A finite-element solution is presented for the heat transfer from radiating and converting fins or fin arrays. Consideration is given to thin, straight fins attached to a base surface for which the temperature varies periodically. Fin-to-fin, fin-to-base, and fin-to-environment radiative interactions are considered. It is assumed that the radiating surfaces are gray, the environment is black, and the surrounding fluid is transparent. An absorption factor technique is employed for the computation of energy exchange within the nonisothermal enclosure of the fin array.(ff\e (h] I Ie [K\e [K\ k L L' Nomenclature = dimensionless amplitude parameter = surface area fin = dimensionless frequency parameter, uL 2 k/pc p = absorption factor = fin thickness = elemental capacitance matrix = global thermal capacitance matrix = specific heat = displacement matrix, 0 0 1 -/th row [D] e = 0 1 j throw 0 0 = base length between adjacent fins = differential absorption factor = functional to be minimized = elemental form of functional to be minimized = elemental internal heat generation column vector = internal heat generation column vector = elemental global convection matrix = convection column vector = variational statement = elemental form of variational statement = elemental global conduction matrix = global conduction matrix = thermal conductivity = length of fin = length of the fin immediately adjacent to the fin under consideration Received Feb. 2, 1978; presented as Paper 78-893 at the 2nd AIAA/ASME Thermophysics and Heat Transfer Conference, Palo We [R] (r} e [t} e K) u X x ij a e 6 Se P CO Q! X V -number of fin elementŝ convection number, hL 2 Ibk = radiation number, eat s b L 2 /2bk -numerical step size parameter -U x] --total heat transfer from the fin = elemental radiation matrix = global radiation matrix = elemental radiation column vector = radiation column vector = temperature = elemental temperature vector = column vector of nodal temperatures = column vector of temperature time derivatives = an environment temperature = temperature at location x, on the fin = temperature at location Xj on the fin = mean temperature of base surface = first derivative of temperature with respect to location = first derivative of temperature with respect to time = internal heat generation = space coordinates of fin = designates AJ•.-x f = Stef an-Boltzmann constant = surface emissivity = time = Kronecker delta = fin density = circular frequency of base temperature oscillation = thermal dif fusivity = convergence interval = time step designation = radiation fin efficiency = combined mode fin efficiency [ ] = £ [D] e [ } e [D]l global matrix = elemental matrix m = ]C \P\e\ )e» column vector e=7 = elemental column vector = transpose of a matrix = inverse of a matrix Downloaded by PRINCETON UNIV. LIBRARY on August 26, 2014 | http://arc.aiaa.org |