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| Essay:History of research models for combined heat and moisture transferSource: Rode, C. and Burch, D.M., 1995: "Empirical validation of a transient computer model for combined heat and moisture transfer"Related: **history of research models for combined heat and moisture transfer Models that predict the dynamic modes of coupled heat and moisture transfer in building constructions are not new inventions. As early as 1958, a simple scheme that calculated the transient distribution of moisture in a concrete roof was presented by Chlusov. Such calculations were done by hand. A more theoretical basis for modeling the coupled transport phenomena in porous media was developed in the late 1950s with the work of Philip and de Vries (1957) and later Luikov (1966). These researchers presented models to calculate the combined heat and moisture transport by two governing partial differential equations using as driving potentials, the moisture content and the temperature. The transport coefficients in these models are nonlinear functions of the driving potentials. This fact, along with the lack of efficient solution techniques available when the theory was developed, meant that it was hardly possible to use the equations to predict the hygrothermal performance of building materials and structures for practical situations. The use of the equations was restricted to analytical studies of simplified cases and small-scale attempts at processing the equations numerically. New measuring techniques provided the necessary raw data to determine the moisture transport coefficients for the above-mentioned transport models as functions of moisture content (van der Kooi 1971; Nielsen 1974). Most of this research was cam-.ed out in the laboratory to analyze the behavior of single materials. Numexical implementation of the theoretical transport models evolved particularly in the early 1980s with the work of researchers such as Kiefsl (1983) and Kohonen (1984). Their efforts helped the theory to be applied in more practical situations by analyzing composite building structures exposed to, realistic indoor and outdoor climatic conditions. The main objective of these numerical models was to use them for research purposes. Today, research produces still more developed simulation todls that are now often multidimensional, complete heat, air, and moisture transport models. A recent overview of existing simple and advanced models is given by Hens and Janssens (1993).
REFERENCES ASHRAE. 1993. 1993 ASHRAE handbook-Fundamentals. Atlanta, Ga.: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. ASTM. 1993. ASTM Test method C 177, Thermal insulation, environmental acoustics. Annual Book of ASTM Standards, vol. 04.06. Philadelphia, Pa.: American Society for Testing and Materials. Burch. D.M., and WC. Thomas. 1994. MOIST-A PC program for predicting heat and moisture transfer in building envelopes. NIST Special Publication 853. Gaithemburg, Md.: National Institute of Standards and Technology, Burch, D.M., W.C. Thomas, and A.H. Fanney. 1992. Water vapor permeability measurements of common building materials. ASHRAE Transactions 98(2). Chlusov, I.E. 1958. On the calculation of moisture in roof constructions. (Original in Russian). CIB Confernce on Flat Roofs, June 9-11, Stockholm. Duff, J.E. 1968. Moisture distribution in wood-frame walls in winter. Forest Products Journal 23(l), Glaser, H. 1959. Graphisches Verfahren zur Untersuchung von Diffusionsvorglinge. Kalfetechnik 10: 345-349. Greenspm L. 1977. Humidity fixed points of binary satmted aqueous solutions. Journal of Rescaroh, National Bureau of Standards SIA: 89-96. Hens, H., and A. Janssens. 1993. Enquiry on HAMCaT codes. Energy Conservation in Buildirigs and Community System PrVmine. Annex 24. Heat, Air and Moisture Transfer in Insulated Envelope Pwts- International Energy Agency, .
Kohonen, R. 1994. A method to analyze the transient hygmthermal bebavior of building materials and cornponents. Publicatim 21. Espoo: Tachrical Research Centri of Finland.
Kanzel, H-M. 1994. Vadahren zur ein- und zweidimensionalen Berechnung des gekoppelten WUme und Feuchtetransport In Bauteilen mit einfachen Kennwerten. Ph.D. thesis. Universitlit Stuttgart
Kyle, D.M., and A. De4arlais. 1994. Assessment of technolognes for constructing self-drying low-slope roofs. ORNL/CON380. Oak Ridge, Tenru Oak Ridge National Laboratory,
Luikov, AN. 1966, Heat andmass transfer in collarrporous bodies. London: Pergamon Press.
Nielsen, A.R 1974. Moisture distributions in cellular concrete during heat and moisture trwvsfer. PhD. thesis. Thenrial Insulation Laboratory Tecbnical University of Denmuk.
Pedersen, C.R. 1990. Cornfifried heat and moisture transfer in building constructions. Ph.D. thesis. Thennal Insulation Laboratory, Technical University of Denmark
Pedersen, C.R. 1991, Cl "4ification of model MATCH. 1,EA, Energy Conservation in Buildings and Community Systems Programme, Annex 24. Report TI-DK-91 /01.
Pedersen, CA, and G. Courville. 1991. A computer analysis of the annual thermal performance of a roof system with slightly wet fibrous glass insulation under transient conditions. Journal of TItemzI Insulation 15:110-136.
Pedersen, C.P., T.W. Petrie, G.E. Courville, A.0. Dojarlais, RW. Childs, and K.E. Wdluts. 1992. Moisture effects in low slope roofs: Drying rates after water addition with various vapor retarders. ORNL/CON-308. Oak Ridge, Tenn.- Oak Ridge National Laboratory.
Philip, J.R., and DA. de Viies. 1957. Moisture movement in porous materials under temperature gradients, Transactions, American Geophysical Union 38.222-232.
Richards, RT, D.M. Burd-~ and W.C. Thorn", 1992, Water va.por sorption measurements of common building materials. ASHRAE Transactions 98(2).
Threlkeld, J.L. 1970. Thermal environmental engineering, pp. 196198. New York, N.Y.- Prentice-Hall, Inc.
van der Kooi, J. 1971. Moisture transport in cellular concrete roofs. Ph.D. thesis. Delft, the Netherlands: Uitgeverij Waltman.
Zarr, R.R., D.M. Burch, T.K. Faison, C.E. Arnold, and M.E. O'Connell. 1987. Calibration of NBS calibrated hot box. Journal of Testing and Evaluation 15(3).
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