Document pp1keQq3Z9qbYd71m07kgO25D

APMACNT MEAN THERMAL CONBUCTTVrTY .. MICROWATT!/(to CM)|R OC/CM) 688 CHAPTER 65 Table 5 .... The Apparent Mean Thermal Conductivity k of Some Selected Multiple Layer Insulations (For IudMm and Mhcfon Ducribfd Mow fab/e) 1962 Guide And Daf0 hmdo- Baflac- f . SJtieidt Duality . for In. Number lb per CM per m. cu ft Wdl B fc* ;A 2 B ;; :.,B 1 1 :A :A : 1. 3 .A ' 1 A1 C1 A: D . "A 2 1 2 1.3 55 . 7.5 1.5 ' 60 7.0 1.0 50 7.0 1.2 52 - 1.5 -- 3.8 1.4 37 6.9 1.5 23 6.9 1.2 29 6.9 2.0 i.2 1.5 48 52 52 7.5 5.9 137 36 137 36 137 36 137 137 36 137 36 137 137 36 137 137 137 0.32X10"* 0.23X10"* .0.30X10"* 0.24X10"* 0.41X10"* 0.35X10"* 0.75X10"* 1.85X10*** 1.39X10"* 0.43X10"* 0.30X10"* 0.49X10-* 0.41X10"* 0.29X10"* 0.64X10"* 1.33X10"* 0.87X10"* - w It) Cod* Deacni A Fiber cbes paper, 0.008 la. thick. 909( B Kber kUm paper. 0-0048 in. thick, 909 C FibervM not, etjicae bonded. 0.008 ; Owcaa-Comfag StbpgkwCarpcmliou. r; Dexter Paper Company,, . Dexter P-- "------thick, ar. fiber d D Nrton net, 0008, in.. 90% rokL ' 1 AHimtfmm foQ, 0.0003 to. thick; Alcoa Ahuaimun Corporation. 3 Ahusimzm foQ, 0.00023 in. thick; Alcoa Atomitmm Corporation. 9 MCaytrwo,isarh.usimaed both ndee. 1.5 to 8.0 oboe per equate, Dobeekmun (bj Pofyttyrene foam, dr-ffltd density = 2 Ch/cu ft (cj isocyanate foomt, COrffl^i density** 6. to .6 A/a ft. I mSBwdl /(M(q an) (K deg/an) - 0.0570 Btu/IM Uq ftl (B <feg/l - 0699 Btv/{hr) (*j ft) (0 deg/inX R8* ^5.... Thermal Conductivities of Some Foams Unevocuated Porous Insulations These may consist of powders, fibers or foams. Heat con duction in such insulations is primarily due to the interstitial gas and is given to a rough approximation by the thermal conductivity of the gas! For example, the mean thermal con* ductavity in the range 76 to 300 K, was 1450 microwatts/(sq cm) (K deg per cm) for a perlite powder containing hydrogen gas at atmospheric pressure. The corresponding value for g^genta 689 Table 6 .... The Apparent Mean Thermal Conductivity of Several Powders (1 h. toMpfc tbkineu/ boundary (Mptrefuru of 540 and 137* 0} and waB ominhritms greater Aon 0.0)- Powder Density (lb/ft*) Gas Preiaae (bud Kg). Silica aerogel Chemically prepared 250A +10% free] silicon dust) by weight j 6.2 6.2 6.2 6.2 7.0 10-* 628* 628 628 10? 8ltoft Perlite, expanded Flame prepared 150-200A +30 mesh +30 mesh - +30 mesh +30 pwh +30 mesh 30+80 mesh 30+80 mesh 30+80 mesh 30+80 mesh --80 mAh --80 mesh --80 mesh -- 80 mah --30 mesh Diatomaceous " earth Alumina, fused Alumina, laminar Mica expanded Lampblack Charcoal 1 peach pita/ 1 -- 100 microns . 50+100 mesh 0 1-10 microns (--20+30 mesh 30% ( -304*15 mesh 70% (--30+15 mesh 70% - 20-30 n*e*h 3.7 3.7 3.7 6.2 6.2 6.2 6.2 8.1 8.1 8.1 8.1 8.7 8.7 8.7 8.7 8.7 fl5.0 (15.6 (l8.0 125 4.4 9.4 9.4 9.4 12.5 30 10" ,630 10"* 10-* 628 - .628 628 I0"* 628 628 628 10-* 628 628 628 10"* 10"* 10"* io-* 10"* io-* 10" 628 628 10"* 10"* Carbon+7% Ash' 30% 44*. 12.5 Calcium silicate (synthetic) .. 0.02 microns (0.02-0.07 microns (0.02-0.07 microns 10.6 22.5 22.5 JU X 10** Btub/(*q ft) (R deg/ft) for boundary temperatorn of 137 and 38 R. 30 X 10~* Btoh/(*q ft) (R deg/ft) for boundary temperature* of 540 and 36 R. * L2 X 10'* Btuh/(sq ft) (K dex/ft) for bousebry tempeiaturea of 137 asd 30 R. 0.45 X 10** Btah/(eq It) (R deg/ft) for boundary temperaturea of 137 and 7.0 RBarometric Pnmtue at Boulder, Colorado. 1 Meetly 0, tad AbOj. 1Q-* 10" io-* 628 ' Inferttffial Gat. __ - Nitrogen Huhnm Hydrogen __ Nitrogen __ -- Nitrogen Helium Hydrogen __ Nitrogen Helium Hydrogen __ Nitrogen Helium Hydrogen -- __ -- -- -- __ Nitrogen Helium -- -- -- . __ -- Nitrogen Conductivity 0tefc/(*q ft) (B deg/H] 12X10-**' 113X10"* 358X10"* 462X10"* 10.5X10"* 12X10"* 107X10"* 12X10"* 10.5X10"* 192X10"* 73SX10"* 845X10-* 7X10-* 188X10"* 728X10"* 838X10-* 5.8X10"* 202X1CT* 780X10-* 840X10"* 6.8X10-*rt-**> 9X10-* 8X10"* 6.8X10"* 10.5X10"* 13.3X10"* 10.6X10"* 290X10-* 867X10-* 7.2X10-* 10.5X10-* 3.6X10"* 4.3X10"* 3-2X10"* 263X10"* hydrogen itself is 1240. Similarly, perlite containing helium gave 1260, and a sample of fiberglas containing helium gave 1330, while the corresponding value for helium gas is 1100. Again, perlite containing nitrogen at atmospheric pressure Save 325, the fiberglae containing nitrogen gave 260 while nitrogen itself would be 170. In the same temperature rangeStyrofoam (air-filled) gave 260 while air is 170. ' Thus it will be seen that an approximation to the conduc tivity of a gas-filled porous insulation can be obtained by taking a value somewhat larger than the conductivity of the Pa itself,in the same temperature range. Data on foams are given in Fig. 15. Plastic foams are permeable to the common gases and if exposed to a foreign gas can show substantial changes in conductivity in a few days time due to exchange of the gas in the cells of the foam. Obviously exposure of such foams to hydrogen or helium should be avoided. Among the powders, silica aerogel (SantoeeT) has superior insulating value unevacuated due to its extremely small effective pore sisc. Evacuated Powders The insulating value of powders is greatly increased by removing the interstitial gas. Fig. 16 shows the effect of in*