Improved Particle Heat Transfer by way of Bimodal Particle Distributions for High Temperature Solar Thermal Energy




Heat Exchanger, High Temperature, Solar Thermal Facilities, Solid Particles


High temperature solar thermal facilities are looking to increase operating temperatures through novel heat transfer media, one such being solid particles. These particles operating at high temperatures will require transferring their thermal energy into another working fluid like supercritical carbon dioxide which can be used in advanced power cycles. Achieving high heat transfer between the particles and supercritical carbon dioxide is essential to high efficiency and low-cost operation. Therefore, optimizing the thermal conductivity of these particles is one potential way to ensure high performance. Traditionally, unimodal particle distributions have been employed in high temperature particle solar power plants. However, ambient temperature testing of bimodal particle distributions has revealed a superior thermal conductivity when compared to its unimodal counterpart at the same temperature. This data was obtained by certified, off-the-shelf instruments that can effectively simulate the conditions a particle would be exposed to in a high temperature solar thermal system. Data obtained in this way suggests that the increased thermal conductively imputed by a bimodal particle distribution is significant at working temperatures in solar facilities. Furthermore, the thermal conductivity of these bimodal particle distributions peaks when the best combination of large and small particles is applied. At high temperatures, binary particle distributions are compared to monodispersed distributions of larger particles where heat transfer is more prolific due to the increased surface radiation. Various thermal conductivity, porosity and heat exchanger models are explored in conjunction with data acquired up to 700 C.


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Ka Man Chung, “Measurement and analysis of thermal conductivity of ceramic particle beds for solar thermal energy storage,” Solar Energy Materials and Solar Cells, vol.230, no.111271, pp. 5, Sept, 2021, doi:

Measurement Acceptance Criteria. [Online]. Available:

Ka Man Chung, Jian Zeng, Sarath Reddy Adapa, Tianshi Feng, Malavika V. Bagepalli, Peter G. Loutzenhiser, Kevin J. Albrecht, Clifford K. Ho, Renkun Chen, Measurement and analysis of thermal conductivity of ceramic particle beds for solar thermal energy storage, Solar Energy Materials and Solar Cells, Volume 230, 2021, 111271, ISSN 0927-0248,

A. B. Yu and N. Standish, “An analytical—parametric theory of the random packing

of particles,” Powder Technol., vol. 55, no. 3, pp. 171–186, Jul. 1988. doi:

C.S. Chang, Y. Deng, A nonlinear packing model for multi-sized particle mixtures, Powder Technol. 336 (2018) 449–464.

R. Bauer, E.U. Schlünder, Effective radial thermal conductivity of packings in gas flow. Part II. Thermal conductivity of the packing fraction without gas flow, Int. Chem. Eng. 18 (1978) 189–204.

S. Yagi, D. Kunii, Studies on effective thermal conductivities in packed beds, AIChE J. 3 (1957) 373–381. doi:

CARBO, “CARBOBEAD Technical Data Sheet,” 2019. [Online]. Available:

N.P. Siegel, M.D. Gross, R. Coury, The Development of Direct Absorption and Storage Media for Falling Particle Solar Central Receivers, J. Sol. Energy Eng. 137 (2015) 041003. doi:

Albrecht, K.J., Carlson, M.D., Laubscher, H.F., Crandell, R., DeLovato, N., Ho, C.K., 2020. Testing and model validation of a prototype moving packed-bed particle-to-sCO2 heat exchanger. Proc. 7Th Int. Conf. Electron. Devices, Syst. Appl. 2306, 030002. doi:

Albrecht K.J., Ho C.K., 2018. Heat Transfer Models of Moving Packed-Bed Particle-to-sCO2 Heat Exchangers. Journal of Solar Energy Engineering 141(3). doi:




How to Cite

Stout, D., Otanicar, T., & Kandadai, N. (2023). Improved Particle Heat Transfer by way of Bimodal Particle Distributions for High Temperature Solar Thermal Energy. SolarPACES Conference Proceedings, 1.

Conference Proceedings Volume


Thermal Energy Storage Materials, Media, and Systems

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