SIST EN 16211:2015
(Main)Ventilation for buildings - Measurement of air flows on site - Methods
Ventilation for buildings - Measurement of air flows on site - Methods
This European Standard specifies simplified methods for the measurement of air flows on site. It provides a description of the air flow methods and how measurements are performed within the margins of stipulated method uncertainties.
One measurement method is to take point velocity measurements across a cross-section of a duct to obtain the air flow. This simplified method is an alternative to the method described in ISO 3966 and EN 12599. This European Standard requests certain measurement conditions (length of straight duct and uniform velocity profile) to be met to achieve the stipulated measurement uncertainties for the simplified method.
Lüftung von Gebäuden - Luftvolumenstrommessung in Lüftungssystemen - Verfahren
Diese Norm gilt für die Messung von Luftvolumenströmen in Lüftungssystemen. Sie legt eine Beschreibung der Verfahren für Luftvolumenströme dar und wie Messungen innerhalb der für das Verfahren vorgeschriebenen Toleranzen durchgeführt werden.
Ein Messverfahren beruht auf der Messung von Punktgeschwindigkeiten über einen Querschnitt einer Luftleitung, um die Luftvolumenströmung zu bestimmen. Dieses vereinfachte Verfahren ist eine Alternative zu dem in ISO 3966 und EN 12599 beschriebenen Verfahren. Diese Norm setzt bestimmte Messumgebungen voraus (Länge gerader Luftleitungen und einheitliches Geschwindigkeitsprofil), die eingehalten werden müssen, um die vorgeschriebenen Toleranzen des vereinfachten Verfahrens zu erreichen.
Systèmes de ventilation pour les bâtiments - Mesurages de débit d'air dans les systèmes de ventilation - Méthodes
La présente Norme européenne spécifie des méthodes simplifiées pour le mesurage des débits d’air sur site. Elle fournit une description des méthodes de débit d’air et comment les mesurages sont réalisés dans les marges d'incertitude de la méthode stipulée.
Une méthode de mesurage est de prendre les mesurages de la vitesse des points sur une section transversale d’un conduit afin d’obtenir le débit. Cette méthode simplifiée est une variante de la méthode décrite dans l’ISO 3966 et l’EN 12599. La présente Norme européenne nécessite que certaines conditions de mesure (longueur de conduit droit et profil de vitesse uniforme) soient satisfaites afin d’obtenir les incertitudes de mesure spécifiées pour la méthode simplifiée.
Prezračevanje stavb - Meritve pretoka zraka v sistemu prezračevanja - Metode
Ta evropski standard določa poenostavljene metode za meritve pretoka zraka v sistemu prezračevanja. Podaja opis načinov pretoka zraka in kako se izvajajo meritve znotraj mejnih vrednosti negotovosti predpisane metode.
Pri eni merilni metodi je treba za izračun pretoka zraka meritve hitrosti točke prenesti prek preseka cevi. Ta poenostavljena metoda je alternativa metodi, opisani v standardih ISO 3966 in EN 12599. Ta evropski standard zahteva, da so izpolnjeni nekateri merilni pogoji (dolžina ravne cevi in enoten hitrostni profil), da je mogoče doseči predpisane merilne negotovosti za poenostavljeno metodo.
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Lüftung von Gebäuden - Luftvolumenstrommessung in Lüftungssystemen - VerfahrenSystèmes de ventilation pour les bâtiments - Mesurages de débit d'air dans les systèmes de ventilation - MéthodesVentilation for buildings - Measurement of air flows on site - Methods91.140.30VLVWHPLVentilation and air-conditioningICS:Ta slovenski standard je istoveten z:EN 16211:2015SIST EN 16211:2015en,fr,de01-september-2015SIST EN 16211:2015SLOVENSKI
STANDARD
SIST EN 16211:2015
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 16211
July 2015 ICS 17.120.10; 91.140.30 English Version
Ventilation for buildings - Measurement of air flows on site - Methods
Systèmes de ventilation pour les bâtiments - Mesurages de débit d'air dans les systèmes de ventilation - Méthodes
Lüftung von Gebäuden - Luftvolumenstrommessung in Lüftungssystemen - Verfahren This European Standard was approved by CEN on 5 March 2015.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2015 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 16211:2015 ESIST EN 16211:2015
EN 16211:2015 (E) 2 Contents Page Foreword . 4 1 Scope . 5 2 Normative references . 5 3 Terms, definitions and symbols . 5 3.1 Terms and definitions . 5 3.2 Symbols . 5 4 Principles and parameters of influence . 7 4.1 Hydraulic diameter . 7 4.2 Flow disturbances . 7 4.3 Air density,
.......................................................................................................................................... 7 4.4 Dynamic pressure, pd ............................................................................................................................ 7 4.5 Corrections for air density,
............................................................................................................... 8 5 Sources of errors .................................................................................................................................. 8 5.1 General ................................................................................................................................................... 8 5.2 Systematic errors .................................................................................................................................. 9 5.3 Random errors ..................................................................................................................................... 10 6 Measurement uncertainty ................................................................................................................... 10 6.1 Overall measurement uncertainty ..................................................................................................... 10 6.2 Standard instrument uncertainty, u1 ................................................................................................. 