Emmanuel K. Glakpe, Ph.D.
Professor

Phone: 202-806-7741
Email: [email protected]

Research Topics
Convective (Free, Forced and Mixed) Heat Transfer, Numerical Methods for Computational Fluid Dynamics, Renewable & Non-Renewable Energy Applications, Efficient Energy Utilization, Thermal State of Charge in Solar Heat Receivers

Summary of Recent Research
A numerical model is developed to predict the thermal performance of solar heat receivers for space solar dynamic power systems. The model includes the multi-conjugate effects of canister outside surface radiation, combined conduction in the canister walls and phase change material (PCM), conduction in the working fluid tube, and convective transport of thermal energy in a low-Prandtl-number gas. Selected measurable parameters are varied to assess their effects on the thermal performance of NASA Lewis Research Center's Ground Test Demonstration (GTD) solar heat receiver, which incorporates the use of a eutectic mixture of LiF-CaF2 as the PCM and a mixture of He/Xe as the working fluid. The numerical results show excellent comparison with GTD experimental results in steady-state mode, and excellent quantitative agreement is observed near sunset in the balanced-orbit and transition modes of cyclic operation.

Results are also obtained on the so-called thermal state-of-charge (SOC) problem relating to solar heat receivers. The concepts of available power and virtual source temperature are used in the development of time-dependent conjugate and primary SOC functions. Baseline conjugate and primary SOC curves are generated based on a priori known baseline system operating conditions. For the baseline primary SOC curve in balanced-orbit mode, there is a 33% energy margin at sunrise. Comparisons in the sensible regime have completely reversed effects in the latent regime since PCM melting and freezing rates contribute a dominant influence on the energy extraction rate from the receiver. Finally, the second conjugate SOC curve is observed to lag (in time) behind the primary SOC curve with respect to operating the solar dynamic system until their respective minimum SOC lines are reached.

Recent Publications
Noorshahi, S., Hall, C., and Glakpe, E., "Natural Convection in a Corrugated Enclosure with Mixed Boundary Conditions", Journal of Solar Energy Engineering, Vol. 118, pp. 50-57, Feb. 1996.

Grimmett, I.W., Hall, C.A., III., Glakpe, E.K., "Three-Dimensional Natural Convection in an Enclosure with a Corrugated Surface Subject to Mixed Boundary Conditions", Proceedings of the International Solar Energy Conference, San Antonio, Texas, April 1996.

Hall, C.A., III., Glakpe, E.K., Cannon, J.N., and Kerslake, T.W., "Modeling Cyclic Phase Change and Energy Storage in Solar Heat Receivers", AIAA Paper No.97-2452, 32nd AIAA Thermophysics Conference, Atlanta, Georgia, June 23-25, 1997;also accepted for publication in the AIAA Journal of Thermophysics and Heat Transfer, July-Sept. 1998.

Hall, C.A., III., Glakpe, E.K., Cannon, J.N., and Kerslake, T.W., "Parametric Analysis of Cyclic Phase Change and Energy Storage in Solar Heat Receivers", Proceedings of the 32nd Intersociety Energy Conversion Engineering Conference, Honolulu, Hawaii, Paper # 97053, Vol. 1, pp. 446-453, July 27-August 1,1997

Hall, C.A., III., Glakpe, E.K., Cannon, J.N., and Kerslake, T.W., "Thermal State-of-Charge in Solar Heat Receivers," Proceedings of the 36th AIAA Aerospace Sciences Meeting and Exhibit, paper # 98-1017, Reno, Nevada, January 1998.