scholarly journals FIRST STEPS TO COUPLED HYDRAULIC AND MECHANICAL CALCULATIONS WITHIN A PARAMETER STUDY TO DEFINE POSSIBLE CORE DESIGNS FOR THE CONVERSION OF FRM II

2021 ◽  
Vol 247 ◽  
pp. 08011
Author(s):  
Kaltrina Shehu ◽  
Cezary Bojanowski ◽  
Aurelien Bergeron ◽  
Winfried Petry ◽  
Christian Reiter
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Rectangular Channel ◽  
Parameter Study ◽  
High Flux ◽  
Code Verification ◽  
Research Reactors ◽  
Friction Factors ◽  
Ansys Cfx ◽  
The Heat Transfer Coefficient

The Forschungs-Neutronenquelle Heinz Meier-Leibnitz (FRM II) is actively participating in the worldwide efforts on developing high-density uranium fuels in order to reduce the enrichment of fuels used in high flux research reactors. This work is part of a parameter study to define possible compatible FRM II core designs for conversion. As a first step, a code-to-code verification is performed and experimental data is used for validation. The Gambill experiment was performed in the early 1960’s in support of the HFIR program and provides results regarding the heat transfer coefficient and friction factors of water flowing through an electrically heated thin rectangular channel. A comparison is made between the Gambill Test and the results simulated by Ansys CFX and STAR-CCM+.

Spatially Resolved Heat Transfer and Friction Factors in a Rectangular Channel With 45-Deg Angled Crossed-Rib Turbulators

2003 ◽  
Vol 125 (3) ◽  
pp. 575-584 ◽  
Author(s):  
P. M. Ligrani ◽  
G. I. Mahmood
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Rectangular Channel ◽  
Test Surface ◽  
Spatially Resolved ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Smooth Channel ◽  
Rib Turbulators

Spatially resolved Nusselt numbers, spatially averaged Nusselt numbers, and friction factors are presented for a stationary channel with an aspect ratio of 4 and angled rib turbulators inclined at 45 deg with perpendicular orientations on two opposite surfaces. Results are given at different Reynolds numbers based on channel height from 10,000 to 83,700. The ratio of rib height to hydraulic diameter is .078, the rib pitch-to-height ratio is 10, and the blockage provided by the ribs is 25% of the channel cross-sectional area. Nusselt numbers are given both with and without three-dimensional conduction considered within the acrylic test surface. In both cases, spatially resolved local Nusselt numbers are highest on tops of the rib turbulators, with lower magnitudes on flat surfaces between the ribs, where regions of flow separation and shear layer reattachment have pronounced influences on local surface heat transfer behavior. The augmented local and spatially averaged Nusselt number ratios (rib turbulator Nusselt numbers normalized by values measured in a smooth channel) vary locally on the rib tops as Reynolds number increases. Nusselt number ratios decrease on the flat regions away from the ribs, especially at locations just downstream of the ribs, as Reynolds number increases. When adjusted to account for conduction along and within the test surface, Nusselt number ratios show different quantitative variations (with location along the test surface), compared to variations when no conduction is included. Changes include: (i) decreased local Nusselt number ratios along the central part of each rib top surface as heat transfer from the sides of each rib becomes larger, and (ii) Nusselt number ratio decreases near corners, where each rib joins the flat part of the test surface, especially on the downstream side of each rib. With no conduction along and within the test surface (and variable heat flux assumed into the air stream), globally-averaged Nusselt number ratios vary from 2.92 to 1.64 as Reynolds number increases from 10,000 to 83,700. Corresponding thermal performance parameters also decrease as Reynolds number increases over this range, with values in approximate agreement with data measured by other investigators in a square channel also with 45 deg oriented ribs.

