The Experts below are selected from a list of 152250 Experts worldwide ranked by ideXlab platform
John R. Thome - One of the best experts on this subject based on the ideXlab platform.
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Flow Pattern based Flow boiling heat transfer model for microchannels
International Journal of Refrigeration-revue Internationale Du Froid, 2013Co-Authors: Etienne Costapatry, John R. ThomeAbstract:Abstract A new Flow Pattern-based prediction method for heat transfer coefficients in microchannels was developed based on recent experimental results for several multi-microchannel evaporators in silicon and copper and for single-microchannel tubes in stainless steel. In the present paper, some updates to the three-zone Flow boiling model for slug Flow are presented, including further proof that the dryout thickness is well represented by setting it equal to the measured channel roughness for the silicon, copper and stainless steel test surfaces. Next, a non-circular channel version of the Cioncolini–Thome unified annular Flow model for convective boiling is proposed. These two methods are joined together into a Flow Pattern-based method using a new heat flux-dependent Flow Pattern transition criterion between slug Flow and annular Flow. The method predicts the results quite accurately and also captures the trends in the heat transfer coefficients well.
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investigation of Flow boiling in horizontal tubes part i a new diabatic two phase Flow Pattern map
International Journal of Heat and Mass Transfer, 2005Co-Authors: Leszek Wojtan, Thierry Ursenbacher, John R. ThomeAbstract:Abstract Several important modifications to the Flow Pattern map of Kattan–Thome–Favrat [J. Heat Transfer 120(1) (1998) 140–147] made, resulting in a significantly new version of the map. Based on the dynamic void fraction measurements described in [Int. J. Multiphase Flow 30 (2004) 125–137], the stratified–wavy region has been subdivided into three subzones: slug, slug/stratified–wavy and stratified–wavy. Furthermore, annular-to-dryout and dryout-to-mist Flow transition curves have been added and integrated into the new Flow Pattern map, identified by distinct trends of the heat transfer coefficient as a function of vapor quality and by Flow Pattern observations to determine (and then predict) the inception and completion of dryout in horizontal tubes.
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update on advances in Flow Pattern based two phase heat transfer models
Experimental Thermal and Fluid Science, 2005Co-Authors: John R. ThomeAbstract:Abstract The Flow Pattern, simplified Flow structure based evaporation model of Kattan et al. [J. Heat Transfer 120 (1998) 140; J. Heat Transfer 120 (1998) 148; J. Heat Transfer 120 (1998) 156] has been updated several times since its original publication and also generalized to intube condensation. The current status of our work on this heat transfer prediction model and Flow Pattern map is described here, covering the following topics: the onset of nucleate boiling, elimination of iterative calculations, evaporation of CO 2 up to pressures as high as 64 bars for tube diameters from 0.9 to 10.0 mm, convective condensation inside horizontal tubes, and the recent experimental verification of the drift flux void fraction model used by the Flow Pattern map and heat transfer model.
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two phase Flow Pattern map for evaporation in horizontal tubes latest version
Heat Transfer Engineering, 2003Co-Authors: John R. Thome, Jean El HajalAbstract:A two-phase Flow Pattern map was originally proposed by Kattan, Thome, and Favrat as part of a new Flow Pattern-based Flow boiling model for predicting local heat transfer coefficients during evaporation in horizontal tubes in the fully stratified Flow regime, the stratified-wavy regime, the intermittent Flow regime, the annular Flow regime, and for annular Flow with partial dryout. Zurcher, Thome, and Favrat improved on this Flow Pattern map by empirically correcting two of the transition boundaries based on extensive new Flow Pattern observations for ammonia, but it still requires an iterative solution of numerous equations. Zurcher, Favrat, and Thome have since proposed an even more detailed method for predicting Flow Pattern transitions by taking into account the intertwined effects of void fraction on Flow transition and Flow Pattern on void fraction, resulting in a map that is very effective but very complex to implement. In the newest version of this map, the goal of which was to simplify the metho...
