UNIVERSITA’ DI PISA
DIPARTIMENTO DI INGEGNERIA CIVILE E INDUSTRIALE
Tesi di Laurea Magistrale in Ingegneria Nucleare
PRE-TEST CFD ANALYSIS OF THE ROD BUNDLE EXPERIMENT
IN THE HEAVY LIQUID METAL FACILITY NACIE-UP
Relatori
Dott. Ing. Nicola Forgione
DICI
Prof. Ing. Walter Ambrosini
DICI
Dott. Ing. Ivan Di Piazza
ENEA
Candidato
Ranieri Marinari
In the context of the studies on GEN. IV/ADS nuclear systems, the correct evaluations of the
temperature distribution in the fuel pin bundle is of central interest. In particular, the use of
lead or lead-bismuth eutectic (LBE) as coolant for the new generation fast reactors is one of
the most promising choices. Due to the high density and high conductivity of lead or LBE, a
detailed analysis of the thermo-fluid dynamic behavior of the heavy liquid metal (HLM) inside
the sub-channels of a fuel rod bundle is necessary in order to support the front-end engineering
design (FEED) of GEN. IV/ADS prototypes and demonstrators. In this frame, the synergy
between numerical analysis by CFD and data coming from large experimental facilities seems
to be crucial to assess the feasibility of the components. At ENEA-Brasimone R.C., large
experimental facilities exist to study HLM free, forced and mixed convection in loops and
pools: e.g. NACIE-UP is a large scale LBE loop for mixed convection experiments. In the
context of the SEARCH FP7 project, an experiment has to be performed in the NACIE-UP
facility to assess the coolability of a 19-pin wire-wrapped electrical bundle (Fuel Pin
Simulator, FPS), with heat flux up to 1 MW/m
2. The bundle is representative of the one
adopted in the MYRRHA concept.
The present master thesis is devoted to the Computational Fluid Dynamic (CFD) analysis of
Heavy Liquid Metal (HLM) cooled Fuel Bundles to be adopted in the Gen-IV nuclear
reactors. The thesis was carried out in collaboration with the ENEA Brasimone research
center, where large experimental facilities are operated to investigate HLM technology and
thermal hydraulics. In particular liquid Lead or Lead-Bismuth Eutectic (LBE) is considered as
working fluid.
A CFD analysis of fluid flow and heat transfer was carried out in the heavy liquid metal (LBE)
cooled bundle test section of the NACIE-UP facility. The model includes the details of the
wire-spacers as well as the entry region of the test section. A turbulence closure approach is
adopted for all the simulations with
7nodes and a resolution of y
+= 1 - 4 at the wall in
the range of interest.
A CFD code validation was carried out on experimental data by ORNL in a similar geometry
cooled by sodium. Results showed a global coherence of the results and a correct description
of the conjugate heat transfer effects. A good agreement was found between numerical and
experimental data, although the RANS approach showed some limitations for the central
sub-channel temperature distributions at high mass flow rates.
Results are compared with the up-to-date correlations on pressure loss and heat transfer and
the experimental range is completely explored by CFD. The thermal structures of the test
section are modelled and the role of conjugate heat transfer was assessed.
Several highlights emerged from the numerical study for the experimental campaign. In
particular, the accuracy in the measurement of heat transfer between rods and fluid was
evidenced as weak point of the experimental test matrix. As a consequence the test matrix was
modified.
i
List of contents
List of figures ... iv
List of tables ... xi
Nomenclature ... xiii
1.
Introduction ... 1
1.1.
Overview of the Technology ... 1
1.1.1.
Sustainability ... 1
1.1.2.
Economics ... 2
1.1.3.
Safety and Reliability ... 3
1.1.4.
Physical Protection ... 4
1.2.
HLM Gen-IV Demonstrator and irradiation facility ... 4
1.2.1.
The MYRRHA reactor ... 4
1.2.2.
Wire wrapped vs. grid spacer solution for the Fuel Assembly ... 6
1.3.
