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1、BRITISH STANDARD BS 4979:1986 Methods for Aerodynamic testing of constant and variable dual or single duct boxes, single duct units and induction boxes for air distribution systems UDC 628.84:697.922.001.42:533.6.08 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:15:50 GMT+00:00 2006, Unco
2、ntrolled Copy, (c) BSI BS 4979:1986 This British Standard, having been prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Committee, was published under the authority of the Board of BSI and comes into effect on 30 April 1986 BSI 10-1999 BS 4979-1 first publish
3、ed December 1973 BS 4979-2 first published July 1974 Combined first revision published April 1986 The following BSI references relate to the work on this standard: Committee reference RHE/2 Draft for comment 84/77503 DC ISBN 0 580 14933 1 Committees responsible for this British Standard The preparat
4、ion of this British Standard was entrusted by the Refrigeration, Heating and Air Conditioning Standards Committee (RHE/-) to Technical Committee RHE/2, upon which the following bodies were represented: Association of Consulting Engineers Building Services Research and Information Association Charter
5、ed Institution of Building Services Engineers Department of Health and Social Security Department of the Environment (Property Services Agency) Department of the Environment (Building Research Establishment) Heating and Ventilating Contractors Association Hevac Association Society of British Gas Ind
6、ustries Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:15:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4979:1986 BSI 10-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3Summ
7、ary of tests2 4Symbols and suffixes2 5Instrumentation3 6Leakage tests4 7Test for flow rate control5 8Boxes with variable rate of air flow at constant inlet pressure7 9Test for flow rate characteristics of single duct units7 10Test for temperature mixing efficiency of dual duct boxes8 11Tests for ind
8、uction boxes9 Figure 1 Leakage test, air supply duct9 Figure 2 Typical air supply arrangement for tests on single duct boxes and/or units12 Figure 3 Typical air supply arrangement for tests on dual duct boxes13 Figure 4 Examples of the determination of “minimum pressure differential”14 Figure 5 Typi
9、cal graph resulting from tests described in 8.415 Figure 6 Typical graph for tests on a single duct unit16 Figure 7 Typical air supply arrangement for mixing efficiency tests showing location of instrumentation17 Figure 8 Mixing efficiency: typical outlet duct arrangement (single outlet)18 Figure 9
10、Mixing efficiency: points of temperature measurement in outlet extension duct of multiple outlet box18 Figure 10 Typical induction box test installation19 Table 1 Symbols3 Table 2 Ranges and accuracies of measurement of air flow meters not employed for determining leakage rate3 Table 3 Ranges and ac
11、curacies of measurement of air flow meters for determining leakage rate3 Table 4 Pressure measuring instruments: range, accuracy and scale intervals4 Table 5 Pressure differentials6 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:15:50 GMT+00:00 20
12、06, Uncontrolled Copy, (c) BSI BS 4979:1986 ii BSI 10-1999 Foreword This revision of BS 4979 has been prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Committee and incorporates in one standard the aerodynamic testing of both constant flow and variable flow r
13、ate assemblies. It supersedes BS 4979-1:1973 and BS 4979-2:1974, which are withdrawn. In preparing this British Standard, account has been taken of current practice in the industry and of the work of ISO/TC 144, Air distribution and air diffusion, in preparing ISO 5220, covering aerodynamic testing
14、and rating of constant and variable dual or single duct boxes and single duct units. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of its
15、elf confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 20, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be
16、indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:15:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4979:1986 BSI 10-19991 1 Scope This British Standard describes methods for the aero-dynamic testing of assemblies suitable for use
17、 with air distribution systems operating at high or low velocity and high or low pressure. The standard describes methods of test for the following: a) leakage; b) flow rate control; c) flow rate characteristics for single duct units; d) temperature mixing efficiency of a dual duct box; e) induced f
18、low rate and secondary air leakage of induction boxes; f) pressure requirement of induction boxes. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard the following definitions apply. 2.1 air dis