11 6.3 Standard method uncertainty, u2 ....................................................................................................... 11 6.4 Standard reading uncertainty, u3 ....................................................................................................... 11 6.5 Expanded measurement uncertainty, Um ......................................................................................... 11 7 Measurement requirements ............................................................................................................... 12 7.1 Method requirements and corrections ............................................................................................. 12 7.2 Measurements using a manometer ................................................................................................... 12 7.3 Measurements using an anemometer ............................................................................................... 13 7.4 Measurements using Pitot static tube .............................................................................................. 13 7.5 Measuring temperature and barometric pressure ........................................................................... 13 7.6 Mean value calculation of measurement signal ............................................................................... 13 8 Methods for measurement of air flows in ducts – ID (In Duct) methods ....................................... 13 8.1 Overview of recommended methods ................................................................................................ 13 8.2 Point velocity measurements using a Pitot static tube (method ID 1) or an anemometer (method ID 2) ....................................................................................................................................... 14 8.2.1 Method description ............................................................................................................................. 14 8.2.2 Preparations to be made at the site of measurement ..................................................................... 15 8.2.3 Measurement procedure .................................................................................................................... 18 8.2.4 Corrections of measured values and calculation of air flow .......................................................... 19 8.2.5 Standard method uncertainty ............................................................................................................ 20 8.3 Fixed devices for flow measurement – Method ID 3 ........................................................................ 20 8.3.1 Method description ............................................................................................................................. 20 8.3.2 Preparations of measurements — Equipment ................................................................................. 20 8.3.3 Measurement procedure .................................................................................................................... 21 8.3.4 Correction of measured values ......................................................................................................... 21 8.3.5 Standard method uncertainty ............................................................................................................ 21 8.4 Tracer gas measurement – Method ID 4 ........................................................................................... 21 8.4.1 Method description ............................................................................................................................. 21 8.4.2 Equipment ............................................................................................................................................ 22 8.4.3 Calculation of air flow ......................................................................................................................... 23 8.4.4 Standard measurement uncertainty .................................................................................................. 23 8.4.5 Conditions for homogeneous mixing of tracer gas ......................................................................... 24 SIST EN 16211:2015
EN 16211:2015 (E) 3 9 Methods for measurement of air flows in Supply ATDs (air terminal devices) – ST (Supply (Air) Terminal (Devices)) methods . 25 9.1 Overview of recommended methods . 25 9.2 Measurement of reference pressure – Method ST 1 . 25 9.2.1 Introduction . 25 9.2.2 Equipment . 26 9.2.3 Correction of measured values . 26 9.2.4 Standard method uncertainty . 27 9.3 Measurement with tight bag – Method ST 2 . 27 9.3.1 Method description . 27 9.3.2 Limitations . 27 9.3.3 Equipment . 27 9.3.4 Preparation . 28 9.3.5 Measurement . 28 9.3.6 Correction of measured values . 28 9.3.7 Standard method uncertainty . 28 9.4 Measurements with flow hood – Method ST 3 . 28 9.4.1 Introduction . 28 9.4.2 Equipment . 29 9.4.3 Measurement . 30 9.4.4 Correction of measured values . 31 9.4.5 Standard method uncertainty . 31 10 Methods for Exhaust ATDs (air terminal devices) – ET (Exhaust (Air) Terminal (Devices)) methods . 32 10.1 Overview of recommended methods . 32 10.2 Measurement of reference pressure at exhaust ATD – Method ET 1 . 32 10.2.1 Method description . 32 10.2.2 Limitations . 33 10.2.3 Equipment . 33 10.2.4 Correction of measured values . 33 10.2.5 Standard method uncertainty . 34 10.3 Measurement using a flow hood – Method ET 2 . 34 10.3.1 Introduction . 34 10.3.2 Equipment . 34 10.3.3 Measurement . 35 10.3.4 Correction of measured values . 36 10.3.5 Standard method uncertainty . 36 Annex A (informative)
Uncertainties . 37 A.1 Examples of calculations . 37 A.2 Compound uncertainties . 38 A.3 Example of applications . 38 Bibliography . 39
SIST EN 16211:2015