Plan of the thesis ... 7
2.
Literature Review on HLM cooled wire-wrap bundles ... 8
2.1.
Definitions ... 8
2.2.
Experimental studies ... 11
2.3.
Numerical studies ... 21
2.4.
Overall Pressure drop ... 35
2.4.1.
Definitions ... 37
2.4.2.
Friction factor correlations for wire-wrapped fuel assemblies ... 37
2.4.3.
Comparative analysis of the available correlations ... 40
2.5.
Overall Heat transfer ... 42
2.5.1. Comparative analysis of the correlations... 46
ii
3.1
General framework ... 50
3.2
The NACIE-UP facility ... 53
3.3
The Fuel Pin bundle Simulator (FPS) ... 57
3.4
Bundle instrumentation ... 60
4.
Models and methods ... 64
4.1
The CFD model of the FPS ... 64
4.1.1.
The preliminary model (only fluid) ... 66
4.1.2.
The solid structures issue ... 67
4.1.3.
The complete model with solid structures ... 67
5.
Code assessment ... 69
5.1.
The ORNL FFM experimental facility ... 69
5.2.
The test section and the rod bundle instrumentation ... 70
5.3.
The CFD model ... 73
5.4
Results ... 74
5.5
Final remarks ... 78
6.
Results ... 79
6.1.
Sensitivity studies ... 79
6.1.1.
The influence of mesh size ... 80
6.1.2.
The influence of Turbulent Prandtl Number ... 82
6.1.3.
The influence of heat flux boundary conditions ... 84
6.1.4.
The influence of the convective scheme ... 85
6.1.5.
The influence of the turbulence model ... 86
6.1.6.
The influence of temperature dependent properties ... 89
6.1.7.
The influence of solid structures ... 89
iii
6.2.1.
Detailed investigation of the numerical test matrix ... 91
6.2.2.
The influence of Reynolds number ... 100
6.2.3.
Overall pressure drop ... 102
6.2.4.
The heat transfer issue ... 106
6.2.5.
The wire pitch model ... 106
6.2.6.
Highlights for the experimental activity on NACIE-UP facility ... 113
7.
Conclusions ... 114
References ... 116
Appendix ... 120
a)
Complete code assessment on the FFM facility ... 120
iv
List of figures
Figure 1-1 Overall view of the MYRRHA reactor with its main components. ... 5
Figure 1-2 Geometrical features of the Fuel Assembly (FA) to be used in MYRRHA. ... 5
Figure 2-1 View of pin bundles (a) 7 pins (b) 19 pins and (c) 217 pins. ... 8
Figure 2-2 Thermal gradient “type a”. ... 10
Figure 2-3 Thermal gradient "type b". ... 10
Figure 2-4 Flow test section with pressure taps. ... 12
Figure 2-5 Axial static pressure in a peripheral sub-channel. ... 12
Figure 2-6 Pressure distribution around wire-wrap rods. ... 13
Figure 2-7 Transverse static pressure at the peripheral hexagonal duct. ... 13
Figure 2-8 Interior sub-channel velocity distribution. ... 14
Figure 2-9 Interior sub-channel flow sweeping data. ... 15
Figure 2-10 Velocity distribution in corner (a) and side (b) sub-channel of WARD facility. ... 16
Figure 2-11 Side sub-channel flow seeping data over an axial wire-wrap pitch. ... 17
Figure 2-12 Average ( ) function for interior, side and corner gaps. ... 17
Figure 2-13 Eddy diffusivity in a wire wrap bundle. ... 17
Figure 2- ... 18
Figure 2- ... 19
Figure 2- ... 20
Figure 2-17 Transverse distribution of horizontal velocity component. ... 21
Figure 2-18 Mesh distribution in helical wire-wrapped pin bundle (left) and bare pin bundle (right)... 22
Figure 2-19 Transverse velocity distribution (m/s): (a) Z = 0 mm, (b) Z = 45 mm, ... 23
Figure 2-20 Outlet sodium temperature distribution in the pin bundle. ... 24
Figure 2-21 Comparison of pin bundle friction factor with and without wire. ... 24
Figure 2-22 Transverse velocity (m/s) at the same height for the 7, 19 and 37 pin bundle. ... 25
Figure 2-23 Time- and spanwise-averaged velocity along channel interfaces for H/D=20.1 (lower curve) and 13.4 (upper curve). ... 27
Figure 2-25 Temperature contours (outlet face). ... 28
Figure 2-24 Cross-stream velocity vector plot (midplane face). ... 28
Figure 2-26 Axial velocity magnitude (outlet face). ... 28
