1、AN AMERICAN NATIONAL STANDARD Single Phase Heat Exchangers ASME PTC 12.5-2000 Date of Issuance: December 31, 2001 This Standard will be revised when the Society approves the issuance of a new edition. There will be no addenda issued to ASME PTC 12.5-2000. Please note: ASME issues written replies to
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8、 of the publisher. The American Society of Mechanical Engineers Three Park Avenue, New York, NY 10016-5990 Copyright 2001 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in U.S.A. FOREWORD Performance tests of industrial heat exchangers are often conducted to compare test
9、 results with manufacturers rating data, to evaluate the cause(s) of degradation, to verify regulatory compliance, or to assess process improvements. All tests have associated costs. Those costs can be great if the test results are inconclusive. Historically, testing heat exchanger performance in op
10、erating processes was not conducted according to standard, acceptable methods; therefore, the results were inconsistent. Many of the unacceptable results have been attributed to small deviations in test conditions and measurement prac tices. In other cases, analysis of the data did not consider all
11、factors which affect performance. As industry implements improvements to reduce costs and increase output, performance margins of process streams tend to be reduced. The need for accurate performance test methods is increasing to meet the commercial demand. A single consistent test philosophy and me
12、thodology including measurement and analysis techniques for delivery of accurate and repeatable heat exchanger test data would provide a foundation to assess performance. Such a test standard has wide applicability in the power, food-processing, chemical and petroleum industries, among others. It wa
13、s with the intent of satisfying these industry needs that the Board on Performance Test Codes (BPTC) authorized the formation of the PTC 12.5 Committee to explore the development of the present Code. The PTC 12.5 Committee began its deliberations late in 1994. An early version of the draft code was
14、subjected to a thorough review by industry, including members of the BPTC. Comments were incorporated in the version which was approved by the Committee on 11 August 1999. PTC 12.5-2000 on Single Phase Heat Exchangers was then approved as a Standard practice of the Society by action of the Board on
15、Performance Test Codes on 8 May 2000. It was approved as an American National Standard by the ANSI Board of Standards Review on September 26, 2000. (Revised 26 September 2000) iii NOTICE All Performance Test Codes MUST adhere to the requirements of PTC 1, GENERAL INSTRUCTIONS. The following informat
16、ion is based on that document and is included here for emphasis and for the convenience of the user of this Code. It is expected that the Code user is fully cognizant of Parts I and Ill of PTC 1 and has read them prior to applying this Code. ASME Performance Test Codes provide test procedures which
17、yield results of the highest level of accuracy consistent with the best engineering knowledge and practice currently available. They were developed by balanced committees representing all concerned interests. They specify procedures, instrumentation, equipment operating requirements, calculation met
18、hods, and uncertainty analysis. When tests are run in accordance with this Code, the test results themselves, without adjustment for uncertainty, yield the best available indication of the actual performance of the tested equipment. ASME Performance Test Codes do not specify means to compare those r
19、esults to contractual guarantees. Therefore, it is recommended that the parties to a commercial test agree before starting the test and preferably before signing the contract on the method to be used for comparing the test results to the contractual guarantees. It is beyond the scope of any Code to
20、determine or interpret how such comparisons shall be made. Approved by Letter Ballot #95-1 and BPTC Administrative Meeting of March 13-14, 1995. iv PERSONNEL OF PERFORMANCE TEST CODE COMMITTEE NO. 12.5 ON SINGLE PHASE HEAT EXCHANGERS OFFICERS Thomas G. Lestina, Chair Benjamin H. Scott, Vice Chair Ge
21、orge Osolsobe, Secretary COMMITIEE PERSONNEL Fernando J. Aguirre, Heat Transfer Research, Inc. Kenneth J. Bell, Oklahoma State University Charles F. Bowman, Chuck Bowman Associates William H. Closser, Jr., C (b) Plate-frame; (c) Plate-fin; (d) Tube-in-plate fin. 3 Single-phase fluid streams, includi
