Document 9MXongb2pj4nZQKYZEa0q8ze

214 CHAPTER 13 1960 Guide Ventilation Air Taken through Coaling Unit Which Become* a Part of the Space Load (tee Equation* 10 and 11) : 1275 X 1.08 (95-80) (0.15) - 3,100 Btuh, sensible. qH - 1275 X 4840 (0.0168-0.0098) (0.15) - 6,480 Btuh, Intent. Ventilation Air Taken through Cooling Unit Which Doe* Not Become a Part of the Space Load (see Equation* 12 and 13): - 1275 X 1.08 (95-80) (1-0.15) = 17,600 Btuh, sensible. q,, rn 1275 X 4840 (0.0168-0.0098) (1-0.15) - 36,715 Btuh, Intent. qt - q + + ** + 9~ - 3100 + 17,600 4- 6480 + 36,715 -- 63,895 Btuh total. Beat Gain from Source* within the Conditioned Space: For the occupants, use the data of Table 27 for moderately active office work. Sensible heat gun *= 85 X 200 = 17,000 Btu per hr. "Latent heat gain =* 85 X 250 -- 21,250 Btu per hr. Total = 38,250 Btu per hr. For the gain from lighting, use Equation 15 with a use factor of unity, and a special allowance factor of 1.20 for the fluorescents and of unity for the tungsten globes. ** => (12,000 X 1-20 + 4000) X 3.41 - 62,700 Btu per hr. For the fan motor, use Equation 16 with a load factor of unity, and omit term Motor Efficiency because the motor is not within the space. ? = 7-5 X 2544 - 19,100 Btu per hr. Moisture Permeation, Miscellaneous Allowance, and the LoadLag Estimate: Moisture permeation will be negligible, since this is a com fort job with a good building construction. There would be some heat gain in the ductwork, but this would not be great because of the short run involved. Practical judgment for this job would suggest that no adjustment for load lag need be made to the Toad as computed. (Refer to Fig. 4). While it is true that inside radiation forms an impor tant part of the total heat gain, it is advisable to be conserva tive in recognising tbe effect of the large, flat, hot roof on the comfort sensation* of the occupant*. Radiation from the rela tively low ceiling, augmented by heat absorption from the lighting fixtures, would produce a sensation of warmth in excess of the nominal effective temperature (see Ch&pteT 6) established by the wet-bulb and dry-bulb temperatures. Hence, it is not desirable to take advantage of every small decrease possible in the peak design load, especially since the peak occurs in mid-afternoon when everything would be rather well warmed. Total Load* and Required Air Quantity through Conditioning Equipment: Tbe total loads are summarised in the following table: Sumhabt or Total Loads--Example 11 tois COKHWBR SzMBZXLa Utm Btc/hb Bto/aa 78,500 5,970 1,085 3,100 17,000 62,700 19,100 187,455 17,600 205,055 2,270 6,480 21,250 30,000 36.715 66.715 Grand total sensible and latent................................... 271,770 Compute the enthalpy difference ratio from Equation 18. A - q**5 t 30^20) X 1076 - 7770. Wi - W. 30^20 Prom the ASHAE Pbtchbomethic Chart, Chapter 3, de termine that the apparatus dew point is 53.9 F. Compute the effective air quantity (Equation 19). Then, 187,455 Qr 7530 elm.. 1.08(80 - 53.9) X 085 (Refer to Chapter 23 for coil selection.) From note under Equation 19 the dry-bulb range will be (80 -- 53.9) X 0.85 " 222 deg, and the dry-bulb temperature of air leaving the coil will be 80 -- 22.2 57.8 F. The drybulb temperature leaving the fan (including the heat supplied by the fan motor) or, delivered into the room, will be (from Equation 21): 187,455 - 19400 t. 80 - 195 60.1 F. 1.08 X 7830 With good distribution and diffusion, tins temperature should not produce objectionable drafts. The various calculations for the sensible, latent, and total beat loads for Example 11 may be summarised as follows: Example 11: Suxmabt OvTOoon Common.......... 09 DB Stacs Common.............. 