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Experimental investigations were conducted to characterize the thermal insulation properties of different natural low-cost materials (coconut fi bers and groundnut shell). A steady state method was used to measure the thermal conductivity by holding the sample between two concentric spheres with heat transferred mainly by conduction from the inner sphere (heat source) through the testing material. For comparison, the same experimental procedure was done for a standard and man-made insulation material, aluminum silicate fi ber. The results showed that for all the materials, the thermal conductivity increases with temperature; and the rates of increase are very similar. Also, two experimental samples were made to measure the moisture transport of the two natural materials: one with groundnut shell (composed of void space and grain) and the other sample with coconut fi bers (composed of void space and fi bers). The percentage of water accumulation due to vapor absorption was calculated for each layer after a pre-set time of experiment (1 h, 2 h, …). A numerical investigation was performed to simulate the transfer process with a general and sound model, and to present the basic features of the transfer process.
air and moisture transport, natural material, porous media, thermal conductivity, thermal insulation.
[1] Papadopoulos, A.M., State of the art in thermal insulation materials and aims for future devel-opments. Energy and Buildings, 37, pp. 77–86, 2005.
[2] Koelet, P.C. & Gray, T.B., Industrial Refrigeration: Principles, Design and Applications, Macmillan: London, pp. 234–384, 1992.
[3] Kodah, Z.H., Jarrah, M.A. & Shanshal, N.S., Thermal characterization of foam-cane (Quseab) as an insulant material. Energy Conservation and Management, 40, pp. 349–367, 1998.
[4] Fan, J., Cheng, X. & Chen, Y.-S. An experimental investigation of moisture absorption and condensation in fi brous insulations under low temperature. Experimental Thermal and Fluid Science, 27, pp. 723–729, 2002.
[5] Edwin, F.S. & William, C.T., Thermal Insulation Building Guide, Robert E. Krieger Publishing Company: Malabar, pp. 1–473, 1990.
[6] Holman, J.P. & Gajda, W.J., Experimental Methods for Engineers, 5th edn. McGraw-Hill: New York, pp. 37–83, 349–379, 1989.
[7] Choudhary, M.K., Karki, K.C. & Patankar, S.V., Mathematical modeling of heat transfer, con-densation, and capillary fl ow in porous insulation on a cold pipe. International Journal of Heat and Mass Transfer, 47, pp. 5629–5638, 2004.
[8] Ergun, S., Fluid fl ow through packed columns. Chem. Eng. Proc., 48, pp. 89–94, 1952.
[9] Udell, K.S., Heat transfer in porous media heated from above with evaporation, condensation, and capillary effects. Journal of Heat Transfer, 105, pp. 485–492, 1983.
[10] Udell, K.S., Heat transfer in porous media considering phase change and capillarity – the heat pipe effect. International Journal of Heat and Mass Transfer, 28, pp. 485–495, 1985.
[11] Darcy, H., Les Fontaines Publiques de la ville de Dijon, Dalment: Paris, 1856.
[12] Wijeysundera, N.E., Zheng, B.F., Iqbal, M., & Hauptmann, E.G., Numerical simulation of the transient moisture transfer through porous insulation. International Journal of Heat and Mass Transfer, 39, pp. 995–1004, 1996.
[13] Larbi, S., Bacon, G., & Bories, S.A., Humid air diffusion with water vapor condensation in porous media. International Journal of Heat and Mass Transfer, 38, pp. 2411–2426, 1995.