Document oep3ypL184mJ9B9bJY4NVYJO3

American Society of Heating and Ventilating Engineers Guide, 1937 with a poor distribution system or with an air supply which is too small to result in uniform distribution without drafts. Some systems of distribution produce drafts with but a few degrees temperature rise, while other systems operate successfully with a temperature rise as high as 35 F. The total air quantity introduced in any particular case is inversely pro portional to the temperature rise, and depends largely upon the judgment and ingenuity of the engineer in designing the most suitable system for the particular conditions. The changes in moisture content resulting from occupation in the atmosphere of a room supplied with various volumes of outside air is shown in Fig. 7. Data are given for an adult, 5 ft 8 in. in height, weighing 150 lb and having a body surface of 19.5 sq ft and for a child,12 years of age, 4 ft 7 in. in height weighing 76.6 lb and having a body surface area of 12.6 sq ft. Also given in Fig. 7 is the temperature of incoming air necessary to maintain a room temperature of either 70 of 80 F as indicated assuming that there is no heat gain or loss to the room by transmission through the walls, solar radiation or other sources. AIR MOVEMENT AND DISTRIBUTION Stagnant warm air, not matter how pure, is not stimulating and it detracts to some extent from the quality of air. Experience, and recent field studies by the A.S.H.V.E. Research Laboratory45 place the desirable air movement between 15 and 25 fpm under ordinary room temperatures during the heating season. Objectionable drafts are likely to occur when the velocity of the air current is 40 fpm and the temperature of the air current 2 F or more below the customary winter room temperature. Higher velocities are not objectionable in the summer time when the air temperature exceeds 80 F. Variations in air movement and temperature in different parts of occupied rooms are often indicative of relative air distribution. The work of the A.S.H.V.E. Research Laboratory indicates that an air movement between 15 and 25 fpm with a temperature variation of 3 F or less in different parts of a room, 36 in. above floor, insure satis factory distribution. Considerable evidence was obtained in these tests to show that measurements of carbon dioxide are not essential for the study of air distribution, or for indirect measurements of outdoor air supply, which can be obtained more conveniently from the increase in moisture content of the ventilating current. HEAT AND MOISTURE GIVEN UP BY HUMAN BODY In conditioning air for comfort and health it is necessary to know the rate of sensible and latent heat liberation, from the human body, which in conjunction with other heat loads (see Chapters 5 and 7) determine the capacity of the conditioner. The data in common 'use are those, of the A.S.H.V.E. Research Laboratory46 shown in Figs. 8, 9, 10 and 11. Other useful data are given in Tables 4, 5 and 6, which are self-explanatory. Classroom Drafts in Relation to Entering Air Stream Temperature, by F. C. Houghten, H. H. Trimble.. Carl Gutberlet and M. F. Licfctenfels (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning . July, 1935). ''Thermal Exchanges between the Bodies of Men Working and the Atmospheric Environment, by F. CHoughten, W. W. Teague. W. E. Miller and W. P. Vant (American Journal of Hygiene, Vol. XIII. No. 2. March. 1931. pp. 415-431). 76 Chapter 3--Physical and Physiological Principles of Air Conditioning Table 4. Relation Between Metabolic Rate and Activity3 Acrmrr Houhlt Meta bolic Rate fob Avg. Person ob Total Heat Dissipated, Btu peb Hour Hourly Sensible Heat Dissipated, Btu per Hour Hourlt Latent Heat Dissipated, Btu per Hour Average Person Seated at Rest.. Average Person Standing at Rest1 384 431 482 Office Worker Moderately Active 490 Clerk, Moderately Active, Standing at Counter...... ........ 600 Book Binder*.----------- ------ ------ 626 Shoe Maker*; Clerk, Very Active Standing at Counter -----Pool Player..............-................... 661 680 Walking 2 mph*. 4; Light Dancing...............-........ -........... Metal Worker*................. ............... Painter of Furniture*--........- 761 862 876 Restaurant Serving, Very Busy- 1000 Walking 3 mph*..--................ -....... 1050 Walking 4 mph*. *; Active Dancing, Roller Skating--------- 1390 Stone Mason*...... .................. .......... 1490 Bowling............ ................................. 1500 Man Sawing Wood*--..................... 1800 Slow Run*--.................... ............ 2290 Walking 5 mph*.......................... 2330 Very Severe Exercise*............... 2560 Maximum Exertion Different People1--................................... 3000 to 4800 225 225 225 225 225 225 225 230 250 277 280 325 346 452 490 490 590 159 206 257 265 375 401 436 450 511 585 596 675 704 938 1000 1010 1210 Moisture Dissipated, per Hour Grains 1070 1390 1740 1790 2530 2710 2940 3040 3450 3950 4020 4560 4750 6330 6750 6820 8170 Lb 0.153 0.199 0.248 0.256 0.362 0.387 0.420 0.434 0.493 0.564 0.575 0.651 0.679 0.904 0.964 0.974 1.167 aMetaholism rates noted based on tests actually determined from the following authoritative sources: 'A.S.H.V.E. Research Laboratory; 'Becker and Hamaiainen:'Douglas, Haldane, Henderson and Schneider; 'Henderson and Haggard; and 'Benedict and Carpenter. Metabolic rates for other activities estimated. Total heat dissipation integrated into latent and sensible rates by actual tests for metabolic rates up to 1250 Btu per hour, and extrapolated above this rate. Values for total heat dissipation apply for all atmos pheric conditions in a temperature range from approximately 60 to 90 F dry-bulb. Division of total heat dissipation rates into sensible and latent heat holds only for conditions having 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. Table 5. Degrees of Perspiration for Persons Seated at Rest Under . Various Atmospheric Conditions Degree of Perspiration* Atmospheric Condition 95 Per Cent Relative Humidity 20 Per Cent Relative Humidity Forehead clammy Body clammv i_ .... Body damn............... Beads on forehead Body wet........ Perspiration on forehead runs and drips ___ Perspiration runs down body. ... E.T. 73.0 73.0 79.0 80.0 84.5 88.0 88.5 D. B. W. B. 73.6 73.6 79.7 80.8 85.4 89.tr 89.5 72.4 72.4 78.4 79.4 84.0 87.6 88.1 E. T. D. B. W. B. 75.0 75:0 81.0 87.0 86.5 94.0 90.0 87.0 87.0 97.5 109.4 108.5 125.2 116.0 60.7 60.7 67.5 75.2 74.6 85.4 79.5 Forty per cent of Bubjects registered degree of perspiration equal to or greater than indicated. 77