# Evaporation From Confined Porous Media Due to Controlled IR Heating From Above

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## Abstract

We report an experimental study of evaporation due to controlled infrared (IR) heating from above from an initially saturated confined porous medium consisting of nearly ‘*mono*-*disperse*’ particles which has been rarely used earlier. We have used three diagnostic tools simultaneously, evaporation rate measurements using a precision weighing balance, surface temperature measurements using IR imaging, and fluorescein dye mixed with water to visualize the drying front and the evaporation sites. IR images show that the first stage, so-called constant rate period (CRP), was maintained due to films of water reaching the top surface from the saturated region below. Gradually reducing evaporation rate in stage 1 is shown to be related to ‘*shrinking evaporating patches*’ on the top surface, clearly revealed as lower-temperature regions in the IR images. End of CRP coincides with disappearance of the low-temperature patches. We give end of CRP in terms of the average depth (*L*_{cap}) of the liquid level from the top surface at that time. *L*_{cap} and duration of CRP are strong functions of the porous medium bead size, transition to stage 2 happening earlier for coarser spheres. The obtained *L*_{cap} values deviated from the predictions of Lehmann et al. (Phys Rev E 77(5):056309, 2008) which we show is due to a small range of pore sizes in the current experiments. For both water and highly volatile n-pentane, we show that *L*_{cap} normalized by a length scale derived from gravity-surface tension force balance goes like *Bo*^{0.20}, for *Bo* varying from 2.0E − 04 to 1.0E − 01; *Bo* is the Bond number. Fluorescein dye imaging shows a different view of the evaporation stages. During CRP, highly concentrated deposits of the fluorescein dye particles, orange in colour, are seen in the top few bead layers. These orange deposits represent the sites on the beads surfaces where the evaporation has taken place. Even with external heating, evaporation from such a porous medium is limited to a finite depth from the evaporating end, similar to the observation by Lehmann et al. (2008) for isothermal evaporation in Hele-Shaw cell.

## Keywords

Evaporation Porous media Thermal imaging Fluorescein dye deposits## Notes

### Acknowledgements

We thank Robert Bosch Centre for Cyber Physical Systems (RBCCPS/ME/JHA/PC 0013), Indian Institute of Science, for funding the work. We appreciate help of Prof. M. S. Bobji (Department of Mechanical Engineering, IISc Bangalore) and Prof. K. R. Sreenivas (JNCASR, Bangalore) during the analysis.

