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5. Acknowledgement This work was supported by the VEGA 1/4204/07 grant of Slovak Grant Agency. 6. References [1]. B. M. BUDAK, A. A. SAMARSKIJ, A.N. TICHONOV Collection of Problems on Mathematical Physic (in Russia, Sbornik zadač po matematičskoj fizike), Moscow, publisher: Nauka, 3rd edition, 1980, pp. 455‐456 [2]. A. V. LYKOV Theory of Thermal Conductivity (in Russia, Teorija teploprovodnosti), Moscow, 1967, publisher: Vysšaja škola,(1.9) formula (25) p. 89, 1.10) formula (28), p. 91). [3]. I. S. GRADSTEIN; I. M. RISHIK, Tables of Integrals, Sums, Series and Products (in Russia, Tablicy integralov, summ, riadov i proizvedenij), publisher FM, Moscow1963, p. 21. [4]. CARSLAW H. S.; JAEGER J. C. Conduction of Heat in Solids, 2 Ed., OXFORD, At the Clarendon Press. London 2003 [5] ČULÍK F.; BANÍK I.; LUKOVIČOVÁ J. Temperature field in a solid body restricted by two parallel planar surfaces, <strong>Proceedings</strong> of Thermophysics 2008, pp. 26‐35 October 2008, Meeting of the Thermophysical Society [6]. VRETENÁR V. Extended version of Pulse transient method, <strong>Proceedings</strong> of Thermophysics, 2005, Contents, pp. 92‐103, October 2005, Meeting of the Thermophysical Society [7]. ČULÍK F. I.; BANÍK I. Determination of temperature field created by planar heat source in a solid body consisting of three parts in mutual thermal contact, International Journal of Thermal Sciences 48 (2009) pp. 204‐208. ELSEVIER. Available online at www.sciencedirect.com 34
Moisture transport through porous materials monitored by the Hot Ball Method Laura Casares García, Ľudovít Kubičár Institute of Physics SAV, Dúbravská cesta 9, SK‐845 11 Bratislava, Slovakia Abstract Cultural and historical monuments are predominantly constructed of porous materials, where moisture plays a dominant role in their deterioration. Considering this fact, we performed experimental measurements of moisture diffusion through porous materials as sandstone. Our experimental studies are focused on a 17% porosity sandstone piece (dimensions 100x50x50mm) from Sander Schilfsandsteingbruch (Germany). A new hot ball method technique was used for monitoring moisture transport. Our sandstone block has been used for one‐dimensional diffusion experiments in which water was diffused through a 50x50mm base surface, while side surfaces remained isolated for moisture transport. Three processes were studied, drying, saturation through a step‐wise regime and water‐pulse regime. With our work we were able to characterize and calibrate the sample, and to study the changes in moisture transport with temperature. Keywords: moisture diffusion, sandstone, hot ball method 1. Introduction Porous structures belong to a branch of materials which have a great number of applications in science, civil engineering and industry. On one hand their excellent thermal insulating properties make them ideal materials for building purposes and on the other hand broad physical and chemical processes take place on their pores, namely freezing/thawing, dissolution, condensation/evaporation, absorption/desorption, moisture transport, saturation/drying. In this paper we will focus on the last ones. In addition, cultural and historical monuments are predominantly constructed of porous materials, where moisture plays a dominant role in their deterioration [1]. Castles, cathedrals and other buildings are attacked by environment due to water, heat, pollutant and underground water. Two factors influence property of an object, namely worsening the thermal insulation due to diffusion of moisture and degradation of material structure due to freeze‐ thaw process of the moisturized structure. Therefore, information regarding moisture transport through sandstone materials will represent a basic assumption for achieving a better understanding and prevention of the aforementioned processes. Nowadays there are different experimental methods for measuring thermophysical properties [2,3,4]. However, only transient methods allow us to obtain information in short enough measuring times so the information obtained corresponds to the thermodynamic state of real applications. The technique of transient methods has motivated the construction of a whole range of new innovative laboratory instruments, as for example hot ball sensors which are the base of our experiment. These sensors in connection with the RTM monitoring system give local information on temperature and thermal conductivity [5,6]. As thermal conductivity of porous 35
Page 1 and 2: Thermophysics 2009 29 th and 30 th
Page 3 and 4: Content Ivan Baník, Jozefa Lukovi
Page 5 and 6: Measurement of the thermo‐physica
Page 7 and 8: As the right side of the previous r
Page 9 and 10: The initial vector k r in the k1, k
Page 11 and 12: 2.4 The computer programs testing T
Page 13 and 14: Investigation of moisture influence
Page 15 and 16: ⎛ t t ⎞ −1 ⋅ ln⎜ ⎝ tm t
Page 17 and 18: Density [kg.m -3 ] 620 600 580 560
Page 19 and 20: for a new building have to be great
Page 21 and 22: Fig.1. Photo of the hot ball sensor
Page 23 and 24: Fig.6.Left: formation of blocks. Ri
Page 25 and 26: 4. Conclusions With this experiment
Page 27 and 28: 1a. Three‐dimensional temperature
Page 29 and 30: n+ ∞ ( ) 4 ( ) ∑ π n= 1 ( 2 1)
Page 31 and 32: a 2 2 ( Fo) ⎛ l ⎞ r = ⎜ ⎟
Page 33: Substitution of ordinates of the in
Page 37 and 38: Data acquired through the hot ball
Page 39 and 40: In this way, the water spreading wa
Page 41 and 42: Thermal conductivity [W m -1 K -1 ]
Page 43 and 44: Relationship between relative permi
Page 45 and 46: ( ) i n Φ − Φ K i = ki i i, cri
Page 47 and 48: Figure 4: Comparison of measured an
Page 49 and 50: Computational modelling of coupled
Page 51 and 52: a ξ = d 2 ( lnκ − lnκ ) lnξ +
Page 53 and 54: on the results of experiments and c
Page 55 and 56: Figures 8a, b: Moisture content (a)
Page 57 and 58: Conclusions The computer simulation
Page 59 and 60: properties as are the bulk density,
Page 61 and 62: elation determined from the measure
Page 63 and 64: In the evaluation of the difference
Page 65 and 66: Heat source I RT-Lab II Specimen Ch
Page 67 and 68: Thermal conductivity [W m -1 K -1 ]
Page 69 and 70: silicon glue epoxy probe hole Figur
Page 71 and 72: Computational modelling of temperat
Page 73 and 74: 1 2 3 EXT. INT. 5-15 50-60 375 5 Nu
Page 75 and 76: Fig. 4 shows a comparison of the re
Page 77 and 78: Envelope D Figs. 14, 15 present the
Page 79 and 80: Application of computational modell
Page 81 and 82: Table 2: Basic material characteris
Page 83 and 84: Temperature [K] 320 300 280 260 240
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Mineral wool has the same effect as
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Nowadays, most of concrete building
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Figure 2: Ceramic dessicator plate
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dessicators are decreased by the pe
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The surface water vapour diffusion
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where h is the Planck constant and
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(a) (b) Figure 2: Schematic picture