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condensation in horizontal tubes part 1 two phase Flow Pattern map
International Journal of Heat and Mass Transfer, 2003Co-Authors: El J Hajal, John R. Thome, Alberto CavalliniAbstract:Abstract A new Flow Pattern map and Flow Pattern based heat transfer model for condensation inside horizontal plain tubes are proposed in this two-part paper. In Part I, a new version of a two-phase Flow Pattern map, originally developed by Kattan et al. [J. Heat Transfer 120 (1998) 140] for Flow boiling, is presented for condensation inside horizontal tubes while a new heat transfer model is presented in Part II. The new Flow Pattern map incorporates a newly defined logarithmic mean void fraction (LM e ) method for calculation of vapor void fractions spanning from low pressures up to pressures near the critical point. Several other modifications are also made that are appropriate for condensation as opposed to evaporation. In the absence of void fraction data at high reduced pressures for these conditions, the new LM e method has been indirectly validated using the convective condensation model for annular Flow and corresponding heat transfer test data at reduced pressures up to 0.8. The new map has also been successfully compared to some recent Flow Pattern observations for condensation and other existing Flow transition criteria and maps.
Alberto Cavallini - One of the best experts on this subject based on the ideXlab platform.
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condensation in horizontal tubes part 1 two phase Flow Pattern map
International Journal of Heat and Mass Transfer, 2003Co-Authors: El J Hajal, John R. Thome, Alberto CavalliniAbstract:Abstract A new Flow Pattern map and Flow Pattern based heat transfer model for condensation inside horizontal plain tubes are proposed in this two-part paper. In Part I, a new version of a two-phase Flow Pattern map, originally developed by Kattan et al. [J. Heat Transfer 120 (1998) 140] for Flow boiling, is presented for condensation inside horizontal tubes while a new heat transfer model is presented in Part II. The new Flow Pattern map incorporates a newly defined logarithmic mean void fraction (LM e ) method for calculation of vapor void fractions spanning from low pressures up to pressures near the critical point. Several other modifications are also made that are appropriate for condensation as opposed to evaporation. In the absence of void fraction data at high reduced pressures for these conditions, the new LM e method has been indirectly validated using the convective condensation model for annular Flow and corresponding heat transfer test data at reduced pressures up to 0.8. The new map has also been successfully compared to some recent Flow Pattern observations for condensation and other existing Flow transition criteria and maps.
Zhijun Zhong - One of the best experts on this subject based on the ideXlab platform.
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Flow Pattern measurement in a full scale silo containing iron ore
Chemical Engineering Science, 2005Co-Authors: J.f. Chen, Jin Y. Ooi, J. Michael Rotter, Zhijun ZhongAbstract:Abstract The Flow Pattern in a silo is important because it affects both the recovery of solids and the pressures on the silo wall during discharge. Wherever mass Flow is not achieved, the boundary of the Flow channel has significant implications for both the functional and structural design of the silo. Many techniques have been used for the study of Flow Patterns in model silos, but most cannot be used at full scale, and very few quality measurements at full scale have ever been made. This paper outlines a full scale experimental study in which the Patterns of solids Flow and the Flow channel boundaries are reliably quantified. The full scale silo was specially designed, constructed and instrumented to exhibit funnel Flow and to make observations of the solids Flow Pattern and the silo wall pressures. It had three outlets: one concentric, one fully eccentric and one in between. Three materials were used: iron ore pellets, slag fines and crushed basalt. This paper describes experiments involving iron ore pellets. The silo was seeded with radio frequency tags whose residence times were measured by detecting them on exit during discharge. The residence time data were studied to deduce the discharge Flow Pattern. This paper presents the results of three different Flow Pattern interpretation techniques: the best of them (mass-time relationships) is shown to give a very clear identification of the solids Flow Pattern and the Flow channel boundary.
J. Michael Rotter - One of the best experts on this subject based on the ideXlab platform.
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the influence of a cone in cone insert on Flow Pattern and wall pressure in a full scale silo
Chemical Engineering Research & Design, 2008Co-Authors: Johannes Hartl, Jin Y. Ooi, Songxiong Ding, M Wojcik, J. Michael Rotter, Gisle G EnstadAbstract:A silo insert is sometimes placed inside the hopper to improve the Flow Pattern of solids in a funnel Flow silo. This paper describes a recent experimental investigation of the Flow Pattern and wall pressures observed during filling and emptying of a cylindrical silo with and without a cone-in-cone insert. The 2.5 m diameter silo had an 8 m high cylindrical section and a 44° conical hopper, and was filled with crushed quartz sand. The wall pressures were measured at ten chosen locations using pressure cells mounted on the wall. To investigate the solids Flow Pattern, markers were placed at fixed positions in the silo during filling and the residence time for each marker during discharge was observed. The Flow Pattern can be inferred from the residence time measurements for the markers and the surface profile observations during discharge. These tests show that a cone-in-cone insert can have a strong influence on both the Flow Pattern during discharge and the pressure acting on the silo wall and its industrial use should be considered cautiously and implemented with care.
