The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
S A Klein - One of the best experts on this subject based on the ideXlab platform.
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performance study of one dimensional models for stratified thermal storage tanks
Solar Energy, 1993Co-Authors: E M Kleinbach, W A Beckman, S A KleinAbstract:Two basic approaches are used to model the temperature distribution in thermal storage tanks for solar domestic hot water (SDHW) systems. In the multinode approach, the tank is divided into N nodes, with an energy balance written for each node. This approach results in a set of N differential equations that can be solved for the temperatures of the nodes as a function of time. In the plug flow approach, segments of liquid of different temperatures and sizes are assumed to move through the tank in a plug flow manner. The sizes of the Fluid elements are determined mainly by the simulation time step and the flow rates. Whenever the Incoming Fluid from the heat source is colder than the Fluid at the top of the tank, “plume entrainment” occurs. A model describing plume entrainment has been incorporated into both the multinode and the plug flow models in the TRNSYS program[1]. A performance study of the TRNSYS tank models has been carried out with experimental data from two different sources. Three performance numbers have been defined for quantifying the accuracy of the models compared with experimental data. Recommendations are given as to which tank model should be used under which conditions.
Paulo J Oliveira - One of the best experts on this subject based on the ideXlab platform.
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tricritical spiral vortex instability in cross slot flow
Physical Review E, 2016Co-Authors: Simon J Haward, Robert J Poole, M A Alves, Paulo J Oliveira, Nigel Goldenfeld, Amy Q ShenAbstract:We examine Fluid flow through cross-slot devices with various depth to width ratios α . At low Reynolds number, Re, flow is symmetric and a sharp boundary exists between the two Incoming Fluid streams. Above an α -dependent critical value, R e c ( α ) , a steady symmetry-breaking bifurcation occurs and a spiral vortex structure develops. Order parameters characterizing the instability grow according to a sixth-order Landau potential, and show a progression from second- to first-order transitions as α increases beyond a tricritical value of α ≈ 0.55 . Flow simulations indicate the instability is driven by vortex stretching at the stagnation point.
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A symmetry-breaking inertial bifurcation in a cross-slot flow
Computers & Fluids, 2014Co-Authors: Robert J Poole, Gerardo N. Rocha, Paulo J OliveiraAbstract:In the current paper we investigate, using a numerical technique, a new bifurcation phenomenon for a Newtonian Fluid flowing through a two-dimensional so-called ‘‘cross-slot’’ geometry. A cross-slot, or cross-channel, geometry is formed by an ‘‘horizontal’’ planar channel along which two Incoming Fluid streams are made to impinge on each other, and an intersecting ‘‘vertical’’ channel which carries the outlet flow, with the other two streams now moving away from the central section and leaving through the vertical channel exits. At low Reynolds numbers (Re) the flow remains steady and symmetric and identical regions of standing recirculation attached to the four corners increase linearly in size with Re .A t a critical Reynolds number (=1490 ± 10) a supercritical pitchfork bifurcation is observed beyond which the unstable symmetrical solution is replaced by a pair of steady asymmetric solutions (each corresponding to larger recirculation regions on one vertical sidewall). The dynamics of the bifurcation are investigated in detail and a comparison made with the bifurcation observed for inertialess viscoelastic Fluid flow.
Amy Q Shen - One of the best experts on this subject based on the ideXlab platform.
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tricritical spiral vortex instability in cross slot flow
Physical Review E, 2016Co-Authors: Simon J Haward, Robert J Poole, M A Alves, Paulo J Oliveira, Nigel Goldenfeld, Amy Q ShenAbstract:We examine Fluid flow through cross-slot devices with various depth to width ratios α . At low Reynolds number, Re, flow is symmetric and a sharp boundary exists between the two Incoming Fluid streams. Above an α -dependent critical value, R e c ( α ) , a steady symmetry-breaking bifurcation occurs and a spiral vortex structure develops. Order parameters characterizing the instability grow according to a sixth-order Landau potential, and show a progression from second- to first-order transitions as α increases beyond a tricritical value of α ≈ 0.55 . Flow simulations indicate the instability is driven by vortex stretching at the stagnation point.
E M Kleinbach - One of the best experts on this subject based on the ideXlab platform.
