Document ymRw5RgJB2pa0mBm5qrw5ykX4

American Society of Heating and Ventilating Engineers Guide, 1935 Ventilation and Air Conditioning Standards Although heat and moisture from the human body constitute the major portion of the cooling load, in most cases where air conditioning is pro vided for comfort and health other factors must also be considered. These include heat from lights, machinery, and processes, as well as the trans mission and infiltration of heat through the building structure. The computations for these factors may be made in accordance with data given in Chapters 5 and 7. PROBLEMS IX PRACTICE 1 What is the purpose and method of conditioning the air of occupied rooms? Chiefly comfort, and the method is to control the temperature, humidity, and air distri bution, and to prevent the accumulation of excessive body odors in the air. Other factors have yet to be studied. 2 What are the most comfortable air conditions? Table 4. Condition of Sensible Perspiration for Persons Seated at Rest Under Various Atmospheric Conditions4 Degree of Perspiration. Atmospheric Condition 95 Per Cent Relative Humidity 20 Per Cent Relative Humidity Comfort standards are not absolute, but they are greatly affected by the physical con dition of the individual, and the climate, season, age, sex, clothing, and physical activity. For the northeastern climate of the United States, the conditions which meet the require ments of the majority of people consist of temperatures between 68 and 72 F in winter and between 70 and 85 F in summer, the latter depending largely upon the prevailing outdoor temperature. The most desirable relative humidity range seems to be between 30 and 60 per cent. 3 Are the optimum conditions for comfort identical with those for health? Forehead clammy............ Body clammy...... ........................ Bodv damp... Beads on forehead____________ Bodv 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. 73.6 73.6 79.7 80.8 85.4 89.0 89.5 W. B. 72.4 72.4 78.4 79.4 84.0 87.6 88.1 E.T. 75.0 75.0 81.0 87.0 86.5 94.0 90.0 D. B. W.B. 87.0 87.0 97.5 109.4 108.5125.2 116.0 60.7 60.7 67.5 75.2 74.6 85.4 79.5 Forty per cent of subjects registered degree of perspiration equal to or greater than indicated. I Table S. Condition of Sensible Perspiration for Persons at Work Under Various Atmospheric Conditions30 There are no absolute criteria of the prolonged effects of various air conditions on health. For the present it can be only inferred that bodily discomfort may be an indication of conditions that may produce poor health. 4 Given dry-bulb and wet-bulb temperatures of 76 F and 62 F, respectively, and an air velocity of 100 fpm, determine: (1) effective temperature of the con dition; (2) effective temperature with still air; (3) cooling produced by the move ment of the air; (4) velocity necessary to reduce the condition to 66 deg effective temperature., ... .. ... .. (1) In Fig. 1 drav; ImejAB through [given '-dry*-ana wet-bulb temperatures. Its intersection with the 100-ft velocity curve gives 69 deg for the effective temperature of the condition. (2) Follow hne/iB \o the right to irsintersection with the20-fpm velocity line, and read 70.4 deg for the effective temperature'for this velocity or so-called still air (3) The cooling produced by tne movement'of the air'is 70.4 -- 69 = 1.4 deg effective temperature. (4) Follow line AB to tht lc't until it crosses the 66 deg effective tempera ture line and interpolate velocity value of 340 fpm to> which the movement of the air Degree of Perspirations Atmospheric Condition ii95 Per Cent Relative | 20 Per Cent Relative Humidity J Humidity 5 Given dry-bulb and wet-bulb temperatures of 75 and 68 F, respectively, first, what is the effective temperature? Second, is this condition warmer or cooler than 80 F dry-bulb and 60 F wet-bulb? E. T.' D.B.* W. B. E.T. D. B. W.B. The first condition is given by the intersection of the 75 F dry-bulb line and the 68 F wetbulb line (Fig. 3). The effective temperature of 72.1 deg is given by the numerical value Forehead clammv-- ............ .... Body clammv.................... Body damp...... . __ Beads on forehead______ Body wet..................... Perspiration on forehead runs and drips.___. Perspiration runs down body .. 59.0 50.0 60.0 68.0 69.0 78.5 79.0 59.4 50.2 60.3 68.5 69.6 79.3 79.8 58.3 49.3 59.3 67.5 68.5 78.0 78.5 69.5 57.0 62.5 76.0 71.0 82.0 81.0 80.5 61.6 69.6 91.0 82.8 100.5 99.8 56.5 44.2 49.5 63.4 53 0 70.2 69.0 of the effective temperature line passing through this point and indicated by the scale along the saturation curve. The second condition is given by the intersection of 80 F dry-bulb and 60 F wet-bulb and is 71.8 deg ET. It is therefore 0.3 deg ET cooler than the first condition. 6 Given 76 F dry-bulb and 61 F wet-bulb. How many degrees difference are there between this condition and the winter comfort line or 66 deg ET? Forty per cent of subjects registered degree of perspiration equal to or greater than indicated. The effective temperature for this condition is given by the intersection of the 76-F drybulb and 61-F wet-bulb lines and is 70 deg ET, which is 4 deg ET warmer than the comfort line. ft In many cases, allowance must also be made for sun effect and for heat 7 I Assume that the design of an air conditioning system for a theater is to be capacity of the building structure in accordance with studies by the based on an outdoor dry-bulb temperature of 95 F and a wet-bulb temperature A.S.H.V.E. Research Laboratory37. Another item to be considered is the radiant heat received by the body from high temperature wall and ceiling surfaces. of 78 F with an indoor relative humidity of 50 per cent. According to Table 2, the dry-bulb temperature in the auditorium should be 80 F. Estimate the sensible and latent beat given up per person. The sensible heat given up per person per hour under this condition may be obtained from Fig. 7. With an abscissa value of 80 F, Curve D for men seated at rest gives a value Transmigion as Influenced by Heat Capacity and Solar Radiation, by F. C. Houghten, I. Blackshaw, E. M. Pugh, and Paul McDermott (A.S.H.V.E. Transactions, Vol. 38, 1932). J on the ordinate scale of 220 Btu per person per hour as the sensible heat loss. The latent heat given up by a person seated at rest per hour may be obtained from Fig. 8. With an 60 61