## References

- Aminzadeh, M., Or, D.: Temperature dynamics during nonisothermal evaporation from drying porous surfaces. Water Resour. Res.
**49**(11), 7339–7349 (2013)CrossRefGoogle Scholar - Aminzadeh, M., Or, D.: Energy partitioning dynamics of drying terrestrial surfaces. J. Hydrol.
**519**, 1257–1270 (2014)CrossRefGoogle Scholar - Aminzadeh, M., Or, D.: Pore-scale study of thermal fields during evaporation from drying porous surfaces. Int. J. Heat Mass Transf.
**104**, 1189–1201 (2017)CrossRefGoogle Scholar - Assouline, S., Narkis, K., Or, D.: Evaporation from partially covered water surfaces. Water Resour. Res. (2010). https://doi.org/10.1029/2010WR009121 CrossRefGoogle Scholar
- Assouline, S., Narkis, K., Gherabli, R., Lefort, P., Prat, M.: Analysis of the impact of surface layer properties on evaporation from porous systems using column experiments and modified definition of characteristic length. Water Resour. Res.
**50**(5), 3933–3955 (2014)CrossRefGoogle Scholar - Bergstad, Mina, Or, Dani, Withers, PhilipJ, Shokri, Nima: The influence of NaCl concentration on salt precipitation in heterogeneous porous media. Water Resour. Res.
**53**(2), 1702–1712 (2017)CrossRefGoogle Scholar - Brutsaert, W., Chen, D.: Desorption and the two stages of drying of natural tallgrass prairie. Water Resour. Res.
**31**(5), 1305–1313 (1995)CrossRefGoogle Scholar - Campbell, R.E.: Evaporation from bare soil as affected by texture and temperature. Vol. 190, Rocky Mountain Forest and Range Experiment Station (1971)Google Scholar
- Carman, P.C.: Fluid flow through granular beds. Transactions-Institution of Chemical Engineers
**15**, 150–166 (1937)Google Scholar - Carman, P.C.: Flow of Gases Through Porous Media. Academic Press, New York (1956)Google Scholar
- Cejas, C.M., Castaing, J.-C., Hough, L., Frétigny, C., Dreyfus, R.: Experimental investigation of water distribution in a two-phase zone during gravity-dominated evaporation. Phys. Rev. E
**96**(6), 062908 (2017)CrossRefGoogle Scholar - Chauvet, Fabien, Duru, Paul, Geoffroy, Sandrine, Prat, Marc: Three periods of drying of a single square capillary tube. Phys. Rev. Lett.
**103**(12), 124502 (2009)CrossRefGoogle Scholar - Dashtian, H., Shokri, N., Sahimi, M.: Pore-network model of evaporation-induced salt precipitation in porous media: the effect of correlations and heterogeneity. Adv. Water Resour.
**112**, 59–71 (2018)CrossRefGoogle Scholar - Fisher, E.A.: Some moisture relations of colloids. I. A comparative study of the rates of evaporation of water from wool, sand and clay. Proc. R. Soc. Lond. A
**103**(720), 139–161 (1923a)CrossRefGoogle Scholar - Fisher, E.A.: Some moisture relations of colloids. II. Further observations on the evaporation of water from clay and wool. Proc. R. Soc. Lond. A
**103**(723), 664–675 (1923b)CrossRefGoogle Scholar - Gardner, H.R., Hanks, R.J.: Effect of sample size and environmental conditions on evaporation of water from soils. USD A Conserv. Res. Rep. No. 9. 14 pp. (1966)Google Scholar
- Geoffroy, S., Prat, M.: A review of drying theory and modelling approaches. In: Drying and Wetting of Building Materials and Components, pp. 145–173. Springer International Publishing (2014)Google Scholar
- Hide, J.C.: Observations on factors influencing the evaporation of soil moisture. Soil Sci. Soc. Am. J.
**18**(3), 234–239 (1954)CrossRefGoogle Scholar - Huinink, H.P., Pel, L., Michels, M.A.J., Prat, M.: Drying processes in temperature gradients–pore scale modelling. Eur. Phys. J. E.
**9**, 487–498 (2002)CrossRefGoogle Scholar - Idso, S.B., Reginato, R.J., Jackson, R.D., Kimball, B.A., Nakayama, F.S.: The three stages of drying of a field soil. Soil Sci. Soc. Am. J.
**38**(5), 831–837 (1974)CrossRefGoogle Scholar - Ishimwe, R., Abutaleb, K., Ahmed, F.: Applications of thermal imaging in agriculture—A review. Advances in Remote Sensing
**3**(03), 128 (2014)CrossRefGoogle Scholar - Israelsen, O.W., West, F.L.R.: Water-holding capacity of irrigated soils. No. 183. Utah Agricultural College Experiment Station (1922)Google Scholar
- Jackson, R.D., Kimball, B.A., Reginato, R.J., Nakayama, F.S.: Diurnal soil-water evaporation: time-depth-flux patterns. Soil Sci. Soc. Am. J.
**37**(4), 505–509 (1973)CrossRefGoogle Scholar - Keen, B.A.: The evaporation of water from soil. J. Agric. Sci.
**6**(pt 4), 456–475 (1914)CrossRefGoogle Scholar - Keita, E., Faure, P., Rodts, S., Coussot, P.: MRI evidence for a receding-front effect in drying porous media. Phys. Rev. E
**87**(6), 062303 (2013)CrossRefGoogle Scholar - Keita, E., Koehler, S.A., Faure, P., Weitz, D.A., Coussot, P.: Drying kinetics driven by the shape of the air/water interface in a capillary channel. Eur. Phys. J. E
**39**(2), 23 (2016)CrossRefGoogle Scholar - Kozeny, J.: Uber kapillare leitung der wasser in boden. R. Acad. Sci. Vienna Proc. Class I
**136**, 271–306 (1927)Google Scholar - Kuehni, S.M.S.S., Bou-Zeid, E., Webb, C., Shokri, N.: Roof cooling by direct evaporation from a porous layer. Energy Build.
**127**, 521–528 (2016)CrossRefGoogle Scholar - Kumar, N., Arakeri, J.H.: Natural Convection Driven Evaporation from a water surface. Procedia IUTAM
**15**, 108–115 (2015)CrossRefGoogle Scholar - Laurindo, J.B., Prat, M.: Numerical and experimental network study of evaporation in capillary porous media@ Phase distributions. Chem. Eng. Sci.
