Heat Transfer, Efficiency and Turn-Down Ratio of a Dynamic Radiative Heat Exchanger

Keywords

Heat transfer, Mass transfer, dynamic radiative heat exchanger, mechanical engineering

Abstract

Efficient heat transfer is critical in the design and optimization of thermal control systems. Static radiative heat exchangers are often simple and reliable systems but typically cannot be adapted to environmental changes. Adaptable radiative heat exchangers can be adjusted in response to variations in the thermal environment or operating conditions and have the potential for increased efficiency and reduced cost. Dynamic control of a radiative heat exchanger is possible through geometric manipulation of a segmented, self-irradiating fin, consisting of rigid panels that are linked by thermal hinges in an accordion arrangement. In this paper, a numerical model is described to predict the temperature profile and efficiency of a radiative heat exchanger, accounting for conduction and self-irradiation. Governing equations are cast in terms of the conduction-radiation interaction parameter, surface emissivity, actuation angle, and the thermal conductance of the hinges linking the panels. Results indicate that a turn-down ratio (largest possible heat rate divided by smallest possible heat rate) of greater than three is possible for realistic panel geometries and materials. Self-irradiation decreases the turn-down ratio, and there is evidence that an optimal number of rigid panels exists for any combination of panel geometry and device temperature. The maximum efficiency occurs when the plates are in the collapsed position, but the heat rate is at a minimum in this configuration. Finally, the properties and geometry of the plates are shown to have a more significant effect on the turn-down ratio than the properties of the thermal hinges.

Original Publication Citation

Mulford, R. B., Jones, M. R., and Iverson, B. D., 2019, "Heat transfer, efficiency and turn-down ratio of a dynamic radiative heat exchanger," International Journal of Heat and Mass Transfer, Vol. 143, pp. 118441. DOI: 10.1016/j.ijheatmasstransfer.2019.118441

Document Type

Peer-Reviewed Article

Publication Date

2019-11

Permanent URL

http://hdl.lib.byu.edu/1877/6494

Publisher

ScienceDirect

Language

English

College

Ira A. Fulton College of Engineering and Technology

Department

Mechanical Engineering

University Standing at Time of Publication

Associate Professor

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