the conduction heat transfer in the solid phase. When the solid conduction is taken into account, a numerical solution is obtained, while an analytical solution is possible when the conduction terms are neglected. In both cases, the optimum values of bed length (in the air flow direction) and particle diameter were obtained from an exergy point of view. Finally, an energy optimization of the heat regenerator was carried out, obtaining the optimal heat regenerator dimensions as a function of gas velocity and gas flow rate. Sat, 10 May 2008 22:00:00 GMT http://hdl.handle.net/10016/2638 2008-05-10T22:00:00Z http://hdl.handle.net/10016/2600 Title: Coherent structures and bubble-particle velocity in 2-D fluidized beds Author(s): Sánchez-Delgado, Sergio; Almendros-Ibáñez, José Antonio; Soria-Verdugo, Antonio; Santana Santana, Domingo José; Ruiz-Rivas, Ulpiano Abstract: This work presents an experimental study to characterize ascending bubbles and granular velocity in the dense phase of a 2-D fluidized bed. Three different non-intrusive techniques based on images obtained with a high speed camera are developed, and applied to the images. First the bubble paths are characterized with time-average concentration maps and the bubble velocities are obtained, using a tracking algorithm over the mass centers of the bubbles. Finally, a PIV (particle image velocimetry) method is used to characterize the particle velocity vectors. This procedure is repeated for different bed aspect ratios, and different superficial gas velocities. This study analyzes the superficial gas velocity influence on the bed behavior, and how the bubble path configuration depends on the bed aspect ratio. The PIV measurements give us information on the location of the recirculation regions and the influence of the superficial gas velocity. Mon, 12 May 2008 22:00:00 GMT http://hdl.handle.net/10016/2600 2008-05-12T22:00:00Z http://hdl.handle.net/10016/1222 Title: Exergy optimization in a steady moving bed heat exchanger Author(s): Soria-Verdugo, Antonio; Almendros-Ibáñez, José Antonio; Ruiz-Rivas, Ulpiano; Santana Santana, Domingo José Abstract: This work provides an exergy analysis of a moving bed heat exchanger to obtain for a range of incoming fluid flow rates the operational optimum and the incidence on it of the relevant parameters such as the dimensions of the exchanger, the particle diameter and the flow rate of the fluid. The MBHE proposed can be analyzed as a cross flow heat exchanger where one of the phases is a moving granular medium. In the present work the exergy analysis of the MBHE is carried out over operation data of the exchanger obtained in two ways: a numerical simulation of the steady state problem and the analytical solution of the simplified (avoiding conduction terms) equations. The numerical simulation is carried over the two steady energy equations (fluid and solid), involving for the solid the convection heat transfer to the fluid and the diffusion term in both directions, and for the fluid only the convection heat transfer to the solid. The analytical solution is the wellknown solution of the simplified problem neglecting conduction effects. Description: Proceedings of: Interdisciplinary Transport Phenomena V: Fluid, Thermal, Biological, Materials and Space Sciences (ITP 2007), 14-19 of October, 2007, Bansko, Bulgaria (Oral paper nº 70) Sun, 31 Dec 2006 23:00:00 GMT http://hdl.handle.net/10016/1222 2006-12-31T23:00:00Z http://hdl.handle.net/10016/1221 Title: Throughflow velocity crossing the dome of erupting bubbles in 2-D fluidized beds Author(s): Almendros-Ibáñez, José Antonio; Sobrino, Celia; Sánchez-Delgado, Sergio; Santana Santana, Domingo José; Vega, Mercedes de; Ruiz-Rivas, Ulpiano Abstract: A new non-intrusive method for measuring the throughflow velocity crossing the dome of erupting bubbles in freely bubbling 2-D fluidized beds is presented. Using a high speed video-camera, the dome acceleration, drag force and throughflow velocity profiles are obtained for different experiments, varying the superficial gas velocity. The acceleration profiles show greater values in the dome zone where the gravity component is negligible. The drag force and the throughflow velocity profiles show a uniform value in the central region of the dome and the total throughflow increases with the superficial gas velocity. Sun, 31 Dec 2006 23:00:00 GMT http://hdl.handle.net/10016/1221 2006-12-31T23:00:00Z