Experimental data on transport coefficients for developing laminar flow in isosceles triangular ducts using the naphthalene sublimation technique

The data presented in this article are related to the research article entitled "Transport coefficients for developing laminar flow in isosceles triangular ducts" (Parise and Saboya, 1999) [1]. The article describes an experiment involving the determination of transport coefficients in the laminar entrance region of 30°, 45°, 60° and 90° isosceles triangular ducts. Data were obtained by application of the naphthalene sublimation technique in conjunction with the heat to mass transfer analogy. Experimental conditions (duct sides made of naphthalene and base made of metal) simulated developing velocity and temperature fields in an isosceles triangular duct with isothermal lateral walls and adiabatic base. The Reynolds number ranged from 100 to 1800 and the duct length to hydraulic diameter ratio, from 2 to 40. The experiment consisted of mounting a test section (triangular duct) with the lateral walls made of naphthalene. Air was forced past the test section and naphthalene walls were weighed prior and after each data run, providing the rate of mass transfer for given flow conditions. Raw data, for a total of 77 experimental runs, include: test section geometry, air flow and mass transfer conditions. Processed data comprise the relevant non-dimensional groups, namely: Reynolds, non-dimensional axial duct length and Sherwood numbers.


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The data presented in this article are related to the research article entitled "Transport coefficients for developing laminar flow in isosceles triangular ducts" (Parise and Saboya, 1999) [1]. The article describes an experiment involving the determination of transport coefficients in the laminar entrance region of 30°, 45°, 60°and 90°i sosceles triangular ducts. Data were obtained by application of the naphthalene sublimation technique in conjunction with the heat to mass transfer analogy. Experimental conditions (duct sides made of naphthalene and base made of metal) simulated developing velocity and temperature fields in an isosceles triangular duct with isothermal lateral walls and adiabatic base. The Reynolds number ranged from 100 to 1800 and the duct length to hydraulic diameter ratio, from 2 to 40. The experiment consisted of mounting a test section (triangular duct) with the lateral walls made of naphthalene. Air was forced past the test section and naphthalene walls were weighed prior and after each data run, providing the rate of mass transfer for given flow conditions. Raw data, for a total of 77 experimental runs, include: test section geometry, air flow and mass transfer conditions. Processed data comprise the relevant non-dimensional groups, namely: Reynolds, non-dimensional axial duct length and Sherwood numbers.  Value of the data The naphthalene sublimation technique has been applied for decades, and is still in use as attested by Refs. [2][3][4][5][6], from years 2016 to 2017. In this respect, the data here presented may provide quantitative information on issues that are not normally addressed by traditional research articles. Examples: (a) Aiming at reducing the mass transfer measuring uncertainty, how long can an experimental run last, Δt e , without affecting the channel geometry? (b) What could be the maximum allowable laboratory temperature variation, ΔT lab ?
Access to the experimental data from this article will assist researchers and designers who have recently been working with heat and mass transfer in triangular ducts [7][8][9], triangular channel heat exchangers [10][11][12] and triangular solar air heaters [7,13], to validate their simulation models or to benchmark their own experimental data.
Finally, the present article may benefit works about triangular ducts with some sort of heat or mass transfer augmentation device, for example, [9][10][11][13][14][15], by providing baseline (no enhancement) data. Table 1 presents the raw data, collected over 77 experimental runs. It includes test section geometry (apex angle, duct length and triangle side length), air flow conditions (air relative humidity, mean ambient temperature, maximum departure from mean ambient temperature, air pressure at rotameter inlet, air volumetric flow rate) and mass transfer conditions (mass of sublimated naphthalene and time duration of run). Table 2, with processed data, contains: hydraulic diameter, Reynolds number, non-dimensional duct length, and the average Sherwood number based on the logarithmic mean naphthalene concentration difference.

Experimental design, materials, and methods
A simple experimental apparatus, consisting of the test section, air flow circuit and instrumentation, was constructed. Fig. 1 shows a schematic of the two naphthalene plates that form the sides of the isosceles triangular test section.
A casting technique was devised to fabricate the naphthalene plates. The casting mold comprised a number of mirror-finished brass pieces, Fig. 2, put together with the help of precision screws, guiding blocks and a pair of C-clamps.
The whole set of Fig. 3 was left to cool down until the excess naphthalene left in the funnel was solidified. When removing the naphthalene plates from the mold, Fig. 4, care should be taken to avoid adhesion of naphthalene in the mold surface, as this would compromise the quality of the surface and, thence, measurements. Other surfaces of the naphthalene plate that would not participate of the sublimation process were covered with a fine adhesive tape. Provision was also made to assure that both plates were in thermal and hygroscopic equilibrium (for no less than 24 h) with laboratory ambient conditions by the start of an experimental run.
The air flow circuit comprised the test section, Fig. 5, plenum chamber, Fig. 6, flow meter, flow control valves and blower. Air was drawn from laboratory into the test section and forced out to external ambient, so that inlet naphthalene concentration could always be assumed as zero. A baffle, Fig. 5, with dimensions about 30 times that of the hydraulic diameter, was placed flush with the test section frontal plane, thus contributing to an undisturbed velocity profile at the duct entrance.
The test section was further isolated from any disturbance with the installation, downstream, of a plenum chamber, Fig. 6.
Finally, Figs. 7 and 8 show photographs of the experimental apparatus and a front view of the test section, respectively.
A brief description of the data reduction equations, from Tables 1 and 2, is presented next. Contrarily to the variables from raw data, SI units [m, s, K, Pa] are assumed in the following equations.
The hydraulic diameter, D h , is given by: where 2α is the triangle apex angle and s, the length of the equal sides of the isosceles triangular duct cross section.     The Reynolds number, Re, is: where U 0 is the average air velocity across the duct, ν, the air kinematic viscosity and, _ V 0 , the air volumetric flow rate, all calculated for air at test section entrance conditions.
The non-dimensional longitudinal length, x þ , is defined as: where L is the longitudinal length of the test section and Sc, the Schmidt number. For naphthalene, one has: The average Sherwood number, Sh b , based on the logarithmic mean naphthalene vapor concentration difference, Δρ n , is calculated in terms of the average mass transfer coefficient, λ b , the mass diffusivity of the air-naphthalene system, D m , and the rate of total mass transfer per unit area^, 1 An ΔmT Δte .  where A n ¼ 2 s L ð8Þ   Δρ n ¼ ρ n;w − ρ n;0 À Á − ρ n;w − ρ n;L À Á ln ρ n;w − ρ n;0 ð Þ ρ n;w − ρ n;L ð Þ ! ð10Þ where ρ n;0 , ρ n;w and ρ n;L are naphthalene vapor concentrations at the duct entrance, duct wall and duct exit, respectively, and are given by: ρ n;0 ¼ 0 air free of naphthalene ð Þ ð 11Þ ρ n;w ¼ P nw R n T w ð12Þ log 10 P n;w ¼ 13:564 − 3729:4 T w ð13Þ Funding sources This work is part of the Master thesis of J.A.R. Parise. It was partially supported by CAPES, Brazilian Ministry of Education, (Post graduate program code: 31005012012P1), and by CNPq, Brazilian Ministry of Science, Technology, Innovation and Communication (Grant no. 312189/2015-0).

Acknowledgments
This work was carried out in the Laboratory of Thermal Sciences of the Pontifícia Universidade Católica do Rio de Janeiro.

Transparency document. Supplementary material
Supplementary data associated with this article can be found in the online version at http://doi. org/10.1016/j.dib.2018.03.090.