BS-5141-2-1977.pdf

BRITISH STANDARD BS 5141-2: 1977 Specification for Air heating and cooling coils Part 2: Method of testing for rating of heating coils UDC 697.97:697.978.001.4 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 16:23:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5141-2:1977 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 Executive Board on 31 March 1977 © BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference RHE/6 Draft for comment 76/71779 DC ISBN 0 580 09691 2 Cooperating organizations The Refrigeration, Heating and Air Conditioning Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Association of Consulting Engineers* Association of Manufacturers of Domestic Electrical Appliances Boiler and Radiator Manufacturers Association Ltd* British Combustion Equipment Manufacturers Association British Gas Corporation British Mechanical Engineering Confederation British Refrigeration and Air Conditioning Association* Building Services Research and Information Association* Chartered Institution of Building Services* Department of Health and Social Security* Department of the Environment Electricity Supply Industry in England and Wales Engineering Equipment Users Association Heating and Ventilating Contractors Association* HEVAC Association* Institute of Fuel Institute of Refrigeration* Institution of Gas Engineers Lloyds Register of Shipping Manufacturers Association of Radiators and Convectors* Ministry of Defence* National Coal Board Society of British Gas Industries Water-tube Boilermakers Association The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Department of the Environment Building Research Establishment Institute of Domestic Heating Engineers Unit Heater Manufacturers Association Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 16:23:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5141-2:1977 © BSI 11-1999i Contents Page Cooperating organizationsInside front cover Forewordii 1Scope1 2References1 3Object of the test1 4Definitions1 5Nomenclature2 6Instrumentation4 7Air flow leakage test5 8Test apparatus5 9Requirements for rating tests6 10Tests required for establishing a rating6 11General test procedures7 12Test results7 13Basic calculations8 14Heat transfer calculations10 15Pressure drop calculations15 16Accuracy and extrapolation16 Appendix A Procedure for heat transfer calculations17 Appendix B Examples of heat transfer test data calculations17 Appendix C Examples of heating duty calculations19 Appendix D Typical values of thermal conductivity21 Figure 1 Typical arrangement of passes22 Figure 2 Typical arrangement of rows23 Figure 3 Types of fins24 Figure 4 Thermometer pockets25 Figure 5 Multijunction differential thermocouple26 Figure 6 Air sampling tubes26 Figure 7 Inverted tube pattern manometer and piezometer ring27 Figure 8 Apparatus for air flow leakage test28 Figure 9 Typical test duct arrangements29 Figure 10 Air flow mixers30 Figure 11 Open-circuit water system31 Figure 12 Closed-circuit water system31 Figure 13 Steam system32 Figure 14 Efficiency of fins of constant thickness33 Figure 15 Efficiency of fins of constant area for heat flow and of spiral fins34 Figure 16 Example of graph of Ra versus (Ra + Rm) prepared from test data35 Figure 17 Example of graph of Rm versus fa35 Figure 18 Example of water-film heat transfer coefficient for tube with turbulators for inlet water temperatures between 40 °C and 120 °C36 Figure 19 Graph of factor F for corrected logarithmic mean temperature for cross-flow single-pass coils37 Figure 20 Example of graph of Ra as a function of velocity vr37 Figure 21 Correction factor Kw for hydraulic pressure drop38 Table 1 Heat transfer variables for test purposes7 Table 2 Allowed variation from mean value of data7 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 16:23:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5141-2:1977 ii © BSI 11-1999 Foreword This Part of this British Standard has been prepared under the authority of the Refrigeration, Heating and Air Conditioning Standards Committee in response to requests from industry. It constitutes a revision of BS 2619 “Method of test and rating for steam-heated air-heater batteries” and BS 3208 “Methods of test and rating for hot-water air-heater batteries”, which will both be withdrawn. This Part is the second of a series concerned with air heating and cooling coils. Where reference is made to British Standards for which no metric version is available, the appropriate British Standard in imperial units shall be used in conjunction with BS 350. Attention is also drawn to BS 3763. 