Figure 2-27 Local pressure distribution (inlet face). ... 28
Figure 2-28 Friction factor predicted for liquid sodium flow by various turbulence models. ... 29
Figure 2-29 Cross flow field produced by the wire wrap in the rod bundle. ... 29
Figure 2-30 Circumferentially averaged Nu predicted for liquid sodium flow by various turbulence models. ... 30
v
Figure 2-33 Friction factor for the 19 pin geometry (H/D = 21). ... 31
Figure 2-32 Nusselt number for the 19 pin geometry (H/D = 21). ... 31
Figure 2-34 (a) Prediction of friction factor development in 7-pin bundle by various tur-bulence models (Re = 0.842 105). (b) Prediction of Nusselt number development in 7-pin bundle by various turbulence models (Re = 0.842 105). ... 32
Figure 2-35 Cross-stream velocity for different wire-pitch (left) and number of pins (right). ... 33
Figure 2-36 Friction factor coefficient for different wire-pitch (left) and number of pins (right). ... 34
Figure 2-37 Global Nusselt number (NuG) development in fuel pin bundles. ... 34
Figure 2-38 Friction factor f as a function of Re for different leads of wire-wrap H . The test parameters: P/D=1.125 , n=19 rods. ... 35
Figure 2-39 Friction factor f as a function of Re for different leads of wire-wrap H . The test parameters: P/D=1.417 , n=19 rods. ... 35
Figure 2-40 Friction factor f as a function of Re for different pitch-to-diameter ratio P/D . The test parameters: H=110 mm , n=19 rods. ... 36
Figure 2-41Predictions of the different correlations vs. the test data for the Nusselt number. ... 48
Figure 2-42 Predictions of the different correlations vs. the test data for the Nusselt number (continuation). ... 49
Figure 3-1 Conceptual sketch of the NACIE-UP facility. ... 50
Figure 3-2 The NACIE-UP facility. ... 54
Figure 3-3 Pipe and Instrumentation Diagram (P&ID) of the NACIE-UP facility. ... 55
Figure 3-4 Schematic layout of the NACIE-UP facility. ... 56
Figure 3-5 The NACIE-UP facility with an highlight of the FPS and its location. ... 57
Figure 3-6 Sketch of the new fuel pin bundle simulator for the NACIE facility. Instrumented pins in red; instrumented sub-channels in orange, wire in black. ... 58
Figure 3-7 Sketch of the pin with the wire helicoidally wrapped. ... 59
Figure 3-8 Cross-section of the NACIE-UP electrical wire-spaced fuel pin bundle simulator. ... 60
Figure 3-9 Wall Embedded TCs locations for pins n. 2,4,6,7,9,16,18,19. ... 61
Figure 3-10 Wall Embedded TCs locations for pin n. 1. ... 61
Figure 3-11 Wall embedded TCs location for pin n.5. ... 62
Figure 3-12 Generic measurement section (z=38, 300, 562 mm) conventionally view from the top, with the location of wall TCs and instrumented channels. ... 62
Figure 4-1 Layout of the preliminary CFD model developed. ... 66
Figure 4-2 A detailed view of the generated mesh. ... 67
Figure 4-3 Layout of the complete CFD model developed. ... 68
Figure 5-1 A schematic layout of the LMFBR-FFM facility. ... 69
vi
Figure 5-3 Locations of ungrounded-junctions in wire-wraps of bundle-2A. ... 71 Figure 5-4 Locations of grounded-junctions in wire-wraps and heater internal thermocouples of bundle-2A. ... 72 Figure 5-5 Layout of the CFD model developed for the bundle-2A. ... 73 Figure 5-6 Comparison of duct (wrap internal) temperature predictions at different heights with TEST SERIES
4-RUN105 experimental results. ... 75 Figure 5-7 Comparison of pin temperature predictions at different heights with TEST SERIES 4-RUN105
experimental results. ... 75 Figure 5-8 Comparison of pin temperature predictions at different heights with TEST SERIES 6-RUN103
experimental results. ... 76 Figure 5-9 Comparison of duct wall temperature predictions at different heights with TEST6-RUN103
experimental results. ... 77 Figure 5-10 Comparison of pin temperature predictions at different heights adopting a finer mesh with the TEST
