scholarly journals CFD SIMULATION OF VERTICAL SEVEN-ROD BUNDLE COOLED WITH SUPERCRITICAL FREON-12

2014 ◽  
Vol 3 (01) ◽  
pp. 17-28 ◽  
Author(s):  
X. Huang ◽  
K. Podila ◽  
Y.F. Rao
Keyword(s):  
Heat Transfer ◽  
Cfd Simulation ◽  
Turbulence Models ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Cfd Simulations ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients ◽  
Rod Bundle ◽  
Flow And Heat Transfer

In this paper, a seven-rod bare bundle was simulated using ANSYS Fluent 6.3.26 to accurately predict the fluid flow and heat transfer behaviour under supercritical flow conditions. Seven turbulence models were compared to identify the appropriate model to predict the experiments performed at the Institute of Physics and Power Engineering on a vertically oriented seven-rod bare bundle cooled with supercritical Freon-12. It was found that predictions of wall temperatures and heat transfer coefficients are sensitive to the choice of turbulence model as well as to the near-wall treatment. Overall, the CFD simulations were able to predict the measured sheath temperature profiles along the length of the bundle within reasonable accuracy.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

scholarly journals Heat Transfer Measurements for Rotating Turbine Discs

1989 ◽  
Author(s):  
G. Qureshi ◽  
M. H. Nguyen ◽  
N. R. Saad ◽  
R. N. Tadros
Keyword(s):  
Heat Transfer ◽  
Coolant Flow ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Rotating Disc ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Rotating Discs ◽  
Turbine Disc ◽  
State Technique

To optimise the turbine disc weight and coolant flow requirements, the aspect of improving thermal analysis was investigated. As a consequence, an experimental investigation was undertaken to measure the rates of convective heat transfer. The constant temperature steady state technique was used to determine the local and average heat transfer coefficients on the sides of rotating discs. The effects of coolant flow rates, CW (3000 ≤ CW ≤ 18600) with two types of cavity in-flow conditions and of the rotational speeds, Reθ (from 4×105 to 1.86×106) on the disc heat transfer were studied and correlations developed. For a rotating disc in confined cavities with superimposed coolant flows, Nusselt numbers were found to be higher than those for the free rotating disc without confinement.

scholarly journals Heat Transfer and Fluid Dynamics Measurements in the Expansion Space of a Stirling Cycle Engine

2006 ◽  
Author(s):  
Nan Jiang ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
High Efficiency ◽  
Stirling Engine ◽  
Transfer Coefficients ◽  
Head Region ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Engine Design ◽  
Region Flow ◽  
Design Calculations

The heater (or acceptor) of a Stirling engine, where most of the thermal energy is accepted into the engine by heat transfer, is the hottest part of the engine. Almost as hot is the adjacent expansion space of the engine. In the expansion space, the flow is oscillatory, impinging on a two-dimensional concavely-curved surface. Knowing the heat transfer on the inside surface of the engine head is critical to the engine design for efficiency and reliability. However, the flow in this region is not well understood and support is required to develop the CFD codes needed to design modern Stirling engines of high efficiency and power output. The present project is to experimentally investigate the flow and heat transfer in the heater head region. Flow fields and heat transfer coefficients are measured to characterize the oscillatory flow as well as to supply experimental validation for the CFD Stirling engine design codes. Presented also is a discussion of how these results might be used for heater head and acceptor region design calculations.

scholarly journals Heat flow and heat transfer coefficient during crystallization under the pressure

2018 ◽  
Vol 157 ◽  
pp. 02036
Author(s):  
Richard Pastirčák ◽  
Ján Ščury ◽  
Tomáš Fecura
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Solidification Process ◽  
Metal Mold ◽  
Transfer Coefficients ◽  
Microstructure Modeling ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Solidification Processes ◽  
Precise Prediction

Estimation of the heat flow at the metal-mold interface is necessary for accurate simulation of the solidification processes. For the numerical simulation, a precise prediction of boundary conditions is required to determine the temperature distribution during solidification, porosity nucleation, microstructure development, and residual stresses. Determination of the heat transfer coefficients at the metal-mold interface is a critical aspect for simulation of the solidification process and the microstructure modeling of the castings. For crystallization under the pressure and for thin-walled castings, HTC evaluation is important due to the very limited freezing time.

Simulation of Heat Transfer to Turbulent Nanofluid Flow in an Annular Passage

2014 ◽  
Vol 925 ◽  
pp. 625-629 ◽  
Author(s):  
C.S. Oon ◽  
A. Badarudin ◽  
S.N. Kazi ◽  
M. Fadhli
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Titanium Oxide ◽  
Convective Heat Transfer Coefficient ◽  
Hot Water ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients

The heat transfer in annular heat exchanger with titanium oxide of 1.0 volume % concentration as the medium of heat exchanger is considered in this study. The heat transfer simulation of the flow is performed by using Computational Fluid Dynamics package, Ansys Fluent. The heat transfer coefficients of water to titanium oxide nanofluid flowing in a horizontal counter-flow heat exchanger under turbulent flow conditions are investigated. The results show that the convective heat transfer coefficient of the nanofluid is slightly higher than that of the base fluid by several percents. The heat transfer coefficient increases with the increase of the mass flow rate of hot water and also the nanofluid.

