thermal analysis of main vessel

7/29/2019 Thermal Analysis of Main Vessel

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Group members

Alwin Zachariah

Ashwin Zachariah

Davis Edvin


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Main vessel is an important structure of the

reactor that holds the entire radioactive primarysodium, core, grid plate, core support structure,inner vessel etc.

The inner vessel divides the sodium pool intohot pool (547C) and cold pool (397C).

The inner vessel is made of two cylindricalshells, viz. the upper shell of larger diameter

and the lower shell of smaller diameterconnected by a conical redan..


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2d dp axis symmetric model of MV coolingsystem


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. The radial distance between the upper shell ofthe inner vessel and the cylindrical portion of themain vessel is only ~ 200 mm.

Because of this short gap, large thermalconductivity of sodium and minimal heat lossfrom main vessel outer surface to the safety

vessel, the main vessel temperature approachesclose to that of the hot pool in this zone.

. The junction between main vessel and top shieldis a critical point in CFBR.


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. It is required to investigate the temperaturedistribution at this junction and its

dependence on the elevation of the thermalbaffle.

The location of this junction and the

elevation of the thermal baffle need to beoptimized.

CFD calculations are essential to develop adetailed understanding of thermal hydraulicsof main vessel cooling system.


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The first step consists of modelling and meshing of axis symmetric mainvessel cooling system.

A 2d dp axis symmetric model is generated in GAMBIT which is a pre-processor for FLUENT.

The model is generated for six different sodium free levels from the triplepoint junction.

The six different cases are 50mm, 100mm, 150mm, 200mm, 250mm and300mm elevation of SFL from triple point junction.

The model for 50mm case is as shown in Fig 1 below. After generating the2d dp axis symmetric model the next step is discretization (Meshgeneration).

The continuum entities are argon, air gap, nitrogen, stainless steel, carbonsteel, insulation, radiation shield, emissivity inside, emissivity outside,adiabatic IHX and concrete wall.


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Fluid /Properties Kg/m3 CP J/Kg K K W/m K NS/m2

Air 1.1277 1007 0.02701 2.837e-05

Argon Ideal gas 520 0.02807 3.572e-05

Nitrogen

Ideal gas

1064.3

0.04104

2.743e-05


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Solid/Properti

es Kg/m3 CP J/Kg K K w/m K

Air-solid 1.1277 1007 0.02701Air-solid 1mm

gap1.1277 1007 200

CS 7850 519 47SS 7781 560 20.1Insulation 196 552 0.05Concrete 2300 819 2.6


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A 2d dp axis symmetric CFD model is considered.

A radiation shield is provided 50mm below the top shield.

Natural convection effects in argon cover gas and inter-vesselNitrogen are modelled by ideal gas law.

The emissivity of sodium free level is 0.05, Steel Surfaces (CS/SS)exposed to MV argon is 0.2 and CS exposed to air is 0.8

The top surfaces of LRP, SRP and RS are maintained at 1200C.

The concrete is maintained at isothermal temperature of 550C.


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For 100% power conditions, the sodium free

level is assigned with isothermal temperatureof 5470C for all the cases and is also assignedwith 2000C and 473.50C for 150mm of SFL.

For 100% power conditions, the inner vesselis maintained at 5470C, the sodium free levelbetween inner vessel and inner thermal baffleat 4800C, the outer thermal baffle surface at

4200C, and MV inner surface at 4200C for allthe cases.


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The result consists of computing for variousparameters such as temperature graphs,

velocity vectors, stream function and surfaceheat flux at various zones of main vesselcooling system.


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50mm elevation with full powerconditions


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Contours of static temperature at 50mm SFLfrom Triple point junction


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Contours of velocity vectors at 50mm SFL fromTriple point junction


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Contours of temperature along y axis at 50mm SFL from Triple pointjunction


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7 Contours of static temperature at 100mm SFL fromTriple point junction


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Contours of velocity vectors at 100mm SFL from Triplepoint junction


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Contours of Stream function at 100mm SFL fromTriple point junction


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Contours of temperature along y axis at 100mm SFL from Triple point junction


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Contours of temperature along curve length at 100mm SFLfrom Triple point junction


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150mm elevation with full power conditions

12 Contours of static temperature at 150mm SFLfrom Triple point junction and full power conditions


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Contours of velocity vectors at 150mm SFL from Triplepoint junction and full power conditions


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Contours of Stream function at 150mm SFL from Triplepoint junction and full power conditions


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Contours of temperature along y axis at 150mm SFLfrom Triple point junction and full power conditions


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Contours of temperature along curve length at 150mmSFL from Triple point junction and full power conditions


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Contours of Stream function at 200mm SFL from Triplepoint junction


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Contours of temperature along y axis at 200mm SFLfrom Triple point junction

Conto rsof temperat realongc r elengthat200mmSFL from


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Contours of temperature along curve length at 200mm SFL fromTriple point junction


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Contours of static temperature at 250mm SFL from Triple point junction


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Contours of Stream function at 250mm SFL from Triplepoint junction


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Contours of temperature along curve length at 250mmSFL from Triple point junction


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Contours of static temperature at 300mm SFL fromTriple point junction


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Contours of velocity vectors at 300mm SFL fromTriple point junction


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Contours of Stream function at 300mm SFLfrom Triple point junction


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Contours of temperature along curve length at 300mm SFL fromTriple point junction


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Elevation(mm)and SFL(K) Surface heat flux (W/m2)50mm&820K -1304.7395100mm&820K -1322.3304150mm&820K -1233.4064150mm&746.5K -881.75812150mm&473K -119.0518200mm&820K -1351.6051

250mm&820K

-1217.6479

300mm&820K -1426.7183


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thermal analysis of main vessel

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