SERIES 6-RUN103 experimental results. ... 77 Figure 5-11 Comparison of pin temperatures predictions at different heights adopting the second order Omega
Reynolds Stress turbulence model with the TEST SERIES 6-RUN103 experimental results. ... 78 Figure 6-1 Detailed representation of the cross-section planes with their nomenclature and their height from the
BOTTOM plane. ... 79 Figure 6-2 Cross sections of the grain size for the coarse mesh (left), the medium mesh (center) and fine mesh
(right). ... 80 Figure 6-3 Axial velocity profiles at the middle of the active zone for : coarse size mesh (left), medium size mesh
(center) and fine size mesh (right). ... 81 Figure 6-4 Swirl velocity profiles at the middle of the active zone for : coarse size mesh (left), medium size mesh
(center) and fine size mesh (right). ... 81 Figure 6-5 Temperature profiles at the middle of the active zone for : coarse size mesh (left), medium size mesh
(center) and fine size mesh (right). ... 82 Figure 6-6 Temperature contours on plane D of the active zone for Prt=1.5 (left) and Prt=1.0 (right). ... 83
Figure 6-7 Temperature contours on plane D of the active zone for Prt=1.5 (left) and Prt=1.0 (right). ... 84
Figure 6-8 Temperature profiles for different heat flux boundary condition : on pin and wire surfaces (left), on pin
surface only (right). ... 84 Figure 6-9 Comparison of temperature distribution on the same cross-section plane (D) adopting a first order
upwind scheme (left) and a high order one (right). ... 85 Figure 6-10 Comparison of temperature contours on plane D between the omega SST model simulation (right)
and the second order Omega Reynolds Stress model simulation; heat flux and mass flow rate conditions are
vii
Figure 6-11 Graph of the ANSYS CFX code temperature results in the active region implementing the SST model
and the Omega Reynold Stress (ORS) model. ... 88
Figure 6-12 Graph of the ANSYS CFX code pressure slope results in the whole model implementing the SST model and the Omega Reynold Stress (ORS) model. ... 88
Figure 6-13 Temperature contours on the same cross-section (plane D) for the constant properties case (right) and the temperature dependent properties case (left). ... 89
Figure 6-14 Simple representation of the complete CFD model with the 19 pins (in orange) and the hexagonal wrap (in grey). ... 89
Figure 6-15 Comparison of temperature contours on the same cross-section for the preliminary model without solid structures (left) and the complete model with solid structures (right). ... 90
Figure 6-16 Eddy viscosity ratio contours for the OF05 (left), OF20 (center) and OF70 (right) cases. ... 92
Figure 6-17 Development of the mainstream velocity component for the 0.5 kg/s case. ... 92
Figure 6-18 Development of the swirl velocity component for the 0.5 kg/s case. ... 93
Figure 6-19 Feature of the swirl velocity component for a wire pitch length (0.5 kg/s case). ... 93
Figure 6-20 Contours of the planes D (left) and E (right) of the SS05 case with a more detailed scale. ... 94
Figure 6-21 Contours of the Tabs variable on the three cross-sections of the heated zone (in orange) for the OF05 case (left) and SS05 case (center). ... 94
Figure 6-22 Pressure slope into the model for the 0.5 kg/s case. ... 95
Figure 6-23 Bulk temperature and pin average temperature for the OF05 and SS05 cases as function of the height from the heated region inlet plane. ... 95
Figure 6-24 Development of the mainstream velocity component for the 2.032 kg/s case. ... 96
Figure 6-25 Development of the swirl velocity component for the 2.032 kg/s case. ... 97
Figure 6-26 Contours of the Tabs on planes C, D and E in the heated zone (in orange) for the OF20 case (a) and SS20 case (b). ... 97