Impingement Cooling in Narrow Rectangular Channel With Novel Surface Features

2016 ◽  
Author(s):  
Sarwesh Narayan Parbat ◽  
Sin Chien Siw ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rectangular Channel ◽  
Jet Impingement ◽  
Test Case ◽  
Target Plate ◽  
Surface Features ◽  
Baseline Case ◽  
The Heat Transfer Coefficient

This paper describes a detailed experimental investigation of narrow jet impingement channel with surface features. Three novel surface features: aerofoil shaped dimple cavities on the target plate, chevron elements extending between the jet issuing plate and the target plate and 45 degree wedges mounted on the jet-issuing plate, are proposed. The narrow rectangular channel is 254 mm × 57.2 mm × 19.1 mm (10” × 2.25” × 0.75”) in dimensions and consists of five jets with a constant diameter, D of 9.525 mm (0.375”). The inter-jet spacing and jet-to-target plate distance is 4D and 2D, respectively. Three test cases with different novel surface features are proposed, and the effect of these surface features on the distribution of heat transfer coefficient on the target plate is characterized using the transient liquid crystal technique. In the first test case, dimpulated surface features are introduced on the target plate. The second case consists of chevron elements which extend between the jet issuing plate and the target plate, while the third case has 45 degree wedges mounted on the jet-issuing plate. The smooth jet impingement channel is used as a baseline case for comparison of the heat transfer coefficient distribution on the target plate. The Reynolds number is defined based on the jet diameter, D and bulk velocity of the jet. The experiments were performed at Reynolds number ranging between 61,000 to 98,000. In order to gain a better insight of the flow field within the channel for each of these features, a steady state numerical simulation was performed for each case using the commercially available software, ANSYS CFX. The boundary conditions for these simulations were set as close to the experimental conditions as possible. For turbulence closure, the Shear Stress Transport (SST) model was used which has been shown to be reasonably accurate with moderate computational costs. The numerical results are in favorable trend compared to the values obtained through experimentation. However, in certain regions, the SST turbulence model has overpredicted the heat transfer coefficient values. The results show that the first test case with dimpulated surface features exhibits the highest heat transfer enhancement among all the tested configurations. This enhancement is approximately 25 percent higher than that of the baseline case. The presence of the chevron elements has minimized the deflection of the jets due to crossflow, but, inhibited the spreading of the impinging jets on the target plate. This, in turn, has reduced the local heat transfer performance quite substantially. In case of the 45 degree wedges, the heat transfer enhancement was augmented at the downstream, which was ultimately caused by the diversion of the crossflow towards the target plate.

Heat Transfer and Pressure Drop in a Helically Coiled Rectangular Duct

1986 ◽  
Vol 108 (2) ◽  
pp. 343-349 ◽  
Author(s):  
V. Kadambi ◽  
E. K. Levy ◽  
S. Neti
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Reynolds Numbers ◽  
Rectangular Duct ◽  
Number Range ◽  
Rectangular Wave ◽  
Friction Factors ◽  
Sudden Transition ◽  
The Heat Transfer Coefficient ◽  
Straight Duct

The present paper deals with experiments using air in three helically coiled rectangular ducts of mean diameters 12.7 cm, 17.8 cm, and 22.8 cm, respectively, made of rectangular wave-guide tubing of dimensions 1.27 cm × 0.64 cm. Pressure variations observed around the ducts were qualitatively in agreement with the expectations for secondary flow. The friction factors change gradually with increasing Reynolds numbers over the range 1200–10,000 without exhibiting a sudden transition from laminar flow to turbulence. At all Reynolds numbers, these are higher than those for a straight duct by 20–100 percent. The heat transfer coefficient is also higher than that for straight ducts ranging between 20–300 percent, depending on the Reynolds number. The largest increases are seen in the Reynolds number range 1200–2500.

On the Influence of the Thickness and Thermal Properties of Heating Walls on the Heat Transfer Coefficients in Nucleate Pool Boiling

1975 ◽  
Vol 97 (2) ◽  
pp. 173-178 ◽  
Author(s):  
U. Magrini ◽  
E. Nannei
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Atmospheric Pressure ◽  
Metal Layer ◽  
Pool Boiling ◽  
Transfer Coefficients ◽  
Heating Wall ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient ◽  
Zinc Nickel

An experimental investigation was conducted under conditions of saturated pool boiling of water at atmospheric pressure on thin, horizontal, cylindrical walls of different metals and thicknesses, electrically heated. The heating walls, ranging in thickness from 5 to 250 μm, were obtained by plating copper, silver, zinc, nickel, and tin on nonmetallic rods. Experiments showed that the heat transfer coefficient can be affected, in particular conditions, by the heating wall thickness. In particular, it resulted that the smaller the thermal conductivity of the metal layer, the higher the influence of the thickness. A semiempirical correlation of the form ΔT = (q/A)nf(κd, √κρc) suitable to correlate the experimental data within ±15 percent in the whole range of variables here investigated is proposed.

