Physics:Pouillet effect
In physics and chemical engineering, the term Pouillet effect refers to an exothermic reaction that takes place when a liquid is added to a powder. Strictly speaking, the heat generated is caused by adhesion of the liquid to the surface of the particles rather than by a chemical reaction.[1] It was first observed in 1802 by Leslie, who noted that heat was evolved when dry sawdust was wetted with water.[2] Claude Pouillet later described this phenomenon in 1822, and it subsequently became known as the "Pouillet effect" in France, and then elsewhere.[3][4]
Negative Pouillet effect
Under certain conditions, a negative Pouillet effect is possible, i.e., heat can be absorbed instead of being released. G. Schwalbe showed that in the case of water below 4 degrees Celsius, the temperature of the system decreases.[5] Joseph Mellor argued that this is due to the negative thermal expansion coefficient of water between 0 and 4 degrees Celsius,[6] with the temperature change [math]\displaystyle{ \Delta T }[/math] given by
[math]\displaystyle{ \Delta T = {{\alpha T}\over{C_p D}} \Delta P }[/math]
where [math]\displaystyle{ \alpha }[/math] is the thermal expansion coefficient, [math]\displaystyle{ C_P }[/math] is the specific heat, [math]\displaystyle{ D }[/math] is the specific gravity, and [math]\displaystyle{ \Delta P }[/math] is the applied pressure due to the addition of the liquid. According to this formula, any liquid with a negative thermal expansion coefficient would be expected to exhibit a drop in temperature.
References
- ↑ Taggart, Arthur F.; Beach, Frederick E. (November 1, 1916). "An Explanation of the Flotation Process". Metallurgical and Chemical Engineering 15 (9): 518–523. https://books.google.com/books?id=TAdEAAAAYAAJ&dq=pouillet+effect+chemical+engineering&pg=PA520. Retrieved 19 February 2022.
- ↑ Leslie, John (1802). "On capillary action". Philosophical Magazine. 1st series 14 (55): 193–205. doi:10.1080/14786440208676183. https://babel.hathitrust.org/cgi/pt?id=pst.000068484644;view=1up;seq=205. From p. 201: Upon wetting paper or linen with water or oil, and " … applying a delicate thermometer, I perceived a very sensible extrication of heat invariably to take place during such combinations. And this effect was the greater in proportion to the previous dryness of the solid. Thus I have sometimes produced a heat of ten degrees by moistening saw-dust which had been parched before the fire."
- ↑ Pouillet (1822). "Mémoire sur de nouveaux phénomènes de production de chaleur" (in French). Annales de Chimie et de Physique. 2nd series 20: 141–162. From p. 142: "À l'instant où un liquide mouille un solide, il y a dégagement de chaleur." (At the instant when a liquid wets a solid, there is a release of heat.)
- ↑ 'Adsorption by powders & porous solids: principles, methodology and applications' Academic Press, 1999.
- ↑ Schwalbe, G. (1905). "Über die beim Benetzen pulverförmiger Körper, insbesondere von Sand, mit Wasser auftretende Wärmetönung, sowie Untersuchungen über das Verhalten von Wasser unter 4° bei diesem Vorgange". Annalen der Physik 321 (1): 32–45. doi:10.1002/andp.19053210105. Bibcode: 1905AnP...321...32S. https://onlinelibrary.wiley.com/doi/10.1002/andp.19053210105. Retrieved 19 February 2022.
- ↑ Mellor, J.W. (1922). A Comprehensive Treatise on Inorganic and Theoretical Chemistry, Volume 1. London: Longmans, Green and Co.. pp. 495–496. https://books.google.com/books?id=jA5GAQAAMAAJ. Retrieved 19 February 2022.
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