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Flow Pattern measurement in a full scale silo containing iron ore
Chemical Engineering Science, 2005Co-Authors: J.f. Chen, Jin Y. Ooi, J. Michael Rotter, Zhijun ZhongAbstract:Abstract The Flow Pattern in a silo is important because it affects both the recovery of solids and the pressures on the silo wall during discharge. Wherever mass Flow is not achieved, the boundary of the Flow channel has significant implications for both the functional and structural design of the silo. Many techniques have been used for the study of Flow Patterns in model silos, but most cannot be used at full scale, and very few quality measurements at full scale have ever been made. This paper outlines a full scale experimental study in which the Patterns of solids Flow and the Flow channel boundaries are reliably quantified. The full scale silo was specially designed, constructed and instrumented to exhibit funnel Flow and to make observations of the solids Flow Pattern and the silo wall pressures. It had three outlets: one concentric, one fully eccentric and one in between. Three materials were used: iron ore pellets, slag fines and crushed basalt. This paper describes experiments involving iron ore pellets. The silo was seeded with radio frequency tags whose residence times were measured by detecting them on exit during discharge. The residence time data were studied to deduce the discharge Flow Pattern. This paper presents the results of three different Flow Pattern interpretation techniques: the best of them (mass-time relationships) is shown to give a very clear identification of the solids Flow Pattern and the Flow channel boundary.
Jin Y. Ooi - One of the best experts on this subject based on the ideXlab platform.
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the influence of a cone in cone insert on Flow Pattern and wall pressure in a full scale silo
Chemical Engineering Research & Design, 2008Co-Authors: Johannes Hartl, Jin Y. Ooi, Songxiong Ding, M Wojcik, J. Michael Rotter, Gisle G EnstadAbstract:A silo insert is sometimes placed inside the hopper to improve the Flow Pattern of solids in a funnel Flow silo. This paper describes a recent experimental investigation of the Flow Pattern and wall pressures observed during filling and emptying of a cylindrical silo with and without a cone-in-cone insert. The 2.5 m diameter silo had an 8 m high cylindrical section and a 44° conical hopper, and was filled with crushed quartz sand. The wall pressures were measured at ten chosen locations using pressure cells mounted on the wall. To investigate the solids Flow Pattern, markers were placed at fixed positions in the silo during filling and the residence time for each marker during discharge was observed. The Flow Pattern can be inferred from the residence time measurements for the markers and the surface profile observations during discharge. These tests show that a cone-in-cone insert can have a strong influence on both the Flow Pattern during discharge and the pressure acting on the silo wall and its industrial use should be considered cautiously and implemented with care.
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Flow Pattern measurement in a full scale silo containing iron ore
Chemical Engineering Science, 2005Co-Authors: J.f. Chen, Jin Y. Ooi, J. Michael Rotter, Zhijun ZhongAbstract:Abstract The Flow Pattern in a silo is important because it affects both the recovery of solids and the pressures on the silo wall during discharge. Wherever mass Flow is not achieved, the boundary of the Flow channel has significant implications for both the functional and structural design of the silo. Many techniques have been used for the study of Flow Patterns in model silos, but most cannot be used at full scale, and very few quality measurements at full scale have ever been made. This paper outlines a full scale experimental study in which the Patterns of solids Flow and the Flow channel boundaries are reliably quantified. The full scale silo was specially designed, constructed and instrumented to exhibit funnel Flow and to make observations of the solids Flow Pattern and the silo wall pressures. It had three outlets: one concentric, one fully eccentric and one in between. Three materials were used: iron ore pellets, slag fines and crushed basalt. This paper describes experiments involving iron ore pellets. The silo was seeded with radio frequency tags whose residence times were measured by detecting them on exit during discharge. The residence time data were studied to deduce the discharge Flow Pattern. This paper presents the results of three different Flow Pattern interpretation techniques: the best of them (mass-time relationships) is shown to give a very clear identification of the solids Flow Pattern and the Flow channel boundary.