Document 06BavMyea4m7QqYqpEw59p5MR

HEATING VENTILATING AIR CONDITIONING GUIDE 1943 CHAPTER 43. PIPE AND DUCT HEAT LOSSES The heat losses through 1, and 2-in. thick 85 pier .cent Magnesia type- of insulation for temperature differences between the pipe and- the surrounding atmosphere up to 280 F are shown in Figs. 2, 3, and- 4. Standard thicknesses of 85 per cent Magnesia pipe covering are not exactly 1 in. However, the loss through any given thickness of insulation can be obtained by interpolation. Also, the losses through any of the 8.T.U. PER LINEAR FOOT PER HOUR PER DEG FAHR TEMPERATURE DIFFERENCE Fig. 2. Heat Loss Through 1 In. Thick 85 per cent Magnesia Type Covering 780 Fig. 3. Heat Loss Through In. Thick 85 per cent Magnesia Type Covering insulations given in Table 8 can be obtained by multiplying the losses obtained from Figs. 2, 3, or 4 by the factors given in Table 9. ; The rate of heat loss from a surface maintained at constant temperature is greatly increased by air circulation over the surface. In the case of well-insulated surfaces, the increases in losses due to air velocity are very small as compared with increases from bare surfaces, because of the fact that air flowing over the surface of the insulation can increase only the rate of heat transfer from surface to. air, and cannot change the interna} 781