Figure 6-27 Development of the mainstream velocity component for the 7.0 kg/s case. ... 98
Figure 6-28 For the 2.032 kg/s case: (right) Bulk temperature and pin average temperature for the SS20 and OF20 cases as function of the height from the heated region inlet plane; (left) Pressure drop against vertical coordinate. ... 98
Figure 6-29 Development of the swirl velocity component for the 7.0 kg/s case. ... 99
Figure 6-30 Contours of the Tabs on planes C, D and E in the heated zone (in orange) for the OF70 case (a) and SS70 case (b). ... 99
Figure 6-31 (right) Bulk temperature and pin average temperature for the SS70 and OF70 cases as function of the height from the heated region inlet plane; (left) Pressure drop slope into the model for the 7.0 kg/s case. ... 100
Figure 6-32 Reynolds number effect on the mainstream velocity component for the test matrix cases ... 101
viii
Figure 6-34 Reynolds number effect on the temperature distribution in the middle plane of the heated region for
the test matrix cases. ... 102
Figure 6-35 Comparison between the CFD results and the available correlations for the pressure drop in the active region. ... 103
Figure 6-36 Comparison between the CFD results and the available correlations for the friction factor in the bundle. ... 103
Figure 6-37 Friction factor slope in a wire pitch length for the 5.0 kg/s case. ... 104
Figure 6-38 Variation of the total pressure drop function with the mass flow rate. ... 105
Figure 6-39 Graph of the variation of the total pressure drop with the mass flow rate. ... 105
Figure 6-40 Wire pitch CFD model developed. ... 107
Figure 6-41 Comparison between the cross-section average HTC in the wire pitch model and in the complete model for the SS20 case... 109
Figure 6-42 Representation of the measuring points on the inlet plane of the wire pitch model (left) and graphic representation of the instrumented pins and sub-channels into the FPS. ... 110
Figure 6-43 Nu2 values calculated for the numerical test matrix against the Peclet number compared with the Ushakov correlation and Mikityuk correlation. ... 112
Figure 1 Nomenclature of the thermocouples adopted in the FFM bundle 2A. ... 120
Figure 2 Operating data for the FFM TEST 4 - RUN 102. ... 121
Figure 3 Graphic comparison of pin temperature predictions with TEST 4 - RUN 102 experimental results... 123
Figure 4 Graphic comparison of duct wall temperature predictions with TEST 4 - RUN 102 experimental results. ... 124
Figure 5 Operating data for the FFM TEST 4 – RUN 105. ... 124
Figure 6 Operating data for the FFM TEST 4 - RUN 202. ... 127
Figure 7 Graphic comparison of pin temperature predictions with TEST 4 - RUN 202 experimental results... 129
Figure 8 Graphic comparison of duct wall temperature predictions with TEST 4 - RUN 202 experimental results. ... 130
Figure 9 Operating data for the FFM TEST 4 - RUN 205. ... 130
Figure 10 Graphic comparison of pin temperature predictions with TEST 4 - RUN 205 experimental results. ... 132
Figure 11 Graphic comparison of duct wall temperature predictions with TEST 4 - RUN 205 experimental results. ... 133
Figure 12 Operating data for the FFM TEST 6 - RUN 103. ... 133
Figure 13 Comparison between the cross-section average HTC in the wire pitch model and in the complete model for the SS05 case. ... 139
Figure 14 Development of the mainstream velocity component for the 1.0 kg/s case. ... 140
Figure 15 Development of the swirl velocity component for the 1.0 kg/s case. ... 140
Figure 16 Contours of the Tabs variable on the three cross-sections of the heated zone (in orange) for the OF10 case (left) and SS10 case (center). ... 141
ix
Figure 17 Bulk temperature and pin average temperature for the OF10 and SS10 cases as function of the height
