1.1 该实践提供了用于预测某些隔热系统的热损失或热增益以及表面温度的算法和计算方法，这些隔热系统可以在现场操作中获得一维、稳态或准稳态传热条件。 1.2 这种做法是基于这样的假设，即隔热系统可以在矩形、圆柱形或球形坐标系中很好地定义，并且隔热系统由均匀、尺寸均匀的材料组成，这些材料可以减少两种不同温度条件之间的热流。 1.3 熟悉绝缘系统设计和分析的合格人员应解决该方法对实际系统的适用性问题。构成隔热系统的材料的物理和热性能数据的范围和质量限制了计算精度。使用此实践的人员必须了解与隔热材料和系统相关的传热理论的实际应用。 1.4 第节描述了可以根据本实践中定义的算法和计算方法生成的计算机程序 7. 这种做法。该计算机程序适用于平板、管道和空心球保温系统。 1.5 以英寸磅为单位的数值应视为标准。括号中给出的值是国际单位制的数学转换，仅供参考，不被视为标准。 1.6 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 隔热材料制造商用图表和表格表示其产品的性能，显示单位表面积或单位管道长度的热增益或热损失。这些数据是针对典型的隔热层厚度、工作温度、表面方向（面朝上、面朝下、水平、垂直）以及不同管道尺寸的管道提供的。隔热层的外表面温度通常显示为提供有关人员保护或表面冷凝的信息。然而，也可能需要关于风速、导管架发射率、环境条件和其他有影响的参数的影响的额外信息来正确选择隔热系统。由于尺寸、温度、湿度、厚度、护套特性、表面发射率、取向和环境条件的大量组合，公布每种可能情况的数据是不现实的 ( 7. ， 8. ) 。 5.2 热绝缘用户面临设计大型热绝缘系统的问题，为了获得所需信息，会遇到大量的工程成本。通过使用准确的工程数据表或可用的计算机分析工具，或两者都可以大大降低这一成本。隔热材料制造商和用户使用这种做法将为预测隔热系统性能提供足够准确的标准化工程数据。然而，重要的是要注意，结果的准确性极其依赖于输入数据的准确性。某些应用程序可能需要特定的数据才能产生有意义的结果。 5.3 本实践中描述的分析程序的使用也可以应用于已设计或现有的系统。在直角坐标系中，练习 C680 可应用于所有类型外壳（如锅炉、熔炉、冷藏室和建筑围护结构）的垂直于平面、水平或垂直表面的热流。 在圆柱坐标系中，练习 C680 可以应用于所有类型管道回路的径向热流。在球面坐标系中，练习 C680 可以应用于流向或来自诸如液化天然气（LNG）的储存流体的径向热流。 5.4 实践 C680 被引用以与指南一起使用 C1055 和实践 C1057 用于加热表面的燃烧危险评估。红外检测、现场热通量测量或两者都经常与实践结合使用 C680 以评估绝缘系统性能和操作系统的耐久性。这种类型的分析通常在系统升级或更换之前进行。 5.5 所有天然或人造来源的多孔和非多孔固体都具有与温度相关的热导率。热导率随温度的变化对于不同的材料是不同的，并且对于在相对较小的温差下操作，平均热导率可能就足够了。 隔热材料( k <0.85｛Btu·in｝/｛h·ft 2. ·°F}）是多孔固体，其中热传递模式包括通过固体和气体部分基质的串联和并联传导，孔隙或间隙表面之间的辐射热交换，以及通过非不透明表面的传输，以及在较小程度上，气体部分内部和之间的对流。在存在辐射和对流传热模式的情况下，测量值应称为表观热导率，如术语所述 C168 造成这种情况的主要原因是，纯热传导的前提不再有效，因为其他传热模式遵循不同的定律。此外，固体基质内的气体、液体或固体的相变或其他机制的相变将提供热导率的温度依赖性的突然变化。例如，绝热材料的气体部分在极冷条件下的冷凝将对绝热材料的表观热导率产生极其重要的影响。 考虑到所有这些，在算术平均温度下使用单个热导率值将提供不太准确的预测，特别是当桥接发生强烈温度依赖性的温度区域时。 5.6 绝缘系统的表面温度和热损失或增益的计算在数学上很复杂，由于该方法的迭代性质，计算机可以最好地处理计算。大多数隔热材料的生产商和消费者都可以随时使用计算机，以允许使用这种做法。 5.7 在本实践中，计算机程序被描述为计算隔热系统的热损失或热增益以及表面温度的指南。这些程序的应用范围和输出的可靠性是输入数据的范围和质量的主要函数。这些程序旨在与“交互式”终端一起使用。在该系统下，中间输出引导用户根据需要对输入参数进行编程调整。 计算机通过程序生成的指令和问题交互控制终端，提示用户响应。这有助于解决问题，并增加计算机成功运行的概率。 5.8 本实践的用户可能希望修改本实践中提供的计算机程序的数据输入和报告部分，以满足个人需求。此外，可能希望额外的计算包括其他数据，例如系统成本或经济厚度。只要用户使用一系列测试用例来验证这些修改，这些测试用例涵盖了新方法的使用范围，那么这些修改就不存在冲突。对于每个测试案例，热流和表面温度的结果必须与使用本文所述实践获得的结果相同（在方法的分辨率范围内）。 5.9 本规程旨在提供符合美国工业常用单位制的输入和输出数据。 尽管输入/输出程序的修改可以提供热流结果的SI等效值，但对于本实践的某些部分，没有这种“公制”等效值。到目前为止，还没有公认的管道和圆柱形保温系统的公制尺寸系统。欧洲使用的尺寸是美国尺寸的国际单位制当量（基于实践 C585 )，每个国家都有不同的名称。因此，尚未编制该规程的SI版本，因为与该规程等效的标准SI会很复杂。当出现管道和隔热材料尺寸的国际标准时，可以重写此做法以满足这些需求。此外，已经证明，这种做法可以用于计算隔热系统以外的情况下的传热；然而，这些计算超出了本实践的范围。

1.1 This practice provides the algorithms and calculation methodologies for predicting the heat loss or gain and surface temperatures of certain thermal insulation systems that can attain one dimensional, steady- or quasi-steady-state heat transfer conditions in field operations. 1.2 This practice is based on the assumption that the thermal insulation systems can be well defined in rectangular, cylindrical or spherical coordinate systems and that the insulation systems are composed of homogeneous, uniformly dimensioned materials that reduce heat flow between two different temperature conditions. 1.3 Qualified personnel familiar with insulation-systems design and analysis should resolve the applicability of the methodologies to real systems. The range and quality of the physical and thermal property data of the materials comprising the thermal insulation system limit the calculation accuracy. Persons using this practice must have a knowledge of the practical application 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 practice is described in Section 7 of this practice. The computer program 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 mathematical conversions to SI units that are provided for information only and are not considered standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Manufacturers of thermal insulation express the performance of their products in charts and tables showing heat gain or loss per unit surface area or unit length of pipe. This data is presented for typical insulation thicknesses, operating temperatures, surface orientations (facing up, down, horizontal, vertical), and in the case of pipes, different pipe sizes. The exterior surface temperature of the insulation is often shown to provide information on personnel protection or surface condensation. However, additional information on effects of wind velocity, jacket emittance, ambient conditions and other influential parameters may also be required to properly select an insulation system. Due to the large number of combinations of size, temperature, humidity, thickness, jacket properties, 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 substantial engineering cost to obtain the required information. This cost can be substantially reduced by the use of accurate engineering data tables, or available computer analysis tools, or both. The use of this practice by both manufacturers and users of thermal insulation will 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 applications may 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 rectangular coordinate system, Practice C680 can be applied to heat flows normal to flat, horizontal or vertical surfaces for all types of enclosures, such as boilers, furnaces, refrigerated chambers and building envelopes. In the cylindrical coordinate system, Practice C680 can be applied to radial heat flows for all types of piping circuits. In the spherical coordinate system, Practice C680 can be applied to radial heat flows 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 to evaluate insulation system performance and durability of operating systems. This type of analysis is often made prior to system upgrades or replacements. 