Horizontal Plate, Heated Face Down — Isothermal
Calculates the average convective heat transfer coefficient and total heat rate for a horizontal plate whose heated surface faces downward (equivalently, a cooled surface facing upward). Warm fluid is trapped beneath the plate and can only drain away at the edges, so this orientation convects much less than the heated-up case — reflected in the smaller leading coefficient (0.27 vs 0.54).
Characteristic Length
Lc=PA=2(L+W)LWRayleigh Number
Properties are evaluated at the film temperature Tf=(Ts+T∞)/2:
Ra=ν2gβ(Ts−T∞)Lc3PrNusselt Number
Nu=0.27Ra1/4(105≤Ra≤1011)Heat Transfer Coefficient and Heat Rate
h=LcNu⋅k,Q=hA(Ts−T∞),A=LWReferences
- Hatfield, D. W. and Edwards, D. K., Int. J. Heat Mass Transfer, vol. 24, p. 1019, 1981.
- Fujii, T. and Imura, H., Int. J. Heat Mass Transfer, vol. 15, p. 755, 1972.
- Incropera, F. P. and DeWitt, D. P., Fundamentals of Heat and Mass Transfer.