Document 2JwB5z16p6mGQdo8nmzOq3eJN

696 CHAPTER 31 1954 Guide A.8.H.V.E. Research Report No. 1204--Entrainment and Jet-Pump Action of Air Streams, by G. L. Tuve, G. B. Priester, and D. K. Wright, Jr. (A.S.H.V.E. Transactions, Vol. 48, 1942, p. 241). - A.S.H.V.E. Research Report No. 1248--Control of Air Streams in Large Spaces, by G. L. Tuve and G. B. Priester (A.S.H.V.E. Transactions, Voi. 50,1944, p. i53). A.S.H.V.E. Research Report No. 1328--The Discharge of Air from a Long Slot, by Alfred Koestel and G. L. Tuve (A.S.H.V.E. Transactions, Vol. 54, 1948, p. 87). .. A.S.H.V.E. Research Report No. 1366--Air Streams from Perforated Panels, by Alfred Koestel, Philip Hermann and G. L. Tuve (A.S.H.V.E. Transactions, Vol. 55, 1949, p. 283). A.S.H.V.E. Research Report No.'1404--Comparative Study of Ventilating Jets from Various Types of Outlets, by Alfred Koestel, Philip Hermann, and G. L. Tuve (A.S.H.V.E. Transactions, Vol. 56, 1950, p. 459). : A.S.H.V.E. Research Report--The Control of Air Streams from a Long Slot, by Alfred Koestel and C. V. Young (A.S.H.V.E. Transactions; Vol. 57, 1951, p; 407). A.S.H.V.E. Research Report--Air Velocities in Ventilating Jets, by G. L. Tuve (A.S.H.V.E. Journal Section, Heating, Piping & Air Conditioning, January 1953, p. 181). ` A.S.H.V.E. Cooperative Research at Kansas State College . A.S.H.V.E. Research Report No. 1327--Downward Projection of Heated Air, by Linn Helander and C. V. Jakowata (A.S.H.V.E. Transactions, Vol. 54, 1948, p. 71). A.S.H.V.E. Research Report (In Cooperation with the Industrial Unit Healer Association)--Maximum Downward Travel of Heated Jets from Standard Long Radius ASMS Nozzles; by Linn Helander, S. M. Yen, and R. E. Crank (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning, March 1953, p. 123). A.S.H.V.E. Cooperative Research--General A.S.H.V.E. Research Reports No. 857, 911 and 966--Measurement of the Plowof Air Through Registers and Grilles, by E. L. Davies (A.S.H.V.E. Transactions, Vol. 36, 1930, p. 201; Vol. 37, 1931, p. 619 and Vol. 39, ; A19.S33.,Hp..V<3.7E3.).Research Report No. 1076--Air Distribution from Side Wall Outlets, by D. W. Nelson and D. J. Stewart (A.S.H.V.E. Transactions, Vol. 44,1938, p. 77), A.S.H.V.E. Research Report No. 1092--The Flow of Air Through Exhaust Grilles, by A. M. Greene, Jr. and M. H. Dean (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 387). A.S.H.V.E. Research Report No. 1155--The Performance of Stack Heads, by D. W. Nelson, D. H. Krans, and A. F. Tuthili (A.S.H.V.E. Transactions, Vol. 46, 1940, p. 205). A.S.H.V.E. Research Report No. 1165--Development of Instruments for the Study of Air Distribution in Rooms, by A. P. Kratz, A. E. Hershey, and R. B. Engdahl (A.S.H.V.E. Transactions, Vol. 46, 1940, p. 351)A. .S.H.V.E. Research Report No. 1206--Performance of Stack Heads Equipped with Grilles, by D. W. Nelson, D. H. Lamb and G. E. Smedberg (A.S.H.V.E. Transactions, Vol. 48, 1942, p. 279). A.S.H.V.E. Research Report No. 1226--Performance of Side Outlets on Horizontal Ducts, by D. W. Nelson.and G. E. Smedberg (A.S.H.V.E. Transactions, Vol. 49, 1943, p. 58). Other Papers Presented at A.S:H.V.E. Meetings A.S.H.V.E. Research Report No'. 1051--The Noise Characteristics of Air Supply Outlets, by D. J- Stewart and G. F. Drake (A^S.H.V.E. Transactions, Vol. 43,1937, p. 81). A.S.H.V.E. Research Report No. 1158--Dirt Patterns on Walls, by R.A. Nielses (A.S.H.V.E. Trans actAio.nSs.H, V.Vo.lE. .46R, e1s9e4a0,rcph. 2R47e)p. ort No. 1361--Balancing Air Delivery of a System of Manifold Air Diffusers, by G. S. Daupbinee and Peter Argentieri (A.S.H.V.E. Transactions, Vol. 55, 1949, p. 213). A.S.H.V.E. Research Report No. 1362--Air Distribution and Draft, by John Rydberg and Per Norback (A.AS..HS..HV..EV..ET.rRanessaecatricohnsR, Vepool.r5t5--, R19o4o9,mp.A2i2r5D). istribution Research for Year 'Round Air Conditioning, Part I--Supply Outlets at One High Sidewall Location, by S. F. Gilman, H. E. Straub, A. E. Hershey, and R. B- Engdahl (A.S.H.V.E. Journal Section, Heating, Piping & Air Conditioning, April 1953, p. 121). A.S.H.V.E. Research Report--Room Air Distribution Research for Year 'Round Air Conditioning, Part II--Supply Outlets at .Three Floor Locations, by H. E. Straub and S. F. Gilman (A.S.H.V.E. Journal Section, Healing, Piping < Air Conditioning, November 1953, p. 145). Miscellaneous Articles