Fiberglass thermal insulators

In temperate and cold regions structures of nearly all kinds require good thermal insulation to reduce heating costs. In the construction industry, thermal insulators made from materials such as fiberglass and foamed plastics have been used widely because they are noncrystalline and incorporate a large void space with high entrapped air content. 

Thermal Thermal insulation (fiberglass. IR radiators, thermal... 

FIGURE 5.172 Thermal conductivity for typical fiberglass pipe insulation. 

Fig. 9.11 Demonstration of thermal insulation capability of octadecane Ti02—PVP nanoflbers (a), where 1 cm of water at 60 °C was allowed to cool in a 4 °C environment in glass vials covered with different insulation jackets. Sample A had no insulation, sample B was half covered with the PCM nanofiber jacket, and sample C was fuUy covered by the PCM nanofiber jacket. Sample D was covered by a jacket of conventional fiberglass (Reprinted with the permission from McCann et al. [12]. Copyright 2006 American Chemical Society) and (b) temperature-regulating capability of PEG/CA fibers, the thermoregulating curves of the hot stage, the electrospun CA fibers, and the PEG/CA fibers with 50 wt% PEG (Reprinted from Chen et al. [32], copyright 2011, with permission from Elsevier)...

The wool process mainly is used to produce discontinued (short) glass fibers for thermal insulation and filtration apphcations. These fibers typically are used in the form of bafts, blankets or boards, and they often are called fiberglass or glass wool. 

Multilayer Insulation Miiltilayer insulation consists of alternating layers of highly reflec ting material, such as aluminum foil or aluminized Mylar, and a low-conduc tivity spacer material or insulator, such as fiberglass mat or paper, glass fabric, or nylon net, all under high vacuum. When properly applied at the optimum density, this type of insulation can have an apparent thermal conduc tivity as low as 10 to 50 jlW/m-K between 20 and 300 K. 

Typically items with a thickness of less than about 1 mm can be treated as thermally thin. This constitutes single sheets of paper, fabrics, plastic films, etc. It does not apply to thin coatings or their laminates on noninsulating substances, as the conduction effects of the substrate could make the laminate act as a thick material. The paper covering on fiberglass insulation batting would be thin pages in a closed book would not. 

Insulation fiberglass is glass wool used for thermal and acoustic insulation of homes, commercial buildings, industrial equipment, and automobiles. It has a sodium aluminoborosilicate-based composition, often with additional modifiers, such as calcium, magnesium, and potassium, which vary by... 

Example 2.4 Estimation of heat flow through a composite wall with constant thermal conductivities A pipe with an outside diameter of 10 cm and a length of 110 m is carrying hot fluid. The pipe is insulated with 0.5 cm thick silica foam and 10 cm thick fiberglass. The pipe wall is at 120°C and the outside surface of the fiberglass is at 30°C. Estimate the heat flow in the radial direction of the pipe. The thermal conductivities of silica foam and fiberglass are 0.055 and 0.0485 W/(m K), respectively. 

Consider steady heat transfer between two large parallel plates at constant temperatures of T = 290 K and Ti = 150 K iliat are L 2 cm apart. Assuming the surfaces to be black (emis-sivity e = 1), determine the rate of heat transfer between the plates per unit surface area assuming the gap betsvecn the plates is (fl) filled with atmospheric air, (6) evacuated, (c) filled svith fiberglass insulation, and (d) filled svith superinsulation having an apparent thermal conductivity of 0.00015 W/m - C. 

A wall is constructed of two layers of 2-cm-thick sheetrock (k = 0.17 W/m C), which is a plasterboard made of two layers of heavy paper separated by a layer of gypsum, placed 18 cm apart. The space between the sbeetrocks is filled with fiberglass insulation (k = 0.035 W/m C). Determine (thermal resistance of the wall and (b) its 2 -value of insulation in 81 units. 

Consider a 3-m-diameter spherical tank that is initially filled with liquid nitrogen at 1 atm and I96°C. The tank is exposed to ambient air at I5°(. with a combined convection and radiation heal transfer coefficient of 35 W/m °C. The temperature of the thin-shellcd spherical tank is observed to be almost the same as the temperature of the nitrogen inside. Determine the rate of evaporation of the liquid nitrogen in the tank as a result of the he.ii transfer from the ambient air if the tank is (<7) not insulated, h) insulated with 5-cm-thick fiberglass insulation k = 0.035 W/m C), and (c) insulated with 2-cm-lhick superinsulation which has an effective thermal conductivity of 0.00005 W/m C. 

The vaporized JP-10 mixed with air is fed to the dump combustor, where the reaction is initiated using a continuous spark igniter. The igniter is inserted into the combustor such that the spark is located in the natural low-velocity recirculation bubble. To avoid condensation of JP-10 on surfaces within the flow circuit, the facility is operated with heated air for approximately 1 hour to achieve a thermal steady state before igniting the combustor. Fiberglass insulation is used to reduce heat loss and the potential for fuel condensation. For the results discussed below, a total mass flow rate of 0.041 kg/s was used, and the reactants entered the combustor plenum at a temperature of approximately 95 °C. 

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