Proposal Number: CTS-0553679 Principal Investigator: Goldstein, Richard J. Affiliation: University of Minnesota Proposal Title: Thermal Convection at High Rayleigh Num bers in Compressed Gases and Saturated Porous Media
The proposed study includes two topics of interest in the area of natural convection heat transfer in a horizontal layer heated from below: heat transfer in a single fluid over a large range of Rayleigh numbers, and heat transfer at high Rayleigh numbers in saturated porous media. The proposal discusses experiments that will describe the flow and measure in a consistent way the Nusselt number variation with Rayleigh number. The study will investigate the heat transfer behavior of a Rayleigh-Benard convection system at Rayleigh numbers up to 10^14 in a pure fluid and 10^6 in a porous medium. Current theories for explaining natural convection heat transfer in a porous medium saturated with a fluid are restricted to low-Rayleigh number flows. While models do exist for high Rayleigh number convection, it has not been possible to experimentally test these theories. We describe an experimental system which can extend the range of Rayleigh numbers by about four orders of magnitude in a single test cell. In addition, the experiments will yield data that will help researchers develop better models for the effective conductivity in porous media.
The results of research on Rayleigh-Benard convection are applicable to a wide variety of engineering applications including nuclear reactor safety issues and energy conservation in buildings, as well as physical phenomena such as convective currents in the oceans and the atmosphere, upwelling of magma in the earth's mantle, and convection in stars. The experimental results will also provide a useful database for engineers and scientists in modeling turbulence. Heat transfer in porous media occurs in a variety of applications ranging from nuclear waste storage to control of wildfires to building insulation. However, experimental data are scarce. The proposed study would generate important data over a range of Rayleigh numbers to enable better modeling of the flow and heat transfer in saturated media. The correlations obtained on porous media heat transfer will be of immediate use to designers of thermal equipment such as packed beds, Stirling engine regenerators, nuclear waste storage containers, and building insulation.
Outreach potential of the current study envisages producing videos for undergraduate and graduate education that explains the chaotic features of thermal convection in highly developed regimes of turbulence. In addition, various educational outreach programs administered by the University of Minnesota will be used to disseminate the results of the study to secondary school students.