**51**(23), 5171–5185 (1996)CrossRefGoogle Scholar - Laurindo, J.B., Prat, M.: Numerical and experimental network study of evaporation in capillary porous media. Drying rates. Chem. Eng. Sci.
**53**(12), 2257–2269 (1998)CrossRefGoogle Scholar - Le Bray, Y., Prat, M.: Three-dimensional pore network simulation of drying in capillary porous media. Int. J. Heat Mass Transf.
**42**(22), 4207–4224 (1999)CrossRefGoogle Scholar - Lehmann, P., Assouline, S., Or, D.: Characteristic lengths affecting evaporative drying of porous media. Phys. Rev. E
**77**(5), 056309 (2008)CrossRefGoogle Scholar - Lemon, E.R.: The potentialities for decreasing soil moisture evaporation loss. Soil Sci. Soc. Am. J.
**20**(1), 120–125 (1956)CrossRefGoogle Scholar - Lloyd, J.R., Moran, W.R.: Natural convection adjacent to horizontal surface of various planforms. J. Heat Transfer
**96**(4), 443–447 (1974)CrossRefGoogle Scholar - Mitarai, N., Nori, F.: Wet granular materials. Adv. Phys.
**55**(1–2), 1–45 (2006)CrossRefGoogle Scholar - Or, D., Lehmann, P., Shahraeeni, E., Shokri, N.: Advances in soil evaporation physics—a review. Vadose Zone J.
**12**(4), 16 (2013)Google Scholar - Prat, M.: Percolation model of drying under isothermal conditions in porous media. Int. J. Multiph. Flow
**19**(4), 691–704 (1993)CrossRefGoogle Scholar - Prat, M.: Recent advances in pore-scale models for drying of porous media. Chem. Eng. J.
**86**(1), 153–164 (2002)CrossRefGoogle Scholar - Qiu, G.Y., Shi, P., Wang, L.: Theoretical analysis of a remotely measurable soil evaporation transfer coefficient. Remote Sens. Environ.
**101**(3), 390–398 (2006)CrossRefGoogle Scholar - Schlünder, E.U.: On the mechanism of the constant drying rate period and its relevance to diffusion controlled catalytic gas phase reactions. Chem. Eng. Sci.
**43**(10), 2685–2688 (1988)CrossRefGoogle Scholar - Schlünder, E.U.: Drying of porous material during the constant and the falling rate period: a critical review of existing hypotheses. Drying Technol.
**22**(6), 1517–1532 (2004)CrossRefGoogle Scholar - Shahraeeni, E., Lehmann, P., Or, D.: Coupling of evaporative fluxes from drying porous surfaces with air boundary layer: Characteristics of evaporation from discrete pores. Water Resour. Res. (2012). https://doi.org/10.1029/2012WR011857 CrossRefGoogle Scholar
- Shaw, T.M.: Drying as an immiscible displacement process with fluid counterflow. Phys. Rev. Lett.
**59**(15), 1671 (1987)CrossRefGoogle Scholar - Sherwood, T.K.: The drying of solids—II. Ind. Eng. Chem.
**21**(10), 976–980 (1929)CrossRefGoogle Scholar - Shokri-Kuehni, S., Vetter, T., Webb, C., Shokri, N.: New insights into saline water evaporation from porous media: Complex interaction between evaporation rates, precipitation and surface temperature. Geophys. Res. Lett.
**44**, 5504–5510 (2017a). https://doi.org/10.1002/2017GL073337 CrossRefGoogle Scholar - Shokri-Kuehni, S.M.S., Rad, M.N., Webb, C., Shokri, N.: Impact of type of salt and ambient conditions on saline water evaporation from porous media. Adv. Water Resour.
**105**, 154–161 (2017b)CrossRefGoogle Scholar - Shokri, N., Lehmann, P., Vontobel, P., Or, D.: Drying front and water content dynamics during evaporation from sand delineated by neutron radiography. Water Resour. Res. (2008). https://doi.org/10.1029/2007WR006385 CrossRefGoogle Scholar
- Shokri, N., Lehmann, P., Or, D.: Critical evaluation of enhancement factors for vapor transport through unsaturated porous media. Water Resour. Res. (2009). https://doi.org/10.1029/2009WR007769 CrossRefGoogle Scholar
- Shokri, N., Or, D.: What determines drying rates at the onset of diffusion controlled stage‐2 evaporation from porous media? Water Resour. Res. (2011). https://doi.org/10.1029/2010WR010284 CrossRefGoogle Scholar
- Suzuki, M., Maeda, S.: On the mechanism of drying of granular beds. J. Chem. Eng. Jpn
**1**(1), 26–31 (1968)CrossRefGoogle Scholar - Thiery, J., Rodts, S., Weitz, D.A., Coussot, P.: Drying regimes in homogeneous porous media from macro-to nanoscale. Physical Review Fluids
**2**(7), 074201 (2017)CrossRefGoogle Scholar - Van Brakel, J.: In: Mujumdar, A.S. (ed.) Advances in Drying, vol. 1, p. 217. Hemisphere, New York (1980)Google Scholar
- Veihmeyer, F.J., Hendrickson, A.H.: The moisture equivalent as a measure of the field capacity of soils. Soil Sci.
**32**(3), 181–194 (1931)CrossRefGoogle Scholar - Yiotis, A.G., Boudouvis, A.G., Stubos, A.K., Tsimpanogiannis, I.N., Yortsos, Y.C.: Effect of liquid films on the drying of porous media. AIChE J.
**50**(11), 2721–2737 (2004)CrossRefGoogle Scholar - Yiotis, A.G., Salin, D., Tajer, E.S., Yortsos, Y.C.: Analytical solutions of drying in porous media for gravity-stabilized fronts. Phys. Rev. E
**85**(4), 046308 (2012a)CrossRefGoogle Scholar - Yiotis, A.G., Salin, D., Tajer, E.S., Yortsos, Y.C.: Drying in porous media with gravity-stabilized fronts: experimental results. Phys. Rev. E
**86**(2), 026310 (2012b)CrossRefGoogle Scholar - Yuan, C., Tingwu, L., Lili, M., Han, L., Yang, W.: Soil surface evaporation processes under mulches of different sized gravel. Catena
**78**(2), 117–121 (2009)CrossRefGoogle Scholar