Document oerobkLVgpeZZDObJMgRnz46r

236 CHAPTER 12 1946 Guide provides sufficient relief in hot weather to be acceptable to the majority of users, ft should 'be emphasized, however, that these are borderline cases that may be acceptable largely in the interest of economy. Com prehensive studies by the A.S.H.V.E. Research Laboratory 30 in coopera tion with office staffs in widely distributed regions, including San Antonio, Minneapolis, Washington, D. C., and New York City (see Fig. 7), show conclusively that lower effective temperatures are required for optimum comfort. The sensation of comfort, insofar as the physical environment is con cerned, is not absolute but varies considerably among certain individuals. Therefore, in applying,the air conditions indicated, it should not be, expected that all the occupants of a room will feel perfectly comfortable. Fig. 12. . Chart for Determining Surface Area of Individuals for Height and Weight Given However, when optimum comfort temperatures are applied in accordance with foregoing recommendations, the majority of the occupants should be comfortable, and it should be expected that there, will be a few too warm and a few too cold. These individual differences among the min ority should be counteracted by suitable clothing. RELATION OF AIR CONDITIONING NEEDS TO METABOLISM To maintain optimum conditions in summertime requires the removal, of heat from the conditioned space. In calculating the cooling load it is always necessary to consider the heat given up'by the occupants. In theaters or similarly densely populated spaces, the occupants may con tribute the greater part of the total load. . The metabolic rate varies with the size of the individual, with the rate of work being performed, and at extreme conditions, with the environ ment. The relative proportions of sensible and latent heat given off also yary widely. The curves in Fig. 9 show the total heat loss (sensible plus.latent) from the average man for four different rates of work. Heat- loss iii this figure is plotted against effective temperature. . Figs, lOand 11 give the sensible and latent losses for the same four work rates,, plotted against dry-bulb temperature. By proper interpolation, it is possible Physiological Principles 237 Table 4. Relation Between Metabolic Rate and Activity a- Hourlt Metabolic Bats for Avg Person or TDoistsailpaHteeadt, . Btu per hour Hourlt Hourly Sensible Latent Heat Did* HEAT DIS SXPATED, SIPATED, at 79 F, Btu per Hour Btu perHour Moisture Dissipated pee Hour per Person Grains Pounds Basal.:-- Seated at RestReading Aloud (Seated)- Standing at RestHand Sewing (Seated)-------Knitting 23 stitches per minute on Sweater- 291 384 420 431 441 462 Dressing and Undressing.--------------------------- Tailor.--------------------- ------------------------------Singing.-- Office Worker Moderately ActiveLight Work Standing-----------------Typewriting Rapidly.------------------ Ironing with 5 lb iron-- Dishwashing--Plates, Bowls, Cups and Saucers 468 482 486 490 549 558 570 .600 Clerk Moderately Active Standing at Counter. 600 Book Binder.---------------------------------- ---- ----Shoemaker. Sweeping Bare Floor 38 Strokes per Minute.... 626 661 672 Pool Player. Walking 2 mph, Light Dancing.------------------ Light Metal Worker (at Bench)-------------------- 680 761 862. Painter of Furniture (at Bench).,------------ ---. 876 Carpenter. Restaurant Serving- Pulling Weight------Walking 3 mph------ - 954 : 1000 1041 1050 1390 Walking Down Stairs.. Stone Mason--:--------BowlingMan Sawing Wood-- 1444 1490 1500 1800 Swimming.--------------- 1986 Running 5.3 mph------- Walking 5 mph.. Walking Very Fast 5.3 mph- 2268 2330 2580 Walking Upstairs- 4365 Maximum Exertion Different People.---- -------. 3000-4800 145 225 225 225 225 225 225 225 225 225 225 225 225 225 225 225 225 229 230 250 277 280 307 325 335 339 452 467 485 490 5_9_0 ... 145 978 0.140 159. 1072 0.153 195 1315 0.188 206 1389 0.198 216 1457 0.208 237 1598 0.228 243 1639 0.234 257 1733 0.248 261 1760 0.251 265 1787 0.255 324 2185 0.312 333 2246 0.321 345 2326 0.332 375 2529 0.361 375 2529 0.361 401 2704 0.386 , 436 2940 0.420 443 2987 0.427 450 3055 0.434 511 3446 0.492 585 3945 0.564 596 4019 0.574 647. 4363 0.623 . 675 4552 0.650 708 4774 0.682 711 4795 0.685 938 6325 0.904 977 6588 0.941 1005 67.77 .0.968 1010 6811 0.973 _12_10 . 8160 1.166 ....... "These metabolic rates were compiled by the A.S.H.V.E. Research Laboratory from actual tests, from other authoritative sources, and from estimates based upon various considerations. ^ Division of .the total heat dissipation into latent and sensible rates is based on actual test data and on various considerations for metabolic rates up to 1250 Btu per hour, and extrapolated for. higher rates. Values for total beat dissipa tion for a person at rest apply for a dry-bulb temperature range from approximately 60 to 90 F;-for other than rest conditions the values apply for a similar but lower temperature range. Below these temperature ranges metabolic rates and total rates of heat dissipation increase, while above these ranges metabolic rates increase slightly and total heat dissipation rates decrease rapidly.- Division of total dissipation rates into sensible and latent heat holds only for a dry-bulb temperature of 79 F. For lower temperatures, sensible heat dissipation increases and latent heat decreases, while for higher temperatures the reverse is true. from Figs. 9, 10 and 11, to determine the sensible and latent heat dissi pation for any work rate and any environmental condition, provided the metabolic rate is known at one elective temperature. For example, if it is found that a certain type of work results in a metabolic rate of approximately 760 Btu per hour for an average person working in an atmosphere of 70 ET, then this total rate of heat dissipation to atmos pheres of various temperatures will be approximately as given by the broken-line curve in Fig. 9. The broken line curves in Figs. 10 and 11 give the rate of sensible and latent heat dissipation of the person for different, dry-bulb temperatures. The metabolic rates for a number of types of: