1、BRITISH STANDARD BS 4856-2: 1975 Methods for Testing and rating fan coil units, unit heaters and unit coolers Part 2: Thermal and volumetric performance for cooling duties: without additional ducting UDC 697.97.001.42 + 697.356.001.42BS4856-2:1975 This British Standard, having been approved by Refri
2、geration,Heating and AirConditioning Industry Standards Committee, was published under the authority ofthe Executive Board on 30September1975 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference RHE/6 Draft for comment 73/34046 DC ISBN 0 580 08903 7 Co-op
3、erating organizations The Refrigeration Heating and Air Conditioning Industry 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
4、Engineers* Association of Manufacturers of Domestic Electrical Appliances Boiler and Radiator Manufacturers Association* British Gas Corporation British Mechanical Engineering Confederation British Oil and Gas Firing Equipment Manufacturers Association British Refrigeration and Air Conditioning Asso
5、ciation* 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* Heating and Ventilating Research Association* HEVAC Association* Institute of Fue
6、l Institute of Refrigeration* Institution of Gas Engineers Institution of Heating and Ventilating 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 Associati
7、on 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 Estab
8、lishment Greater London Council Oil Companies Materials Associations Unit Heater Manufacturers Association Amendments issued since publication Amd. No. Date of issue CommentsBS4856-2:1975 BSI 12-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3
9、 Definitions 1 4 Nomenclature 2 5 Objects of the tests 3 6 Limitations of accuracy of the test method 3 7 Testing conditions 3 8 Steady state conditions 3 9 Instrumentation 4 10 Test equipment 5 11 Air temperature measurements 5 12 Primary fluid measurements 6 13 Test facility 6 14 Thermal rating: r
10、esults and analysis 6 15 Air volume flow rate measurements 7 16 Enclosure sweating tests and condensate disposal tests 8 17 Electrical rating test 8 18 Psychrometric test method 8 19 Air volume flow measurement for psychrometric test method 9 20 Rating tests (psychrometric test method) 10 21 Example
11、s (psychrometric test method) 12 Figure 1 Thermometer pockets 14 Figure 2 Multi-junction differential thermocouple 15 Figure 3 Inverted U-tube manometer 15 Figure 4 Shields for thermometer and thermocouple 16 Figure 5 Air sampling tubes 17 Figure 6 Air flow chamber 19 Figure 7 Chilled fluid test equ
12、ipment 20 Figure 8 Piezometer ring 21 Figure 9 Extended air flow chamber 22 Figure 10 Room temperature measuring stations 24 Figure 11 Inlet temperature measurement 25 Figure 12 Water temperature correction factor K w 26 Figure 13 Determination of air flow rate 26 Figure 14 Example of recirculation
13、correction factor 27 Figure 15 Heat transference 28 Figure 16 Rating example 29 Figure 17 Primary fluid plus metal thermal resistance 29 Table 1 Steady state conditions 4 Table 2 Enclosure swear test conditions 8 Table 3 Sensible cooling test series 10 Table 4 Sensible and latent cooling test series
14、 11 Table 5 Calculation of sensible cooling duty at room temperature of25 C 12 Table 6 Results for example of sensible and latent cooling 12 Publications referred to Inside back coverBS4856-2:1975 ii BSI 12-1999 Foreword Part 2 of this British Standard has been prepared under the authority of the Re
15、frigeration, Heating and Air Conditioning Industry Standards Committee in response to requests from industry. The committee acknowledge their debt to the Heating and Ventilating Research Association for the Associations work in formulating the psychrometric method of testing which appears in this st
16、andard. Part 1 of this standard covers units for heating duties, without additional ducting, and it is intended that further Parts will deal with units fitted with ducting, and acoustic aspects of testing. Two different methods of thermal test are given in this Part, a gravimetric method and a psych
17、rometric method. If variations in condensate flow rate are within the requirements specified (seeclause8) it is considered that the gravimetric method provides the data required. If this proviso is not met then the psychrometric test method is used. The unit cooler psychrometric tests given in this
18、Part are very similar to those given for unit heaters in Part1, with the exception of the latent cooling tests. Two approaches to the latent loading problem are presented, one a fixed point test which will yield accurate comparative data and a second test series for general rating purposes. The latt
