Document EdDdqDgJELyyvDKeyZVZ5gj64

220 CHAPTER U 1960 Guide separate system of distribution piping is generally not re quired. The heating capacity of finned tube varies over a wide range depending on tube sue, fin size and thickness, spacing of fins, and the materials used. A major portion of the heat transferred to the room to be heated is by convection. The heating capacity of finned-tube heat-distributing units is determined by test. The Institute of Boiler and Radiator Manufacturers has developed a testing and raring code for finned-tube type of radiation* Heat loss calculations for finned-tube heating systems are the same as those used for other types of radiation. Ratings are expressed in Btuh per linear foot or square feet Equiva lent Direct Radiation per linear foot for steam, and Btuh per linear foot for water. ' RATINGS OF HEAT-DISTRIBUTING UNITS Radiators A standard method of testing radiators was adopted by the ASHAE in 1927.* This Code was withdrawn but the method is still used in industry. It provides for a standard test room, the temperature of which is to be maintained at 70 F, measured in the center of the room at an elevation of 5 ft above the floor. The steam temperature in the radiator is to be 215 F, which corresponds to 15.6 psia. The weight of condensate per hour, under these standard conditions, mul tiplied by the difference in the enthalpy of the steam enter ing the radiator and that of the condensate leaving the radiator, gives the radiator output in Btu per hour (Btuh). If the rating in square feet Equivalent Direct Radiation is desired, divide this output by 240 (which by definition is the Btuh equivalent of 1 sq ft EDR). Correction of output from non-standard test conditions to output at 70 F room and 215 F steam may be made by multiplying the output under test by the ratio (Standard temperature difference, steam -- air)1-* (Test temperature difference, steam -- air)1J Convectors The generally accepted method of testing and rating both ferrous and non-ferrous convectors, is given in Commercial Standard CS140-47, Testing and Rating Convectors' which has been developed cooperatively by the Convector Manu facturers Association, the Institute of Boiler and Radiator Manufacturers, other members of the trade, and the Na tional Bureau of Standards. This Commercial Standard con tains details covering construction and instrumentation of the test booth or room and procedures for determining both steam and water ratings. Steam ratings are expressed in square feet EDR and Btu per hour (Btuh). Water ratings are expressed in Btuh at specified water temperature drops and average water tem peratures. Under the provisions of Commercial Standard CS140-47 the rating of a top outlet convector is established at a value not in excess of the test capacity (which is the heat ex tracted from the steam or water in the convector under standard test conditions). For convectors with other types of enclosures or cabinets a percentage that varies up to a maxi mum of 15 percent depending on the height and type of enclosure or cabinet is added for heating effect.*1 The addi tions made for hearing effect must be shown in the manu facturer's literature. Table 6....Factors to Convert 1= B=R Finned-Tube Steam Ratings to Hot Water -Ratings at Temperatures Indicated Average Temperature FsiiOf Average iodiatot Teaperotvte r"`'" 150 0.45 200 0.86 155 0.49 205 0.91 160 0.53 210 0.95 165 0.57 215 1.00 170 0.61 220 1.05 175 0.65 225 1.09 180 0.69 230 1.14 1S5 0.73 235 1.20 190 0.78 240 1.25 195 0.82 Baseboard The generally accepted method of testing and rating base boards is covered in the / = B = R Testing and Rating Code for Baseboard Radiation.