1、ASME PTC 12.5-2000 Single Phase Heat Exchangers 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 inquiries concerning interpret
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8、can Society of Mechanical Engineers Three Park Avenue, New York, NY 10016-5990 Copyright Q 2001 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Primed in U.S.A. FOREWORD Performance tests of industrial heat exchangers are often conducted to compare test results with manufacturers
9、 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 operating processes was not c
10、onducted 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 factors which affect perfo
11、rmance. 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 methodology including measur
12、ement 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 was with the intent of satis
13、fying 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 subjected to a thorough re
14、view 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 Performance Test Codes on
15、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 information is based on that
16、 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 III of PTC 1 and has read them prior to applying this Code. ASME Performance Test Codes provide test procedures which yield results of the
17、 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 methods, and uncertaint
18、y 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 results to contractua
19、l 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 determine or interpr
20、et how such comparisons shall be made. Approved by Letter Ballot #95-l and BPTC Administrative Meeting of March 13-l 4, 1995. PERSONNEL OF PERFORMANCE TEST CODE COMMITTEE NO. 12.5 ON SINGLE PHASE HEAT EXCHANGERS OFFICERS Thomas G. Lestina, Chair Benjamin H. Scott, Vice Chair George Osolsobe, Secreta
21、ry COMMITTEE 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. Single-phase fluid streams, including liquid-to-liq- uid, g
22、as-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 perform- ance parameters
23、determined in accordance with this Code are expected to lie within the band described by the overall uncertainty interval stated below. Performance Parameter Note (VI Expected Uncertainty Note W Overall Heat Transfer Coefficient, U* Heat Transfer Rate, Q* Nozzle-to-Nozzle Pressure Loss, dP,* NOTES:
24、(1) At reference conditions. (2) Based on 95% confidence. *3-10% *3-l 0% *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 characteristic of sin
25、gle-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 Series on Instruments and
26、 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 inlet temperature. co
27、ld stream temperature change: the difference be- tween the outlet and inlet temperatures of the cold stream (t, - tj). design conditions: performance conditions upon which the design of the heat exchanger was based. effective mean temperature difference: the log mean temperature difference corrected
28、 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 cold fluid (see p
29、ara. 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 of the hot st
30、ream ( Tj - TO). 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. (D.1.) and (D.2). Except where otherwise noted, the log mean temperature difference for c
31、ountercurrent 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 fall within t
32、he 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 operating conditions
33、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 OY,X = (b) obtain a heat balance betw
34、een hot and cold fluids streams and confirm steady state conditions; (c) perform calculations to predict performance at reference conditions; (d) analyze uncertainty of test measurements and performance calculations. 3.1 .l Accurate Measurements. The measurement uncertainty of the hot and cold strea
35、m flow rates, inlet temperatures, outlet temperatures, and pressures shall be appropriate to ensure that the uncertainties of U*, Q*, and AP,_,* are within the range specified in para. 1.3. Consideration for instrument calibration, spatial variation, installation practices, data acquisi- tion method
36、s, process variations and random instru- ment error is needed to ensure that the measurements conform to this requirement (see para. 5.2.3). As a benchmark, the calibration uncertainty for tempera- ture measurements shall be less than +0.2”F (kO.1 “C), the total flow measurement uncertainty shall be
37、 less than -1-5% of measured flow, and the total pressure measurement uncertainty shall be less than *l% of reading (see paras. 4.4, 4.5, and 4.7). Lower uncertainties may be needed to meet the uncertainty range for U*, Q*, and AP,+* specified in para. 1.3. Measurement of outlet temperatures with th
38、e appropriate uncertainty requires careful examination of spatial variation since outlet temperatures are not uniform for most heat exchangers (see para. 4.2.4). 3.1.2 Heat Balance. Steady state conditions shall be maintained during a test. The cold stream heat transfer rate shall be calculated base
39、d on the cold stream measurements, and the hot stream heat trans- fer rate shall be calculated based on the hot stream measurements. The differences in the cold stream heat transfer rate and hot stream heat transfer rate shall be assessed to confirm a heat balance is maintained as specified in para.
40、 5.3.1.4. 3.1.3 Performance Calculation. A performance pa- rameter (overall heat transfer coefficient, heat transfer rate, or pressure loss) shall be calculated based on average test measurements and adjusted to reference conditions. Reference conditions represent design or baseline conditions and a
41、re typically different than test conditions. The adjustments of overall heat trans- fer coefficient, heat transfer rate and pressure loss are expressed as follows: 1 L+ 4u u*=(J (3.1) Q* = QQ (3.2) AP,_,* = (b) flow measurements of the hot and cold streams; (c) pressure measurements; (d) specific he
42、ats of the hot and cold streams; 13 ASME PTC 12.5-2000 (e) heat transfer coefficients streams; of the hot and cold (0 idealizations used in the calculation of mean temperature difference (such as variable heat transfer coefficient along flow length and nonuniform temper- ature distribution); and (g)
43、 adjustment of pressure loss from test to refer- ence conditions including contributions attributed to flow measurements, roughness (i.e., friction factor), and pressure loss correlations. The uncertainty of the temperature, flow and pres- sure measurements shall be propagated through all calculatio
44、ns for overall heat transfer coefficient, heat transfer rate, and pressure loss including any interme- diate calculations of mean temperature difference. The test uncertainty varies for different heat ex- changer designs and operating conditions. The ex- pected uncertainties in para. 1.3 are for a r
45、ange of typical single phase heat exchanger applications based on 95% confidence. For overall heat transfer coefficient and heat transfer rate, an uncertainty of *SoA is considered to be the best attainable based on idealized conditions where the temperature mea- surement uncertainty is +0.2”F, flow
46、 measurement uncertainty is within (c) Heat exchanger operating conditions including constraints on test conditions; (d) Definition of reference conditions (four of the six process variables); (e) System alignment and steady state criteria; (0 Cleanliness condition of heat exchanger; (g, Scope and c
47、riteria for equipment inspections prior to test; (h) Identification of known damage or deficiency (e.g., plugged tubes); (i) Schedule for performing pre-test inspections, calibrations, preliminary testing, and performance testing; (i) Number, use, installation, and location of tem- perature, pressur
48、e, and flow sensors; (k) Instrument accuracy, calibration methods, stor- age and handling practices; (I) Configuration of data acquisition system includ- ing type of equipment used and frequency of measure- ments, number of test runs, and duration of test runs; (m) Acceptance of test results includi
49、ng acceptable deviations; (n) Heat exchanger mechanical data (see Table 3.1);l (0) Methods f o calculation and associated uncer- tainty for heat exchanger thermal model parameters including all thermal physical properties (see Table 3.2). 3.2.2 Definition of Reference Conditions. Test con- ditions cannot be controlled to the extent that a specified set of conditions can be duplicated. To allow comparison of measured performance to the desired performance, the results must be adjusted to specified reference conditions. Adjustment of the results to a set of reference conditions is also n