EN 16211:2015 (E) 4 Foreword This document (EN 16211:2015) has been prepared by Technical Committee CEN/TC 156 “Ventilation for buildings”, the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by January 2016, and conflicting national standards shall be withdrawn at the latest by January 2016. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. Measurement methods which are both correct and easy to use are developed and standardized to enable the commissioning and operational monitoring of air processing installations. Interior climate and air quality can often be improved considerably if the heating and ventilation system is managed in a way that ensures good functioning in the long term. It is thus important that the system is designed and constructed to allow measurement and monitoring to be performed using established and approved methods. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 16211:2015
EN 16211:2015 (E) 5 1 Scope This European Standard specifies simplified methods for the measurement of air flows on site. It provides a description of the air flow methods and how measurements are performed within the margins of stipulated method uncertainties. One measurement method is to take point velocity measurements across a cross-section of a duct to obtain the air flow. This simplified method is an alternative to the method described in ISO 3966 and EN 12599. This European Standard requests certain measurement conditions (length of straight duct and uniform velocity profile) to be met to achieve the stipulated measurement uncertainties for the simplified method. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 12792, Ventilation for buildings — Symbols, terminology and graphical symbols EN 14277, Ventilation for buildings — Air terminal devices — Method for airflow measurement by calibrated sensors in or close to ATD/plenum boxes 3 Terms, definitions and symbols 3.1 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12792 apply. 3.2 Symbols The following symbols are used. SIST EN 16211:2015
EN 16211:2015 (E) 6 Symbol Description SI Unit Symbol Description SI Unit t Time s O Perimeter m
Density kg/m3 p Pressure Pa s Standard conditions air density = 1,2 kg/m3 pd Dynamic pressure Pa r Real density kg/m3 ps Static pressure Pa ¡ tracer Tracer gas density kg/m3 pt Total pressure Pa ¡ duct Duct air density kg/m3 pu Measured pressure Pa A Cross-section Area m2 ûp Differential pressure Pa a, b, c, etc. Dimensions of length mm ûpu Measured differential pressure Pa L Mixing length mm q Air flow m3/s, l/s H Height of duct mm qk Corrected air flow m3/s, l/s W Width of duct mm qs Tracer gas flow m3/s, l/s B Barometric pressure hPa qs¡duct Tracer gas flow at duct temperature m3/s, l/s C Contaminant concentration ppm qstracer Tracer gas flow at rotameter temperature m3/s, l/s Ci Initial tracer gas concentration ppm qt Total air flow m3/s, l/s Cs Tracer gas concentration in stationary condition ppm qu Measured air flow m3/s, l/s D Diameter mm Ç Temperature °C Dh Hydraulic diameter mm Çduct Temperature in duct °C kc coverage factor - Çtracer=Temperature of tracer gas °C k1 Correction factor for density - V Volume m3 k2 Correction factor for duct shape - v Air velocity m/s k Flow factor - vs Standard air velocity m/s L1 Smaller dimension of a rectangular duct mm vr Real air velocity m/s L2 Larger dimension of a rectangular duct mm vm Air velocity, mean value m/s u1 Standard Instrument uncertainty -
u2 Standard Method uncertainty -
u3 Standard Reading uncertainty -
um Standard measurement uncertainty -
Um Expanded measurement uncertainty -
SIST EN 16211:2015
EN 16211:2015 (E) 7 4 Principles and parameters of influence 4.1 Hydraulic diameter The hydraulic diameter is the diameter of a circular duct which causes the same pressure drop at equal air velocity and equal friction coefficient, and is defined by the following formula: Dh = 4 „ A/O
(1) For a rectangular duct this becomes: Dh = 2 „ L1 „ L2 / (L1+ L2)
(2) where
L1 and L2
are the sides of the duct. For a circular duct this becomes: Dh = D
(3) 4.2 Flow disturbances Flow disturbances in ducts result in irregular velocity profiles. NOTE Flow seldom has a symmetrical appearance except after long straight sections. The symmetry is often disturbed by varying resistance, for example after a bend, an area decrease or an area increase. The velocity profile also becomes disturbed by a damper and T-piece as well as before and after a fan. 4.3 Air density,
The density of dry air varies with air pressure and temperature in accordance with the following approximating formula: 27315129310132527315,,,,Bρϑ=⋅⋅+ (4) NOTE The relative humidity of the air (RH) has very little influence on the density of air at room temperature. The density of air at 20 °C and 1 013,25 hPa which is saturated with water vapour is only approximately 1 % less than equivalent dry air. In a low-pressure system it is hardly necessary to consider the influence of static pressure on air density. In a high-pressure system, however, it can be necessary. The calculation is then performed as follows: 00127315129310132527315,,,,,sBpρϑ+⋅=⋅⋅+ (5) 4.4 Dynamic pressure, pd When measuring with a Pitot static tube a dynamic pressure is measured. The dynamic pressure can be used to calculate the air velocity by the use of the following formula: 22dp⋅= (6) SIST EN 16211:2015
EN 16211:2015 (E) 8 4.5 Corrections for air density,
