Twin-city Airflow Measuring System Using Piezometer Ring - E Manuel d'utilisateur télécharger pdf

One of the following equations is used to measure

the flow:

ACFM = C1

(∆P/ρ)

where: A = Actual inlet funnel throat area (square

feet) - from tables on pages 2 and 3

∆P = The differential in static pressure from

the piezometer ring and the front

pressure tap (inches w.g.)

ρ = Air density (pounds mass/cubic foot)

C1 = Value from Table 1 below

The equations can be simplified by assuming standard

density and assuming funnel dimensions match drawing

dimensions. The following tables show the factor (F) for

each fan size and type. The equation then becomes the

following:

For standard air (ρ = 0.075 lb/ft

ACFM = F ∆P

where: F = factor from tables on pages 2 and 3

∆P = The differential in static pressure

from the piezometer ring and the

front pressure tap (inches w.g.)

Twin City Fan now offers an air measuring device as an

option on centrifugal fans. It is based on the principle

of a flow nozzle. The inlet cone of the fan is used as

the flow nozzle. By measuring the pressure drop through

the inlet cone, the flow can be calculated. The system

consists of a piezometer ring mounted in the throat and

a static pressure tap mounted on the face of the inlet

cone. A differential pressure transducer and a digital

display can be provided. The display must be capable

of performing the square root function in order to read

out in CFM directly. By testing fans in the laboratory,

Twin City Fan was able to determine flow coefficients for

various fan types. The flow coefficients were combined

to give the equations listed below by fan type. Based

on testing performed in Twin City Fan’s laboratory, the

accuracy of the system was determined to be +/- 5%.

The pressure drop is measured from the tap located

on the face of the funnel to the piezometer ring in the

throat. The inlet tap is connected to the high-pressure

side of the transducer and the piezometer ring is con-

nected to the low-pressure side.

Measurement of Airflow

The equations below are accurate for flow estimation for flows from 40% to 100% of wide-open volume. According

to testing done previously at Twin City Fan, several factors affect the accuracy of this method of determining flow.

The equations below assume the following:

• There are no vanes or other obstructions in or near the inlet

• Even flow entering the funnel (no pre-swirl)

• Standard wheel to inlet cone overlap

• Accurate determination of air density at the inlet

• Free inlet (consult Twin City Fan for ducted inlet factors)

Non-Standard Density Method Standard Density Method

Product

Free Inlet

C1*

Ducted Inlet

EPFN/EPQN (Arr. 1 or 4), Sizes 122-165

EPLFN/EPLQN, Sizes 122-165

753.06 794.06

EPFN/EPQN (Arr. 1 or 4), Sizes 182-982

EPLFN/EPLQN, Sizes 182-982

MPLFN/MPLQN,MPLFS/MPLQS

692.03 740.14

EPF/EPQ (Arr. 3), Sizes 122-165 726.39 765.94

EPF/EPQ (Arr. 3), Sizes 182-982 667.52 713.93

MPQN, Sizes 122-165 753.06 794.06

MPQN, Sizes 182-490 692.03 740.14

APF/APQ 753.06 794.06

BC/BCS/BAF SWSI 735.42 786.56

BC/BCS/BAF DWDI 1470.84 1573.12

TSL/TFE 735.42 753.56

QSL/QFE/QIFE/TVIFE 696.00 735.83

BAE-SW ** 720.40 735.80

BAE-DW** 1440.80 1471.60

RB (Std. Inlet Bell) 913.33 997.49

HIB/RTF 727.94 785.07

HAF 790.17 760.92

VBC/VAF 1414.00 NA

* Values for ducted C1 factors are based on

duct diameter matching standard inlet collar

diameter.

** BAE sizes smaller than 182 use BC\BCS\BAF

Factors.

ES-105

September 2014

Airflow Measuring System

Using Piezometer Ring

INSTALLATION, OPERATION & MAINTENANCE MANUAL

Table 1: C1 Values

1 2 3 4

Résumé du contenu

Page 1 - Using Piezometer Ring

One of the following equations is used to measure the flow: ACFM = C1 * A * (∆P/ρ) where: A = Actual inlet funnel throat area (square

Page 2

2 Twin City Engineering Supplement ES-105SizeEPF/EPQFree InletFEPFN/EPQNEPL-SeriesFree InletFEPF/EPQDucted InletFEPFN/EPQNEPL-SeriesDucted InletFA122

Page 3

Twin City Engineering Supplement ES-105 3Table 8: MPQNSizeFree InletFDucted InletFA122 944.92 996.36 0.344150 1206.40 1272.08 0.439165 1518.58 1601.

Page 4

TWIN CITY FAN & BLOWER | WWW.TCF.COM5959 Trenton Lane N | Minneapolis, MN 55442 | Phone: 763-551-7600 | Fax: 763-551-7601 Selecting a pr

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Twin-city Airflow Measuring System Using Piezometer Ring - E Manuel d'utilisateur

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