We conclude that ^(©o/?) is a more accurate upper bound for the conversion efficiency of diluted and undiluted black-body radiation. This upper bound has been used without rigorous justification [14], The new formula we propose is especially useful for small y (Fig. 1). ACKNOWLEDGEMENT I am indebted to my colleague I. Mihalcea for deriving equation (26). REFERENCES [1]MUSER, H. (1957) Z. Phys., 148, pp. 380-390. [2] Spanner, D.C. (1963) Nature, 198, pp. 934-937. [3]Petela, R. (1964) Journal of Heat Transfer, 86, pp. 187-192. [4] Bell, L.N. (1964) Soviet Physics—JETP, 19, pp. 756-759. [5] Leontovich, N.A. (1975) Soviet Physics—Usp., 17, pp. 963-964. [6] Press, W.H. (1976) Nature, 264, pp. 734-735. [7] Landsberg, P.T. & Tonge, G. (1979) Journal of Physics A: Mathematics General, 12, pp. 551-562. [8]Jetter, S.J. (1981) Solar Energy, 26, pp. 231-236. [9] Vos, A. DE (1983) American Journal of Physics, 53, pp. 570-573. [10]Bejan, A. (1988) Advanced Engineering Thermodynamics (New York, Wiley). [11]BAdescu, V. (1989) International Journal of Energy, 14, pp. 237-239. [12]Hoogendorn, C.J. (1986) Optical properties of selective layers, in: H. Yuncu & B. Kilkis (Eds) Solar Energy Utilisation. Fundamentals and Applications, p. 26 (Ankara, EIEI Printing Shop). [13]BAdescu, V. (1989) International Journal of Energy, 14, pp. 571-573. [14]BAdescu, V. (1988) Entropie, 145, pp. 41-45.
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