Document JNO0xkkQqMxVwDkpexgj1q5r

American Society of Heating and Ventilating Engineers Guide, lflaoM Determining the Quantity of Dust in Air by Impingement, by F. B. Rowley and John Beal (A.S.H Transactions, Vol, 35,1929). "'n.vja Determining Lines ofEqual Comfort, by F. C. Houghten and C. P. Yagloglou (A.S.H.V.E. Trans^-^^sH Vol. 29. 1923. p. 361). .. _ ,, ,, Cooling tiffed on Human Beings ProducedbyVariousAtr Velocities, by F. C. Houghten and r Vagloglou (A.S.H.V.E. Transactions, Vol. 30. 1924. p. 193). uM Practical Application of Temperature. Humidity and Air Motion Data to Air Conditioning Problem. 1 3 F ' CSomHeouPghhytseino,loWgic. aWl .RTeeaactgiounes, Wto.HEig. hMiTlleemr p(eAr.aStu.Hre.sV.aEn.dTHraunmsidacititeios,nsb,yVWol,. 3J3.,1M9c2C7o),nnell and F bryI3 Houghten <A.S.H.V.E. Transactions, Vol. 29, 1923, p. 122). V.1 Air'Motion. High Temperatures and Various Humidities-Rcndimuon Human Beings, byW. J. McConnell 1 F. C. Houghten (A.S.H.V.E. Transactions. Vol. 30. 1924, p. 167). J Heat and Moisture Loss from the Human Body and Its Relation to Air Conditioning Problems, by R r 1 \HoLuegmhHinumwiditwy'PTseyacghuoem.etwric. CEh.arMts,illbeyr Man.dC.WW. . PT.omYalinnsto(nA(.AS..SH..HV..VE..ET. rTarnasnascatciotinosn,sV, VooLl.8355'.f1og*)V| 418 Chapter 27 VENTILATION SYSTEMS Motive Forces in Natural Ventilation; Natural Ventilation Sys tems* Mechanical Ventilation Systems; Combined and Split Systems; Upward and Downward Systems of Air Distribution; Inlets and Outlets; Designing a Ventilating System; Equipment for Obtaining Synthetic Air Chart Percentages. P ' IN the advance of civilization man has changed from an outdoor to an indoor creature. As construction methods have improved, buildings have become tighter, and methods of renewing the air in occupied spaces have been developed. Likewise, as the art of creating and maintaining satisfactoty atmospheric conditions indoors has progressed, modern sys tems of air conditioning, which involve the control of temperature and humidity as well as the factors of air distribution and the rate of air change, have become fixed in the lay mind as systems of ventilation. These newer ' developments are treated in Chapter 29, Air Conditioning of Buildings, whereas this chapter deals primarily with the general methods whereby air change is effected in confined spaces. , Ventilation systems may be classified as natural and mechanical. Natuf. ral systems are those which employ natural forces only to bring about the ; desired air change, whereas mechanical systems are those in which air motion is obtained by mechanical means. MOTIVE FORCES IN NATURAL VENTILATION The forces employed in natural ventilation for the displacement of air in buildings, are the wind and gravity. The action of the wind in inducing air change is obvious. In gravity systems the movement of air is pro duced by the head or pressure difference resulting from the difference in density between the air in ducts or flues and that of the outside air. If such forces were constant and not variable it would be easy to design satisfactory systems of natural ventilation which would employ the wind or gravity either singly or in unison. Since atmospheric conditions are varying constantly, the results are not readily susceptible of control. Be fore the necessity for exact control of ventilation was appreciated, and before the methods of exercising such control were discovered or applied, advantage was taken of these natural forces, whenever they were favor able, to improve conditions. Thus, if the wind is blowing, windows opened on the windward and leeward sides of a room will effect an air change, even though there be no difference in temperature between outdoors and indoors. On the other hand, if appropriate openings for ingress and egress be provided, even 419