1、Designation:C68008 Designation: C680 10Standard Practice forEstimate of the Heat Gain or Loss and the SurfaceTemperatures of Insulated Flat, Cylindrical, and SphericalSystems by Use of Computer Programs1This standard is issued under the fixed designation C680; the number immediately following the de
2、signation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides the a
3、lgorithms and calculation methodologies for predicting the heat loss or gain and surfacetemperatures of certain thermal insulation systems that can attain one dimensional, steady- or quasi-steady-state heat transferconditions in field operations.1.2 This practice is based on the assumption that the
4、thermal insulation systems can be well defined in rectangular, cylindricalor spherical coordinate systems and that the insulation systems are composed of homogeneous, uniformly dimensioned materialsthat reduce heat flow between two different temperature conditions.1.3 Qualified personnel familiar wi
5、th insulation-systems design and analysis should resolve the applicability of themethodologies to real systems. The range and quality of the physical and thermal property data of the materials comprising thethermal insulation system limit the calculation accuracy. Persons using this practice must ha
6、ve a knowledge of the practicalapplication of heat transfer theory relating to thermal insulation materials and systems.1.4 The computer program that can be generated from the algorithms and computational methodologies defined in this practiceis described in Section 7 of this practice.The computer p
7、rogram is intended for flat slab, pipe and hollow sphere insulation systems.1.5 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information only and are not considered standard.1.6 Thi
8、s standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2
9、.1 ASTM Standards:2C168 Terminology Relating to Thermal InsulationC177 Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of theGuarded-Hot-Plate ApparatusC335 Test Method for Steady-State Heat Transfer Properties of Pipe InsulationC518 Test Method for S
10、teady-State Thermal Transmission Properties by Means of the Heat Flow Meter ApparatusC585 Practice for Inner and Outer Diameters of Thermal Insulation for Nominal Sizes of Pipe and TubingC1055 Guide for Heated System Surface Conditions that Produce Contact Burn InjuriesC1057 Practice for Determinati
11、on of Skin Contact Temperature from Heated Surfaces Using a Mathematical Model andThermesthesiometer2.2 Other Document:NBS Circular 564 Tables of Thermodynamic and Transport Properties of Air, U.S. Dept of Commerce3. Terminology3.1 DefinitionsFor definitions of terms used in this practice, refer to
12、Terminology C168.3.1.1 thermal insulation systemfor this practice, a thermal insulation system is a system comprised of a single layer or layersof homogeneous, uniformly dimensioned material(s) intended for reduction of heat transfer between two different temperature1This practice is under the juris
13、diction ofASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal Measurement.Current edition approved Aug. 1, 2008. Published September 2008. Originally approved in 1971. Last previous edition approved in 2004 as C680-044. DOI:10.1520/C0680-08.Cur
14、rent edition approved Nov. 1, 2010. Published March 2010. Originally approved in 1971. Last previous edition approved in 2008 as C680 - 08. DOI: 10.1520/C0680-10.2For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of
15、 ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technical
16、ly possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C
17、700, West Conshohocken, PA 19428-2959, United States.conditions. Heat transfer in the system is steady-state. Heat flow for a flat system is normal to the flat surface, and heat flow forcylindrical and spherical systems is radial.3.2 SymbolsThe following symbols are used in the development of the eq
18、uations for this practice. Other symbols will beintroduced and defined in the detailed description of the development.where:h = surface transfer conductance, Btu/(hft2F) (W/(m2K) hiat inside surface; hoat outside surfacek = apparent thermal conductivity, Btuin./(hft2F) (W/(mK)ke= effective thermal c
19、onductivity over a prescribed temperature range, Btuin./(hft2F) (W/(mK)q = heat flux, Btu/(hft2)(W/m2)qp= time rate of heat flow per unit length of pipe, Btu/(hft) (W/m)R = thermal resistance, Fhft2/Btu (Km2/W)r = radius, in. (m); rm+1 rm= thicknesst = local temperature, F (K)ti= inner surface tempe
