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제목 Pressure Drop의 이해
작성자 관리자 작성일 2015-07-14
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## Why Pressure Drop Matters in Subatmospheric Applications

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Pressure drop is an important physical and financial consideration when working with subatmospheric and vacuum applications. Pressure drop is the loss of line pressure caused by frictional resistance in the flow path. Everything causes some degree of frictional resistance on the fluid flowing, such as a valve, fittings and tubing, and this results in the loss of pressure. By determining how much pressure drop each part causes, you can calculate how much pressure you need to run your process. The lower the total pressure drop of the system, the less gas is needed to run it, which saves you money.

## How Pressure Drop Works

Static pressure affects the amount of pressure drop across an Alicat mass flow meter, and this is important to consider when choosing a device for use in sub-atmospheric pressures. Alicat devices calculate flow rates by measuring the differential pressure across a laminar flow stack. Since the flow is laminar, we can use the Hagen-Poiseuille equation to calculate the pressure drop caused by an Alicat device. The equation is notated as follows:

∆P= 8μLQ/(πr^4)

Where:
ΔP = pressure drop
L = length of pipe
η = viscosity of the fluid
Q = volumetric flow rate