from the heated region inlet plane. ... 141 Figure 18 Pressure slope into the model for the 1.0 kg/s case. ... 142 Figure 19 Comparison between the cross-section average HTC in the wire pitch model and in the complete model
for the SS10 case. ... 142 Figure 20 Development of the mainstream velocity component for the 3.0 kg/s case. ... 143 Figure 21 Development of the swirl velocity component for the 3.0 kg/s case. ... 143 Figure 22 Contours of the Tabs variable on the three cross-sections of the heated zone (in orange) for the OF30
case (left) and SS30 case (center). ... 144 Figure 23 Bulk temperature and pin average temperature for the OF30 and SS30 cases as function of the height
from the heated region inlet plane. ... 144 Figure 24 Pressure slope into the model for the 3.0 kg/s case. ... 145 Figure 25 Comparison between the cross-section average HTC in the wire pitch model and in the complete model
for the SS30 case. ... 145 Figure 26 Development of the mainstream velocity component for the 4.0 kg/s case. ... 146 Figure 27 Development of the swirl velocity component for the 4.0 kg/s case. ... 146 Figure 28 Bulk temperature and pin average temperature for the OF40 and SS40 cases as function of the height
from the heated region inlet plane. ... 147 Figure 29 Bulk temperature and pin average temperature for the OF40 and SS40 cases as function of the height
from the heated region inlet plane. ... 147 Figure 30 Pressure slope into the model for the 4.0 kg/s case. ... 148 Figure 31 Comparison between the cross-section average HTC in the wire pitch model and in the complete model
for the SS40 case. ... 148 Figure 32 Development of the mainstream velocity component for the 5.0 kg/s case. ... 149 Figure 33 Development of the swirl velocity component for the 5.0 kg/s case. ... 149 Figure 34 Bulk temperature and pin average temperature for the OF50 and SS50 cases as function of the height
from the heated region inlet plane. ... 150 Figure 35 Bulk temperature and pin average temperature for the OF50 and SS50 cases as function of the height
from the heated region inlet plane. ... 150 Figure 36 Pressure slope into the model for the 5.0 kg/s case. ... 151 Figure 37 Comparison between the cross-section average HTC in the wire pitch model and in the complete model
for the SS50 case. ... 151 Figure 38 Development of the mainstream velocity component for the 6.0 kg/s case. ... 152 Figure 39 Development of the swirl velocity component for the 6.0 kg/s case. ... 152
x
Figure 40 Bulk temperature and pin average temperature for the OF60 and SS60 cases as function of the height
from the heated region inlet plane. ... 153 Figure 41 Bulk temperature and pin average temperature for the OF60 and SS60 cases as function of the height
from the heated region inlet plane. ... 153 Figure 42 Pressure slope into the model for the 6.0 kg/s case. ... 154 Figure 43 Comparison between the cross-section average HTC in the wire pitch model and in the complete model
for the SS60 case. ... 154 Figure 44 Comparison between the cross-section average HTC in the wire pitch model and in the complete model
xi
List of tables
Table 1-1 Brief overview of the innovative reactor concepts selected by GIF. ... 2
Table 1-2 MYRRHA specifications. ... 4
Table 2-1 Predicted pressure loss in simulations using meshes with three nominal aspect ratio. ... 27
Table 2-2 Application range and uncertainty for the friction factor correlations illustrated. ... 40
Table 2-3 Details of correlations and their applicable ranges for pin bundle heat transfer. ... 46
Table 2-4 The mean absolute error -mean-square error r for the predictions of the different correlations. ... 47
Table 3-1 Experimental Test Matrix to be adopted for the NACIE-UP campaign to assess the natural circulation PLOFA condition in the MYRRHA. FA ... 52
Table 3-2 Azimuthal angles of the generatrices where the bulk thermocouples are located for each sub-channel instrumented. ... 63