19、er is based on the bypass factor method (see for example: Carrier, Cherne, Grant and Roverts. Modern air conditioning, heating and ventilating). Where reference is made to British Standards for which no metric version is available then the appropriate British Standard in imperial units should be use
20、d in conjunction with BS350 “Conversion factors and tables”; attention is also drawn to BS3763 “The International System of units (SI)” and PD5686 “The use of SI units”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsi
21、ble 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, pages1 to 30, an inside back cover and a back cover. This standard has been
22、updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS4856-2:1975 BSI 12-1999 1 1 Scope Part 2 of this British Standard deals with methods of carrying out thermal and volumetric tests of unit coolers without a
23、dditional ducting. The unit coolers operate with or without condensation on the coils. The unit coolers are of the type used for cooling and dehumidifying purposes under frost-free conditions of operation. The cooling medium used is water or other heat transfer fluid (excluding volatile refrigerants
24、). The range of approximate air volume flow rates is between25 10 3 m 3 /s and5m 3 /s. The tests are to be carried out on units in an essentially clean condition. This standard applies to units having operating temperatures of primary fluid within the range 0 C to27 C. The primary fluids used are; w
25、ater, brine, glycol, heat transfer fluid. The minimum temperature differential (see14.2) of the primary fluid under test is3 C. There is no restriction on the mounting of these units for testing provided that they are tested whilst mounted in a way representative of their intended use. The standard
26、specifies performance characteristics that are to be obtained from a unit. Although the requirements of the methods for individual tests may be followed to determine the performance of a unit at one specified set of conditions, where the performance at conditions other than those of the actual test
27、are to be stated the full schedule of tests specified in the standard have to be made. 2 References The titles of the British Standards referred to in this standard are listed on the inside back cover. 3 Definitions For the purposes of this Part of this British Standard the following definitions app
28、ly. 3.1 unit cooler or fan coil unit a fluid-to-air heat exchanger apparatus through which air is passed by an electrically powered fan. This unit may or may not contain filters 3.2 reference air conditions (cooling) temperature20 C, absolute pressure1.013 bar 1) , relative humidity43%, and density1
29、.2kg/m 3 3.3 room discharge air flow of a unit rate of flow of air from the room-side outlet of the unit 3.4 room intake air flow of a unit rate of flow of air into the unit from the conditioned space 3.5 local recirculation flow of conditioned air directly from the room-side outlet to the room-side
30、 inlet of the unit 3.6 bypass factor (B) it is assumed, for calculation purposes, that only a portion of the total air passing over the heat-exchanger surface (the coil) contacts the surface; the remaining air is assumed to bypass the surface and to leave unchanged from its entering condition 3.7 ne
31、t total room cooling effect (of a unit) total available capacity of the unit for removing sensible and latent heat from the space to be conditioned 3.8 room dehumidifying effect available capacity of the unit for removing moisture from the space to be conditioned 3.9 net room sensible cooling effect
32、 available capacity of the unit for removing sensible heat from the space to be conditioned 3.10 total heat transferred the total heat transferred (Q T ) is assumed to be related to the thermal resistances of the unit, thus: Q T= %t m /(SR a + R wm ) where the symbols are as given in clause4 NOTEBy
33、rearranging this equation it can be seen that for a given air and water flow rate, a graph of %t m /Q Tversus S will yield a straight line of slope R aand will intercept R wm . Once R ais known, it is possible to calculate the bypass factor and consequently to obtain the coil performance for various
34、 inlet conditions. 1) 1 bar=10 5N/m 2 =100 kPa. The bypass factor B = (t ao t B )/(t a t B ) = (h ao h B )/(h ai h B ) = exp 1/(R aCp am a ) where the symbols are as given in clause4.BS4856-2:1975 2 BSI 12-1999 3.11 rated voltage(s) voltage(s) shown on the nameplate of the unit 3.12 rated frequency