When presenting a measured air flow or velocity, it should be stated if it is the real air flow or the flow converted to standard conditions that is presented. The measurements should correspond to the designed air flow values of the system (real or standard air flow). The methods in this standard present the measurements as real air flow. How to convert between standard and real velocity is described in 4.5. The same conversion is also valid for air flow. The real flow rate of air is as it is at the present temperature and barometric pressure of the air. Standard air flow is used to present the air flow at standard condition of 1 013,25 hPa and 20 °C. A fan transports approximately the same amount of air independent of air density. The amount of standard flow changes with air density. The instrument in use can measure real or standard air flow or it could require calibration conditions to display correctly. Compensate accordingly, especially when used for other conditions than calibration condition or standard conditions of 1 013,25 hPa and 20 °C. The barometric pressure will decrease with altitude and also vary with weather. Convert real flow or velocity to standard flow or velocity by using the following formula: vs = vr „ r / s (7) 5 Sources of errors 5.1 General There are many factors which affect the measurement results which shall be checked in connection with measuring. These factors are for example: a)
calibration equipment, which shall be regularly compared with a traceable norm (calibration unit); b)
calibrated measurement instruments; c)
calibration intervals; d)
examination of instruments’ long term stability; e)
instruments’ temperature or density compensation; f)
random instrument uncertainties; g)
random reading uncertainties; h)
variations in the measured quantity; i)
measurement methods adapted to different installation cases; j)
random uncertainties in measurement methods; k)
measurement methods’ influence on the flow rate; l)
variations in the exterior climate; m)
air flow stability. SIST EN 16211:2015
EN 16211:2015 (E) 9 Certain sources of error are difficult to manipulate, others can be reduced or even eliminated. Errors in given data input can be the result of measurements which have been affected by system errors or temporary disturbances. Errors in measurement data can be divided into: • gross errors, which can happen as a result of the human factor and should be avoided to comply with this standard; • systematic errors; • random errors. 5.2 Systematic errors According to the definition, systematic errors occur if the individual measurement values deviate in the same direction from the “true” value or if they vary in a regular fashion. The result of measurements where systematic errors occur can appear as in Figure 1.
Key 1 systematic Error X time Y value Figure 1 — Explanation of systematic error The circles represent measured numbers which lie randomly spread around the true value and which according to the definition are thus free from systematic errors. The crosses represent results of measurements where the measured numbers lie too high, for example as a result of an uncalibrated measuring instrument being used. This error can easily be rectified by calibrating the instrument and determining a correction. The following applies to a correction: Correction = (estimate of true value) – (read value) or (Read value) + (correction) = estimate of true value Estimates of true values are also often called measured values. To make corrections it is recommended to add a correction value (positive or negative) instead of multiplying with a correction factor. Calibration is a part of the determination of the systematic errors of an instrument, which allows the understanding of the calibration uncertainty, to eventually set up the instrument or correct the measurements and by its repetition to assess the drift uncertainty. SIST EN 16211:2015
EN 16211:2015 (E) 10 An instrument shall always be able to give a correct measured value. This means that calibration shall take place at regular time intervals. It is recommended that electronic instruments used for pressure, flow and velocity measurements are calibrated regularly according to their drift to obtain the uncertainty required. The instrument and other equipment that influence the measurement result (e.g. the bag in the tight bag measuring method) should be calibrated using a method with a (known) low uncertainty, traceable to international calibration standards. Calibration tables where corrections, or alternatively the real value, are evident should be used. 5.3 Random errors Even if systematic errors are successfully eliminated, repeated measurements of the same quantity cannot produce identical results despite the measurements being made thoroughly. This type of error is usually defined as a result of chance and is called uncertainty. This means that the size and character of the uncertainty cannot be accounted for in advance. There are several possible sources of random uncertainties, e.g. reading uncertainties, instrument uncertainties, method uncertainties, problem of repeatability due to the operator, variation of the environmental conditions, etc. In general, the random uncertainties can be reduced by increasing the number of measured points or by increasing the time of measurement thanks to instruments with mean value function. The random uncertainties due to the reading, the instrument and the method are discussed in more detail in Clause 6. 6 Measurement uncertainty 6.1 Overall measurement uncertainty The overall measurement uncertainty should be presented as expanded measurement uncertainty with a coverage probability of approximately 95 %. See 6.5. and the Example in Annex A. When calculating uncertainty using Formula (8) the uncertainties shall all have the same coverage probability of approximately 68 %. The measurement standard uncertainty, um, is calculated using the following formula: um = (u21 + u22 + u23)½
(8) where
u1, u2 and u3
are random standard uncertainties with a coverage probability of approximately 68 %; u1 is the standard instrument uncertainty, such as hysteresis, temperature compensation, drift, etc. The instrument uncertainty is normal distributed; u2 is the standard method uncertainty, resulting from deviations from the calibration method for the measurement method. In this type are also included deviations from the calibration curve for series-produced measurement devices, dampers or terminals with in-built measurement outlets. The method uncertainty is normal distributed; u3 is the standard reading uncertainty. The reading uncertainty is rectangular distributed for digital instruments. SIST EN 16211:2015
