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Experimental and Computational Studies of Thermal Mixing in Next Generation Nuclear Reactors

Landfried, Douglas Tyler (2016) Experimental and Computational Studies of Thermal Mixing in Next Generation Nuclear Reactors. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The Very High Temperature Reactor (VHTR) is a proposed next generation nuclear power plant. The VHTR utilizes helium as a coolant in the primary loop of the reactor. Helium traveling through the reactor mixes below the reactor in a region known as the lower plenum. In this region there exists large temperature and velocity gradients due to non-uniform heat generation in the reactor core. Due to these large gradients, concern should be given to reducing thermal striping in the lower plenum. Thermal striping is the phenomena by which temperature fluctuations in the fluid and transferred to and attenuated by surrounding structures. Thermal striping is a known cause of long term material failure. To better understand and predict thermal striping in the lower plenum two separate bodies of work have been conducted. First, an experimental facility capable of predictably recreating some aspects of flow in the lower plenum is designed according to scaling analysis of the VHTR. Namely the facility reproduces jets issuing into a crossflow past a tube bundle. Secondly, extensive studies investigate the mixing of a non-isothermal parallel round triple-jet at two jet-to-jet spacings was conducted. Experimental results were validation with an open source computational fluid dynamics package, OpenFOAM®. Additional care is given to understanding the implementation of the realizable k-ε and Launder Gibson RSM turbulence Models in OpenFOAM®. In order to measure velocity and temperature in the triple-jet experiment a detailed investigation of temperature compensated hot-wire anemometry is carried out with special concern being given to quantify the error with the measurements. Finally qualitative comparisons of trends in the experimental results and the computational results is conducted. A new and unexpected physical behavior was observed in the center jet as it appeared to spread unexpectedly for close spacings (S/Djet = 1.41).


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Landfried, Douglas Tylerdtl5@pitt.eduDTL5
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairKimber,
Committee MemberJana,
Committee MemberSchaefer,
Committee MemberChyu, Minkingmkchyu@pitt.eduMKCHYU
Date: 26 January 2016
Date Type: Publication
Defense Date: 17 November 2015
Approval Date: 26 January 2016
Submission Date: 24 November 2015
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 167
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Mechanical Engineering and Materials Science
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Turbulent Jets, Turbulent Mixing, Thermal Striping, Nuclear Power, Very High Temperature Reactor, Heat Transfer, Computation Fluid Dynamics, Constant Temperature Anemometry, Constant Current Anemometry, OpenFOAM
Date Deposited: 26 Jan 2016 15:03
Last Modified: 15 Nov 2016 14:31


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