Document 3QZ5mMq3XYjGXM4XO0jMyVN26

American Society of Heating and Ventilating Engineers Guide, 1932 Velocity Head or Pressure: The head or pressure required to create the velocity of flow, that is, the head or pressure required to accelerate the mass from a state of rest to the velocity at the point measured. Ventilation: Air change. Natural Ventilation: Air change produced by natural forces (wind and gravity) only. Mechanical Ventilation: Air change produced by mechanical means (fans and blowers). Warm Air Heating System: A warm air heating plant consists of a heating unit (fuel-burning furnace) enclosed in a casing, from which the heated air is distributed to the various rooms of the building through ducts. If the motive head producing flow depends on the difference in weight between the heated air leaving the casing and the cooler air entering the bottom of the casing, it is termed a gravity system. A booster fan may, however, be used in conjunction with a gravity-designed system. If a fan is used to produce circulation and the system is designed especially for fan circulation, it is termed a fan furnace system or a centralfanfurnace system. A fan furnace system may include air washers, filters, etc. Wet-Bulb Temperature: The lowest temperature which a water wetted body will attain when exposed to an air current. (This is the temperature of adiabatic saturation.) Wet Return: That part of a return main of a steam heating system which is filled with water of condensation. (The wet return usually is below the level of the water line in the boiler, although not necessarily so.) ABBREVIATIONS British thermal unit...... .......... ...Btu calorie..-!....................... ....... ...... .....cal centigram........... ......................... ......eg centimeter______ ___ _______ _ __ cm centimeter-gram-second......... .....Cgs cubic................ .................... :____ ...... cu cubic foot............. ....................... -CU ft cubic feet per second........... . __ cfs cubic feet pier minute............... ...cfm degree......................................... -deg degree centigrade......... ............ ....... C degree Fahrenheit_________ _ ____F direct-current (as adjective).. -d-c feet per minute................... ..... ...fpm feet per second.......... ............... . .....fps foot.... ................ -____ _____ .............ft gallon....................--........................ gal gallons per minute___ ____ -------gpm gallons per second____ ___ -..... gps horseprower............................ .....hp inch____ ______ ____________ ........... in. meter............... ...... ................ ......--m miles per hour....... ....... ...... ........ mph minute...... ...... .............. ........ ..........min ounce______ ___ --............... .. _______ oz parts per million...... ........... -------ppm revolutions per minute...... ........ rpm revolutions per second...... .....rps square foot--__________ __ ____ sq ft square inch........................... ......sq in. 8 Chapter 2 ESTIMATING HEAT LOSSES .Procedure to be Followed; Inside Temperatures; Outside Temperatures; Wind Movement; Heat Sources; Examples of Heat Loss Computations THE size of the heating plant required for a building is based on the maximum heat demand. This maximum heat demand depends on many factors, most of which are seldom, if ever, in equilibrium. These include the following: 1. Outside temperature. 2. Rain or snow. 3. Sunshine or cloudiness. 4. Wind velocity. 5. Heat transmission of exposed parts of building. 6. Infiltration of air through cracks, crevices and open doors and windows. 7. Heat capacity of materials. 8. Rate of absorption of solar radiation.of exposed materials. 9. Inside temperatures. 10. Stratification of air. 11. Type of heating system. 12. Ventilation requirements. 13. Period and nature of occupancy. 14. Temperature regulation. Outside Conditions {The Weather) Building Construction I Inside Conditions The inside conditions vary from time to time, the physical properties of the building construction may change with age, and the outside conditions are changing constantly. Just what the worst combination of all of these variable factors is likely to be in-any particular case is therefore con jectural. Because of the nature of the problem; extreme precision in estimating heat losses at any time is very unlikely. However, studies now in pro gress at the A.S.H.V.E. Research Laboratory will, it is hoped, increase the accuracy with which it is possible to combine all' of the various factors involved to determine the maximum effect thereof. The data published in this and Chapters 3, 4, and 28 have been largely derived from the investigations,at the A.S.H.V.E. Research Laboratory since it was established in 1919, and also at cooperating institutions. Studies of sun effect and heat capacity have been under way for about two years. The procedure to be followed in determining the heat loss from any building can be divided into seven consecutive steps, as follows: 1. Determine on the inside air temperature, at the breathing line, which is to be maintained in the building during the coldest weather. (See Table 1, p. 10). 9