22、ng liquid-to-liq uid, gas-to-liquid, and gas-to-gas are included. Ex cluded from this Code are heat exchangers used in condensation, vaporization, fired, direct contact, non-newtonian fluid, and more than two-fluid appli cations. 1.3 EXPECTED UNCERTAINTY The values of the overall uncertainty of perf
23、orm ance parameters determined in accordance with this Code are expected to lie within the band described by the overall uncertainty interval stated below. Performance Parameter Note (1 ) Overall Heat Transfer Coefficient, U* Heat Transfer Rate, Q* Nozzle-to-Nozzle Pressure Loss, .tlP,.,n* NOTES: (1
24、) At reference conditions. (2 Based on 95% confidence. Expected Uncertainty Note (2) 3-10% 3-10% 3-12% This page intentionally left blank.SINGLE PHASE HEAT EXCHANGERS ASME PTC 12.5-2000 SECTION 2 - DEFINITIONS AND DESCRIPTION OF TERMS 2.1 TERMS In this Section, only those terms are defined which are
25、 characteristic of single-phase heat exchangers and the requirements for testing them. For the definition of all other physical terms, or the description of instru ments used in this Code, reference is made to the litera ture and particularly to PTC 2, Definitions and Values, and to the PTC 19 Serie
26、s on Instruments and Apparatus. calibration uncertainty: the uncertainty attributed to instrument calibration practices including the instru ment linearity, hysteresis, and repeatability along with the accuracy of the calibration equipment. cold stream: flow stream with the lower heat ex changer inl
27、et temperature. cold stream temperature change: the difference be tween the outlet and inlet temperatures of the cold stream (t0 - t;). design conditions: performance conditions upon which the design of the heat exchanger was based. effective mean temperature difference: the log mean temperature dif
28、ference corrected for deviations from true countercurrent flow conditions. fouling: accumulated foreign material such as corro sion products or any other deposits on the heat transfer surface. heat transfer area: the area of the wall surface over which heat is transferred from the hot fluid to the c
29、old fluid (see para. 3.2.3). heat transfer rate: the amount of heat transferred from the hot stream to the cold stream per unit of time. hot stream: flow stream with the higher heat ex changer inlet temperature. hot stream temperature change: the difference be tween the inlet and outlet temperatures
30、 of the hot stream (T; - T0). hydraulic resistance: resistance to flow due to form losses and friction in the heat exchanger. 5 log mean temperature difference: the logarithmic average temperature difference defined by Eqs. (0.1.) and (0.2). Except where otherwise noted, the log mean temperature dif
31、ference for countercurrent flow is used in this Code. overall heat transfer coefficient: the heat transfer rate per unit of heat transfer area per unit of effective mean temperature difference. overlap of error bar: that portion of the uncertainty interval in which the true value must lie and still
32、fall within the uncertainty interval of two or more measurements of the same value. pressure loss: loss of total pressure across the heat exchanger due to hydraulic resistance. process variables: hot and cold stream inlet and outlet temperatures and flow rates. reference conditions: process operatin
33、g conditions defined by fixing four of the six variables (see para. 3.2 .2). sensitivity coefficient: the change in the calculated result due to an incremental change in a contributing factor. For an arbitrary result Y and contributing factor x, the sensitivity coefficient is EY,x = ()Y!8x. temperat
34、ure difference: the difference between a hot stream temperature and the corresponding cold stream temperature. test run: a complete set of performance data that will allow analysis of heat exchanger capability per this Code. total measurement uncertainty: the uncertainty in measurement due to the co
35、mbined effects of all systematic error (or bias) and random error associated with instrument calibration, spatial variation, installa tion practices, data acquisition, and process varia tions (see para. 5.2.3). uncertainty: the uncertainty is the interval about the measurement or result that contain