20、rature of the insulation, F (K)t1= inner surface temperature of the systemto= temperature of ambient fluid and surroundings, F (K)x = distance, in. (m); xm+1 xm= thickness = effective surface emittance between outside surface and the ambient surroundings, dimensionlesss = Stefan-Boltzmann constant,
21、0.1714 3 10-8Btu/(hft2R4) (5.6697 3 10-8W/(m2K4)Ts= absolute surface temperature, R (K)To= absolute surroundings (ambient air if assumed the same) temperature, R (K)Tm=(Ts+ To)/2L = characteristic dimension for horizontal and vertical flat surfaces, and vertical cylindersD = characteristic dimension
22、 for horizontal cylinders and spherescp= specific heat of ambient fluid, Btu/(lbR) (J/(kgK)hc= average convection conductance, Btu/(hft2F) (W/(m2K)kf= thermal conductivity of ambient fluid, Btu/(hftF) (W/(mK)V = free stream velocity of ambient fluid, ft/h (m/s)y = kinematic viscosity of ambient flui
23、d, ft2/h (m2/s)g = acceleration due to gravity, ft/h2(m/s2)b = volumetric thermal expansion coefficient of ambient fluid, R-1(K-1)r = density of ambient fluid, lb/ft3(kg/m3)DT = absolute value of temperature difference between surface and ambient fluid, R (K)Nu = Nusselt number, dimensionlessRa = Ra
24、yleith number, dimensionlessRe = Reynolds number, dimensionlessPr = Prandtl number, dimensionless4. Summary of Practice4.1 The procedures used in this practice are based on standard, steady-state, one dimensional, conduction heat transfer theoryas outlined in textbooks and handbooks, Refs (4,5,20,21
25、,22,30). Heat flux solutions are derived for temperature dependent thermalconductivity in a material. Algorithms and computational methodologies for predicting heat loss or gain of single or multi-layerthermal insulation systems are provided by this practice for implementation in a computer program.
26、 In addition, interested partiescan develop computer programs from the computational procedures for specific applications and for one or more of the threecoordinate systems considered in Section 6.4.1.1 The computer program combines functions of data input, analysis and data output into an easy to u
27、se, interactive computerprogram. By making the program interactive, little training for operators is needed to perform accurate calculations.4.2 The operation of the computer program follows the procedure listed below:4.2.1 Data InputThe computer requests and the operator inputs information that des
28、cribes the system and operatingenvironment. The data includes:4.2.1.1 Analysis identification.4.2.1.2 Date.4.2.1.3 Ambient temperature.4.2.1.4 Surface transfer conductance or ambient wind speed, system surface emittance and system orientation.4.2.1.5 System DescriptionMaterial and thickness for each
29、 layer (define sequence from inside out).4.2.2 AnalysisOnce input data is entered, the program calculates the surface transfer conductances (if not entered directly) andlayer thermal resistances. The program then uses this information to calculate the heat transfer and surface temperature. Theprogra
30、m continues to repeat the analysis using the previous temperature data to update the estimates of layer thermal resistanceuntil the temperatures at each surface repeat within 0.1F between the previous and present temperatures at the various surfacelocations in the system.C680 1024.2.3 Program Output
31、Once convergence of the temperatures is reached, the program prints a table that presents the input data,calculated thermal resistance of the system, heat flux and the inner surface and external surface temperatures.5. Significance and Use5.1 Manufacturers of thermal insulation express the performan
32、ce of their products in charts and tables showing heat gain or lossper unit surface area or unit length of pipe. This data is presented for typical insulation thicknesses, operating temperatures, surfaceorientations (facing up, down, horizontal, vertical), and in the case of pipes, different pipe si
33、zes. The exterior surface temperatureof the insulation is often shown to provide information on personnel protection or surface condensation. However, additionalinformation on effects of wind velocity, jacket emittance, ambient conditions and other influential parameters may also be requiredto prope
34、rly select an insulation system. Due to the large number of combinations of size, temperature, humidity, thickness, jacketproperties, surface emittance, orientation, and ambient conditions, it is not practical to publish data for each possible case, Refs(31,32).5.2 Users of thermal insulation faced
35、with the problem of designing large thermal insulation systems encounter substantialengineering cost to obtain the required information. This cost can be substantially reduced by the use of accurate engineering datatables, or available computer analysis tools, or both. The use of this practice by bo
36、th manufacturers and users of thermal insulationwill provide standardized engineering data of sufficient accuracy for predicting thermal insulation system performance. However,it is important to note that the accuracy of results is extremely dependent on the accuracy of the input data. Certain appli
37、cationsmay need specific data to produce meaningful results.5.3 The use of analysis procedures described in this practice can also apply to designed or existing systems. In the rectangularcoordinate system, Practice C680 can be applied to heat flows normal to flat, horizontal or vertical surfaces fo
38、r all types ofenclosures, such as boilers, furnaces, refrigerated chambers and building envelopes. In the cylindrical coordinate system, PracticeC680 can be applied to radial heat flows for all types of piping circuits. In the spherical coordinate system, Practice C680 can beapplied to radial heat f
39、lows to or from stored fluids such as liquefied natural gas (LNG).5.4 Practice C680 is referenced for use with Guide C1055 and Practice C1057 for burn hazard evaluation for heated surfaces.Infrared inspection, in-situ heat flux measurements, or both are often used in conjunction with Practice C680 t
40、o evaluate insulationsystem performance and durability of operating systems. This type of analysis is often made prior to system upgrades orreplacements.5.5 All porous and non-porous solids of natural or man-made origin have temperature dependent thermal conductivities. Thechange in thermal conducti
41、vity with temperature is different for different materials, and for operation at a relatively smalltemperature difference, an average thermal conductivity may suffice. Thermal insulating materials (k tUwhere a1, a2, a3, b1, b2, b3 are constants, andtLand tUare, respectively, the lower and upperinfle
42、ction points of an S-shaped curveAdditional or different relationships may be used, but the main program must be modified.8. Report8.1 The results of calculations performed in accordance with this practice may be used as design data for specific job conditions,or may be used in general form to repre
43、sent the performance of a particular product or system. When the results will be used forcomparison of performance of similar products, it is recommended that reference be made to the specific constants used in thecalculations. These references should include:8.1.1 Name and other identification of p
44、roducts or components,8.1.2 Identification of the nominal pipe size or surface insulated, and its geometric orientation,8.1.3 The surface temperature of the pipe or surface,8.1.4 The equations and constants selected for the thermal conductivity versus mean temperature relationship,8.1.5 The ambient
45、temperature and humidity, if applicable,8.1.6 The surface transfer conductance and condition of surface heat transfer,8.1.6.1 If obtained from published information, the source and limitations,8.1.6.2 If calculated or measured, the method and significant parameters such as emittance, fluid velocity,
46、 etc.,8.1.7 The resulting outer surface temperature, and8.1.8 The resulting heat loss or gain.8.2 Either tabular or graphical representation of the calculated results may be used. No recommendation is made for the formatin which results are presented.9. Accuracy and Resolution9.1 In many typical com
47、puters normally used, seven significant digits are resident in the computer for calculations.Adjustmentsto this level can be made through the use of “Double Precision;” however, for the intended purpose of this practice, standard levelsof precision are adequate. The formatting of the output results,
48、 however, should be structured to provide a resolution of 0.1 % forthe typical expected levels of heat flux and a resolution of 1F (0.55C) for surface temperatures.FIG. 2 Thermal Conductivity vs. Mean TemperatureC680 1011NOTE 1The term “double precision” should not be confused with ASTM terminology
49、on Precision and Bias.9.2 Many factors influence the accuracy of a calculative procedure used for predicting heat flux results. These factors includeaccuracy of input data and the applicability of the assumptions used in the method for the system under study. The system ofmathematical equations used in this analysis has been accepted as applicable for most systems normally insulated with bulk typeinsulations. Applicability of this practice to systems having irregular shapes, discontinuities and other variations from th