EN 16211:2015 (E) 11 6.2 Standard instrument uncertainty, u1 Even after correcting a read value or a measured mean value with regards to different influences, there still remain random uncertainties in measurements. Instrument uncertainty includes calibration uncertainty and uncertainty from the instrument itself, such as hysteresis, temperature compensation, drift, etc. Information on this uncertainty shall be supplied by the instrument manufacturer and it is important to check that the coverage probability of approximately 68 % is used. The user shall make an estimate of the standard instrument uncertainty that also includes hysteresis, drift, environmental influence, etc. Some instruments have an upper and lower uncertainty value (limit) and the uncertainty can in this case be judged to be rectangular distributed: 31valueu= (9) Corrections are known errors and not included in the instrument uncertainty. Correct the measu
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Lüftung von Gebäuden - Luftvolumenstrommessung in Lüftungssystemen - VerfahrenSystèmes de ventilation pour les bâtiments - Mesurages de débit d'air dans les systèmes de ventilation - MéthodesVentilation for buildings - Measurement of air flows on site - Methods91.140.30VLVWHPLVentilation and air-conditioningICS:Ta slovenski standard je istoveten z:FprEN 16211kSIST FprEN 16211:2014en,fr,de01-november-2014kSIST FprEN 16211:2014SLOVENSKI
STANDARD
kSIST FprEN 16211:2014
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
FINAL DRAFT
FprEN 16211
September 2014 ICS 17.120.10; 91.140.30 English Version
Ventilation for buildings - Measurement of air flows on site - Methods
Systèmes de ventilation pour les bâtiments - Mesurages de débit d'air dans les systèmes de ventilation - Méthodes
Lüftung von Gebäuden - Luftvolumenstrommessung in Lüftungssystemen - Verfahren This draft European Standard is submitted to CEN members for unique acceptance procedure. It has been drawn up by the Technical Committee CEN/TC 156.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2014 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. FprEN 16211:2014 EkSIST FprEN 16211:2014
FprEN 16211:2014 (E) 2 Contents Page Foreword . 4 1 Scope . 5 2 Normative references . 5 3 Symbols and definitions . 5 4 Principles and parameters of influence . 6 4.1 Hydraulic diameter . 6 4.2 Flow disturbances . 7 4.3 Air density,
.......................................................................................................................................... 7 4.4 Dynamic pressure, pd ........................................................................................................................... 7 4.5 Corrections for air density,
............................................................................................................... 7 5 Sources of errors .................................................................................................................................. 8 5.1 General ................................................................................................................................................... 8 5.2 Systematic errors .................................................................................................................................. 9 5.3 Random errors ..................................................................................................................................... 10 6 Measurement uncertainty ................................................................................................................... 10 6.1 Overall measurement uncertainty ..................................................................................................... 10 6.2 Standard instrument uncertainty, u1 ................................................................................................. 11 6.3 Standard method uncertainty, u2 ....................................................................................................... 11 6.4 Standard reading uncertainty, u3 ....................................................................................................... 12 6.5 Expanded measurement uncertainty, Um ......................................................................................... 12 7 Measurement requirement ................................................................................................................. 12 7.1 Method requirements and corrections ............................................................................................. 12 7.2 7.2 Measurements using a manometer ............................................................................................. 12 7.3 Measurements using an anemometer ............................................................................................... 13 7.4 Measurements using Pitot static tube .............................................................................................. 13 7.5 Measuring temperature and barometric pressure ........................................................................... 13 7.6 Mean value calculation of measurement signal ............................................................................... 14 8 Methods for measurement of air flows in ducts – ID (In Duct) methods ....................................... 14 8.1 Overview of recommended methods ................................................................................................ 14 8.2 Point velocity measurements using a Pitot static tube – (method ID 1) or an anemometer (method ID 2) ................................................................................................................. 