5.5 All porous and non-porous solids of natural or man-made origin have temperature dependent thermal conductivities. The change in thermal conductivity with temperature is different for different materials, and for operation at a relatively small temperature difference, an average thermal conductivity may suffice. Thermal insulating materials ( k < 0.85 {Btu·in}/{h·ft 2 ·°F}) are porous solids where the heat transfer modes include conduction in series and parallel flow through the matrix of solid and gaseous portions, radiant heat exchange between the surfaces of the pores or interstices, as well as transmission through non-opaque surfaces, and to a lesser extent, convection within and between the gaseous portions. With the existence of radiation and convection modes of heat transfer, the measured value should be called apparent thermal conductivity as described in Terminology C168 . The main reason for this is that the premise for pure heat conduction is no longer valid, because the other modes of heat transfer obey different laws. Also, phase change of a gas, liquid, or solid within a solid matrix or phase change by other mechanisms will provide abrupt changes in the temperature dependence of thermal conductivity. For example, the condensation of the gaseous portions of thermal insulation in extremely cold conditions will have an extremely influential effect on the apparent thermal conductivity of the insulation. With all of this considered, the use of a single value of thermal conductivity at an arithmetic mean temperature will provide less accurate predictions, especially when bridging temperature regions where strong temperature dependence occurs. 5.6 The calculation of surface temperature and heat loss or gain of an insulated system is mathematically complex, and because of the iterative nature of the method, computers best handle the calculation. Computers are readily available to most producers and consumers of thermal insulation to permit the use of this practice. 5.7 Computer programs are described in this practice as a guide for calculation of the heat loss or gain and surface temperatures of insulation systems. The range of application of these programs and the reliability of the output is a primary function of the range and quality of the input data. The programs are intended for use with an “interactive” terminal. Under this system, intermediate output guides the user to make programming adjustments to the input parameters as necessary. The computer controls the terminal interactively with program-generated instructions and questions, which prompts user response. This facilitates problem solution and increases the probability of successful computer runs. 5.8 The user of this practice may wish to modify the data input and report sections of the computer programs presented in this practice to fit individual needs. Also, additional calculations may be desired to include other data such as system costs or economic thickness. No conflict exists with such modifications as long as the user verifies the modifications using a series of test cases that cover the range for which the new method is to be used. For each test case, the results for heat flow and surface temperature must be identical (within resolution of the method) to those obtained using the practice described herein. 5.9 This practice has been prepared to provide input and output data that conforms to the system of units commonly used by United States industry. Although modification of the input/output routines could provide an SI equivalent of the heat flow results, no such “metric” equivalent is available for some portions of this practice. To date, there is no accepted system of metric dimensions for pipe and insulation systems for cylindrical shapes. The dimensions used in Europe are the SI equivalents of American sizes (based on Practice C585 ), and each has a different designation in each country. Therefore, no SI version of the practice has been prepared, because a standard SI equivalent of this practice would be complex. When an international standard for piping and insulation sizing occurs, this practice can be rewritten to meet those needs. In addition, it has been demonstrated that this practice can be used to calculate heat transfer for circumstances other than insulated systems; however, these calculations are beyond the scope of this practice.