* This Code contains details cover ing construction and instrumentation of the test booth or room, procedures for determining steam ratings, and licens ing provisions for the obtaining of approval of these ratings. Baseboard ratings include an allowance for heating effect of 15 percent, added to the test capacity. The addition made for heating effect must be shown in the manufacturer's literature. Steam ratings are expressed in Btuh per linear foot or square feet EDR per linear foot. Water ratings are expressed in Btuh per linear foot, at specified water flow rates and average water temperatures. Finned-Tube The generally accepted method of testing and rating finned-tube units is covered in the / = B = R Testing and Rating Code for Finned-Tube (Commercial) Radiation.* This Code contains details covering construction and instru mentation of the test booth or room, procedures for deter mining steam and water ratings, and licensing provisions for the obtaining of these ratings. Steam ratings are expressed in Btuh per linear foot or square feet EDR per linear foot. Water ratings are determined from steam ratings and are ex pressed in Btuh per linear foot at specified water flow rates and average water temperatures. The rating of a finned-tube unit in an enclosure having a top outlet is established at a value not in excess of'the test capacity (which is the heat extracted from the steam or water in the unit under standard test conditions). For finned-tube with other types of enclosures or covers a per centage is added for heating effect which varies up to a maximum of 15 percent depending on the height and type of enclosure or cover. The additions made for heating effect must be shown in the manufacturer's literature. Corrections for Non-Standard Conditions The heat output of a radiator, convector, baseboard or finned-tube heat-distributing unit is an exponential function of the temperature difference between the air in the room Radiators;'Convectors, Baseboard and Finned-Tube Units 221 Table 7.... Correction Factors for Direct Cast-Iron Radiators and Convectors* Shea Pnst. (Approx.) Heoftwp Temp. F Gaga Ab* Steam or Vacuus Lb per In. Hg Sq In. 80 Room Temperature F 75 70 65 60 55 50 3.7 150 2.58 2 35 2.17 2.00 1.86 1.73 1.62 20.3 4.7 160 2.17 2.00 1.86 1.73 1.62 1.52 1.44 17.7 6.0 170 1.86 1.73 1.62 1.52 1.44 1.35 1.28 14.6 7.5 180 1.62 1.52 1.44 1.35 1.28 1.21 1.15 10.9 9.3 190 1.44 1.35 1.28 1.21 1.15 1.10 1.05 6.5 11.5 200 1.28 1.21 1.15 1.10 1.05 1.00 0.96 Lb gar Sq bw 1 15.6 215 1.10 1.05 1.00 0.96 0.92 0.88 0.85 6 21 230 0.96 0.92 0.88 0.8b 0.81 0.78 0.76 15 30 250 0.81 0.78 0.76 0.73 0.76 0.68 0.66 27 42 270 0.7C 0.68 0.66 0.64 0.62 0.69 0.58 52 67 300 0.58 0.57 0.55 0.53 0.52 0.51 0.49 51mm fna Hiding Gag* In. Hg Ab* Sq In. Temp. F Wafer 80 Met Aar Temperature F 75 70 65 60 55 50 22.4 3.7 150 3.14 2.83 2.57 2.35 2.15 1.98 1.84 20.3 4.7 160 2.57 2.35 2.1b 1.98 1.84 1.71 1.59 17.7 6.0 170 2.15 1.98 1.84 1.71 1.59 1.49 1.40 14.6 7.5 180 1.84 1.71 1.59 1.49 1.41 1.32 1.24 10.9 9.3 190 1.59 1.49 1.40 1.32 1.24 1.17 1.11 6.5 11.5 200 1.40 1.32 1.24 1.17 1.11 1.05 1.00 lb per Sq In. 1 15.6 215 1.17 1 11 1.05 1.00 0.95 0.91 0.87 6 21 230 1.00 0.95 0.91 0.87 0.83 0.79 0.76 15 30 250 0.83 0.79 0.76 0.73 0.7C 0.68 0.65 27 42 270 0 7(1 0.68 0.65 0.63 0.61 0.58 0.56 52 67 300 0.56 0.54 0.53 0.61 0.49 0.48 0.47 To determine tie sise of a redixtar or coovector fee mgiven space, multiply the beet lom of the apace in Bta per boar by the proper factor from the above table and select radiator or eonrector heviog an equivalent Bta per hoar rating. An alternate method is to divide the heat loes in Bta per hoar by 240 and multiply the result by the proper factor from the above table and select radiator