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 itself 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 38, 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 indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 16:23:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5141-2:1977 © BSI 11-19991 1 Scope This Part of BS 5141 gives a method of testing for rating of duct-mounted air heating coils with hot water or dry saturated steam as the heating medium within the range of variables given in Table 1. 2 References The titles of the publications referred to in this standard are listed on the inside back cover. 3 Object of the tests The object of the tests is to provide a fundamental means of establishing the rating of coils operating in other than test conditions by applying test data obtained from a prototype coil (or coils). 4 Definitions For the purposes of this British Standard the following definitions apply. 4.1 heating coil a water-to-air or steam-to-air heat exchanger of the tubular type, through which air is passed by mechanical means over the external surface, such as is normally connected into a system of ventilation ductwork. The heat exchanger surface considered is of the extended surface, externally finned type 4.2 reference conditions temperature 20 °C, absolute pressure 1.013 bar1), relative humidity 43 %, density 1.200 kg/m3 4.3 rows the number of banks of tubes in the direction of air flow (see Figure 1) 4.4 passes the number of times the water or steam in any one circuit crosses the air flow (see Figure 2) 4.5 similar coils a range of coils having the same a) water/steam tube size, spacing, arrangement (in-line or staggered, see Figure 1) and internal construction; b) water or steam flow geometry, the general method of combining rows and circuits (see Figure 2); c) fin type, construction and spacing (see Figure 3). 4.6 turbulator a device inside a tube to increase heat transfer 1) 1 bar = 105 N/m2 = 100 kPa Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 16:23:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5141-2:1977 2 © BSI 11-1999 5 Nomenclature SymbolDescriptionUnits ADiSurface area of ductwork between inlet samples and centre of coilm2 ADoSurface area of ductwork between outlet sampler and centre of coilm2 AFCoil face aream2 AiCoil internal surface area (nt; di lt 103)m2 AoCoil external surface area (AP + As)m2 APArea of exposed tubesm2 AsTotal surface area of coil fins (both sides); where fin collars are employed, the collar is taken as part of the exposed tube aream2 AtCross-sectional area of coil tube (bore area)m2 BCoil surface area ratio (Ao/Ai) cpaSpecific heat capacity of airkJ/(kg K) cpwSpecific heat capacity of waterkJ/(kg K) cpamSpecific heat capacity of air at mean air temperaturekJ/(kg K) cpwmSpecific heat capacity of water at mean water temperaturekJ/(kg K) diTube internal diametermm doTube external diametermm FFactor for corrected logarithmic mean temperature faAir-side film transfer coefficientW/(m2 K) fvSteam-side film transfer coefficientW/(m2 K) fwWater-side film transfer coefficientW/(m2 K) fwsWater-side film transfer coefficient for smooth bore tubesW/(m2 K) fwtWater-side film transfer coefficient for tubes fitted with turbulatorsW/(m2 K) gAcceleration due to gravitym/s2 KiHeat leakage coefficient for air inlet sectionkW/K KoHeat leakage coefficient for air outlet sectionkW/K KwCorrection factor for hydraulic pressure drop kThermal conductivity of insulating materialW/(m K) ktThermal conductivity of tube wall materialW/(m K) kfThermal conductivity of fin materialW/(m K) lcLength of one complete water circuitm ltLength of each coil water tubem LLatent heat of evaporation of steam at the test steam pressurekJ/kg maAir mass flow ratekg/s mvCondensate mass flow ratekg/s mwWater mass flow ratekg/s ncNumber of circuits ntNumber of tubes in coil nNumber of rows in test coil n½Number of rows in coil under consideration PbBarometric pressurebar Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 16:23:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5141-2:1977 © BSI 11-19993 SymbolDescriptionUnits PviSteam inlet pressure (gauge)bar %pcCoil air pressure dropPa %prCoil air pressure drop corrected to reference densityPa %prn½Coil air pressure drop corrected to reference density for coil of n½ rowsPa %pwHydraulic pressure drop (measured)Pa %pwcHydraulic pressure drop corrected for heat differences between coil inlet and outletPa %pwctHydraulic pressure drop at reference temperaturePa QMean heat transferredkW QaHeat transferred on air sidekW QvHeat transferred on steam sidekW QwHeat transferred on water sidekW ROverall thermal resistancem2 K/W