David Calamas
Assistant Professor, Department of Engineering Georgia Southern University
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Biography
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Education
University of Alabama
Ph.D.
University of Alabama
M.S.
Clemson University
B.S
Articles
Experimental Effectiveness of Sierpinski Carpet Fractal Fins in a Natural Convection Environment
Journal of Heat TransferCalamas, D., Dannelley, D., and Keten, G
2017
When certain fractal geometries are used in the design of fins or heat sinks, the surface area available for heat transfer can be increased while system mass can be simultaneously decreased. In order to assess the thermal performance of fractal fins for application in the thermal management of electronic devices, an experimental investigation was performed. The experimental investigation assessed the efficiency, effectiveness, and effectiveness per unit mass of straight rectangular fins inspired by the first four iterations of the Sierpinski carpet fractal pattern. The thermal performance of the fractal fins was investigated in a natural convection environment with thermal radiation accounted for. Fin performance was analyzed under power inputs of 2.5, 5, 10, and 20 W. While fin efficiency was found to decrease with fractal iteration, fin effectiveness per unit mass increased with fractal iteration. In addition, a fractal fin inspired by the fourth iteration of the Sierpinski carpet fractal pattern was found to be more effective than a traditional straight rectangular fin of equal width, height, and thickness. When compared to a traditional straight rectangular fin, or the zeroth fractal iteration, a fin inspired by the fourth fractal iteration of the Sierpinski carpet fractal pattern was found to be on average 3.63% more effective, 16.19% less efficient, and 65.99% more effective per unit mass. The amount of the total heat transfer attributed to thermal radiation was also dependent on fractal iteration. Thermal radiation accounted for, on average, 57.00% of the total heat transfer for the baseline case, or zeroth fractal iteration. Thermal radiation accounted for 53.67%, 50.33%, 48.84%, and 45.84% of the total heat transfer for the first, second, third, and fourth fractal iterations, respectively.
Performance Characteristics of a Biologically-Inspired Solid-Liquid Heat Exchanger
Experimental Heat TransferCalamas, D., and Baker, J.
2014
System performance of a solid single-fluid compact heat exchanger with tree-like flow passages has been experimentally examined. The results, presented in the form of commonly defined dimensionless parameters, demonstrate that system performance can be characterized in a mode similar to traditional compact heat exchanger designs. Pressure forces were found to dominate inertia forces at low Reynolds numbers. Correlations of the Euler number, Nusselt number, Colburn factor, and friction factor as a function of Reynolds number were utilized to compare system performance to traditional two-fluid compact heat exchangers.
Flow Behavior and Pressure Drop in Porous Disks with Bifurcating Flow Passages
Journal of Fluids EngineeringCalamas, D., Baker, J., and Sharif, M.
2013
The performance of a porous disk with hierarchical bifurcating flow passages has been examined. The hierarchical bifurcating flow passages in the heat exchanger mimic those seen in the vascular systems of plants and animals. The effect of bifurcation angle, porosity, and pore size on the pressure drop across a porous disk was examined computationally. The pressure drop across the porous disk was found to increase as the pore size decreased. As the bifurcation angle increased the pressure drop also increased. At high porosities the bifurcation angles did not have an impact on the pressure drop across the porous disk due to flow behavior. Similarly, the effect of bifurcation angle on pressure drop decreased as the pore size increased.
Tree-Like Branching Fins: Performance and Natural Convective Heat Transfer Behavior
International Journal of Heat and Mass TransferCalamas, D., and Baker, J.
2013
The performance of tree-like fins with varying bifurcation angle, scale, material, width-to-thickness ratio, and heat flux was examined. Overall system performance was examined computationally. The computational results have been validated, verified, and cast in terms of commonly defined dimensionless parameters. Tree-like fins were found to be more effective and had lower base temperatures than the rectangular fins. Fin effectiveness was found to increase with increasing bifurcation angle while fin efficiency and base temperatures were found to decrease with increasing bifurcation angle. Base temperatures were highest for the largest width-to-thickness ratios and smallest for materials with relatively higher thermal conductivities. The microscale tree-like fin studied had the highest effectiveness and efficiency as well as the lowest base temperatures when compared to the mesoscale and macroscale fins of the same geometry.
Behavior of Thermally Radiating Tree-Like Fins,” Journal of Heat Transfer
Journal of Heat TransferCalamas D., Baker J.
2013
The performance of tree-like fins with varying bifurcation angle, surface emissivity, material, width-to-thickness ratio, and base heat rate was examined. Overall system performance was examined computationally. The computational results have been validated, verified, and cast in terms of commonly defined dimensionless parameters. Tree-like fins were found to be more effective and more efficient than the rectangular fins. Fin efficiency and effectiveness were found to increase with increasing bifurcation angles while base temperatures were found to decrease with increasing bifurcation angles. As expected, base temperatures were highest for the largest width-to-thickness ratios and smallest for materials with relatively higher thermal conductivities.