convector bavins an equivalent eqoaze foot rating, Tn ilirtmiiiTMiftiohnitiTuniparitT rrf mitsfnrnri nrm-mrTfTT im--ri--m irn other than the faaino ones with the mediom at a temperature of US F, and the room texnperatsre at 70 F in the caae of a radiator, ana the inlet air tern- Teai.TSTi> itfABin rase of a oonveetor, divide tee faatisif capacity at tee and the heating medium in the room-heating unit, or, ex pressed as an equation H < e(i. -- O* (1) where H -- heat output, Btu per hour (Btuh). c -- a constant determined by test from Equation 1. t, = average temperature of heating medium, Fahrenheit. For hot water the arithmetical average of the entering and leaving water temperatures is used. L -- room air temperature, Fahrenheit. Air temperature 60 in. above the floor is generally used for radiators while the entering air temperature is used for all other ^ types of heating units. tj =* an exponent which'equals 1.3 for east-iron radiators, 1.4 for baseboard radiation, and 1.5 for convectors. For finned-tube units n varies with both air and heat- Table 8 .... Correction Factors for Finned-Tube and Baseboard Radiation* Sfuaut Framra (Approx.) Heating Medium Temp. F Gage Ab* Vacuum lb per Water tn. Hg Sq In. 80 Factor* for Famed-Tube Met Air Temperature F 75 70 65 60 55 50 22.4 20.3 17.7 14.6 10.9 6.5 3.7 4.7 6.0 7.5 9.3 11.5 Lb per Sq tn. 1 15.6 6 21 15 JO 27 42 52 67 150 2 80 2.50 2.20 1.95 1.81 1.67 1.54 160 2.34 2.-14 I 94 1.75 1.62 1.50 1.37 170 2.01 1.86 1.70 1.56 1.46 1.36 1.28 180 1.76 1.65 1 53 1.42 1.32 1.24 1.15 190 1.53 1.45 1.36 1.28 1.20 1.12 1.03 200 1.38 1.31 1.24 1.16 1.09 1.02 0.95 215 1.17 1.12 1 06 1.00 0.95 0-9C 0.85 230 1.00 0.97 0 93 0.90 0.86 0.82 0.78 250 0 88 0 85 0,82 0.78 0.75 0.71 0.67 270 0.75 0.73 0.79 0.6S 0.65 U.6i 0.59 300 0.62 0.60 0.58 0.56 0.54 0.52 0.50 Sfeam Pressure (Approx.) lemp. r Gage Ab* Steam or Vacuum Lb per to. Hg Sq In. 80 Met Air Temperature F 75 70 65 60 55 22.4 3.7 150 2.86 2.61 2 38 2.20 2.03 1.89 1.76 20.3 4.7 160 2.38 2.2C 2.08 1.8$ 1.76 1.64 1.56 17.7 6.0 170 2.03 1.8S 1.76 1.64 1.54 1.44 1.38 14.6 7.6 180 1.76 1.64 1.55 1.44 1.3? 1.2S 1.23 10.9 9.3 190 1.54 1.44 1.3 J 1.29 1.22 l.lt 1.09 6.5 11.5 200 1.38 1.29 1.23 1.16 1.09 1.05 1.00 Lb per Sq In. 1 15.6 215 1.16 1 to l 05 i.a 0.95 0.92 0.88 6 21 230 i.a 0.96 0.92 0.81 0.84 0.81 0.77 15 30 250 0.84 0.82 0.71 0.76 0.73 0.71 0.68 27 42 270 0.73 0.7( 0.61 0.66 0.63 0.61 0.59 52 67 300 0.58 0.57 0.55 0.53 0.52 0.61 0.49 a Xo determiiM ft* hatof capacity under o^nsiitinn, other than tee base earn with tee heating medium at a temperature of SIS F, and the inlet air tem perature at 6$ P, divide the beating capacity at the basis rating coadtttosa oy tee proper factor from the above table. iog medium temperatures. Correction factors to con vert outputs at standard rating conditions to outputs at other conditions are given in Tables 6, 7, and 8. Endosure, Paint, Humidity Effect The general effect of an enclosure placed about a direct radiator is to restrict the air fiow, and diminish the propor tion of output due to radiation. Enclosures of proper design /may, however, improve the heat distribution within the room as compared to the heat distribution obtained with an unenclosed radiator.** For a radiator or cast-iron baseboard the finish coat of paint affects the beat output. Oil paints of any color will give about the same results as unpainted black or rusty surfaces, but an aluminum or a bronze paint will reduce the heat emitted by radiation. The net effect may be a re duction of 10 percent or more in the total heat output of the radiator.** " " Some commercial enclosures and shields for use on direct radiators are equipped with water pans for the purpose of