1、NA-04-9-3 Were on Deadline-Printing Press Heat Gain Is More (or Less) than Just Motor Load Dennis J. Wessel, P.E. Fellow ASHRAE ABSTRACT Historically, heat gain from a newspaper printing press has been a conversion of inputpower to heat. This method of calculation has resulted in the installation of
2、grossly oversized cooling equipment. Recently developed information from press vendors has resulted in the determination ofsensible heat gain to the space ofapproximately 50% ofthepeakpower input, but it is implied over an eight-hour period. The offsetprintingprocess uses a water-based dampening sol
3、ution with as much as 60% being evaporated into the space. This evaporation implies a latent cooling load equal to 40% to 50% of the sensible gain from the press. This cooling require- ment is signcant and cannot be overlooked. INTRODUCTION Newspaper printing plants typically include a significant a
4、mount of equipment that is required to perform and support both the printing process and the output fi-om the printing press. The greatest equipment load is presented to the space by the printing press, which is obviously the entire reason for the building. The press usually consists ofmany printing
5、 units (or printing couples) in a line, which are stacked two, three, four, or more high. The printing units may each have a relatively large motor or the whole press alignment might have a single or a few motors driving the entire press. In addition, the press has reel stands (to feed the paper to
6、the press), roll handling equipment, folders, and conveyors to deliver the completed newspaper to the “mail” room, where the papers are prepared for delivery. DEFINITIONS Before beginning the discussion of the conditioning requirements of printing plants, the following terminology should be defined:
7、 Blanket cylinder: Rubber cylinder that receives ink from the printing plate and then prints the ink on the paper. Damping (or fountain) solution: Water-based solution used with oil-based inks, applied to the printing plate to permit the ink to release to the blanket cylinder or the paper. Direct un
8、d ofset lithography: Use of a lithographic plate to transfer ink to the paper or to a blanket cylinder (offset), which prints on the paper. Printing couple: Combination of plate cylinders and blanket cylinders that prints on one side of the paper. Two couples form a printing unit for printing on bot
9、h sides of the paper. Reel stand: Structure that supports printing media being delivered into the press. Also called apaster because the end of the paper from a fresh roll is “pasted” to the end of a depleted roll. Web: The thread of paper that winds through the print- ing press. Historic Press Heat
10、 Gain Without heat gain information on the printing press from the manufacturer, the initial reaction to determining the heat gain to the press hall from the electrically powered press is to use the power input or motor HP and directly convert this input to heat. The method to perform this conversio
11、n is indicated in the 2001 ASHRAE Handbook-Fundamentals in Chapter 29, Dennis Wessel is vice president and director of mechanical engineering for Karpinski Engineering, Inc., of Cleveland, Ohio. 02004 ASHRAE. 871 Table 3. Average Efficiencies and Related Data Representative of Typical Electric Motor
12、s - Location of Motor and Driven Equipment with Respect to Conditioned Space or Airstream A B C Motor Name- Full Motor Motor Motor or Motor Driven Driven Driven Rated Efti- Equip- Equip- Equip- Horse- Motor Nominal ciency, ment in, ment in, ment out, power Type rpm Yo Buh Btdh Btu/h plate Load in, o
13、ut, in, I I l l 0.05 Shaded pole 0.08 Shaded pole 0.125 Shaded pole 0.16 Shaded pole 0.25 Split phase 0.33 Split phase 0.50 Split phase 0.75 3-Phase 1 3-Phase 1.5 3-Phase 2 3-Phase 3 3-Phase 5 3-Phase 7.5 3-Phase IO 3-Phase 15 3-Phase 20 3-Phase 25 3-Phase 30 3-Phase 40 3-Phase 50 3-Phase 60 3-Phase
14、 75 3-Phase 100 3-Phase 125 3-Phase 150 3-Phase 200 3-Phase 250 3-Phase I I 1500 35 1500 35 1500 35 1500 35 1750 54 1750 56 1750 60 1750 72 1750 75 1750 77 1750 79 1750 81 1750 82 1750 84 1750 85 1750 86 1750 87 1750 88 1750 89 1750 89 1750 89 1750 89 1750 90 1750 90 1750 90 1750 91 1750 91 1750 91
15、360 i 30 580 200 900 320 1160 400 1180 640 1500 840 2120 1270 2650 1900 3390 2550 4960 3820 6440 5090 9430 7640 15,500 12,700 22,700 19,100 29,900 24,500 44,400 38,200 58,500 50,900 72,300 63,600 85,700 76,300 114,000 102,000 143,000 127,000 172,000 153,000 212,000 191,000 283,000 255,000 353,000 3
16、18,000 420,000 382,000 569,000 509,000 240 380 590 760 540 660 850 740 850 1140 1350 i 790 2790 3640 4490 6210 7610 8680 9440 12,600 15,700 18,900 2 1,200 28,300 35,300 37,800 50,300 699.000 636.000 62.900 Location of Motor and Driven Equipment with Respect to Conditioned Space or Airstream A B C Fu
17、ll Motor Motor Load in, Motorout, in, Motor Driven Driven Driven Motor Effi- Equip- Equip- Equip- Rated, Motor Nominal ciency, ment in, ment in, ment out, kW Type rpm YO W W W 0.04 Shaded pole 0.06 Shaded pole 0.09 Shaded pole 0.12 Shaded pole 0.19 Split phase 0.25 Split phase 0.37 Split phase 0.56
18、3-Phase 0.75 3-Phase 1.1 3-Phase 1.5 3-Phase 2.2 3-Phase 3.7 3-Phase 5.6 3-Phase 7.5 3-Phase 11.2 3-Phase 14.9 3-Phase 18.6 3-Phase 22.4 3-Phase 30 3-Phase 37 3-Phase 45 3-Phase 56 3-Phase 75 3-Phase 93 3-Phase 110 3-Phase 150 3-Phase 190 3-Phase i 500 1500 1500 1500 1750 1750 1750 1750 I750 1750 i
19、750 1750 1750 1750 1750 1750 1750 1750 I750 I750 1750 1750 1750 i 750 i 750 1750 1750 I750 35 35 35 35 54 56 60 72 75 77 79 81 82 84 85 86 87 88 89 89 89 89 90 90 90 91 91 105 35 170 59 264 94 340 117 346 188 439 246 62 1 3 72 776 557 993 747 1453 1119 1887 1491 2763 2238 4541 3721 6651 5596 8760 71
20、78 13009 11 192 17 i40 14913 21 184 18635 25 110 22370 33401 29885 41 900 37210 50395 44829 62 i15 55962 82918 74719 103430 93 172 123 060 111 925 163 785 149 135 70 110 173 223 158 194 249 217 249 334 396 525 817 1066 1315 i 820 2230 2545 2765 3690 4600 5538 6210 8290 i0 342 11 075 14 738 91 204805
21、 186346 18430 From 2001 ASHME Handbook-Fundamentals, Chapter 29. Figure 1 ASHRAE motor heut gain tuble (le): I-P; right: SI). “Nonresidential Cooling and Heating Load Calculation Procedures,“ Table 3, “Average Efficiencies and Related Data Representative of Typical Electric Motors“ (Figure 1). That
22、method of heat gain calculation has historically been utilized and has resulted in the installation of cooling equipment that is grossly oversized. Experience with existing printing plants found oversized and deactivated cooling equipment and air- handling units. A few of the larger press manufactur
23、ers have recently begun providing heat gain information based on their historical data gathering on this subject. This has resulted in the provision of time-weighted heat gain data for use by the design engineer in calculating the space gain and subsequent conditioning requirements. Current Heat Gai
24、n As the press increases from a full stop to full speed operation, the equipment inertia is overcome, bearings and other components begin to heat up, and power consumption reduces. At the same time, the massive steel structure of the printing units absorbs the heat from the press, which is then rele
25、ased to the space over time by convection and as radiated heat. The information provided by two major manufacturers indicates space heat gain between 20% and 60% ofpeak power consumption. Additionally, the peak occurs between five and nine hours after initial press start-up. Typical press heat relea
26、se to the space, presented as a percentage of the peak power input to two presses at one to nine hours after press start-up, is represented in Figure 2. 872 ASHRAE Transactions: Symposia Printing Press Heat Gain vs Power 60.00% f 50.w3% o - 40.00% u, 2 30.00% g 20.00% 1 o. 0096 O. 00% Figure 2 Space
27、 heat gain vs. length of operation. Manufacturer B provides information in a manner that represents heat gain over time as a percentage of power input times the heat radiation factor at that particular time (see Figure 3). According to Manufacturer B, the information provided indicates that at apart
28、icular moment, the heat gain to the space is a function of the power input at that time, which is represented on a time-weighted basis as the heat gain times the power draw at that particular point in time. This graph indicates that the power consumption reduces as the heat gain is increasing, with
29、each reaching their minimum or maximum values, respectively, at approximately nine hours after the start of the press. The resultant space heat gain for Manufacturer B is very similar to the values provided by Manufacturer A, as presented in Figure 2. Manufacturer A, however, recommends the use of a
30、 reduction factor of 80% of the calculated heat gain to account for typical reduced speed operation. This manufacturer goes further to recommend an additional 70% factor for “simultaneity.” This results in a cooling load of KW The peak heat gain values provided are based on the press operation at fu
31、ll speed. The operation of those presses with which the author has experience would indicate that these presses are seldom operated at maximum speed for any length of time. Maximum speed may be attained during the printing of papers for a few holidays, such as Thanksgiving, each year. Additionally,
32、some operators run their presses at or near maxi- mum speed for short durations of time. At other times, these presses may only reach a maximum of 50% to 10% of full speed. This does not preclude, however, the operator from maintaining the press at full speed operation with press runs of shorter dur
33、ation. After all, the cost of the press is related to the x 60% x 80% x 10% = KW x 33.6%. maximum attainable speed and number of papers per hour that can be produced so the owner achieves the greatest return on investment if maximum speed is maintained. It is the recommendation of Manufacturer A tha