19、tribution the transportation of air to and from the treated space or spaces generally by means of ducts 2.2 dual duct box an assembly that includes a mixing section in order to mix two air flows of different conditions in predetermined portions, which are automatically adjusted by control valves, an
20、d means of regulating the air flow at a predetermined value 2.3 single duct box an assembly having one air inlet and means of regulating the air flow rate at a predetermined value. Some single duct boxes have facilities for easily varying the predetermined value 2.4 single duct unit an assembly havi
21、ng one air inlet, the flow rate of which may be adjusted by a manually operated valve 2.5 casing an enclosure normally housing other components and generally made of metal lined with material for thermal insulation and/or acoustic attenuation. Connections are provided for the inlet(s) and outlet(s)
22、2.6 flow rate controller a device mounted within the casing for the purpose of maintaining a constant air flow rate through the casing when the pressure differential between the high and low pressure sides varies within the limits for which the equipment is designed NOTEA flow rate controller normal
23、ly maintains constant air flow rate to within 5 % of the maximum air flow rate of the device from the pressure differential range of about 0.1 kPa to 1.5 kPa (1 mbar to 15 mbar). The three different types of flow rate controller are: a) mechanical constant flow rate controller. Self-actuating and de
24、riving its power from the air stream and not from any external force; b) mechanical variable flow rate controller. The same as a) but with its flow rate value varied by an external signal; c) pneumatic, electric, etc. flow rate controller. A controller deriving its power from an external source. Thi
25、s type of controller can be of either the constant or variable type. 2.7 induction box a variable flow rate assembly in which the secondary air flow from the surrounding space is induced by means of primary air in order to provide a substantially constant output flow rate, the control signal being p
26、rovided by a thermostat or similar device 2.8 mixing section a section for mixing two air streams at different temperatures or humidities, having two inlet ducts with valves controlling the flow rate of air being discharged by each duct into the casing NOTEValves can be operated by electric or pneum
27、atic actuators or by direct system pressure actuation. 2.9 valve a component inserted into air ducts permitting modification of the air resistance of the system and consequently changing the air flow rate and shutting off the air flow completely Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01
28、 09:15:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4979:1986 2 BSI 10-1999 2.10 control valve a component inserted into air ducts permitting modification of the air resistance of the system and consequently controlling the air flow rate and providing shut-off of the air flow 3 Summary of tests
29、3.1 General The tests for each type of equipment are listed in 3.2 to 3.5. 3.2 Dual duct boxes 3.3 Single duct boxes 3.4 Single duct units 3.5 Induction boxes 4 Symbols and suffixes 4.1 Symbols The symbols used in this British Standard are as defined in Table 1. 4.2 Suffixes The suffixes used in thi
30、s British Standard are as follows. a) 1 is the inlet of the unit under test. b) 2 is the outlet of the unit under test. c) c is the cold side. d) h is the hot side. e) u is the measuring point upstream of the flow meter. a) Test for control valve leakage.See 6.1 b) Test for casing leakage.See 6.2 c)
31、 Test for flow rate control (constant or variable).See clause 7 d) Test for temperature mixing.See clause 10 a) Test for control valve leakage.See 6.1 b) Test for casing leakage.See 6.2 c) Test for constant flow rate control. See clause 7 d) Test for variable flow rate control: 1) throughout the ope
32、rating range; 2) if capable of being reduced to zero; 3) if fitted with an inlet valve.See clause 8 a) Test for inlet damper leakage.See 6.1 b) Test for casing leakage.See 6.2 c) Test for flow rate characteristics. See clause 9 a) Tests for leakage.See 11.1 b) Tests for induction flow rate.See 11.2
33、c) Tests for pressure requirements.See 11.3 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:15:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4979:1986 BSI 10-19993 Table 1 Symbols 5 Instrumentation 5.1 Air flow rate measurement 5.1.1 Air flow meters, with the exception of those employed
34、 to determine leakage rate, shall have the ranges and accuracies shown in Table 2. Table 2 Ranges and accuracies of measurement of air flow meters not employed for determining leakage rate 5.1.2 Air flow meters employed to determine leakage rate shall have the ranges and accuracies shown in Table 3.
