Document GG2LLme20e72K8k9L4mwQpn7

American Society of Heating arid Ventilating Engineers Guide, 1934 Table 1. Average Maximum Design Dry-Bulb Temperatures, Design Wet-Bulb Temperatures, Wind Velocities, and Wind Directions for June, July, August, and September (Continued) Stats ClTT Average Maximum Design -Dht-Bdlb Design Wet-Bolb Summer Wind Vstocrrr MPH PNBT.ULING Suumeb Wind Dihection Texas. Utah.... Vt.___ _ Va.... . Wash.... W. Va. Wis....... Wyo___ .. Dallas................ Galveston_____ San Antonio...... Houston............. El Paso.......... ..... .. Salt Lake City.,. . Burlington......... . Norfolk............... Richmond.--...... . Seattle-------------- Spokane.............. . Parkersburg....... . Madison..... Milwaukee.......... . Cheyenne............ 99 93 100 93 98 . 95 85. 91 . 95 83 89 90 89 87 85 76 79 78 79 69 67 71 76 76 61 63 74 73 72 62 9.4 9.7 7.4 7.7 6.9 8.2 8.9 10:9 . 6.2. 7.9. 6.5 5.3 8.1 10.4 9.2 S S SE S E SE S S SW s SW SE SW s s tory1 has shown that a large error may be introduced into the calculations by failure to consider the periodical character of heat flow resulting from the diurnal movement of the sun and the heat capacity of the structure, which determine the timing and magnitude of the heat wave flowing through the wall into a building on a hot, sunny day. Unfortunately, despite intensive study, all data on solar radiation Table 2. Heat Equivalents of Various Devices, Btu Lights and electric appliances------------Motors...................................................... Restaurant coffee urns, 10-gal capacity. Dish warmers per 10 sq ft of shelf.... .... Restaurant range--4 burners and oven. Residence gas range Giant burner.--................................... Medium burner..................................... Oven........................................... ........... Pilot-................................................... Electric Range Small burner Medium burner..................................... Large burner.......................................... Oven....................................................... Appliance connection............................ Warming compartment______________ 3415 per kilowatt 2546 per horsepower hour 16000 per hour 6000 per hour 100,000 per hour 12000 per hour 9000 per hour 1000 per cu ft of space 250 per hour 3412 per hour 4100 per hour 7700 per hour 10236 per hour 2250 per hour 1023 per hour xFor further information on this subject see following A.S.H.V.E. research papers: Coefficients of Heat Transfer as Measured under Natural Weather Conditions, by F. C- Houghten and C. G- F. Zobel (A.S.H. V.E. Transactions. Vol- 34, 1928); Absorption of Solar Radiation in Its Relation to the Temperature, Color, Angle and Other Characteristics of the Absorbing Surface, by F. C. Houghten and Carl Gutberiet (A.S.H.V.E. Transactions, Vol. 36, 1930);-Heat Transmission as Influenced by Heat Capacity and Solar Radiation, by F. C. Houghten, J. L. Blackshaw, B. M. Pugh and Paul McDermott (A.S.H.V.E.'.Trans actions, Vol. 38. 1932). 118 Chapter 8--The Cooling. Load through building walls are too theoretical and mathematically complicated to be of much practical value to the heating and ventilating engineer. Accordingly, the customary rule-of-thumb method of adding an arbitrary . 25 F to the dry:bulb temperature difference in calculating the heat transmission through a wall or roof which may be exposed to the sun for any appreciable length of time is given as a workable solution to an ex ceedingly complex problem. Solar Radiation Fig. 1 shows the total amount of solar energy in Btu per square foot per hour received during the day by a surface normal to the rays of the sun, by a horizontal surface, and by east, west, and south walls. The curves are drawn from A.S.H.V.E. Laboratory data obtained by pyrheliometer, are based on sun time, and are for a perfectly clear day on August 1 at a north latitude of 40 deg. Data from these curves may be used with little error for most United States latitudes and for all of the hotter months of the year. The absorption of solar radiation by an interior surface depends upon the character of the surface, the angle of the surface with respect to the direction of the radiation, and the angle and type of glass through which the radiant rays pass. The heat absorption by a black oilcloth surface perpendicular to the sun's rays was found to be as high as 273 Btu per square foot per hour, based on tests conducted by the A.S.H.V.E. Re search Laboratory in Pittsburgh8. Lamp black, red brick dust, and aluminum bronze painted surfaces perpendicular to the sun's rays showed respectively 94.0, 63.4, and 28.2 per cent as high a rate of absorp tion as the black oilcloth. Transmission Through Class In considering the effect of glass on heat absorption, several factors must be considered. As the sun's rays impinge against and pass through an intervening sheet of glass, some radiation is reflected directly from each of the two glass surfaces, and some is absorbed by the glass depending upon its character and thickness. AH of the heat reflected by the glass surfaces and most of that absorbed- within the glass is stopped from passing through the glass into a room. The A.S.H.V.E. tests indicated that a single pane of double strength glass absorbs from 8.9 to 16.5 per cent of the solar radiation passing through it when the impingement is normal. For smaller angles of impingement, the glass retards percentages of the total radiant energy approximately in proportion to the sine of the angle. Experiments* indicate a glass absorption of 16.7 per cent for one pane of glass and 37.5 per cent for two panes separated by a 1%-in. air space. In a recent paper by the A.S.H.V.E. Research Laboratory* it was shown `Absorption of Solar Radiation in Relation to the Temperature, Color, Angle, and Other Characteristics of the Absorbing Surface, by F. C. Houghten and Carl Gutberlet (A.S.H.V.E. Transactions, Vol. 36,1930). `Field Studies of Office Building Cooling (A.S.H.V.E. Research Paper), by J. H. Walker. S. S. Sanford, and E. P. WelMA.S.H.V.E. Transactions, Vol. 38, 1932). `Radiation of Energy Through Glass by J. L. Blackshaw and F. C. Houghten (A.S.H.V.E. Journal Section, Heating; Piping and Air Conditioning, October, 1933). 119