35、(s) frequency(s) shown on the nameplate of the unit 4 Nomenclature For the purposes of this Part of this British Standard the following nomenclature applies. Symbol Quantity Unit A Free area of units cooled air outlet m 3 B Bypass factor c pa Specific heat capacity of air kJ/(kg K) c p Specific heat
36、 capacity of primary fluid kJ/(kg K) c pw Specific heat capacity of water kJ/(kg K) E Power dissipated in the room by the unit kW h ai Inlet air enthalpy kJ/kg (dry air) h ao Outlet air enthalpy kJ/kg (dry air) h B Enthalpy of saturated air at temperature t B kJ/kg (dry air) %h Difference of air ent
37、halpy across coil kJ/kg (dry air) K w Temperature correction factor L Latent heat of evaporation kJ/kg M Total mass flow of primary fluid kg M r Net weight of condensate formed during test kg m a Air mass flow rate kg/s m r Condensate mass flow rate kg/s m w Primary fluid mass flow rate kg/s %p m Pr
38、imary fluid pressure drop Pa %p t Primary fluid pressure dropat reference temperature (8 C) Pa Q Net total room cooling effect kW Q, Q 2 Total heat transferred when connected to air flow chamber kW Q D Room dehumidifying effect kW Q S Net room sensible cooling effect kW Q T Total heat transferred (p
39、rimary fluid side) kW Q Ta Total heat transferred (airside) kW Q TR Total heat transferred with no recirculation kW q f Primary fluid volume flow rate m 3 /s q fr Primary fluid volume flow rateat reference temperature(8 C) m 3 /s q m Air volume flow rate at measured conditions m 3 /s q r Air volume
40、flow rate at reference conditions m 3 /s R Overall appliance thermal resistance C/kW R a Air side appliance thermal resistance C/kW R m Mean overall appliance thermal resistance C/kW R wm Primary fluid plus coil metal appliance thermal resistance C/kW a Air density at measured conditions kg/m 3 F Ai
41、r density at the temperature and absolute pressure of the flow meter kg/m 3 f Primary fluid density at mean liquid temperature kg/m 3 fr Primary fluid density atreference temperature (98 C) kg/m 3 r Air density at reference condition kg/m 3 S Ratio of sensible heat to total heat T Duration of test s
42、 t a Unit inlet air temperature (dry bulb) C t ao Unit outlet air temperature (dry bulb) C t B Apparatus dew point temperature C t i Inlet primary fluid temperature C t o Outlet primary fluid temperature C Symbol Quantity UnitBS4856-2:1975 BSI 12-1999 3 5 Objects of the tests The object of the tests
43、 is to establish the performance of the unit over a specified range of primary fluid conditions and room temperatures. The test procedures set out in this standard are for the determination of. a) the net total room cooling effect; b) the room dehumidifying effect, c) the net room sensible cooling e
44、ffect; d) the primary fluid mass flow rate and pressure drop; e) the nominal air flow rate, f) freedom from sweating on the unit enclosure or casework; g) adequate condensate disposal 6 Limits of accuracy of the test method The test method, including the instrumentation, is suitable for obtaining re
45、sults within the following limits of accuracy: 7 Testing conditions 7.1 Primary fluid. The unit shall be tested at a minimum of three primary fluid inlet temperatures. The selected temperatures shall cover the range of duty over which the unit is to be rated. 7.2 Room air conditions. The room air te
46、mperature (dry bulb) range shall be chosen within the limits5 C to30 C, depending on the intended use of the unit. The room air (wet bulb) temperatures shall be then chosen to cover the related range corresponding to the intended use of the unit. 7.3 Primary fluid flow rate. For duties to be quoted
47、over a range of primary fluid flow rates, tests shall be carried out at a minimum of three primary fluid flow rates spaced approximately equally to cover the range over which the unit is to be rated. 7.4 Electrical supply conditions. The tests shall be carried out at the rated voltage and frequency
48、of the unit. 7.5 Nominal rating. In the absence of a specified set of conditions, where a single nominal rating figure is required, the total cooling capacity under the following conditions shall be used: 7.6 Complete description of unit performance. Where a complete description of the units perform
49、ance over a range of conditions is required, it will be necessary to vary the primary fluid temperature, the room air conditions and the primary fluid flow rate so that a family of the required performance curves may be made. The quantities shown on the four curves will be Q S , Q Dplotted against, respectively, t R , t R , t iandm w . 8 Steady state conditions Tests shall be carried out under steady state conditions and these are considered to be established if, during
