Impact of wall potential on the fluid–wall interaction in a cylindrical capillary and a generalized Kelvin equation

In the present work a generalized Kelvin equation for a fluid confined in thick-walled cylindrical capillary is developed. This has been accomplished by including the potential energy function for interaction between a solid wall of a capillary and a confined fluid into the Kelvin equation. Using the Lennard–Jones 12–6 potential, an explicit form of the potential energy functions as expressed by hypergeometrical functions have been derived—firstly, for the interaction between a solid wall and a test atom placed at an arbitrary point in a long open-end capillary, and thereafter for the body–body interaction between the solid wall and a confined Lennard–Jones fluid. Further, this generalized Kelvin equation has been applied to detailed description hysteresis phenomena in such capillaries. All numerical calculations have been carried out for the model argon–graphite system at 90 K.