80 DB 78 WB (9 WB 0-0168 Hqxidixt Ratio QDQSS Humiditt Ratio Dirmoct.................... 19 0.0070 Sensible Load Transmission Btu/Hr Roof 4000 sq ft X 53* X 054 -...................... 72,000 S. wall 405 sq ft X 6 X 0.41 -...................... 995 E. wall 765 sq ft X 11* X 0.52 --................... 4,380 N. wall ex. 170 sq ft X 3" X 0.52 -.............. 265 N. & W. party wall 1065 sq ft X 2* X 0.26 - 550 Floor none Door 35 sq ft X 15 X 0.59 -........................... 310 All glass and rest of doors --........................... 3,020 Solar Radiation S. glass 60 sq ft X 13 -............. 8. glass (doors) 35 sq ft X 42 = E. glass (doors) 18 sq ft X 14 -- N. glass 30 sq ft X 15 -............. 780 1,470 250 450 Internal Load Infiltration 67 cfm X 1.08 X 15* -................ 1,085 Ventilation 1275 efm X 1.08 X 15 X 0-15 -. 3,100 lights (12,000 X 1.20 + 4000) 3.41 -............ 62,700 People 85 X 200-............................................. 17,000 Motor, fan 7.5 hp X 2544 -............................ 19,100 Total Sensible Space Load 187,455 Latent Load Infiltration 67 cfm X 4840 X 0.0071 -........... 2,270 Ventilation 1275 cfm X 4840 X 0.0071 X 0.15.. 6,480 People 85 X 250-................................................ 21,250 Total Latent Space Load....................... 30,000 Ventilation Aib Which Dora Nor Become Past or Space Load Sensible 1275 cfm X 1.08 X 15 X (1-0.15) -.................... 17,600 Latent 1275 cfm X 4840 X 0.0071 X (1-0.15) -................ 36,715 Grand Total Load...... ............................ 271,770 Cooling load 215 LETTER SYMBOLS USED IN CHAPTER 13 a -- fraction of incident solar radiation absorbed, dimen sionless; subscripts D, d, and t refer to direct, diffuse, and total, respectively. 0 -- solar altitude, degrees. y -- wall solar azimuth, degrees. t n emissivity, dimensionless. 9 -- incident angle, degrees. t -- fraction of incident solar radiation transmitted, dimen sionless. Subscripts D, d, and t refer to direct, diffuse, and total, respectively. -- solar azimuth, degrees. <fr -- wall azimuth, degrees. A -- area across which heat is being transferred, square feet. b -- fraction of air passing through coil which does not con tact surfaces, coil bypass factor. / -- unit surface conductance, Btu per (hour) (square foot) (Fahrenheit degree). Subscripts c, r, o, and t refer to convection, radiation, outdoor, and indoor, respectively. Of -- fraction of total window area receiving direct solar radiation when shaded by window reveal, dimensionless. & -- enthalpy of air per pound of dry air, Btu per pound. Subscripts i, o, and s refer to indoor, outdoor, and sup ply air, respectively. 1 -- incident solar radiation, Btu per (hour) (square foot). Subscripts D, d, Dn, and t refer to direct, diffuse, direct normal, and total solar radiation, respectively. K -- cosine of angle of incidence for direct solar radiation striking a surface, dimensionless. k -- thermal conductivity of building material, Btu per (square foot) (hour) (Fahrenheit degree per inch). I -- height of window, feet. If -- the permeance of the specimen in perms or grains per (square foot) (hour) (inch of mercury vapor pressure difference). Q -- rate of entry of outdoor air, cubic feet per minute. Qrm -- required air quantity through conditioning equipment, cubic feet per minute:'" q -- instantaneous rate of heat transfer, Btu per hour. q, -- instantaneous latent heat load, Btu per hour. ?