ISSN Online: 2688-7231
ISBN Online: 978-1-56700-478-6
Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2017)
3D COUPLED CFD SIMULATION OF INTERMEDIATE HEAT EXCHANGER OF FUTURE FAST BREEDER REACTORS
Abstract
Future commercial fast reactors are envisaged to have
twin-unit concept, with each unit generating 1500 MW of
thermal power. Due to the increased power, there are many
dimensional and flow changes in components including the
Intermediate Heat Exchanger (IHX). IHX is a counter current
shell and tube heat exchanger with power rating of 375 MWt
each. There are 3900 tubes arranged in circular pitch
surrounding a central down comer. The primary sodium flows
from the top through the inlet window and exits at the bottom through the outlet window. The secondary sodium flows from top through a central downcomer and flows upwards through the tubes. There is significant length in the tube bundle where the primary sodium flows across the IHX tubes (near the inlet window and outlet window). However, it flows along the IHX tubes in the remaining portion. The peripheral tubes near the inlet window face higher primary sodium temperature and the flow rate decreases while it flows towards the downcomer. Due to mixed radial and axial flow of primary sodium and counter-current flow of secondary sodium, the tubes are subjected to varying temperatures. These non-uniform temperatures cause compressive and tensile loads on the tubes. Generally, tubes in outer rows face hot primary sodium and the temperature of these tubes can be limited by
increasing the secondary flow. Towards understanding the
flow and temperature distributions in the IHX and finalize the secondary side flow zoning to have an acceptable thermal
load, comprehensive 3-dimensional CFD studies have been
carried out. In the present investigation, a 3D 60 ° sector model of IHX comprising of 675 tubes along with primary and secondary sodium is considered. The flow and temperature distributions of primary sodium in the shell side and secondary sodium inside tubes have been solved as a
conjugate problem. Parametric studies have been carried out,
by varying the number of rows receiving enhanced secondary
flow and the enhanced flow rate. It is seen that the case of 7 outer most rows of tubes receiving 30% more secondary flow than the interior rows, provide minimum thermal load.