The Dynamics of Liquid Cooling in Half-Coil Jackets

2008 ◽  
Vol 3 (1) ◽  
Author(s):  
Jayakumar Natesan Subramanian ◽  
Farouq S. Mjalli
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mathematical Model ◽  
Liquid Temperature ◽  
Liquid Cooling ◽  
Shell Side ◽  
Stirred Vessel ◽  
Model Predictions ◽  
Temperature Dynamics ◽  
The Heat Transfer Coefficient

The heat transfer cooling of a hot liquid in a stirred vessel has been studied experimentally with coolant flowing through a half-coil around the vessel. Correlations have been developed for the heat transfer coefficient of the half coil jacket. A mathematical model for the half coil jacket liquid temperature dynamics and its analytical solution is used to find the shell side temperature profile as a function of time. It is found that the model predictions are in satisfactory agreement with the experimental data and that the developed correlation is superior to previously published correlations for similar systems.

Analysis of Heat Transfer and Fluid Flow Through a Spirally Fluted Tube Using a Porous Substrate Approach

1994 ◽  
Vol 116 (3) ◽  
pp. 543-551 ◽  
Author(s):  
Vijayaragham Srinivasan ◽  
Kambiz Vafai ◽  
Richard N. Christensen
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Porous Substrate ◽  
The Finite Element Method ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Friction Factors ◽  
Flow Through ◽  
Good Agreement

An innovative approach was opted for modeling the flow and heat transfer through spirally fluted tubes. The model divided the flow domain into two regions. The flutes were modeled as a porous substrate with direction-dependent permeabilities. This enabled modeling the swirl component in the fluted tube. The properties of the porous substrate such as its thickness, porosity, and ratio of the direction-dependent permeabilities were obtained from the geometry of the fluted tube. Experimental data on laminar Nusselt numbers and friction factors for different types of fluted tubes representing a broad range of flute geometry were available. Experimental data from a few of the tubes tested were used to propose a relationship between the permeability of the porous substrate and the flute parameters, particularly the flute spacing. The governing equations were discretized using the Finite Element Method. The model was verified and applied to the other tubes in the test matrix. Very good agreement was found between the numerical predictions and the experimental data.

scholarly journals Influence of fin thickness on heat transfer and flow performance of a parallel flow evaporator

2019 ◽  
Vol 23 (4) ◽  
pp. 2413-2419 ◽  
Author(s):  
Haijun Li ◽  
Enhai Liu ◽  
Guanghui Zhou ◽  
Fengye Yang ◽  
Zhiyong Su ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Comprehensive Evaluation ◽  
Reynolds Numbers ◽  
Parallel Flow ◽  
Heat Transfer Factor ◽  
Heat Transfer Capacity ◽  
Fin Thickness ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

This paper studies numerically the influence of the louver?s fin thickness on heat transfer and flow performance of a parallel flow evaporator, a comprehensive evaluation and analysis of the five structures at different Reynolds numbers are systematically carried out. Comparison of the numerical results with the experimental data shows good agreement with maximal errors of 12.16% and 5.29% for the heat transfer factor and the resistance factor, respectively. The results show that the heat transfer coefficient and the pressure drop increase with the increase of the thickness of the louver fins when the Reynolds number is a constant. The analysis of the comprehensive evaluation factor shows that the A-type fin is the best, and it can effectively strengthen the heat exchange on the air side and improve the heat transfer capacity of the system. The research results can provide reference for the structural optimization of the louver fins.

scholarly journals Modeling Film-Coolant Flow Characteristics at the Exit of Shower-Head Holes