36、s the true value for a given confidence level (see ASME PTC 19.1 ). ASME PTC 12.5-2000 SINGLE PHASE HEAT EXCHANGERS 2.2 LETTER SYMBOLS Symbols used in multiple sections of this Code are described here. Symbols which are not in this list are defined in the text immediately following their usage. The
37、equations in this Code are based on any consistent set of units. The units in the following list are one example of consistent units both for U.S. Customary and 51/metric systems. Symbol A Ai,pipe Ao, pipe boataAcq bEMTO, mixing di EMTD F Definition Reference heat transfer area (see para. 3.2.3) Col
38、d side heat transfer area Hot side heat transfer area Flow area of inlet pipe Flow area of outlet pipe Heat transfer area of wall Systematic uncertainty attributed to calibration Systematic uncertainty attributed to data acquisition Systematic uncertainty attributed to a non-uniform temperature dist
39、ribution over a flow cross section Systematic uncertainty attributed to a variable heat transfer coefficient along the flow length Systematic uncertainty attributed to instrument installation practices Systematic uncertainty attributed to spatial variation Constant pressure specific heat Constant pr
40、essure specific heat of the cold stream Constant pressure specific heat of the hot stream Inside tube diameter Outside tube diameter Outside diameter of unfinned portion of tube Effective mean temperature difference Configuration correction factor for deviation from true countercurrent flow (see App
41、endix D) 6 Units U.S. Customary Sl ft2 m2 ft2 m2 ft2 m2 ft2 m2 ft2 m2 ft2 1m2 Units of measurement parameter Units of measurement parameter Units of measurement parameter Units of measurement parameter Btu/(lbm-F) U/(kg-C) Btu/(lbm-F) U/(kg-C) Btu/(lbm-F) U/(kg-C) ft m ft m ft m Of (DC) Dimensionles
42、s SINGLE PHASE HEAT EXCHANGERS Symbol g h k Ki, pipe Ko, pipe f L LMTD m Nu Pr Q Oave Definition Gravitational acceleration Units conversion constant, 4.17(1 08) in U.S. Customary units, 1 in metric units Calculated hydraulic resistance = tJP/m11 (see para. 5.4.7) Individual heat transfer coefficien
43、t Cold side heat transfer coefficient Hot side heat transfer coefficient Thermal conductivity Thermal conductivity of wall Loss coefficient of inlet pipe and fittings Loss coefficient of outlet pipe and fittings Effective length of tubes between tubesheets Length of tubes Log mean temperature differ
44、ence Mass flow rate Cold stream mass flow rate Hot stream mass flow rate Number of tubes Nusselt number = hd!k Measured upstream pressure Prandtl Number = c,lk Heat transfer rate for the heat exchanger Average heat transfer rate for a test run based on the hot and cold stream heat transfer rates Ave
45、rage heat transfer rate at reference conditions based on multiple test runs Cold stream heat transfer rate 7 U.S. Customary ft/h,-2 lbm-ft/lbf-h,-2 Btu/(hr-ft2-F) Btu/(hr-ft2-F) Btu/(hr-ft2-F) Dimensionless Dimension less ft ft lbm/hr lbm/hr lbm/hr Dimensionless Dimensionless lbf/ft2 absolute Dimens
46、ion less Btu/hr Btu/hr Btu/hr Btu/hr ASME PTC 12.5-2000 Units Sl Pa(s/kgtl (m (m kgls kglsl kglsl Pal absolute W W W W ASME PTC 12.5-2000 Symbol Re Rr rr T; t; u Ucp Definition Hot stream heat transfer rate Thermal resistance of the cold stream film based on the heat transfer rate Q, Rc = 1 I(T)chcA
47、c) Reynolds number = pVdl J.1-Thermal resistance of the hot stream film based on the heat transfer rate Q, Rh = 1 I(T)hhhAh) Thermal resistance of fouling on both the hot and cold stream sides based on the heat transfer rate Q Average thermal resistance due to fouling on both the hot and cold stream
48、 sides based on the heat transfer rate per unit area, rr = Rr A Thermal resistance of the wall separating the hot and cold stream based on the heat transfer rate Q Hot stream inlet temperature Hot stream outlet temperature Cold stream inlet temperature Cold stream outlet temperature Wall temperature
49、 Student t Overall heat transfer coefficient Uncertainty of specific heat (see para. 5.3.1.1) Uncertainty of average thermal resistance of film based on heat transfer rate per unit area Uncertainty of the difference in average thermal resistance of film between reference and test conditions based on heat transfer rate per unit area Uncertainty interval of hydraulic resistance ratio greater than the best estimate see Eq. (5.19) 8 SINGLE PHASE HEAT EXCHANGERS U.S. Customary Btu/hr Dimensionless Dimensionless Btu/(hr-ft2-F) (hr-ft2-F)/
