vapor pressure difference
21Lighter than air — Some gases are buoyant in air because they have densities lower than that of air (about 1.2 kg/m3, 1.2 g/l). Lighter than air gases are used to fill craft called aerostats, which include free balloons, moored balloons, and airships, to make the… …
22NPSH — This article is about Net Positive Suction Head. For the band commonly abbreviated to NPSH, see Natalie Portmans Shaved Head. For the fire hose coupling thread, see Glossary of firefighting equipment#N. Hydraulic circuit NPSH is an initialism for …
23Cavitation — is defined as the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure. Cavitation is usually divided into two classes of behavior: inertial (or transient)… …
24Heat transfer — is a discipline of thermal engineering that concerns the exchange of thermal energy from one physical system to another. Heat transfer is classified into various mechanisms, such as heat conduction, convection, thermal radiation, and phase change …
25Siphon — Not to be confused with Psiphon. This article is about the domestic device. For the animal organ, see siphon (disambiguation). Siphon principle …
26Activity (chemistry) — In chemical thermodynamics, activity (symbol a) is a measure of the “effective concentration” of a species in a mixture, meaning that the species chemical potential depends on the activity of a real solution in the same way that it would depend… …
27Stirling engine — Alpha type Stirling engine. There are two cylinders. The expansion cylinder (red) is maintained at a high temperature while the compression cylinder (blue) is cooled. The passage between the two cylinders contains the regenerator …
28Environmental scanning electron microscope — Wool fibers imaged in an ESEM by the use of two symmetrical plastic scintillating backscattered electron detectors …
29Brazing — This article is about the metal joining process. For the cooking technique, see braising. Brazing practice Brazing is a metal joining process whereby a filler metal is heated above and distributed between two or more close fitting parts by… …
30Geology of Mars — Mars   Mars as seen by the Hubble Space Telescope Designations …
