Review The Naphthalene Sublimation Technique P. R. Souza Mendes Department of Mechanical Engineering, Pontif[cia Universidade Cat61ica--RJ, Rio de Janeiro, Brazil liThe naphthalene sublimation technique is reviewed in detail. The fundamen- tals on which it relies are discussed, and then its basic characteristics and typical procedures are presented. The discussion focuses on the different ways the technique can be used to obtain experimental heat transfer information. Finally, a large number of papers on the subject in the heat transfer literature are briefly discussed to illustrate the potential of the technique. Keywords: naphthalene sublimation technique, heat and mass transfer analogy INTRODUCTION The naphthalene sublimation technique is an experimental technique employed to determine heat transfer coefficients in convection flows. The basic characteristic of the technique is that the heat transfer problem to be investigated is replaced by an analogous mass transfer problem. In the laboratory, only mass transfer experiments are performed, and then heat transfer results are obtained by exploring the concept of analogy between heat and mass transfer. Naphthalene (C ioH 8) is employed in the mass transfer experiments because of some of its properties, such as the fact that it sublimes at room temperature, its low toxicity, and its good casting and machining properties. This paper is intended to be an introductory text on the naphthalene sublimation technique. It is subdivided into three main sections. In the first section, the analogy between heat and mass transfer is discussed. The second section deals with the peculiarities of the naphthalene sublimation technique, and the third section reviews some heat transfer problems investigated using the technique. THE ANALOGY BETWEEN HEAT AND MASS TRANSFER In this section, the fundamentals of the analogy between heat and mass transfer processes are outlined. A thorough under- standing of this analogy is important for a proper application of the naphthalene sublimation technique. Pure Diffusion Heat diffusion in solids and in quiescent fluids is related to the temperature distribution in the medium by means of Fourier's law [Eq. (1)]. This law states that heat diffusion is driven by a temperature gradient and its intensity depends upon the thermal conductivity of the medium where it takes place. q = -r grad T (1) In a similar manner, diffusion of mass in solids and in quiescent fluids is related to the mass-fraction field in the medium by means of Fick's law [Eq. (2)], which says that mass diffusion occurs in a two-component mixture due to a mass-fraction gradient of one of the components in the mix- ture. Furthermore, mass diffusion also depends on the mass difffusivity of one component in the other. j = - - ,O C--,~AB grad O)A (2) Heat and mass diffusion are transport processes that origi- nate from molecular activity. In both cases, the aforemen- tioned laws [Eqs. (1) and (2)] are widely accepted for most situations of practical interest. Moreover, the two rate equa- tions display identical forms, the heat flux q corresponding to the mass flux j, temperature T corresponding to mass frac- tion w A, and so forth. Forced-Convection Flows For heat transfer to laminar flows, the principle of conserva- tion of energy yields, for constant-property fluids in the absence of heat sources, dT -- = o~div(grad T) (3) dt where d(*)/dt stands for the material derivative of *, de- fined as d(*)/dt -- O(*)/Ot + v • grad(*). Equation (3) states that the rate of change of temperature experienced by any material particle of the flowing fluid is due to heat diffusion at its instantaneous position. Similarly, for laminar flow of a fluid mixture of two nonreactant species A and B, the following equation is ob- tained if the principle of mass conservation is evoked for species A: dw A - ~Aa div(grad t0A) (4) dt Address correspondence to Professor P. R. Souza Mendes, Department of Mechanical Engineering, Pontificia Universidade Cat61ica--RJ, Rua Marqu6s de S~o Vicente 225, Rio de Janeiro, RJ 22453, Brazil. Experimental Thermal and Fluid Science 1991; 4:510-523 © 1991 by Elsevier Science Publishing Co., Inc., 655 Avenue of the Americas, New York, NY 10010 0894-1777/91/$3.50 Sl0