Measuring Air Distribution and Grille Performance in Air Conditioning, by G. L. Tuve (A.S.H.V.E. Journal Section, Heating, Piping A Air Conditioning, November 1937, p. 700). Air Discharge from Narrow Slots, by F. F. Stevenson (Heating, Piping <fc Atr Conditioning, May 1941, P308, and June 1941, p. 368. Discussed by J. R. Fellows and D. W. Nelson, loc. cit., September 1941, p. 558 andV5e5r9t)i.cal Air Distribution in Tall Buildings, by Sturm (Heating, Piping <fc Air Conditioning, June 1947, p- 69 aEnfdficSieepntteAmibreDr 1is94tr7i,bpu.ti9o3n). in Theatre. (Heatim, Piping and Air Conditioning, Question of the MonthAugTuesstt1E94v7e,rpy. A10ir7;CSoenpdteitmiobneinrg19S4y7,stpe.m11, 3b;yNLo.veTm.-Abevre1r9y4a7n, dp.J1.0B3)l.ack. (Heating and Ventilating, June 1948 p.B9a6l)a. ncing an Air Conditioning System, by L. R. Phillips. (Refrigerating Engineering, July 1950, p. Ill)What is a Draft? (Heating. Piping & Air Conditioning, Open for Discussion. May 1951, p. 67, July 1951, P- 71, SSeevpet.n1Q95u1e,spt.io6n9s, oJnanDuuacryts1a9n5d2, Gp.ri1ll1e3s,.M(Harecahti1n9g5,2P, pip.i7n3g).& Air Conditioning, Question of the Month. Maf 1952A, ipr.D1i0s6traibndutJiounlyS1t9u5d2ie. ps,, b1y11R). . V. MartelH and H. O. Scarlett (Heating, Piping & Air Conditioning, No* vember 1952, p. 77. Discussed by W. O. Huebner, loc. cit. Jan. 1953, p. 119 and.by the Authors, March 1953 d. 85). CHAPTER 32 AIR DUCT DESIGN Pressure Losses, Friction Losses, Circular Equivalents of Rectangular Ducts, Dynamic Losses, Pressure Loss in Elbows, Losses Due to Area Changes, Pressure Changes, Duct Design Methods and Examples, Duct Construc tion Details, Heat Losses from Ducts, Maintenance AIR ducts for the transmission of the air in forced air heating, veritilating, cooling, or air conditioning systems must be carefully designed for functional as well as economical reasons. The design should be based upon the fundamental laws of fluid flow in pipes, and should take into ac count recent analytical and experimental studies which complement and substantiate the fundamental laws. The basic equations of the flow of fluids will be found in Chapter 4, Fluid Flow. PRESSURE LOSSES Air ducts impose resistances to air flow which must be overcome by pressure differences resulting from the expenditure of energy in maintaining the flow. Since the flow of air, in ventilating and air conditioning work, takes place under very small pressure differences, the assumption that the gas density remains constant throughout the flow will cause only a negligi ble error. It is therefore possible to use the equation for incompressible fluids (liquids) for the flow of air in a duct, instead of the complicated thermodynamic formulas for air discharge under conditions of adiabatic flow, which would be necessary if pressure differences were large. A reasonably precise estimate of the flow resistances offered by the system is essential for satisfactory duct design. The theoretical resistance of an air handling system can be computed from the methods and data given in this chapter. The actual resistance for any given installation, however, may vary considerably from the calculated resistance because of variation in the smoothness of materials, the type of joints used and the ability of the workmen to manufacture the system in accordance with the design. It is best to select fans and motors of sufficient size to provide a factor of safety. Dampers should be installed in each branch outlet to balance the system. The drop in pressure in air transmission systems is due to friction losses and dynamic losses. Pressure increases and decreases may also be caused by changes in duct areas, with resulting conversion of velocity pressure to static pressure, and vice versa. The friction losses for turbulent flow (which occur in all practical air flow problems) are due to the friction of air against the sides of the duct, and to .internal friction between the air molecules. Phe dynamic losses are caused by changes in the direction or in the velocity f air flow, and may be caused by changes in size and shape of the crosssection of the duct, by bends (elbows), and by obstructions to flow offered Ay dampers. rniCiiun LOSSES Pressure drop in a straight duct is caused by surface friction, and this 'notion loss is most readily calculated by means of the Air Friction Charts, 697