14 8.2.1 Method description ............................................................................................................................. 14 8.2.2 Preparations to be made at the site of measurement ..................................................................... 16 8.2.3 Measurement procedure .................................................................................................................... 19 8.2.4 Corrections of measured values and calculation of air flow .......................................................... 19 8.2.5 Standard method uncertainty ............................................................................................................ 21 8.3 Fixed devices for flow measurement – method ID 3 ....................................................................... 21 8.3.1 Method description ............................................................................................................................. 21 8.3.2 Preparations of measurements ......................................................................................................... 21 8.3.3 Measurement procedure .................................................................................................................... 21 8.3.4 Correction of measured values ......................................................................................................... 22 8.3.5 Standard method uncertainty ............................................................................................................ 22 kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 3 8.4 Tracer gas measurement – method ID 4 . 22 8.4.1 Method description . 22 8.4.2 Equipment . 23 8.4.3 Calculation of air flow . 24 8.4.4 Standard measurement uncertainty . 24 8.4.5 Conditions for homogeneous mixing of tracer gas . 25 9 Methods for Supply ATDs (air terminal devices) – ST (Supply (Air) Terminal (Devices)) methods . 26 9.1 Overview of recommended methods . 26 9.2 Measurement of reference pressure – method ST 1 . 26 9.2.1 Introduction . 26 9.2.2 Equipment . 28 9.2.3 Correction of measured values . 28 9.2.4 Standard method uncertainty . 28 9.3 Measurement with tight bag – method ST 2 . 28 9.3.1 Method description . 28 9.3.2 Limitations . 29 9.3.3 Equipment . 29 9.3.4 Preparation . 29 9.3.5 Measurement . 29 9.3.6 Correction of measured values . 30 9.3.7 Standard method uncertainty . 30 9.4 Measurements with flow hood – method ST 3 . 30 9.4.1 Introduction . 30 9.4.2 Equipment . 31 9.4.3 Measurement . 33 9.4.4 Correction of measured values . 33 9.4.5 Standard method uncertainty . 33 10 Methods for Exhaust ATDs (air terminal devices) – ET (Exhaust (Air) Terminal (Devices)) methods . 34 10.1 Overview of recommended methods . 34 10.2 Measurement of reference pressure at exhaust ATD – method ET 1 . 34 10.2.1 Method description . 34 10.2.2 Limitations . 35 10.2.3 Equipment . 35 10.2.4 Correction of measured values . 35 10.2.5 Standard method uncertainty . 36 10.3 Measurement using a flow hood – method ET 2 . 36 10.3.1 Introduction . 36 10.3.2 Equipment . 36 10.3.3 Measurement . 38 10.3.4 Correction of measured values . 38 10.3.5 Standard method uncertainty . 38 Annex A (Informative) Uncertainties . 39 A.1 Examples of calculations . 39 A.2 Compound uncertainties . 40 A.3 Example of applications . 40 Bibliography . 42
kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 4 Foreword This document (FprEN 16211:2014) has been prepared by Technical Committee CEN/TC 156 “Ventilation for buildings”, the secretariat of which is held by BSI. This document is currently submitted to the Unique Acceptance Procedure. Measurement methods which are both correct and easy to use are developed and standardized to enable the commissioning and operational monitoring of air processing installations. Interior climate and air quality can often be improved considerably if the heating and ventilation system is managed in a way that ensures good functioning in the long term. It is thus important that the system is designed and constructed to allow measurement and monitoring to be performed using established and approved methods. kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 5 1 Scope This European Standard specifies simplified methods for the measurement of air flows on site. It provides a description of the air flow methods and how measurements are performed within the margins of stipulated method uncertainties. One measurement method is to take point velocity measurements across a cross-section of a duct to obtain the air flow. This simplified method is an alternative to the method described in ISO 3966 and EN 12599. This European Standard requests certain measurement conditions (length of straight duct and uniform velocity profile) to be met to achieve the stipulated measurement uncertainties for the simplified method. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 12792, Ventilation for buildings - Symbols, terminology and graphical symbols EN 14277, Ventilation for buildings - Air terminal devices - Method for airflow measurement by calibrated sensors in or close to ATD/plenum boxes 3 Symbols and definitions For the purposes of this European Standard, the terms and definitions of EN 12792 apply. The following symbols are used in the report. Symbol Description SI Unit Symbol Description SI Unit t Time s O Perimeter m
Density kg/m3 p Pressure Pa s Standard conditions air density = 1,2 kg/m3 pd Dynamic pressure Pa r Real density kg/m3 ps Static pressure Pa × tracer Tracer gas density kg/m3 pt Total pressure Pa × duct Duct air density kg/m3 pu Measured pressure Pa A Cross-section Area m2 ûp Differential pressure Pa a,b,c. Dimensions of length mm ûpu Measured differential pressure Pa L Mixing length mm q Air flow m3/s, l/s H Height of duct mm qk Corrected air flow m3/s, l/s kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 6 W Width of duct mm qs Tracer gas flow m3/s, l/s B Barometric pressure hPa qs×duct Tracer gas flow at duct temperature m3/s, l/s C Contaminant concentration ppm qstracer Tracer gas flow at rotameter temperature m3/s, l/s Ci Initial tracer gas concentration ppm qt Total air flow m3/s, l/s Cs Tracer gas concentration in stationary condition ppm qu Measured air flow m3/s, l/s D Diameter mm × Temperature °C Dh Hydraulic diameter mm ×duct Temperature in duct °C kc coverage factor - ×tracer=Temperature of tracer gas °C k1 Correction factor for density - V=Volume m3 k2 Correction factor for duct shape - v=Air velocity m/s k Flow factor - vs Standard air velocity m/s L1 Smaller dimension of a rectangular duct mm vr Real air velocity m/s L2
