BS-3122-1-1990 ISO-917-1989.pdf

BRITISH STANDARD BS 3122-1: 1990 ISO 917:1989 Refrigerant compressors Part 1: Methods of test for performance Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:31:25 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3122-1:1990 This British Standard, having been prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 31 July 1990 © BSI 12-1999 First published as “Rating and testing of refrigeration compressors” April 1959 First revision March 1977 Second revision July 1990 The following BSI references relate to the work on this standard: Committee reference RHE/4 Draft for comment 87/73247 DC ISBN 0 580 18449 8 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Refrigeration, Heating and Air Conditioning Standards Policy Committee (RHE/-) to Technical Committee RHE/4, upon which the following bodies were represented: British Refrigeration Association Chartered Institution of Building Services Engineers Department of the Environment (Property Services Agency) Heating and Ventilating Contractors Association Institute of Refrigeration Institution of Mechanical Engineers Polytechnic of the South Bank Process Plant Association Retail Consortium Rotating Electrical Machines Association (BEAMA Ltd.) Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:31:25 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3122-1:1990 © BSI 12-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope and field of application1 2References1 3Definitions1 Section 1. Determination of refrigerating capacity and of volumetric efficiency 4General procedure2 5Basic test conditions and deviations3 6Basis of calculations3 7Test methods4 8Method A: Secondary fluid calorimeter5 9Method B: Flooded system refrigerant calorimeter6 10Method C: Dry system refrigerant calorimeter7 11Methods D1 and D2: Refrigerant vapour flowmeter8 12Method F: Refrigerant liquid quantity using a flowmeter9 13Method G: Water-cooled condenser10 14Method J: Refrigerant vapour cooling10 15Method K: Calorimeter in compressor discharge line11 Section 2. Determination of the power, isentropic efficiency and coefficient of performance 16General procedure20 17Determination of the power input20 18Determination of the isentropic efficiency20 19Determination of the coefficient of performance20 Section 3. Reporting of results 20Test report21 Annex A Type and calibration of measuring instruments and accuracy of measurement22 Annex B Symbols used in the text for calculations23 Annex C Estimation of errors25 Figure 1 Method A13 Figure 2 Method B13 Figure 3 Method C14 Figure 4 Circuit diagrams for methods D1 and D215 Figure 5 Method F16 Figure 6 Method G17 Figure 7 Method J18 Figure 8 Method K19 Figure 9 Log p versus h diagram27 Figure 10 Example showing the determination of the errors in the enthalpy values for method G (see Figure 6)29 Table 1 Combinations of tests X and Y4 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:31:25 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3122-1:1990 ii © BSI 12-1999 National foreword This Part of BS 3122 has been prepared under the direction of the Refrigeration, Heating and Air Conditioning Standards Policy Committee and is identical with ISO 917:1989 “Testing of refrigerant compressors” published by the International Organization for Standardization (ISO). It is a full technical revision of BS 3122-1:1977 which is now withdrawn. ISO 917 was produced as a result of international discussion in which the UK took a prominent part. The Technical Committee has reviewed the provisions of ISO 916-1 and ISO 1662, to which reference is made in the text, and has decided that they are acceptable for use in conjunction with this Part of BS 3122. A related British Standard to ISO 1662:1971 is BS 4434:1989 “Specification for safety aspects in the design, construction and installation of refrigerating appliances and systems”. 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. Cross-references International StandardCorresponding British Standard ISO 5167:1980BS 1042 Measurement of fluid flow in closed conduits Section 1.1:1981 Specification for square-edged orifice plates, nozzles and venturi tubes inserted in circular cross section conduits running full (Technically equivalent) ISO 5168:1978BS 5844:1980 Methods of measurement of fluid flow: estimation of uncertainty of a flow-rate measurement (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 30, 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, Wed Nov 29 05:31:25 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3122-1:1990 © BSI 12-19991 1 Scope and field of application The provisions of this International Standard apply only to single-stage refrigerant compressors of the positive-displacement type. Selected test methods are described for the determination of the refrigerating capacity, the power, the isentropic efficiency and the coefficient of performance. These test methods provide results of sufficient accuracy to permit consideration of the suitability of a refrigerant compressor to operate satisfactorily under any set of basic test conditions required for a given refrigeration installation. Attention is drawn in particular to a number of special precautions necessary to reduce testing losses to a minimum. This International Standard applies only to tests carried out at the manufacturers works, or wherever the necessary equipment for testing to the accuracy required can be made available. The types and calibration of measuring instruments and the accuracy of measurement are specified in Annex A, which forms an integral part of this International Standard. The test methods described may also be used as a guide for the testing of other types of refrigerant compressors. NOTETests on complete refrigeration installations are dealt with in ISO 916-1. Annex B and Annex C, which provide additional information, do not form integral parts of this International Standard. 2 References ISO 916-1, Refrigeration systems Test methods Part 1 : Testing of systems for cooling liquids and gases using a positive displacement compressor1). ISO 1662, Refrigerating plants Safety requirements. ISO 5167, Measurement of fluid flow by means of orifice plates, nozzles and Venturi tubes inserted in circular cross-section conduits running full. ISO 5168, Measurement of fluid flow Estimation of uncertainty of a flow-rate measurement. 