Document MJE7D86gangL9LN5DV22Xak7x

American Society of Heating and Ventilating Engineers Guide, 1934 Example S. What <s the probable inleakage of air for a room with three windows on the first floor, if the wind velocity is 15 mph? The building is 90 ft high and is equipped with architectural projected steel windows with two ventilators each with a total perimeter of 24 ft of %4,-in. crack. Further, find the probable inleakage in similar rooms on the top floor and ori the third floor 30 ft from the ground. Solution. On the first floor the equivalent wind velocity is Me = -v/151 + 1.75 X 45 or 17.5 mph. Leakage for this type of window is given in Table 2 (interpolating) as 102 cu ft per foot of crack per hour. The total leakage rate (Q) is equal to 3 X 24 X 102 or 7344 cu ft per hour. For a similar room on the top floor, with the same exposure, the equivalent wind velocity is Afe = -t/lfi* -- 1.75 X 45 or 12 mph for which the leakage is 66.4 cu ft per ft of crack per hour. The total inleakage of air into the room (Q) is equal to 3 X 24 X 66.4 or 4780 cu ft per hour. For a similar room 30 ft above the ground, Me = \/15* + 1.75 X 15 or 16 mph for which the unit crack leakage will be 93.6 cu ft per hour, and the total leakage for the room will be 6740 cu ft per hour. REFERENCES Air Leakage, by Houghten and Schrader (A.S.H.V.E. Transactions, Vol. 30. 1924). Air Infiltration through Various Types of Brick Wall Construction, by Larson, Nelson and Braatz (A.S.H.V.E. Transactions, Vol. 35. 1929). Infiltration through Plastered and Unplastered Brick Walls, by F. C. Houghten and Margaret Ingels (A.S.H.V.E. Transactions, Vol. 33, 1927). . Air Leakage around Window Openings, by C. C. Schrader (A.S.H.V.E. Transactions, Vol. 30, 1924). Effect of Frame Calking and Storm Sash on Infiltration around and through Windows, by Kichtmann and Braatz (A.S.H.V.E. Transactions. Vol. 34, 1928). Air Leakage on Metal Windows in a Modern Office Building, by Houghten and O'Connell (A.S.H.V.E. Transactions, Vol. 34, 1928). The Weathertightness of Rolled Section Steel Windows, by Emswiler and Randall (A.S.H.V E. Trans actions, Vol. 34, 1928). Air Leakage through a Pivoted Metal Window, by Houghten and O'Connell (A.S.H.V.E. Transactions, .Vol. 34. 1928). Pressure Difference across Windows in Relation to Wind Velocity, by Emswiler and Randaii (A.S.H.V.E. Transactions, Vol. 35, 1929). Air Infiltration Through Various Types of Wood Frame Construction, by Larson, Nelson and Braatz (A.S.H.V.E. Transactions, Vol. 36. 1930). ." Neutral Zone in Ventilating, by J. Ev Emswiler (A.S.H.V.E. Transactions. Vol. 32. 1926). Air, Infiltration Through Double-Hung Wood Windows, by Larson. Nelson and Kubasta (A.S.H.V.E. Transactions, Vol. 37, 1931). Flue Action in Tall Buildings, by H. L.` Alt (Hearing, Piping and Air Conditioning, May, 1932). Air Infiltration-Through Steel Framed Windows, by D. O..Rusk, V. H. Cherry and L. Boelter {Heating, Piping and Air Conditioning, October,. 1932). 5102 A Chapter 7 THE HEATING LOAD Factors Governing Heat Demand, Procedure, Temperatures, Wind Movement, Heat Sources Other Than Heating Plant, Example, Condensation IN the design of any type of heating system, the maximum probable heat demand must be accurately estimated in order that the apparatus installed shall be of sufficient capacity to maintain the desired temperature at all times. The factors which govern this maximum heat demand-- most of which are seldom, if ever, in equilibrium--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 arid open doors and windows. 7. Heat capacity of materials. 8. Rate of absorption of solar radiation by 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 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 com jectural. Because of the nature of the problem, extreme precision in estimating heat.losses at any time.is,very unlikely, . ... .. . 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, or the 30-in. line, which is to be maintained in the building during the coldest weather. (See Table 1). 2. Determine on an outside air temperature fordesign purposes; based onthe minimum temperatures recorded in the locality: in question, which. ,wi/J provide, for all but the most severe weather conditions. Such conditions as may existjor.pnly.a few. consecu tive hours, are readily taken care of by the heat" capacity' of the. building, itself. (See Table-2). . ... f. y;..:.': ss i" ; 3. Select or compute the heat.transmission Coefficients for dutside:wall$ and'glasa; 103