Pressure loss - Pressure loss

Fluids flowing inside equipment or pipes lose some of their energy due to friction caused by viscosity, and even if the kinetic and potential energy upstream and downstream are the same, the pressure downstream is lower than the upstream. This is the pressure loss caused by friction. Pressure loss in laminar flow inside a circular pipe is expressed by the Hagen-Poiseuille equation (Poiseuille flow). Pressure loss in turbulent flow can be calculated using dimensional analysis or the similarity law of energy dissipation, and is expressed by the Fanning equation

Here, f is the pipe friction coefficient, ρ is the fluid density, Δp is the pressure loss, u is the average flow velocity inside the pipe, gc is the gravity unit conversion factor, L _is the length of the pipe or layer, and D is the pipe diameter. The upstream and downstream pressure difference will only match the pressure loss in a horizontal, straight pipe with a constant diameter and no inserted objects.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

装置内あるいは管のなかを流れる流体は，粘性にもとづく摩擦によってエネルギーの一部が失われ，上流，下流の運動エネルギーおよび位置エネルギーが同一でも，下流における圧力が上流より低下する．この摩擦により低下した圧力をいう．層流における円管内流れの圧力損失は，Hagen-Poiseuilleの式(ポアズイユの流れ)で表される．乱流における圧力損失は，次元解析あるいは，エネルギー散逸の相似則から求められ，Fanningの式

で表される．ここで，fは管摩擦係数，ρは流体密度，Δpは圧力損失，uは管内平均流速，g_c は重力単位換算係数，Lは管または層の長さ，Dは管の直径である．上流，下流の圧力差が圧力損失と一致するのは，管径一定の水平でまっすぐな管で，途中に挿入物がない場合だけである．

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