Document LKBmQ14rV4e1BM0wDy4QExrdQ

Heating Ventilating Air Conditioning Guide 1939 Chapter 3. Physical & Physiological Principles or Air Conditioning Table 2. Desirable Inside Conditions in Summer Corresponding to Outside Temperatures3 Occupancy Over 40 Min moderate humidity, and that it dries up the mucous membranes in such a way as to increase susceptibility to colds and other respiratory dis orders " 38, 39- Owing to the cooling effect of evaporation, higher tem Outbids Dbt-Bulb Deo F Effective Temperature AmInside Conditions Dry-Bulb Deg F Wet-Bulb Deg F Dew-Point Deg F Relative Humid ity Per Cent peratures are necessary, and this condition may lead to discomfort and lassitude. Moist air, on the other hand, interferes with the normal evaporation of moisture from the skin, and again may cause a feeling of oppression and lassitude, especially when the temperature is also high. 100 75 83 66 56 40 75 82 67 59 45 75 81 68 61 51 75 80 70 65 60 For the premature infant, a high relative humidity of about 65 per cent is demonstrably beneficial to health and growth" until the infants reach a weight of about 5 lb. No such clear-cut evidence exists in the case of adult persons. In the comfort zone experiments of the A.S.H.V.E. 95 74 82 64 53 36 74 81 66 57 44 74 80 67 60 51 74 79 68 62 57 Research Laboratory, the relative humidity was varied between the limits of 30 and 70 per cent approximately, but the most comfortable range has not been determined. In similar experiments at the Harvard 74 78 70 66 68,, School of Public Health, the majority of the subjects were unable to is 90 73 81 63 52 36 73 80 64 54 41 detect sensations of humidity (i.e., too high, too low, or medium) when the relative humidity was between 30 per cent and 60 per cent with 73 79 66 59 50 ordinary room temperatures. This is in accord with studies by Howell61, 73 78 67 61 56 it 85 72 80 61 48 32 72 79 63 53 41 :! 72 78 64 56 46 Miura42 and others. The limitation of the comfort zones in Fig. 6 with respect to humidity must not be taken too seriously. Relative humidities below 30 per cent 72 77 66 60 56 may prove satisfactory from the standpoint of comfort, so long as ex 80 71 78 61 49 36 71 77 63 54 45 71 76 64 57 52 71 75 66 61 61 tremely low humidities are avoided. In mild weather comparatively high relative humidities are entirely feasible, but in cold or sub-freezing weather they are objectionable on account of condensation and frosting on the windows. They may even cause serious damage to certain building Applicable to individuals engaged in sedentary or light muscular activity. materials of the exposed walls by condensation and freezing of the mois ture accumulating inside these materials. Unless special precautions are but a few minutes in the cooled space, observations36 indicate a schedule . about 1 deg dry-bulb or effective temperature higher than that shown in Table 2. Laboratory experiments with exposures of 2 to 10 min indicate temperatures 2 to 10 F higher than those in Table 2 but with much lower . relative humidities. It should be kept in mind that southern people, with their more sluggish taken to properly insulate the affected surfaces, it will be necessary to reduce the degree of artificial humidification in sub-freezing weather to less than 40 per cent, according to the outdoor temperature. Information on the prevention of condensation on building surfaces is given in Chapter 7. The principles underlying humidity requirements and limitations are discussed more fully elsewhere". heat production and lack of adaptability, will demand a comfort zone The purpose of artificial humidification may be easily defeated by several degrees higher than that for the more active people of northern failure to change the spray water of the humidifier at least daily. Where climates. Instead of the summer comfort .line standing at 71 deg as here this condition occurs, the air is characterized by a lack of freshness, and given, it was found to be much higher for foreigners in Shanghai where under extreme conditions by a musty, sour odor in the conditioned space. climatic conditions are similar to those of our gulf states. This difference in adaptability of people forms a very real problem for air conditioning engineers. Cooling of theaters, restaurants, and other public buildings in et al (Journal Experimental Medicine, 1921, VoT 34Tp. 11).------- ---------- - ' ouiarr, southern climates cannot be based on northern standards without con ,, arandCCoSui^f S*?' Cavity and Post-Nasal Space to Chilling of the Body Surfaces, by A. Goldman, siderable modification. p 151) ("oncurrent St3<ly of Bacteriology of Nose and Throat {Journal Infectious Diseases, 1921, Vol. 29, Optimum Humidity Just what,the optimum range of humidity is, is a matter of conjecture. There seems to exist a general opinion, supported by some: experimental and statistical data, that warm, dry air is less pleasant than air of a jj Oto".TKol'.!0d0L^%i!!,U)2nati0nS f the NoSe' Pharytut and Tonsils' br Mudd' Stuart, et al (Am. ^Loc. Cit. Note 24. "Humidity and Comfort, by W. H. Howell (The Science Press, April, 1931). Temperature and Sense of Comfort, by U. Miura "How Cool? Inside Temperature Should Depend Upon Type of Occupancy, by J. H. Walker (Beating { and Ventilating, October, 1932). ." ' *| Bid!rrfn^o^llo0 July ^ P Kratz, University of Illinois (Engineering Experiment Station 66 i 67 X