34、t the net release of sensible heat to the space for calculation and condi- tioning equipment selection purposes should be as low as 35% to 50% of the peak power input after approximately eight hours of press operation based on a typical speed of 60% of maximum and heat gain of 60% of full power. Thi
35、s sensible heat gain to the press hall over time for two presses operating at full speed is represented in Table 1. As a method of comparing various presses on an equivalent basis, the number of “couples” is indicated in Table 1. Each press is made up of a series of single printing units integrated
36、into apress. Each of these units is called a “couple” because each uses two back-to-back printing cylinders. Since each press may have a different number of couples, based on the needs of the printing company, ali presses require a different horsepower input to operate. The reduction of the press po
37、wer input and horsepower to a per unit basis provides a convenient basis of comparison. The heat gain values presented in Tables 1 and 2 are based on the operation of the presses at full speed over the time periods indicated. The typical printing press may be as tall as 60 t (10.3 m) from the bottom
38、, at the “reel” room, to the top. The reel level is typically separated from the press hall by a floor or a “table top,” and the press heat gain information is usually provided for the entire press. Figure 4 shows a diagram of the press represented as Manufacturer B. This diagram shows a press with
39、52 couples and five folders. This press has four paper webs from each side to the folders. ASHRAE Transactions: Symposia 873 1.5.3 Heat radiation from the press Average values, based on experience. 80 O 12 3 4 5 6 7 8 9 10 11 12 Running of the press in hours (h) Figure 3 Manufacturer B powedheat gai
40、n cuwe. A number of press manufacturers indicate that the hcat gain to the reel level can be as much as 17% of the total press gain. Therefore, conditioning of the reel level typically requires a separate cooling distribution system, which requires the delivery of 17% of the total cooling to that le
41、vel. However, since the gain at the reel level is proportional to the total press gain, properly balanced constant volume HVAC distribution can be considered, given a relatively low heat gain envelope. Press Latent Gain In addition to and perhaps of greater impact than the sensible heat gain, certai
42、n printing operations release latent heat to the space. The offset lithograph printing process uses a water-based damping solution sprayed on the rotating printing plates. This permits the ink to release from the plate to the blanket cylinder and then to the paper. As much as 60% of the water in thi
43、s solution is evaporated into the space from the drying newsprint as well as from overspray from the plates, which rotate at speeds as high as 60,000 to 70,000 pages per hour (1,000 to 1200 rpm) for the newer presses. This evaporation can imply a latent cooling load to the press hall equal to 40% to
44、 50% of the sensible gain from the press. This cooling requirement is significant and cannot be overlooked. The sensible, latent, and total space heat gains from two recently installed presses after three, five, and eight hours of press operation are indicated in Table 2. Consideration of only the s
45、ensible gain could result in the application of space conditioning equipment that can maintain the dry-bulb temperature, but the relative humidity level would be extremely elevated. For example, consider only the press heat gain and ignore for now the impact of outside air and envelope loss, and con
46、sider the conditioning requirement of the press hall to maintain 75F (23.9“C) dry bulb for Manufacturer A. Referring to Figure 5, the desired room condition is represented as Point A. The total load associated with the cooling of the supply air from point A to B (at 55“F, 12.8“C), which indicates a
47、hypothetical sensible only cooling, is the difference in the enthalpy from Point C to D. This sensible cooling load requires the delivery of (1,598,5 i 3 Btuh/ (20 x 1 .OS) = 74,000 cfm (34,923 L/s) of 55F (12.8OC) supply air. This represents a total heat removal of 74,000 cfm x 4.5 x (28.2 - 23.2)
48、= 1,665.1 MBH (138.8 tons of cooling) (34,923 L/s x 1.2 x 47.6 - 36.0 kJ/kg = 488 kW). In reality, 874 ASHRAE Transactions: Symposia Table la. Sensible Space Gain Related to Power Input (i-P) I I l I Table lb. Sensible Space Gain Related to Power input (SI Units) ASHRAE Transactions: Symposia 875 Ta
49、ble 2a. Total Press Heat Gain (i-P) Manufacturer A Manufacturer B Sensible Latent Total Total Sensible Latent Total Total (Hours) (Kw) (Kw) (KW) PerCouple (KW) (Kw) (KW) Per Couple Peak 780.87 412.39 1,193.26 18.08 56.1 1 1,567.40 1,623.5 I 31.22 Table 2b. Total Press Heat Gain (SI) - 5 8 468.52 247.43 715.96 10.85 307.55 123.43 430.98 8.29 468.52 247.43 715.96 10.85 363.08 145.72 508.80 9.78 93% Figure 4 Diagram ofpress unit B. a cooling coil-even a shallow coil-would remove some moisture based on the apparatus dew point and would probably deliver air at, say, 55F
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