Document B887GnvzNDvZaoNRe3Kkq5rNL

296 CHAPTER 12 1952 Guide . Table 25. Instantaneous Rates of Heat Gain Dub to Transmitted Directand.Diffuse Solar, Radiation by Unshaded Walls of 8-in Hollow Glass Block of Types II, III, IV, IVA and V Patterns Multiply the Table SS Values for Type I by These Percentage Factors For Clear Atmospheres and 18 Deg Declination, North (August 1) For SO, 10, and SO Deg North Latitude - Note: To obtain total instantaneous heat gain add adjusted Table SS values to the Table 24 values. Instantaneous Hbat Gaik Dub to Transmitted Solar Radiation as a Pebcbntaob op Ttpb i Pattern Sun Time . Type n Pattern Ttpb III Pattern AM-* i N, NW, W, 8W NE E SE s N, NW, W, SW NE E SE S 5 a.m. 6 7 8 9 10 11 12 7pan. 6 5` 4 3 .2 1. r PM -- 100 100 100 . 100 100 100 100 100 N. NE, E, SE 100 .100 95 95 90 90 95 90 95 85 95 95 100 95 100 100 NW l W 100 90 90 90 ' 90 95 95 100 SW 100 100 100 100 90 95 100 100 S 70 70 70 70 70 70 70 70 N, NE, E,SE 70 70 65 65 65 60 65 60 65 65 70 70 70 70 70 70 NW W 70 70 70 70: 65 70 65 70 70 65 75 65 80 75 75 90 SW S Sun TXmb Ttpb IV Pattern Type IVA Pattern AM -- i N, NW, W, SW NE E SE s. N, NW, W, SW NE E SE S 5 Bjn. 6 .7 8 0 10 11 12 7pja. 6 5 4 8 2 1 85 45 35 75 55 55 45. 35 80 55 55 45 35 60 . 55 55 45. 30 40 55 55 , 50 25 30 60 55 55 35 30 50 55 55 45 35 40 55 55 55 50 45 pi-* N, NE, IS, SE NW W : SW -S Sun Time Ttpb V Pattern AM -- .1 ,5 ajn 8 7 8 9 10 . . 11 12 N. NW, W. SW NE E SE s 7pjn. 6 6 4 3 2 1 80 60 60 60 60 GO 60 GO 35 35 30 GO 35 35 30 60 35 40 35 60 50 65 50 60 80 90 90 60 70 105- 105 90* 60 80 110 105* 60 GO 85 115* 55 55 55 55 55 55 55 55 N, NE, E,SE 45 35 35 35 35 40 45 45 50 65 55 85 55 70 55 55 NW W 30 55 30 55 35 55 45 55 65 50 90 60 105 95 100 115 SW S Designation of Block Type II--Semi-Light DiffusingIII--Light Diffusing IV--Light Diffusing IVA--Light Diffusing V--Light Directing ; PL- . . N, NE, E, SE NW W SW S * Reduce by 30% (or 30 deg N lntitude only. Table-26. Approximate Corrections to Tables 17 and 24 for Deviations from Indoor and Outdoor Design Temperatures For each degree the design room temperature exceeds 75 F, subtract correction. For each degree the design outdoor dry-bulb temperature exceeds 96 F, add correction. Apply these corrections to each value in Table 17 or Table 24. Guss Type Single Flat or Rolled Figured Glass Double-Flat Glass and Glass Block Correction Btu per (hr) (sq pt) 1.0 0.5 . Cooling Load 297 centages given in Table 25. Note that corrections' are the same for all latitudes, and that they vary only on the surfaces exposed to the direct sun. The convection, and radiation gain values for all blocks are so nearly the same that a single table suffices. Note, however, that corrections must be made for certain hours for east and west facing walls of some patterns. Example IS: Find the total instantaneous heat gain through an,east wall of 8-in. hollow glass block of Type V pattern at 8 a.m. and 50 deg north latitude. The design temperatures are 75 F indoors and 95 F maximum outdoor dry-bulb, clear atmosphere. . Solution: The gain due to transmitted solar radiation is found from Table 23 for Type I pattern. The factor for Type V is found from Table 25. The convection and radiation gain is found from Table 24 (note the footnote). The total instantaneous heat gain is, from Equation 7a, g = 86 X 0.65 + 28 X 1.4 = 95.2 Btu per (hr)(sq ft). Effect of Deviations from Design Conditions If the indoor temperature differs from 75 F, or the design outdoor drybulb temperature differs from 95 F, corrections can be made to the convec tion and radiation gain values for flat glass, rolled figured glass, and glass block according to the schedule in Table 26. The effect of the humid industrial type atmosphere is to cause a con siderable reduction in heat gain, if all factors except solar intensity remain the same. Reference 19 gives heat gain values for four orientations at 40 deg north latitude on August 1 for several types of flat glass and glass block, and solar intensities typical of humid industrial atmospheres. These data show that the following approximate reductions, based on total gain for the day, can be expected: 20 percent for all types of glass and glass block in east or west facing walls; 10 percent for south facing flat glass,; 5 percent for south facing glass block walls. Shading of Glass Areas--Design Tables The effects and possibilities of shading should be carefully investigated whenever the heat gain from glass is a large portion of the cooling load. Vertical glass, which is not mounted in the plane of the building surface, is partially shaded by the setback. If a vertical window of height l and width w be set back from the plane of the building a distance s, the fraction of the total area of the window which receives direct solar radiation is: where n tan r,r, tan 0 tan y Tt tan y -f cos y cos y (10) rj = s/1, r, = s/w, 0 = solar altitude, and y is the wall solar azimuth (see Fig. 1). Values of /3 and y for various latitudes and August 1 are given in Table 7. Special cases not covered by the tabulated data may be solved analy tically;21 however, the design conditions chosen will yield a satisfactory approximation if used without correction for any time during the summer period. Example 16: Estimate the total instantaneous rate of heat gain for a west win dow 3 ft wide by 5 ft high, with a setback of 6 in., for August 1 and 40 deg north latitude at 3:00 pm (sun time). Solution: From Table 16, the instaneous' rate of heat gain, due to transmitted direct and diffuse solar radiation, is 180 Btu per hr. From Table 7,0 is 45.5 deg and