Heat Transfer to Steam-Water Annular Dispersed Flow in Vertical Annulus

1971 ◽  
Vol 8 (7) ◽  
pp. 400-405
Author(s):  
Ichiro IKEMOTO ◽  
Masaharu TAKAYASU ◽  
Nobuyuki UENO ◽  
Itaru MICHIYOSHI
2001 ◽  
Author(s):  
C. Frepoli ◽  
A. J. Ireland ◽  
L. E. Hochreiter ◽  
F. B. Cheung

Abstract The droplet injection experiments to be performed in a 7 × 7 rod bundle heat transfer test facility are being simulated using an advanced thermal hydraulics computer code called COBRA-TF. A current version of the code, which provides a three-dimensional, two-fluid, three-field representation of the two-phase flow, is modified to facilitate the simulation of the droplet field produced by the injection system in the test facility. The liquid phase is split into a continuous liquid field and droplet field where a separate momentum and mass equation is solved for each field, with the effects of spacer grids being properly accounted for. Pre-test analyses using the modified COBRA-TF code have been conducted for different injection conditions. Results indicate that there are specific ranges of conditions that can be simulated within the facility constraints to provide for validation of the dispersed flow film boiling models. The numerical results also show important effects of the spacer grids on the local heat transfer in the dispersed flow film boiling regime.


1980 ◽  
Vol 102 (3) ◽  
pp. 508-512 ◽  
Author(s):  
S. Wong ◽  
L. E. Hochreiter

Analysis is carried out for dispersed flow heat transfer under reactor emergency cooling conditions. The present formulation explicitly reveals an extra dependence of the heat transfer coefficient and Nusselt number on the mean vapor temperature for droplet dispersed flow which is not found in single phase flow heat transfer. The heat transfer results obtained from three different geometries—an infinite square array of cylindrical rods, an annulus and a circular pipe—are compared; all have the same hydraulic diameter. It is found that, within the framework of the present analysis, results for the annulus and the rod bundles agree well when the pitch-to-diameter ratio is 1.5 or greater. The circular pipe is in general a poor approximation for rod bundle geometries except at a pitch-to-diameter ratio of about 1.3 which is typical of present day light water reactor fuel assemblies.


Author(s):  
Y. A. S. El-Masry ◽  
Y. Abd Elmaboud ◽  
M. A. Abdel-Sattar

Abstract Gold nanoparticles (AuNPs) are increasingly being widely used in several biomedical applications for their compatibility of synthesis and less toxicity. The mixture of gold and titanium oxide nanoparticles is suspended in water to make a new class of nanofluid, which is called a hybrid nanofluid. The problem of direct current (DC)/alternating current (AC) magnetohydrodynamic (MHD) micropump of the hybrid nanofluid through a porous medium in the gap between vertical coaxial microtubes with heat transfer has been discussed. The mathematical model is established and then solved with the help of the Laplace transform. The inversion of the transformed functions is calculated numerically. The velocity, the flowrate, the pressure, and the heat transfer are discussed graphically. The higher concentration of the mixture of particles enhances the stream so that the required pressure is small. Moreover, it is found that the variation of the Nusselt number is noticeable by increasing the concentrations of nanoparticles, but this variation vanishes near the outer tube.


Author(s):  
Yang Liu ◽  
Qianqian Jia ◽  
Haijun Jia

Because annulus channel can be used to develop high efficiency compact heat exchangers, the heat transfer in annulus channel has become great interest to researchers in recent years. Most of the studies focus on the vertical concentric and horizontal eccentric annulus. The investigations about single phase force convection heat transfer inside a vertical eccentric annulus are not enough. In this work, force convection heat transfer is numerically studied to determine the eccentricity effect inside a vertical annulus. For this purpose, full Reynolds-averaged Navier-Stokes equations along with energy equations are solved in a 3-D grid. The discrete method of the equations is based on finite-volume method and the turbulence model is RNG k-ε model. The radius ratio of the annulus is 0.8 in this work. Heat flux of one wall is constant while the other is insulated. Firstly, the feasibility and exactness of the numerical method is proved by comparing the Nusselt number with experiment in concentric annulus. Then the effect of eccentricity is studied in detail.


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