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......
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