RaThermal resistance of air filmm2 K/W RfFin thermal resistancem2 K/W RmMetal thermal resistancem2 K/W RtTube wall thermal resistancem2 K/W RvThermal resistance of steam film (based on Ao)m2 K/W RwThermal resistance of water film (based on Ao)m2 K/W taAmbient temperature (dry bulb)°C taiInlet air temperature (dry bulb)°C taoOutlet air temperature (dry bulb)°C taic, taoctai and tao corrected for heat losses or gains°C t½aiInlet air temperature (wet bulb)°C t½aoOutlet air temperature (wet bulb)°C tviInlet steam temperature°C tvsDry saturated steam temperature corresponding to steam inlet pressure Pvi (from steam tables)°C twiInlet water temperature°C twoOutlet water temperature°C twmMean water temperature; (twi + two)/2°C %tmCorrected logarithmic mean temperature difference between air and water°C vrAir velocity at coil face at reference conditionm/s vwMean water velocitym/w XbInner radius of finmm XeOuter radius or equivalent radius of finmm YfFin thicknessmm YiThickness of insulating materialmm Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 16:23:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5141-2:1977 4 © BSI 11-1999 6 Instrumentation 6.1 Temperature measurement 6.1.1 The measurement of temperature shall comply with the requirements of BS 1041. If liquid-in-glass thermometers are used, they shall be graduated in intervals not exceeding 0.1 °C, and shall comply with the requirements of BS 593, partial immersion ranges. All temperature-measuring instruments shall be calibrated against an NPL calibrated thermometer to a precision of 0.1 °C. 6.1.2 Water and steam temperatures shall be measured by means of instruments inserted into oil-filled pockets similar to those in Figure 4. 6.1.3 For water temperature differences below 5 °C, it is necessary to take special care and the differential thermocouple system shown in Figure 5 is recommended, together with a separate measurement of inlet water temperature. 6.1.4 The inlet and outlet air temperatures shall be measured by means of the system given in BS 4194 (Appendix D). The measurement system shall be connected to sampling tubes similar to those shown in Figure 6. 6.2 Flow measurement 6.2.1 The measurement of water flow at temperatures up to 95 °C shall preferably be by means of direct weighing (although one of the methods described in BS 1042 may be used). The measurement of water flow at temperatures over 95 °C shall be made by one of the methods described in BS 1042. Greek symbols DescriptionUnits ¾, ¸Parameters defined in 14.1.1.2 ½Surface effectiveness ÌFin efficiency ÔDensitykg/m3 ÔrReference air density (1.2 kg/m3)kg/m3 Suffices aair bbarometric; inner radius of fin ccalculated; circuits; corrected Dduct eouter radius of fin Fface ffin iinlet; insulating; internal mmean; metal oexternal; outlet pexposed tubes; pressure rreference condition(s) ssmooth; surface treference temperature; tube(s); turbulator Ttotal vsteam wwater Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 16:23:29 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5141-2:1977 © BSI 11-19995 When direct weighing is used, the water leaving the test rig shall be collected in vessels of known weight and weighed to an accuracy of 0.1 % over the range of weights used in the test. The weight of each vessel used shall not exceed 50 % of its normal contents. The net weight of each charge shall be recorded by weighing the vessel both after emptying the previous charge and after filling. The vessels shall be covered to prevent loss by evaporation. 6.2.2 The measurement of steam flow shall be be weighing the condensate. The weighing apparatus shall be as described in 6.2.1. 6.2.3 The measurement of air flow shall be as specified in BS 1042-1 or, alternatively, a flow meter shall be used calibrated in situ by the methods given in BS 1042-2. 6.3 Pressure measurement 6.3.1 Side wall tappings for measurement of hydraulic pressure drop shall be fitted adjacent to the coil. The tappings shall be as specified in Figure 7 and shall be connected to form a piezometric ring. An inverted U-tube manometer, similar to that shown in Figure 7, shall be employed for the measurement of hydraulic pressure drop. 6.3.2 Steam pressure gauges shall comply with the requirements of clause 30 a) of BS 1780:1960. They shall be at least 150 mm in diameter and shall have a total scale range not more than three times the measured pressure. For pressures below 0.3 bar (gauge), a liquid manometer is desirable. 6.3.3 Wall static air pressures shall be measured with static taps conforming to the specifications given in BS 1042-2. A minimum of four taps shall be symmetrically dispose