Effusion Posted on 9th November 201525th July 2021 by ThePD (The Project Definition) An Effusion is the flow of a gas through a pore or capillary into a vacuum or another gas. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Technology and tagged gas, process. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.