Comparison of Geometric Absorption Factors With Geometric Mean Beam Lengths

1963 ◽  
Vol 85 (3) ◽  
pp. 287-288
Author(s):  
J. A. Wiebelt
Keyword(s):  
Heat Transfer ◽  
Energy Transfer ◽  
Geometric Mean ◽  
Radiation Heat Transfer ◽  
Radiation Heat

The use of geometric mean beam lengths as compared to the use of geometric absorption factors for evaluation of energy transfer by radiation heat transfer with a participating gas is examined for perpendicular rectangles.

Harvesting Nanoscale Radiation Heat Transfer With Pyroelectric Materials

2009 ◽  
Author(s):  
Jin Fang ◽  
Hugo Frederich ◽  
Laurent Pilon
Keyword(s):  
Heat Transfer ◽  
Energy Transfer ◽  
Energy Conversion ◽  
Electromagnetic Waves ◽  
Waste Heat ◽  
Radiation Heat Transfer ◽  
Low Frequency ◽  
Working Fluid ◽  
Radiation Heat ◽  
New Device

Pyroelectric energy conversion offers a novel, direct energy-conversion technology by transforming time-dependent temperature directly into electricity. It makes use of the pyroelectric effect to create a flow of charge to or from the surface of a material as a result of heating or cooling. However, existing pyroelectric energy converter can only operate at low frequency due to relatively low heat transfer rate between the pyroelectric materials and the working fluid subjected to oscillatory fluid flow between hot and cold sources. On the other hand, energy transfer by thermal radiation between two semi-infinite solids can be enhanced by several orders of magnitude as the gap separating them reduces to subwavelength size thanks to interference and tunneling of electromagnetic waves across the gap. This paper proposes a novel way to harvest nanoscale radiation heat transfer for direct pyroelectric energy conversion of waste heat into electricity. A new device is investigated numerically by accurately modeling nanoscale radiation heat transfer between the pyroelectric materials and hot and cold surfaces. Performance of the pyroelectric converter is predicted at various frequencies. The result shows that rapid energy transfer and higher operating frequency can be achieved to increase efficiency and power density.

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