#< -- instantaneous space latent ventilation load, Btu per hour. Sa -- instantaneous latent ventilation load which does not become a part of space load, Btu. q -- latent beat load due to moisture transmission through materials, Btu per (hour) (square foot). ft -- instantaneous sensible heat load, Btu per hour. fn -- instantaneous space sensible ventilation load, Btu per hour. fn -- instantaneous sensible ventilation load which does not become a part of space load, Btu per hour. 9* " ?. + ft, also q.i + q* + , Btu per hour. Bt -- low temperature radiant energy received from outdoor . ^surrounapra (does not indudS'Bolar radiation), Btu per (hour) (squire foot of receiving surface). R - radiant energy emitted by a black body, Btu per (hour) (square foot). Subscripts go and L refer to outdoor sur faces of glass and building, respectively. S -- rate of heat storage within a glass section, Btu per (hour) (square foot). t. -- sol-air temperature, Fahrenheit. tf( -- temperature of indoor glass surface, Fahrenheit. I,, -- temperature of outdoor glass surface, Fahrenheit. <4 -- indoor air temperature, Fahrenheit. t -- 24-hr cyclic average sol-air temperature, Fahrenheit. t, -- outdoor air temperature, Fahrenheit. t, -- room supply air dry-bulb temperature, Fahrenheit. U -- overall coefficient of heat transfer of a structural sec tion, Btu per (square foot) (hour) (Fahrenheit degree). v, -- volume of outdoor air per pound of dry air, cubic feet, to -- width of window, feet. W -- humidity ratio, pounds moisture per pound of dry air. Subscripts *, o, and s refer to indoor, outdoor, and sup ply air, respectively. REFERENCES 1 Application Engineering Standards for Air Conditioning for Comfort (Air Conditioning and Refrigerating Machinery Association, Inc., 1947, p. 4). * W. V. Consolazio and L. J. Pecora: Minimal replenish ment air required for living spaces (ASHVE Transactions. Vol. 53, 1947, p. 127). * Recommended Safe Practice of the NBPU for Hospital Operating(Notional Board of Fire Underwriters Pam- * P. Moon: Proposed standard solar radiation curves for engineering use (Journal of the Franklin Institute, Vol. 230, November 1940, p. 583). ` C. O. Mackey: ASHVE Research Repost No. 1268-- Summer weather data and sol-air temperature--Study of dati> for Lincoln, Nebr. (ASHVE Transactions, Vol. 51. 1945. P- 93). * C. O. Mackey and E. B- Watson: Summer weather data and sol-air temperature--Study of data for New York City (ASHVE Transactions, Vol. 51,1945, p. 75). * G. A. HeDdrikson and J. H. Walker: Summer cooling for comfort as affected by solar radiation (Beating and Ventilating. VoJ. 29, November 1932, p. 14). * Tables of Computed Altitude and Azimuth (U. S. Navy Dept. Hydrographic Office Bulletin No. 214, Vol. 1-9, 1940). * The American Nautical Almanac (G. S. Naval Observatory, annual). w F. C. Houghten, J. L. Blackshaw, E. M. Pugh, and Paul McDermott: ASHVE Research Report No. 923--Heat trans mission as influenced by heat capacity and solar radiatioo (ASHVE Transactions, Vol. 38, 1932. p. 231). J. 8. Alford, J. E. Ryan, and F. O. Urban: Effect of neat storage and varia tion in outdoor temperature and solar intensity on beat trans fer through walls (ASHVE Transactions, Vol. 45, 1939, p. 369). Victor Paschkis: Periodic heat flow in building walls determined by electrical analogy method (ASHVE Trans actions, Vol. 48,1942, p. 75). C. 6. Mackey and L. T. Wright. Jr.: Periodic beat flow--Homogeneous walls or roofs (ASHVE Transactions, Vol. 50, 1944, d. 293). C. 0. Mackey and L. T. Wright, Jr.: Periodic heat flow--Composite walls or roofs (ASHVE Transactions, Vol. 52, 1948, p. 283). H. A. Johnson: Periodic heat transfer at the inner surface of a homogeneous wall (ASHVE Transactions, Vol. 54, 1948, p. 143). 11 F. C. Houghten, Carl Gutberlet, and A. A. Roeenburg: The effect of solar radiation on the beat transmission tbrougn walls (American Society of Testing Materials Symposium on Thermal Insulating Materials, 1939). F. C. Houghten, H. T. Olson, and Carl Gutberlet: ASHVE Research Report No. 1157--Summer cooling load as affected