Larger dimension of a rectangular duct mm vm Air velocity, mean value m/s u1 Standard Instrument uncertainty -
u2 Standard Method uncertainty -
u3 Standard Reading uncertainty -
um
Standard measurement uncertainty -
Um Expanded measurement uncertainty -
4 Principles and parameters of influence 4.1 Hydraulic diameter The hydraulic diameter is the diameter of a circular duct which will cause the same pressure drop at equal air velocity and equal friction coefficient, and is defined by the following formula: Dh = 4 „ A/O
(1) kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 7 For a rectangular duct this becomes: Dh = 2 „ L1 „ L2 / (L1+ L2)
(2) where L1 and L2 are the sides of the duct. For a circular duct this becomes: Dh = D
(3) 4.2 Flow disturbances Flow disturbances in ducts result in irregular velocity profiles. NOTE Flow seldom has a symmetrical appearance except after long straight sections. The symmetry is often disturbed by varying resistance, for example after a bend, an area decrease or an area increase. The velocity profile will also become disturbed by a damper and T-piece as well as before and after a fan. 4.3 Air density,
The density of dry air varies with air pressure and temperature in accordance with the following approximating formula: ϑρ+⋅⋅=2732731013293,1B
(4) NOTE The relative humidity of the air (RH) has very little influence on the density of air at room temperature. The density of air at 20 °C and 1013 hPa which is saturated with water vapour is only approximately 1 % less than equivalent dry air. In a low-pressure system it is hardly necessary to consider the influence of static pressure on air density. In a high-pressure system, however, it can be necessary. The calculation is then performed as follows: ϑρ+⋅⋅+⋅=273273101301,0293,1spB
(5) 4.4 Dynamic pressure, pd When measuring with a Pitot static tube a dynamic pressure is measured. The dynamic pressure can be used to calculate the air velocity by the use of the following formula: 22vpd⋅=ρ (6) 4.5 Corrections for air density,
When presenting a measured air flow or velocity, it should be stated if it is the real air flow or the flow converted to standard conditions that is presented. The measurements should correspond to the designed kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 8 air flow values of the system (real or standard air flow). The methods in this standard present the measurements as real air flow. This subclause describes how to convert between standard and real velocity. The same conversion is also valid for air flow. The real flow rate of air is as it is at present temperature and barometric pressure. Standard air flow is used to present the air flow at standard condition of 1013 hPa and 20 °C (68 °F). The fan transports approximately the same air flow independent of the air density. The amount of standard flow will change with air density. No corrections for air density are required during the proportional balancing of terminals and branch ducts providing that the entire installation is balanced under the same running conditions. For this reason, heaters in terminals and branch ducts, for example, shall be switched off. The instrument in use can measure real or standard air flow or it could require calibration conditions to display correctly. Compensate accordingly, especially when used for other conditions than calibration condition or standard conditions of 1013 hPa and 20 °C. The barometric pressure will decrease with altitude and also vary with weather. To calculate from real velocity or real air flow to standard velocity or standard air flow use the following formula: vs = vm „ m / s
(7) Heating or cooling devices in the duct between the fan and the place of measurement shall be switched off while measuring air flow or air velocity. 5 Sources of errors 5.1 General There are many factors which affect the measurement results which shall be checked in connection with measuring. Examples of these are: a) Calibration equipment, which shall be regularly compared with a traceable norm (calibration unit); b) Calibrated measurement instruments; c) Calibration intervals; d) Examination of instruments’ long term stability; e) Instruments’ temperature or density compensation; f) Random instrument uncertainties; g) Random reading uncertainties; h) Variations in the measured quantity; kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 9 i) Measurement methods adapted to different installation cases; j) Random uncertainties in measurement methods; k) Measurement methods’ influence on the flow rate; l) Variations in the exterior climate; m) Air flow stability. Certain sources of error are difficult to manipulate, others can be reduced or even eliminated. Errors in given data input can be the result of measurements which have been affected by system errors or temporary disturbances. Errors in measurement data can be divided into: • gross errors, which can happen as a result of the human factor and should be avoided to comply with this standard; • systematic errors; • random errors. 5.2 Systematic errors According to the definition, systematic errors occur if the individual measurement values deviate in the same direction from the “true” value or if they vary in a regular fashion. The result of measurements where systematic errors occur can appear as in Figure 1.
