Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.755213
Title: Instability and mixing of flow of supercritical water between subchannels
Author: Mohd Amin, Muhsin
ISNI:       0000 0004 7428 2119
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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Abstract:
The effects of flow acceleration due to thermal expansion and those due to buoyancy have been investigated to study the flow and heat transfer behaviour in the flow of water at a supercritical pressure in a channel with a tight gap. The objective of these investigations is to develop a better understanding of the turbulent flow behaviour and heat transfer between subchannels specifically relevant to Supercritical Water-cooled Reactor (SCWR). Large eddy simulations with an SGS WALE model are carried out in a trapezoid annulus, which represents a tightly packed rod bundle configuration. The studies considered are (i) forced convection to study the flow acceleration due to thermal expansion and (ii) mixed convection to study the buoyancy influences. In the case of forced convection, large flow structures have been observed in the narrow gap all heating cases considered, but such flow structures are much weaker in higher heat fluxes. The main reason for the weakening flow structures in the high heating cases is the severe variations of thermal properties. In particular, the streamwise fluctuations are reduced significantly downstream of the heated channel. The spanwise turbulence component reflecting the swinging flow structure is also found to be the highest in the narrow gap across the channel, but reduces as in forced convection swinging flow structure is weakened. The effect of variations of thermal properties has been found to be very similar to that of buoyancy. In the case of mixed convection, the behaviour of the flow and heat transfer in the low buoyancy influence case is very similar to that of the forced convection. In high buoyancy influence cases, significant heat transfer deterioration has been found to occur. It has been demonstrated that the swinging flow structures in the narrow gap in high buoyancy case are almost non-existent downstream in the heated channel. A number of potential reasons have been identified that the heat transfer deterioration in high buoyancy influences. They include the significantly reduced streamwise turbulence, disappearing of large flow structures as well as low mixing, and lastly significant variations of thermal properties.
Supervisor: He, Shuisheng Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.755213  DOI: Not available
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