3 Definitions NOTEA complete list of symbols and units used in the calculations, together with their definitions, is given in Annex B. 3.1 refrigerating capacity of a refrigerant compressor Í0 product of the mass flow rate of refrigerant through the compressor, as derived from the test, and the difference between the specific enthalpy of the refrigerant at the measuring point at the inlet of the compressor and the specific enthalpy of the saturated liquid at the temperature corresponding to the test discharge pressure at the measuring point at the outlet of the compressor 3.2 volumetric efficiency, ½V ratio of the actual volume rate of flow at suction conditions, measured at the position specified in 4.3.2, to the displacement of the compressor 3.3 power input, P power at the compressor shaft for an open compressor or power at the motor terminals for a hermetic motor compressor (or semi-hermetic motor compressor) together with the power absorbed by such ancillaries as are necessary to sustain the operation of the compressor, e.g. oil pump 3.4 isentropic efficiency, ½i ratio of the product of the actual mass flow and the change in isentropic enthalpy across the compressor to the power input 3.5 coefficient of performance, ¼ ratio of the refrigerating capacity to the power input NOTEIt should be made clear in the test report whether the power input referred to is that measured at the compressor shaft or that at the motor terminals. 1) At present at the stage of draft. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:31:25 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3122-1:1990 2 © BSI 12-1999 Section 1. Determination of refrigerating capacity and of volumetric efficiency 4 General procedure 4.1 Method of determination of refrigerating capacity and volumetric efficiency The determination of the refrigerating capacity of a compressor comprises a) the evaluation of the mass flow rate of the refrigerant, obtained for each test method used by means of an apparatus which is inserted in the outer part of the test circuit, between the outlet and the inlet of the compressor, as described in clauses 8 to 15, and b) the determination from recognized tables, of the thermodynamic properties of the refrigerant, of the specific enthalpy of the refrigerant in the saturated-liquid state at the compressor discharge pressure and its specific enthalpy at the compressor suction pressure and temperature. The volumetric efficiency is determined using the equation given in 6.7.2. During the test, the refrigerant compressor should be furnished with all auxiliary equipment and accessories necessary for its satisfactory operation in normal use. 4.2 Tests All tests shall comprise two test methods, a test X and a test Y, which shall be carried out simultaneously. 4.2.1 Test Y shall, wherever possible, be a different type of test than test X, so that its results are obtained independently from those of test X. 4.2.2 The values of the estimated errors for the refrigerating capacity shall be calculated for test X (sÍ0X) and for the selected test Y (sÍ0Y) (see Annex C). 4.2.3 Specifications for test X and test Y and for their possible combinations are given in clause 7. 4.2.4 The results of test X and test Y for the refrigerating capacity shall be accepted provided that they correlate within ± 4 % (see Annex C). 4.2.5 For results valid in accordance with 4.2.4, the refrigerating capacity and the volumetric efficiency shall be taken as the mean of the test X and test Y results. The values of the estimated errors (sfX and sfY) for test X and test Y, calculated as described in 4.2.2 and Annex C, shall be used to determine the total estimated error (to one significant figure) for the valid result using the formula (sfX2 + sfY2)/21/2. 4.3 General rules In order to ensure that the results obtained are within the required limits of accuracy, it is essential to observe the following rules, and the instructions given in the note to 4.3.4 should be taken into account. 4.3.1 All instruments and auxiliary measuring apparatus shall be correctly located in relation to the compressor inlet and outlet, and shall be calibrated against master instruments of certified accuracy and adjusted if necessary to give readings within the limits of accuracy prescribed in Annex A. 4.3.2 The pressure and temperature at the suction inlet to the compressor shall be measured at the same point which shall be located on a straight run of pipeline, at a distance of (or as close as possible to) eight times the pipe diameter, ahead of the point of entry or of the stop valve, if one is fitted. The diameter of the pipe shall be consistent with that of the flange on the compressor for a length of at least sixteen times the pipe diameter. 4.3.3 The pressure and temperature at the discharge outlet of the compressor shall be measured at the same point which shall be located on a straight run of pipeline, at a distance not less than eight times the pipe diameter after the point of outlet or the stop valve, if one is fitted. The diameter of the pipe shall be consistent with that of the flange on the compressor for a length of at least sixteen times the pipe diameter. 4.3.4 The correct refrigerant and lubricating oil charges shall be present in the circulation system. Efficient oil separators shall be fitted in the discharge line of the compressor unless it is shown by measurement that the oil pumping rate is less than 1,5 % of the refrigerant mass flow rate. If a separator is used, arrangements shall be made to return the separated oil direct to the compressor lubricating system. If the compressor is designed for use on a normal oil returning circuit, the oil from the separator shall be returned to the suction line between the measuring apparatus and the compressor suction connection. No refrigerant shall be added during the test, and no oil shall be added to enclosed crank cases which communicate with the refrigerant circuit. During the whole of the test run, the circuit shall contain only the refrigerant and the lubricating oil in such conditions of purity that normal operation in the continuous running of the compressor will be assured and the precision of the test measurements will not be affected within the agreed tolerances. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 05:31:25 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3122-1:1990 © BSI 12-19993 NOTEThe complete elimination of liquid refrigerant and lubricating oil would be difficult to achieve. However, the error arising from these factors at the inlet of the compressor can generally be reduced to such an extent as to be negligible by a) ensuring that the refrigerant vapour is sufficiently superheated at the inlet to the compressor (for this purpose a suction superheater may be required, and any heat supplied to it from an external source should be duly recorded), and b) providing an efficient oil separator on the discharge line of the compressor. In general, a correction for the effect of the lubricating oil is not necessary if the oil content of the oil-liquid refrigerant mixture is such as to cause an error not exceeding 1,5 % of the refrigerating capacity. 4.3.5 The system shall be tested for freedom from leaks of refrigerant and oil. The absence of non-condensable gases shall be confirmed by appropriate means. 4.3.6 The system shall be protected against abnormal air currents. 4.4 Test period 4.4.1 The tests specified refer exclusively to a refrigerant compressor operating continuously under conditions such that, for a specified period, fluctuations in all the factors likely to affect the results of a test remain between the limits prescribed and show no definite tendency to move outside these limits. These conditions are termed steady working conditions. 4.4.2 After the com