35、 Table 3 Ranges and accuracies of measurement of air flow meters for determining leakage rate 5.1.3 Leakage flow rates measured by other devices such as variable area flow meters or integrating flow meters of the positive displacement type shall be calibrated in accordance with 5.1.5. SymbolQuantity
36、 Corresponding SI unit Dimensions AInternal cross-sectional area of ductm2L2 DeEquivalent diameter mL pAbsolute static pressurePa M L1 T2 paAtmospheric pressurePa M L2 T2 pd Velocity pressure Pa M L1 T2 prStagnation (or absolute total) pressurePa M L1 T2 psStatic gauge pressure (p pa)Pa M L1 T2 ptTo
37、tal pressure (pr pa)Pa M L1 T2 pFlow meter pressure differencePa M L1 T2 ptConventional total pressure differential for an air density of 1.2 kg/m3 at the inlet to the assembly under testPaM L1 T2 qvVolume rate of air flow at the flow meterm3/sL3 T1 qvLLeakage volume rate of air flow through a close
38、d inlet valve or variable flow rate controller set for zero flowam3/sL3T1 vVelocitym/sLT1 yConventional value of energy loss per unit massJ/kgL2 T2 Air densitykg/m3M L3 Thermodynamic temperatureKG Celsius temperatureCF a Or the appropriate measurable value, in suitable units, relating to the positio
39、nal indication of the control valve, or the setting of the variable air flow rate controller, for electric, system-powered or other types of assembly. 4A - v 2 2 - - RangeAccuracy of measurement m3/s% 0.07 to 72.5 0.007 to 0.075 RangeAccuracy of measurement m3/sm3/s% 0.0185 NOTEAir flow meters compl
40、ying with BS 1042-1.1 and BS 1042-1.2 will satisfy the accuracies given in 5.1.1 and 5.1.2 and do not require calibration. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 09:15:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4979:1986 4 BSI 10-1999 5.1.4 Meters requiring calibration in situ
41、shall be calibrated using the pitot static tube traverse technique described in BS 1042-2.1 for a minimum of five flow rates equally spaced throughout the range of the flow meter. 5.1.5 Flow meters shall be checked at intervals not exceeding 24 months. One of the following test methods shall be empl
42、oyed. a) For flow meters complying with BS 1042-1.1 and BS 1042-1.2, all critical dimensions shall be checked. b) For flow meters initially calibrated in situ, recalibration shall be carried out using the same conditions as used for the initial calibration. c) For flow meters removable from the test
43、 installation, a check shall be made at a minimum of five flow rates equally spaced throughout the range of the flow meter against a flow meter complying with BS 1042-1.1 and BS 1042-1.2. 5.2 Pressure measurement 5.2.1 Total pressure. A pitot tube as described in BS 1042-2.1 shall be used for all me
44、asurements of total pressure at a point in a duct. 5.2.2 Static pressure 5.2.2.1 A pitot static tube as described in BS 1042-2.1 shall be used for all measurements of static pressure at a point in a duct. 5.2.2.2 Static taps as described in BS 1042-2.1 shall be used to measure wall static pressure.
45、5.2.3 Pressure measuring instrumentation 5.2.3.1 Pressure shall be measured with either a pressure transducer as described in BS 4509-1 or a liquid-filled manometer. 5.2.3.2 Pressure measuring instruments shall have the ranges and accuracies shown in Table 4. 5.2.3.3 Pressure measuring instruments s
46、hall have scale intervals not greater than those shown in Table 4. Table 4 Pressure measuring instruments: range, accuracy and scale intervals 5.2.3.4 Pressure measuring instruments shall be recalibrated at intervals not greater than 24 months. 5.3 Temperature measurement Measurement of temperature
47、shall be by means of mercury-in-glass thermometers, resistance thermometers or thermocouples. Instruments shall be graduated or give readings in intervals not greater than 0.5 K and shall be calibrated to an accuracy of 0.25 K. 6 Leakage tests 6.1 Valve leakage 6.1.1 Principle. To measure control va
48、lve leakage or leakage past a variable flow rate controller in the shut-off position under conditions of actual operation with the valve closing against the maximum recommended static pressure conditions. NOTESince small flow rates (substantially zero) exist during the closed valve condition, the fl
49、ow rate means used to measure these small flow rates will have a high pressure loss when the valve is open. This precludes a high pressure in the inlet duct until the valve approaches the closed position. As the valve is closed and the flow rate decreases, the inlet static pressure will increase to approximately the recommended maximum inlet pressure. 6.1.2 Test installation. An air supply duct as shown typically in Figure 1 shall be connected to the inlet of the closed valve and/or control
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