2000 ◽  
Author(s):  
Vijay K. Garg
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Coolant Flow ◽  
The Heat Transfer Coefficient

Abstract The coolant flow characteristics at the hole exits of a film-cooled blade are derived from an earlier analysis where the hole pipes and coolant plenum were also discretized. The blade chosen is the VKI rotor with three staggered rows of shower-head holes. The present analysis applies these flow characteristics at the shower-head hole exits. A multi-block three-dimensional Navier-Stokes code with Wilcox’s k-ω model is used to compute the heat transfer coefficient on the film-cooled turbine blade. A reasonably good comparison with the experimental data as well as with the more complete earlier analysis where the hole pipes and coolant plenum were also gridded is obtained. If the 1/7th power law is assumed for the coolant flow characteristics at the hole exits, considerable differences in the heat transfer coefficient on the blade surface, specially in the leading-edge region, are observed even though the span-averaged values of h match well with the experimental data. This calls for span-resolved experimental data near film-cooling holes on a blade for better validation of the code.

The Effect of Density Variation on Heat Transfer in the Critical Region

1961 ◽  
Vol 83 (2) ◽  
pp. 176-181 ◽  
Author(s):  
Yih-Yun Hsu ◽  
J. M. Smith
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Critical Point ◽  
Critical Region ◽  
Large Density ◽  
The Heat Transfer Coefficient

The heat-transfer coefficient between fluid and tube wall in turbulent flow depends upon the physical and thermal properties of the fluid. When density changes across the diameter of the tube are large (for example, when the fluid is near the critical point), the variable density can affect the transfer of momentum and heat. Equations are developed for predicting the magnitude of this effect on the heat-transfer coefficient. Deissler’s [5] expressions for the eddy diffusivity are employed in solving the equations for heat and momentum transfer. For flow in vertical tubes large density variations can also affect the heat transfer by inducing natural convection. By considering the influence of body forces on the shear stress, equations are derived to predict the effect of natural convection on the heat-transfer coefficient for turbulent flow. The results indicate that the effect is significant only for relatively high Grashof numbers and low Reynolds numbers. Such conditions may be encountered in flow of a fluid near its thermodynamic critical point. The derived equations are applied for carbon dioxide flow in the critical region under the conditions for which experimental data were measured by Bringer and Smith [2]. Because of the high Reynolds and low Grashof numbers, natural convection is not significant. However, the effect of the large density variations is found to be significant, and the predicted results agree well with the experimental data.

Heat Transfer in a Two-Pass Rectangular Channel (AR=1:4) Under High Rotation Numbers

2007 ◽  
Author(s):  
Yao-Hsien Liu ◽  
Michael Huh ◽  
Je-Chin Han ◽  
Sanjay Chopra
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Leading Edge ◽  
Parameter Study ◽  
First Passage ◽  
Test Channel ◽  
Sharp Bend ◽  
Buoyancy Parameter ◽  
Sharp Turn

This paper experimentally investigated the rotational effects on heat transfer in a two-pass rectangular channel (AR=1:4), which is applicable to the channel near the leading edge of the gas turbine blade. The test channel has radially outward flow in the first passage through a re-directed sharp bend entrance and radially inward flow in the second passage after a 180° sharp turn. In the first passage, rotation effects on heat transfer are reduced by the re-directed sharp bend entrance. In the second passage, under rotating conditions, both leading and trailing surfaces experienced heat transfer enhancements above the stationary case. Rotation greatly increased heat transfer enhancement in the tip region up to a maximum Nu ratio (Nu/Nus) of 2.4. The objective of the current study is to perform an extended parameter study of the low rotation number (0–0.3) and low buoyancy parameter (0–0.2) achieved previously. By varying the Reynolds numbers (10000–40000) and the rotational speeds (0–400 rpm), the increased range of the rotation number and buoyancy parameter reached in this study are 0–0.67 and 0–1.9, respectively. The higher rotation number and buoyancy parameter have been correlated very well to predict the rotational heat transfer in the two-pass, 1:4 aspect ratio flow channel.

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