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[7] BLUM, V.; HART, G. L. W.; WALOR
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Analysis of moisture hysteresis of
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The water content during scanning b
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All analysed cellulose based materi
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Thermodilatometry of ceramics using
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of the dilatometric cell with the s
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thermal expansion / % 2 1,5 1 0,5 0
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[8] KAMSEU, E. ; LEONELLI, C. ; BOC
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heating, the temperatures were meas
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temperature difference [°C] 140 12
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temperature difference [°C] 180 16
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[4] ČÍČEL, B. - NOVÁK, I. - HOR
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space and the crystallization press
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20 mm face to the penetrating KNO3
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Cb [kg/m 3 (sample)] 1800 1600 1400
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D [m 2 /s] 1.0E-03 1.0E-04 1.0E-05
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Thermomechanical modelling of matur
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ε ε (velocity rates) a x , t . By
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ε ε w v The process of redistribu
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Conclusion In this paper we have br
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most popular among direct technique
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• Closed pores (not available for
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espective volume of inclusions frac
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Summary Among the indirect methods
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Thermal, hygric and salt‐related
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The water vapor diffusion coefficie
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Thermal properties Thermal conducti
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On the other hand, apparent moistur
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Thermal conductivity.. [Wm -1 K -1
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Properties of innovative materials
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or hygrothermal analysis of buildin
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where Da is the diffusion coefficie
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The bending and compressive strengt
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moisture diffusivity which was caus
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Abstract: Thermal conductivity in d
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, (5) where λ is thermal conductiv
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4.Measured values and calculation I
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Acknowledgements This research has
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3 Results During heating, the struc
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Acknowledgment This work was suppor
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mixture by short mixing, the mixtur
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detected by MIP and thus the intrus
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diffusion. The general Arrhenius eq
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Thermal conductivity measurement of
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S s o 2 4 4 λ ∇ T = wεσ ( T
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steel (20 W m ‐1 K ‐1 ) is arou
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significant larger cross‐section.
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Water and heat transport properties
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The open porosity ψ0 [%], bulk den
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Table 3: Basic material parameters
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Acknowledgements This research has
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comparison of results we can determ
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specimen and heat source R at infin
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6.E-04 4.E-04 ΔU (V) 2.E-04 0.E+00
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[3] KUBIČÁR Ľ. Pulse method of m
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silicate binders as partial replace
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Table 2. Mechanical properties HPC
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HPC Table 5. Water transport proper
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The results obtained for using high
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aerospace engineering, cryogenic en
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4 ⎡ ′ ⎤ Δθ( t) = ⎢ l ∫
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Alloy Components Weight Percent, [%
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Figure 8: Final results of the ther
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Figure 11: Preliminary results of t
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In case of the FeNi35, FeNi39 and F
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Experimental Methods Compressive st
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Type of mixture Water transport pro
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Thermal properties The thermal para
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Identification of Some Thermophysic
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Physical model of the direct proble
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2 ( λ − Bi) sin( λ) − 2λ Bic
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To calculate the sensitivity coeffi
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symmetry of the specimen when the t
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Figure 5: View of experimental setu
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During the inverse calculations the
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temperature dependence for the blac
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4. Conclusions The results of the t
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cross‐planar direction applying s
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3. Thermal diffusivity identificati
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Table 2: Effect of the convective h
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[2] BODZENTA, J.; BURAKA, B.; NOWAK
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doc. Ing. Jiří Vala, CSc. Brno Un
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263
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