Abstract
It is reported that temperature rises at wetting front during water infiltration into soil. The temperature goes back to the background value after passage of water front. Different explanations have been provided for source of energy causing temperature spike. Some have contributed it to heat of condensation released due to condensation of vapor on “dry” solid surface. Some other stated that the heat of wetting or heat of adsorption is responsible for the temperature rise. In this research, we revisited this issue. First, we provide a comprehensive review about occurrence of temperature spike at a wetting front. Then, we report about experiments we performed on the rise of water in dry paper. Using infrared and optical imaging techniques, we could monitor temperature changes in time and space. For all samples maximum temperature rise occurred at the wetting front. The magnitude of temperature spike depended on paper material, thickness, and liquid composition. It was larger for cellulose-fiber-based paper than for plastic-based paper. For a given paper type, thicker samples showed a larger temperature spike. Adding salt to the water caused reduction of temperature spike. It was concluded that replacement of air-solid interface with water-solid interface releases energy, which causes temperature rise.
Highlights
Spontaneous imbibition of water is an important process in many natural and industrial porous media
Given the fact that the interfacial tension is directly related to the interfacial energy per unit area, we can state that a porous solid filled by the non-wetting phase has a higher energy than when it is filled with the wetting phase, under isothermal conditions
As the temperature spike is completely controlled by interfacial energies, we investigated the effect of changing water properties in order to reduce its affinity to the solid phase
Summary
Spontaneous imbibition of water is an important process in many natural and industrial porous media. The spontaneous imbibition would be stronger, the larger the affinity of the solid phase for a given fluid is. This is clearly reflected in the definition of capillary pressure on both microscale and macroscale. Where r is the tube radius, θ is the contact angle, and γwn is the interfacial tension between the wetting and non-wetting fluid phases This equation can be combined with Young’s equation (equilibrium balance of forces for a contact line) to obtain: www.nature.com/scientificreports/. For Pc to be positive, there must be a net decrease of the energy of all interfaces when the saturation of the wetting phase increases This is the basis of spontaneous imbibition
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
