Document pmaxROXBooY4Y7K106zKkN5ZX

American Society of Heating and Ventilating Engineers- Guide for the growth of each variety of mildew, but this growth can h tS inhibited by depriving the mildew of water or by the use of ch treatments. Too high a temperature (over 100 deg. fahr.), cornh''^! with low relative humidity, may cause the book materials to ber^l brittle. A temperature much below freezing (25 deg. fahr.) ma-y01^! permanent deterioration of the glue. y cau^e4 The relative humidity should be maintained between 40 per cent ' a 70 per cent, although these limits may be exceeded in either direction?^ short periods of time. If the relative humidity gets much below 40 cent, first the glue and then the paper will tend to become brittle TV*' will not cause any permanent damage unless the book is used, or rath : abused, while, in this condition. Subsequent increase in humidity wht bring the materials back to their normal condition. If the relatiV* humidity gets much above 80 per cent, the growth of mildew may & expected. , -sag The tendering, brittleness, and yellowing of books, which are usually 3 looked upon as signs of age may be caused by oxygen plus moisture or by sulphuric acid. The effects can be diminished by. using a grade of `J paper which is as nearly pure cellulose as practicable. The deterioration of the leather bindings can be retarded by occasional applications of -J neats-foot oil. Sometimes leather and paper contain small amounts of J? sulphuric acid, put in during the manufacturing process. Such leather M or paper is not so suitable for book making as that which is entirely free ii from acid. The glue used in making books should contain a preservative !^f to prevent any decomposition from the growth of bacteria or mildew., f It should also contain some plasticizing agent, such as glycerol, to offset the effect of exposure to low humidity. Books should be protected, as far as possible, from exposure to direct sunlight, since this accelerates the deteriorating action of other agencies. 11. OZONE AND VENTILATION ; The Guide, 1930, contains a bibliography and description of the physi cal, chemical and germicidal qualities of ozone, with instructions and formulae covering its most effective applications. Ozone is a product of short wave ultra-violet light and is especially valuable in ventilation as a deodorant. The process of ozonating in addition to producing ozone also supplies a considerable percentage of ionized oxygen. Any air which has received ionized oxygen is comparable with the unheated bracing pure air of the country on a sunny spring day. 12. UNIT `COOLERS" An interesting development is the production of unit recirculating heat absorbers for cooling and dehumidifying the air in rooms occupied by human beings. A device similar to a unit heater, equipped with an electric fan and having a drainage connection to care for condensation is placed within the room, and the cooling accomplished by means of brine circu lated through the apparatus. In the case of non-poisonous refrigerants, direct expansion within the heat transfer-surfaces is permissible. For ordinary applications, an air-cooling machine of this type will absorb approximately the heat required to melt 100 lb of ice per hour. 532 KM ~t > `J' _ 33--Special Applications of Heating and Ventilation JHGHAP*45' relit ' 13. ZONING OF HEATING AND VENTILATION Hfe-aVers are paying more and more attention to the control of heating entflating equipment with reference to the changing daily outside fetaatial fuel savings are possible with central manual control where^Theating may be accentuated on the colder sides of the building, or US on the warmer sides of the building. Savings in the fuel cost of fP^Fapartment houses and office buildings are often made possible by ^ control by zones. Much of the fuel saving by this zoning is PilliLf by the prevention of too many open windows on the leeward or IllSy sides of the building. lRemote-controlled, electrically or pneumatically-operated valves are PHuhable, arlcj the design of any large building which has no provision Irri'zoned operation is subject to criticism. The various remote supply sSafoes may be operated by thermostats or may be under manual control, iSjy throwing one switch either type of control may be selected. It is ioosiible also to indicate at a central point, accurately and at low cost, Ithe temperatures throughout the building, which information of course furnishes the inspiration for use of .the manual controls. The effect of Bsunshine on building heat-demand may thus be followed around the IipbuSi^ldifnugrtheearc,hvdearyy. simple refinement may cause the fuel-burning device, isuch as stoker or oil burner or gas flame to be shut down whenever the jkLSbzone valve closes, and to resume operation whenever the first zone ^valve opens, no matter which one this may be. ^ 14. SUN EFFECT ON BUILDINGS Ip^The absorption of solar radiation in the summer by the surfaces of a BJuiIding exposed to the sun has an important bearing on the capacity of refrigerating equipment required for air conditioning. These surfaces |imay be the exterior walls or the roof of the building, or interior surfaces J^which receive the sun's rays through window glass. fifeat Transfer through Exterior Walls and Roofs pSyWhen equilibrium has been established, and the rate of heat flow is jKoiiaefore constant, the heat transmitted per hour through a wall or roof JB||is equal to the product of the conductance of the structure from the |||j?exterior surface to the interior air and the difference between the exterior J*v.:;'surface temperature and the interior air temperature. This relation is ||pts=expressed as follows: II ~ Ci(tr -- t) (1) ^'..Vihere H = Heat transmitted through wall or roof, Btu per hour per square foot. Ci -- Conductance of wall or roof between exterior surface and interior air, Btu per hour per square foot, per degree Fahrenheit difference in temperature. h ~ Exterior surface temperature, degrees Fahrenheit. t => Interior air temperature, degrees Fahrenheit. Under actual conditions, the heat flow due to sun effect is almost never 'n equilibrium because of the heat capacity of the wall or roof structure. 533