Comparison of Thermal Insulation Materials

Other thermal insulation materials are known besides the three described above. These materials are compared in Table 19, which shows that the thermal conductivity can be reduced by a factor of 2—4 by evacuation in the evacuated state it is below 10mWm K for all materials. The lowest conductivity is shown for foil insulations, but this requires an extremely low pressure of 10 mbar which is difficult to obtain in practical applications which ought to last for ten years. 

Microporous insulation represents a good compromise its thermal conductivity reaches 4—8 mW m K in a pressure range of only 0.1-1 mbar. Another advan- 

Microporous insulation represents a good compromise its thermal conductivity reaches 4-8 mW m in a pressure range of only 0.1-1 mbar. Another advantage is its maximum operating temperature of 800-900 °C. This ensures the stability of the insulating layer around the battery, even in abuse situations. 

---

Figure 39.4. Comparison of thermal insulation values Aerocore versus common insulation materials (R-value in units of ft. °Fh Btu ).

PT. 3. COMPARISON OF THE EFFECTIVE THERMAL INSULATION FOR INTERSTITIAL MATERIALS UNDER COMPRESSIVE LOADS. PTS. 4 AND 5. INVESTIGATION OF THERMAL ISOLATION MATERIALS AND THEIR APPLICATION IN FLANGE JOINTS. 

Beds of aerogel granulate or powder are used for technical thermal insulation (Part 15), because they offer specific advantages in comparison to standard insulation materials, e.g., they can be poured into complicated shaped cavities. Opacified aerogel powders and granulates are used as thermal insulation in space applications [55], automotive applications... 

Thermal insulations are made from natural or processed materials and combined to provide properties that meet the needs of specific installations. Obviously, all desired properties are not available in any one insulation. Hence, selection ol thermal insulation lor specific uses involves comparisons for each use. and some high thermal resistance l/f-value) may... 

The absorption of impurity centres is observed in the transparency domains of semiconductors and insulators, which are limited by their intrinsic electronic and vibrational absorptions. Further, a brief account of the relevant physical processes and an overview of the intrinsic optical properties of these materials and of their dependence on temperature, pressure and magnetic field is given in this chapter. Some semiconductors have been or are now synthesized in quasi-monoisotopic (qmi) forms because of improvements in their physical properties like thermal conductivity. A comparison of their intrinsic optical properties with those of the crystals of natural isotopic composition is also given. The absorption related to free carriers, due mostly to doping is also discussed at the end of this chapter. A detailed account of the optical properties of semiconductors can be found in the books by Yu and Cardona [107] and by Balkanski and Wallis [4]. 

The durian peel and coconut coir mixture was then used to develop low thermal conductivity particleboards. It was reported that the mixture ratio of durian peel and coconut coir was optimum at 10 90 by weight. In comparison with durian only particleboards and coconut only particleboards, the mixture particleboards showed better properties, except for the modulus of elasticity. The mixture particleboard is of lower thermal conductivity, which is suitable for ceiling and wall insulating materials. With more development, it will not be impossible to use this material for furniture applications. 

Paul H L, DiUer K R (2003) Comparison Thermal Insulation Performance of Fibrous Materials for the Advanced Space Suit. J Biomechanical Engineering 125 639-647. 

Figure 39.4 also shows a comparison of the values for thermal insulation of Aerocore versus commonly used insulation materials proving the superior property of this material. 

In the case of systems in which the filled valence band and the next unoccupied band are separated by a considerable energy gap the electric potential required for the transition and hence to produce conductivity is large. Such material behaves as insulators. The intermediate case where the energy gap exist but is relatively small in comparison with thermal energies correspond to... 

Microsphere Insulation. Good thermal-insulation performance has also been achieved by using packed, hollow glass spheres, typically of a size ranging from 15 to 150/xm in diameter and coated on the exterior with a film of low emittance material such as aluminum. These hollow spheres, which generally have a wall thickness of 0.5-2.0 m, substantially increase the conduction thermal resistance but markedly reduce the heat capacity and the mass relative to solid particles. Further, hollow microspheres offer a lightweight and low heat capacity alternative to MLI. A comparison of these two insulations is presented in Table 7.4. 

In comparison with metallic materials, the use of plastics is limited to relatively moderate temperatures and pressures (230°C is considered high for plastics). Plastics are also less resistant to mechanical abuse and have high expansion rates, low strengths (thermoplastics), and only fair resistance to solvents. However, they are lightweight, are good thermal and electrical insulators, are easy to fabricate and install, and have low friction factors. 

Thermal Conductivity. The results of the thermal conductivity, k, tests are given in Table VII for four different mixture ratios representing S/A ratios of 1.3 to 10. The data indicate that additional sulfur had little effect on the thermal conductivity, which averaged 11.7 X 10 4 cal-cm/ cm2-sec-°C (3.40 X Btu-in./ft2-hr-°F). A comparison with the value obtained for the A/C system of 15.77 cal-cm/cm2-sec-°C (4.57 Btu-in./ft2-hr-°F) would indicate that the thermal conductivity is about 25% less for S-A—S than for A/C. This is attributed to the higher air void contents in the former which add to the insulative characteristics of the material. 

---