Table 4-1 The LBE properties implemented in the CFD simulation. ... 67
Table 5-1 Comparison between the geometrical parameters of the Fontana Bundle 2A and the test section of the NACIE-UP facility. ... 71
Table 5-2 Sodium properties implemented in the CFD model. ... 74
Table 5-3 Operating data of TEST SERIES 4 RUN 105 case. ... 75
Table 5-4 Operating data of test series 6 run 103 case. ... 76
Table 6-1 Data setting of the reference case studied in the sensitivity analysis.. ... 80
Table 6-2 Turbulent Prandtl number effect case data. ... 83
Table 6-3 Turbulence model effect case data. ... Errore. Il segnalibro non è definito. Table 6-4 Numerical test matrix developed for the pre-test analysis of the NACIE-UP pin bundle; the average sub-channel velocity usc , the Reynolds number and the Peclet number are also reported. ... 91
Table 6-5 CFD numerical test matrix for the wire pitch model: WPXX cases. ... 108
Table 6-6 Complete list of the asymptotic HTC1 values calculated for the test matrix cases simulated. ... 109
Table 6-7 Complete list of T results for the test matrix cases in the complete model and in the wire pitch model. ... 111
Table 6-8 Complete list of Nu2 results for the test matrix cases in the complete model and in the wire pitch model. ... 111
Table 1 Comparison between the experimental data and the CFD results of pin temperature values on the different thermocouples (TEST 4 - RUN 102). ... 122
Table 2 Comparison between the experimental data and the CFD results of duct wall temperature values on the different thermocouples (TEST 4 - RUN 102). ... 123
Table 3 Comparison between the experimental data and the CFD results of pin temperature values on the different thermocouples (TEST 4 - RUN 105). ... 125
xii
Table 4 Comparison between the experimental data and the CFD results of duct wall temperature values on the
different thermocouples (TEST 4 - RUN 105). ... 126 Table 5 Comparison between the experimental data and the CFD results of pin temperature values on the
different thermocouples (TEST 4 - RUN 202). ... 128 Table 6 Comparison between the experimental data and the CFD results of duct wall temperature values on the
different thermocouples (TEST 4 - RUN 202). ... 129 Table 7 Comparison between the experimental data and the CFD results of pin temperature values on the
different thermocouples (TEST 4 - RUN 205). ... 131 Table 8 Comparison between the experimental data and the CFD results of duct wall temperature values on the
different thermocouples (TEST 4 - RUN 205). ... 132 Table 9 Comparison between the experimental data and the CFD results of pin temperature values on the
different thermocouples (TEST 6 - RUN 103). ... 134 Table 10 Comparison between the experimental data and the CFD results of duct wall temperature values on the
different thermocouples (TEST 6 - RUN 103). ... 135 Table 11 Comparison between the CFD results of pin temperature values on the different thermocouples
obtained adopting two different mesh sizes (TEST 6 - RUN 103). ... 136 Table 12 Comparison between the CFD results of duct wall temperature values on the different thermocouples
obtained adopting two different mesh sizes (TEST 6 - RUN 103). ... 137 Table 13 Comparison between the CFD results of pin temperature values on the different thermocouples
obtained adopting two different turbulence models (TEST 6 - RUN 103) ... 138 Table 14 Comparison between the CFD results of duct wall temperature values on the different thermocouples
obtained adopting two different turbulence models (TEST 6 - RUN 103). ... 138 Table 15 Test matrix developed for the pre-test analysis of the NACIE-UP pin bundle; the average sub-channel
velocity usc , the Reynolds number and the Peclet number are also reported. ... 139