Key 1 Systematic Error X Time Y Value Figure 1- Explanation of systematic error The circles represent measured numbers which lie randomly spread around the true value and which according to the definition are thus free from systematic errors. kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 10 The crosses represent results of measurements where the measured numbers lie too high, for example as a result of an uncalibrated measuring instrument being used. This error can easily be rectified by calibrating the instrument and determining a correction. The following applies to a correction: Correction = (estimate of true value) – (read value) or (Read value) + (correction) = estimate of true value Estimates of true values are also often called measured values. To make corrections it is recommended to add a correction value (positive or negative) instead of multiplying with a correction factor. Calibration is a part of the determination of the systematic errors of an instrument, which allows the understanding of the calibration uncertainty, to eventually set up the instrument or correct the measurements and by its repetition to assess the drift uncertainty. An instrument shall always be able to give a correct measured value. This means that calibration shall take place at regular time intervals. It is recommended that electronic instruments used for pressure, flow and velocity measurements are calibrated regularly according to their drift to obtain the uncertainty required. The instrument and other equipment that influence the measurement result (e.g. The bag in the tight bag measuring method) should be calibrated using a method with a (known) low uncertainty, traceable to international calibration standards. Calibration tables where corrections, or alternatively the real value, are evident should be used. 5.3 Random errors Even if systematic errors are successfully eliminated, repeated measurements of the same quantity cannot produce identical results despite the measurements being made thoroughly. This type of error is usually defined as a result of chance and is called uncertainty. This means that the size and character of the uncertainty cannot be accounted for in advance. There are several possible sources of random uncertainties, e.g. reading uncertainties, instrument uncertainties, method uncertainties, repeatability due to the operator, variation of the environmental conditions, etc. In general, the random uncertainties can be reduced by increasing the number of measured points or by increasing the time of measurement thanks to instruments with mean value function The random uncertainties due to the reading, the instrument and the method are discussed in more detail in Clause 6. 6 Measurement uncertainty 6.1 Overall measurement uncertainty The overall measurement uncertainty should be presented as expanded measurement uncertainty with a coverage probability of approximately 95 %. See 6.5. and the example in Annex A. It is important that when kSIST FprEN 16211:2014
FprEN 16211:2014 (E) 11 calculating uncertainties using formula (8) they shall all have the same coverage probability of approximately 68 %. The measurement standard uncertainty, um, is calculated using the following formula: um = (u21 + u22 + u23)½
(8) where u1, u2 and u3 are random standard uncertainties with a coverage probability of approximately 68 %. u1 = standard instrument uncertainty, such as hysteresis, temperature compensation, drift etc. The instrument uncertainty is normal distributed. u2 = standard method uncertainty, resulting from deviations from the calibration method for the measurement method. In this type are also included deviations from the calibration curve for series-produced measurement devices, dampers or terminals with in-built measurement outlets. The method uncertainty is normal distributed. u3 = standard reading uncertainty. The reading uncertainty is rectangular distributed for digital instruments. 6.2 Standard instrument uncertainty, u1 Even after correcting a read value or a measured mean value with regards to different influences, there still remain random uncertainties in measurements. Instrument uncertainty includes calibration uncertainty and uncertainty from the instrument itself, such as hysteresis, temperature compensation, drift etc. Information on this uncertainty shall be supplied by the instrument manufacturer and it is important to check that the coverage probability of approximately 68 % is used. The user shall make an estimate of the standard instrument uncertainty that also includes hysteresis, drift, environmental influence, etc. Some instruments have an upper and lower uncertainty value (limit) and the uncertainty can in this case be judged to be rectangular distributed:
31valueu=
(9) Corrections are known errors and not included in the instrument uncertainty. Correct the measurement values by using corrections from the calibration certificate. Even after correcting a read value or a measured mean value with regards to different influences, such as corrections, there still remains random uncertainties in measurements. Instrument uncertainty includes calibration uncertainty and uncertainty from the instrument itself, such as hysteresi
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