Doctoral Dissertations

Keywords and Phrases

Gaseous Dynamics; Heat Transfer; Heat Transfer Coefficient; Natural Circulation; Prismatic Very High-temperature Reactor (VHTR); Residence Time Distribution (RTD)


"This research focuses on establishing a range of scaled separate and integral effects experiments for studying thermal-hydraulic behavior occurring within a component or region of the prismatic very high-temperature reactor (VHTR) such as plenum-to-plenum heat transfer and gaseous dynamics during natural circulation. Natural circulation of the coolant is the leading capability for VHTR to transport the decay heat from the core to the reactor vessel during accident scenarios. To address this need, a scaled-down facility is designed and developed with only two channels with upper and lower plena. The emphasis is placed on high-resolution and high-fidelity experimental data for local heat transfer and gaseous dispersion measurements utilizing sophisticated techniques under different operating conditions. These techniques are 1) non-invasive flush wall mounted heat transfer coefficient probe to measure reliably the heat flux and surface temperature along the flow channels, and by measuring simultaneously these two variables and the flowing fluid, the heat transfer coefficient can be obtained, 2) radial temperature sensor adjuster to measure radial temperature variations of the coolant along the flow channels, and 3) advanced gaseous tracer technique to accurately measure the residence time distribution (RTD) in an of flow systems by injecting pulse change gas tracer and then monitoring its concentration at the exit. The measured RTD is utilized to quantify the gas dispersion and identify the degree of mixing in the system. The obtained local heat transfer and gaseous dispersion data in this study will provide high spatial and temporal resolutions benchmarking data for validating heat transfer and gaseous dispersion computations and correlations that are integrated with CFD simulations"--Abstract, page iv.


Al-Dahhan, Muthanna H.

Committee Member(s)

Al-Dahhan, Muthanna H.
Wang, Jee C.
Liang, Xinhua
Rezaei, Fateme
Usman, Shoaib


Chemical and Biochemical Engineering

Degree Name

Ph. D. in Chemical Engineering


Nuclear Energy Research Initiative (U.S.)


Financial support of Nuclear Energy Research Initiative (U.S.) NEUP 13-4953 (DENE0000744)


Missouri University of Science and Technology

Publication Date

Fall 2017

Journal article titles appearing in thesis/dissertation

  • Investigation of natural convection heat transfer in a unique scaled-down dual-channel facility
  • Experimental investigation of the helium natural circulation heat transfer in two channels facility using varying riser channel heat fluxes
  • Experimental study of the effect of helium pressure on the natural convection heat transfer in a prismatic dual-channel circulation loop
  • Axial dispersion and mixing of coolant gas within a separate-effect prismatic modular reactor


xvi, 167 pages

Note about bibliography

Includes bibliographic references.


© 2017 Ibrahim Ahmed Said Abdallah, All rights reserved.

Document Type

Dissertation - Open Access

File Type




Thesis Number

T 11207

Electronic OCLC #