Calibration of External Heat Transfer Coefficients During Cooling of a Partially-Filled Water Tank Using Measured Temperature-Time Data

2018 ◽  
Author(s):  
Vishal Ramesh ◽  
Sandip Mazumder ◽  
Gurpreet Matharu ◽  
Dhaval Vaishnav ◽  
Syed Ali ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Measured Temperature ◽  
Water Tank ◽  
Time Data ◽  
Transfer Coefficients ◽  
Ansys Fluent ◽  
Heat Transfer Coefficients ◽  
Computational Fluid Dynamics Cfd ◽  
Temperature Time

A combined Computational Fluid Dynamics (CFD) and experimental approach is presented to determine (calibrate) the external convective heat transfer coefficients (h) around a partially-filled water tank cooled in a climactic chamber. A CFD analysis that includes natural convection in both phases (water and air) was performed using a 2D-axisymmetric tank model with three prescribed average heat transfer coefficients for the top, side and bottom walls of the tank. The commercial CFD code ANSYS-Fluent™, along with User-Defined Functions (UDFs), were utilized to compute and extract temperature vs. time curves at five different thermocouple locations within the tank. The prescribed h values were then altered to match experimentally obtained temperature-time data at the same locations. The calibration was deemed successful when results from the simulations exhibited match with experimental data within ±2°C for all thermocouples. The calibrated h values were finally used in full-scale 3D simulations and compared to the experimental data to test their accuracy. Predicted 3D results were found to agree with experimental results within the error of the calibration, thereby lending credibility to the overall approach.

Squeal and Thermal Analysis of Automobile Disc Brake Rotors

2015 ◽  
Vol 764-765 ◽  
pp. 369-373
Author(s):  
Wei Hsin Gau ◽  
Kun Nan Chen ◽  
Chin Yuan Hung
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Finite Element ◽  
Aluminum Alloy ◽  
Cast Iron ◽  
Cfd Simulation ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Brake Rotors

The brakes of an automobile are among the most critical components regarding the safety features, and disc brakes are the most common type used in passenger vehicles. In this research, the squeal phenomena of a swirl-vent brake rotor and the thermal analysis of two straight-vent brake rotors, made of cast-iron and aluminum-alloy, are investigated. For the squeal analysis, finite element models are created and analyzed using a prestressed modal analysis with complex eigen-solutions. For the thermal analysis, heat transfer coefficients on the surfaces of a rotor as functions of time are first estimated by CFD simulation, and then imported to a thermal analysis program as the boundary condition. Finally, the temperature distribution of the rotor can be calculated by finite element analysis. The simulation results show that vortices will arise in the vented passages of straight-vent rotors, which means less heat carried away and lower heat transfer coefficients. The swirl-vent brake design is clearly better for thermal ventilation. Furthermore, under the same condition, aluminum-alloy rotors exhibit more uniform temperature distributions with smaller temperature gradients than cast-iron rotors do.

Heat Transfer to Mercury Flowing In Line Through an Unbaffled Rod Bundle: Experimental Study of the Effect of Rod Displacement on Rod-Average Heat Transfer Coefficients

1969 ◽  
Vol 91 (4) ◽  
pp. 568-580 ◽  
Author(s):  
P. J. Hlavac ◽  
O. E. Dwyer ◽  
M. A. Helfant
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Uniform Heat Flux ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Rod Bundle

An experimental study of heat transfer to mercury flowing in line through an unbaffled rod bundle was carried out. The “rods” were special electrical heaters whose claddings had different thicknesses and thermal conductivities. The experiments were carried out under a thermal boundary condition approaching that of uniform heat flux in all directions at the inner wall of the rod cladding. It was found that displacement of a rod from its symmetrical position can result in a large reduction in its average heat transfer coefficient. This reduction increases exponentially with the amount of displacement. For a given direction and amount of displacement, the reduction is little affected by variations in cladding thickness and conductivity but is affected considerably by flow rate. Not only does the displaced rod suffer a reduction in its own average heat transfer coefficient, but so do those toward which it is displaced. At the same time, the average coefficients of the rods from which it is displaced remain about the same. Thus the overall average coefficient of the group of affected rods goes down when a single rod is displaced.

The Effect of Entrance Configuration on Local Heat-transfer Coefficients in Subsonic Diffusers

1972 ◽  
Vol 94 (4) ◽  
pp. 355-359 ◽  
Author(s):  
E. O. Stoffel ◽  
J. R. Welty
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Transfer Equations ◽  
Subsonic Diffuser

The effects of square and reentrant entrances on flow regimes (no “appreciable” separation, large transitory stall, and fully developed two-dimensional stall) and local heat-transfer coefficients were determined with air flowing through a symmetrical, plane-wall, two-dimensional subsonic diffuser with one of the diverging walls heated and maintained isothermal. Flow and heat-transfer studies were made for the following ranges: 2θ = 0 to 45 deg, L/W = 6 to 18, and Rextut = 4 × 104 to 3 × 105. Results indicated that 2θ, L/W, and entrance configuration greatly affected the flow regime and heat transfer. Equations relating Um′ to Ut, Ur to Ut, and equations of the type Nu = C Pr0.6Rex0.8 are presented. For the configurations tested, heat-transfer rates were greater for reentrant than for square entrances.

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