NUMERICAL, EXPERIMENTAL AND ANALYTICAL STUDY OF THERMAL HEATING OF SPHERE AND DISK SHAPED BIOCRYSTALS EXPOSED TO 3 RDGENERATION SYNCHROTON SOURCES

The thesis is broadly divided into three major parts. In the first part, thermal imaging is used to experimentally measure temperature and a numerical model is developed to predict the thermal heating of a sample exposed to 3rd generation synchrotron X-ray beams. In this study we have experimentally measured heating by the beam using infrared imaging and used these measurements along with a theoretical numerical model to help understand the heating process. Specifically, the temperature rise of 1mm and 2mm glass spheres (sample surrogates) exposed to an intense X-ray beam and cooled in a uniform flow of nitrogen gas at two different flow rates is modeled, analyzed, and experimentally tested in an actual synchrotron beam. The heat transfer including external convection and internal heat conduction, was theoretically modeled using computational fluid dynamics (CFD) to predict the temperature variation in the interior and on the surface of the sphere when subjected to the X-ray beam. In the next part a heated disk cooled in a uniform stream of air is numerically investigated. Finite Volume Method (FMV) is used to study the effect of orientation of disk and imposed boundary conditions on the local and average heat transfer coefficients. Also a Nusselt number (Nu) correlation is developed, in terms of Reynolds (Re) and Prandtl number (Pr), for predicting forced convective heat transfer over isothermal or isoflux circular disk geometry at low Reynolds numbers (Re) in the range 10 to 150.Three different orientations of the disk are studied, where the disk orientation with respect to the flow is: a) parallel; b) inclined at 45; c) normal. Finally, in the last part the biocrystal along with the mother liquor is modeled as a short cylinder (i.e. disk). Both local “spot” heating and full heating of the crystal are considered. Two analytical models are developed that depicts the temperature variation within the crystal. A 1-D analytical solution is developed by treating the sample to be an annular “thin” fin; solutions presented revealing the radial variation in temperature distribution caused by small versus large beam size. Next a two-dimensional analytical solution is reported for full heating of biocrystal showing the depth wise spatial temperature variation in the disc. Results are reported considering more realistic sample sizes, X-Ray fluxes and flux densities and exposures.