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performance study of one dimensional models for stratified thermal storage tanks
Solar Energy, 1993Co-Authors: E M Kleinbach, W A Beckman, S A KleinAbstract:Two basic approaches are used to model the temperature distribution in thermal storage tanks for solar domestic hot water (SDHW) systems. In the multinode approach, the tank is divided into N nodes, with an energy balance written for each node. This approach results in a set of N differential equations that can be solved for the temperatures of the nodes as a function of time. In the plug flow approach, segments of liquid of different temperatures and sizes are assumed to move through the tank in a plug flow manner. The sizes of the Fluid elements are determined mainly by the simulation time step and the flow rates. Whenever the Incoming Fluid from the heat source is colder than the Fluid at the top of the tank, “plume entrainment” occurs. A model describing plume entrainment has been incorporated into both the multinode and the plug flow models in the TRNSYS program[1]. A performance study of the TRNSYS tank models has been carried out with experimental data from two different sources. Three performance numbers have been defined for quantifying the accuracy of the models compared with experimental data. Recommendations are given as to which tank model should be used under which conditions.
Haifeng Fan - One of the best experts on this subject based on the ideXlab platform.
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Homogeneous Zn isotopic compositions in the Maozu Zn-Pb ore deposit in Yunnan Province, southwestern China
Ore Geology Reviews, 2019Co-Authors: Hongjie Zhang, Chaoyi Xiao, Hanjie Wen, Xiangkun Zhu, Zhilong Huang, Jia-xi Zhou, Haifeng FanAbstract:Abstract The Sichuan-Yunnan-Guizhou (SYG) metallogenic province, southwestern Yangtze Block, is one of the most important Zn-Pb repositories in China, with more than 200 million tons (Mt) of Zn-Pb ores. The source regions for the regional Zn-Pb mineralization in the SYG are still controversial, mostly in regard to the Emeishan flood basalts, basement rocks and host rocks. The Maozu Zn-Pb deposit is geographically close to the SYG center, which could also indicate that it is closer to the regional Zn-bearing Fluid center than those deposits along the SYG margin. However, the origin of the ore-forming Zn in the Maozu deposit has not been constrained until now. In this study, the Zn and S isotopic compositions and Fe and Cd concentrations of the sphalerite from the Maozu deposit are investigated to evaluate the Zn isotopic fractionation during sphalerite precipitation, the source regions of the ore-forming zinc and sulfur, and the center of the regional Zn-bearing Fluid system. It is suggested that the Zn isotopic fractionation between the sphalerite and original Fluid during sphalerite precipitation could be limited due to the striking decrease in the temperature of the Incoming Fluid. The Zn isotopic variation of the sphalerite from four mining levels in the Maozu deposit is really small (−0.06 to +0.23‰), which could be attributed to heterogeneous Zn isotopic compositions in original Incoming Fluid rather than Zn isotopic fractionation during sphalerite deposition. As such, in the Maozu deposit, the Zn isotopic compositions of original hydrothermal Fluid could approximately be represented by the Zn isotopic signals documented in sphalerite (−0.06 to +0.23‰). We found that the Zn isotopic signatures of Incoming Fluid are largely overlapped with those of the basement rocks (+0.10 to +0.34‰), signifying that the ore-forming Zn could be predominantly sourced from the basement rocks. However, in the Maozu deposit, the ore-forming sulfur is most likely derived from the sulfur-bearing evaporates hosted in the country rocks via thermochemical sulfate reduction (TSR). The contrasting sources of ore-forming zinc and sulfur suggest the mixing of Zn-bearing Fluid from the basement rocks and sulfur-bearing Fluid from the host rocks, which could be responsible for the sharp decrease in the temperature of the Incoming Fluid in the Maozu deposit. Combined with the results of previous studies, the integrally lower Zn isotopic compositions of sphalerite in the Maozu deposit compared to those deposits along the SYG margin may demonstrate that the Maozu deposit is closer to the regional Zn-bearing Fluid center. If this is the case, Zn isotopes could be an effective proxy to trace the Zn source of Zn-enriched ore deposits and to identify the regional Zn-bearing Fluid center of Zn-enriched metallogenic provinces.
