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Compressed Air Pipe Sizing Designer (CompAir v2.0)

compressed air piping designer - 3 model equations to find flowrate, pipe size & pressure drop

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CompAir: Compressed Air Pipe Sizing Designer

Traditionally, tables or charts are used for manual calculations. With CompAir program designed for mobility, you can now do pipe sizing at anytime, anywhere. CompAir program is engineered for ultimate flexibility with 3 built-in model equations for solving flowrate, pipe size and pressure drop.

The 3 model equations adopted in CompAir program are

(1) General Compressible Flow Equation.

(2) IoP (Institute of Plumbing) / CAGI (Compressed Air and Gas Institute) model.

(3) BCAS (British Compressed Air Society) model.

Aim: creating a mobile design environment (ShowMe!) for the practising engineers & designers in today's mobile world.

Results: Instant solutions at your fingertips.

Highlights:

- a small Windows Mobile Phone / Windows PC program for pipe design of Compressed Air system.

- 3 model equations available for pipe sizing with various options.

- 4 options available to solve pipe sizing problems: find flowrate, find pressure drop, find pipe size (PD method) and find pipe size (Vel method).

- built-in data, guides, etc.

- "save to file" function for printing.

- individually selectable SI-IP units.

The selectable SI-IP units available are:

Parameters

selectable SI-IP units

pressure

bar, kPa, psi, in.wg

pipe diameter

mm, in

pipe length

m, ft

velocity

m/s, ft/s

flowrate

l/s, cmh, cfh, cfm

Design Explained 1: General Compressible Flow Equation

Calculating pressure loss with the General Compressible Flow equation allows selection of material roughness, thus allowing Moody friction factor to be calculated for any flow regime. With computer program doing the work for you, this method is feasible and practical now. The General Flow equation gives the most accurate results.

For Air at STP conditions, the General Compressible Flow equation can be reduced to the following form with Specific gravity = 1 and Compressibility factor = 1 approx. (see Note 1 below):

Note 1: For engineering calculation, we can expect that the behaviour of air within pressure and temperature ranges in compressed air application can be approximated as an ideal gas with reasonable accuracy. For example, at 300 ^{o}K, the compressibility factor ranges from 0.9987 (at 5 bar) to 0.9950 (at 20 bar).

Did you know ? . . .

In Roman numeral system, one M refers to one Thousand (i.e., M = 1000; MM = 1000 x 1000).

In Metric system, one K refers to one Thouasand (i.e., K = 1000).

Design Explained 2: IoP/CAGI & BCAS models

As solving the General Flow equation is tedious, various forms of simplified equation are available for manual calculations. Most of the simplified equations are derived from the General Flow equation with assumptions for steel pipe application.

The IoP uses the following form of simplified equation:

PD = K L Q^{2} / (CR d^{5.3})

where Q = free air flow rate (l/s)

d = inside diameter of pipe (mm)

PD = pressure drop (bar)

CR = compression ratio

L = pipe length (m)

K = constant (800)

It is noted that "Compressed Air and Gas Handbook" published by CAGI uses the same formula for its tables.

Notably, publications by BCAS generally adopts the following form of simplified equation: