1、Designation: C680 10C680 14Standard 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 designation in
2、dicates 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 algorithms an
3、d 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 thermal insu
4、lation 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 with insulatio
5、n-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 have a knowled
6、ge 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 program is in
7、tended 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 This standard d
8、oes 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 Documents2.1 ASTM Stan
9、dards: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 Steady-State
10、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 Determination of Skin C
11、ontact 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 Definitions:3.1.1 For definitions of terms used in this practice, refer to Termi
12、nology C168.1 This practice is under the jurisdiction ofASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal Measurement.Current edition approved Nov. 1, 2010Sept. 1, 2014. Published March 2010December 2014. Originally approved in 1971. Last pre
13、vious edition approved in 20082010as C680 - 08.C680 - 10. DOI: 10.1520/C0680-10.10.1520/C0680-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Docume
14、nt Summary page on the ASTM website.This 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 technically possible to adequately depict all changes accurately, ASTM rec
15、ommends 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 C700, West Conshohocken, PA 19428-2959. United States13.1.2 therma
16、l 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 temperatureconditions. Heat transfer in the system is steady-state. Heat
17、flow for a flat system is normal to the flat surface, and heat flow forcylindrical and spherical systems is radial.3.2 Symbols:3.2.1 The following symbols are used in the development of the equations for this practice. Other symbols will be introducedand defined in the detailed description of the de
18、velopment.where:h = surface transfer conductance, Btu/(hft2F) (W/(m2K) hi at inside surface; ho at outside surfacek = apparent thermal conductivity, Btuin./(hft2F) (W/(mK)ke = effective thermal conductivity over a prescribed temperature range, Btuin./(hft2F) (W/(mK)q = heat flux, Btu/(hft2) (W/m2)qp
19、 = 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 temperature of the insulation, F (K)t1 = inner surface temperature of the systemto = temperature of ambien
20、t fluid and surroundings, F (K)x = distance, in. (m); xm+1 xm = thickness = effective surface emittance between outside surface and the ambient surroundings, dimensionless = Stefan-Boltzmann constant, 0.1714 10-8 Btu/(hft2R4) (5.6697 10-8 W/(m2K4)Ts = absolute surface temperature, R (K)To = absolute
21、 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 for horizontal cylinders and spherescp = specific heat of ambient fluid, Btu/(lbR) (J/(kgK)hc =
22、 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) = kinematic viscosity of ambient fluid, ft2/h (m2/s)g = acceleration due to gravity, ft/h2 (ms2) = volumetric thermal expansion coe
23、fficient of ambient fluid, R-1 (K-1) = density of ambient fluid, lb/ft3 (kgm3)T = absolute value of temperature difference between surface and ambient fluid, R (K)Nu = Nusselt number, dimensionlessRa = Rayleith number, dimensionlessRe = Reynolds number, dimensionlessPr = Prandtl number, dimensionles
24、s4. 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 (1,2,3,4,5,6). Heat flux solutions are derived for temperature dependent thermalconductivity in a material
25、. 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. In addition, interested partiescan develop computer programs from the computational procedures for
26、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 use, interactive computerprogram. By making the program interactive, little training for operators is
27、 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 describes the system and operatingenvironment. The data includes:4.2.1.1 Analysis identification.4.2.1.
28、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 layer (define sequence from inside out).C680 1424.2.2 AnalysisOnce input data is entered, the progr
29、am 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. Theprogram continues to repeat the analysis using the previous temperature data to update the estimat
30、es 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.4.2.3 Program OutputOnce convergence of the temperatures is reached, the program prints a table that presents the input
31、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 performance of their products in charts and tables showing heat gain or lossper unit surface area or unit len
32、gth 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 sizes. The exterior surface temperatureof the insulation is often shown to provide information on pers
33、onnel protection or surface condensation. However, additionalinformation on effects of wind velocity, jacket emittance, ambient conditions and other influential parameters may also be requiredto properly select an insulation system. Due to the large number of combinations of size, temperature, humid
34、ity, thickness, jacketproperties, surface emittance, orientation, and ambient conditions, it is not practical to publish data for each possible case, Refs(7,8).5.2 Users of thermal insulation faced with the problem of designing large thermal insulation systems encounter substantialengineering cost t
35、o 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 both manufacturers and users of thermal insulationwill provide standardized engineering data of sufficie
36、nt 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 applicationsmay need specific data to produce meaningful results.5.3 The use of analysis procedures describ
37、ed 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 for all types ofenclosures, such as boilers, furnaces, refrigerated chambers and building envelopes. In
38、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 flows to or from stored fluids such as liquefied natural gas (LNG).5.4 Practice C680 is referenced for
39、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 to evaluate insulationsystem performance and durability of operating systems. This type of analysis is
40、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 conductivity with temperature is different for different materials, and for operation at a relatively smalltem
41、perature difference, an average thermal conductivity may suffice. Thermal insulating materials (k tUwhere a1, a2, a3, b1, b2, b3 are constants, andtL and tU are, respectively, the lower and upperinflection points of an S-shaped curveAdditional or different relationships may be used, but the main pro
42、gram 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 represent the performance of a particular product or system. When the results will be used forcomparison
43、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 products or components,8.1.2 Identification of the nominal pipe size or surface insulated, and its ge
44、ometric 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 temperature and humidity, if applicable,8.1.6 The surface transfer conductance and condition of surf
45、ace 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, etc.,8.1.7 The resulting outer surface temperature, and8.1.8 The resulting heat loss or gain.8.2 Ei
46、ther tabular or graphical representation of the calculated results may be used. No recommendation is made for the formatin which results are presented.C680 14119. Accuracy and Resolution9.1 In many typical computers normally used, seven significant digits are resident in the computer for calculation
47、s.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, however, should be structured to provide a resolution of 0.1 % forthe typical expected lev
48、els of heat flux and a resolution of 1F (0.55C) for surface temperatures.NOTE 1The term “double precision” should not be confused with ASTM terminology on Precision and Bias.9.2 Many factors influence the accuracy of a calculative procedure used for predicting heat flux results. These factors includ
49、eaccuracy 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 theone-dimensional heat transfer assumptions should be handled on an individual basis by professional engineers familiar with thosesystems.
