The spectra of turbulent heat flux H(k) in Rayleigh-Benard convection with and without uniform rotation are presented. The spectrum H(k) scales with wave number k as similar to k(-2). The scaling exponent is almost independent of the Taylor number Ta and Prandtl number Pr for higher values of the reduced Rayleigh number r (>10(3)). The exponent, however, depends on Ta and Pr for smaller values of r (<10(3)). The probability distribution functions of the local heat fluxes are non-Gaussian and have exponential tails. Published by AIP Publishing.

X iv :1 60 5. 00 46 9v 1 [ ph ys ic s. fl udy n] 2 M ay 2 01 6 Spectra and probability distributions of thermal flux in turbulent Rayleigh-Bénard convection Hirdesh K. Pharasi, Deepesh Kumar, Krishna Kumar, and Jayanta K. Bhattacharjee Department of Physics, Doon University, Dehradun-248 001, India Department of Chemical and Materials Engineering, University of Alberta, Edmonton AB-T6G 2V4, Canada Department of Physics, Indian Institute of Technology, Kharagpur-721 302, India Harish-Chandra Research Institute, Allahabad-211 019, India

The fluid coking process is an example of an upgrading process that uses hot solids to heat and crack bitumen into more valuable products. When feed liquid is sprayed into a fluid bed of hot solids, the solids tend to agglomerate, giving simultaneous heating, reaction, and disintegration processes. The reaction of mixtures of three Athabasca vacuum residues and fluid coke particles was investigated by heating them in Curie point reactors in an induction furnace up to 530 degrees C. Small scale reactors with machined wells were fabricated from Curie point alloy. The yield of coke was measured as a function of the ratio of liquid to solid, heating rate, and feed type. Coke yields were insensitive to heating rates from 5 to 120 degrees C/s, at a constant final temperature. Bubbling was observed as the ratio of liquid feed in the mixture was raised above a threshold, depending on the reactivity of the feed used. Bubbling was observed to increase with greater heating rates, but it had little effect on ultimate coke yield. Coke yield increased with the fraction of bitumen on particles for all feed types tested. When the coke yields were normalized using the microcarbon residue content of the feeds, the results did not give a single trend when plotted with fraction of feed present in the mixtures.