Page 284 - Applied Process Design For Chemical And Petrochemical Plants Volume III

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246 Applied Process Design for Chemical and Petrochemical Plants

Table 10-48
“Q” Heat Loss from Bare NPS Pipe, Btu/(lin ft) (hr)
Ambient Air Temperature 70°F, Natural Circulation

Pipe Temperature, °F (English Units)
NPS Pipe
Pipe 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 dia. mm

1 13 75 165 287 444 649 901 1,218 1,602 2,075 2,644 3,317 21.3
/ 2
3 16 93 204 353 547 801 1,113 1,508 1,984 2,576 3,282 4,122 26.7
/ 4
1 20 114 250 433 674 989 1,379 1,865 2,462 3,194 4,080 5,123 33.4
1
1 / 4 24 141 312 541 843 1,237 1,728 2,342 3,091 4,010 5,123 6,433 42.2
1
1 / 2 27 159 352 613 955 1,403 1,960 2,661 3,514 4,568 5,841 7,345 48.2
2 33 196 432 753 1,176 1,732 2,423 3,295 4,355 5,665 7,251 9,133 60.3
1
2 / 2 40 233 516 899 1,408 2,077 2,907 3,956 5,235 6,817 8,732 11,005 73.0
3 48 280 620 1,083 1,695 2,505 3,511 4,784 6,337 8,259 10,582 13,344 88.9
1
3 / 2 55 317 701 1,226 1,922 2,841 3,987 5,434 7,201 9,390 12,039 15,189 101.6
4 61 354 784 1,370 2,149 3,179 4,467 6,094 8,079 10,545 13,513 17,049 114.3
6 87 503 1,122 1,976 3,105 4,604 6,479 8,858 11,769 15,366 19,740 24,909 168.3
8 111 644 1,436 2,530 3,988 5,927 8,356 11,433 15,211 19,895 25,568 32,293 219.1
10 136 791 1,769 3,114 4,918 7,312 10,325 14,147 18,812 24,621 31,679 40,051 273.0
12 159 930 2,076 3,664 5,809 8,627 12,194 16,721 22,248 29,133 37,501 47,429 323.3
14 174 1,009 2,258 3,989 6,316 9,404 13,301 18,236 24,279 31,844 40,965 51,856 355.6
16 197 1,142 2,560 4,529 7,160 10,697 15,124 20,769 27,663 36,257 46,689 59,089 406.4
18 221 1,282 2,873 5,074 8,032 12,010 16,992 23,346 31,109 40,788 52,539 66,456 457.2
20 244 1,416 3,168 5,618 8,897 13,270 18,777 25,810 34,432 45,147 58,159 73,691 500.8
24 289 1,683 3,772 6,679 10,595 15,825 22,375 30,836 41,112 53,958 69,536 88,221 609.6
30 351 2,042 4,642 8,242 13,103 19,606 27,758 38,299 51,107 67,125 86,558 109,872 762.0
36 421 2,450 5,570 9,890 15,724 23,527 33,309 45,959 61,328 80,550 103,860 131,846 914.4
38 93 149 205 260 315 371 423 482 539 593 649
Pipe Temperature, °C (Metric Units)

Used by permission: Turner, W. C., and Malloy, J. F. Handbook of Thermal Insulation Design Economics for Pipe and Equipment, ©1980. R. E. Krieger Publishing
Company. Joint edition with McGraw-Hill Book Company, Inc. All rights reserved.

r 1 outside radius of any (if used) intermediate layer of I. Heat Loss through Insulation for Process Pipe
insulation, in.
2
R s outside surface resistance, (°F)(hr)(ft )/Btu An alternate presentation of Chapman and Holland 227 is
t temperature difference (t 1 t ave ) between inside useful.
surface of pipe insulation and average outside air Heat transfer from the surface of an insulated or uninsu-
temperature, °F lated pipe in air involves convection and radiation. In still air
L thickness of insulation, in. more heat is lost by radiation than convection. The heat loss
t a temperature of ambient air, °F
from an insulated or bare pipe is, in Btu/hr:
t o temperature of inner surface of insulation, °F
t s temperature of outer surface of insulation, °F Q h a ¿ A a 1T s T a 2 (10-272)
X insulation thickness, ft
where T s surface temperature of insulated or bare pipe in con-
Note: For k, subscript 1 first (inner) layer of insulation. tact with air, °F
If more than one has a different k value, subscript 2 sec- h a heat transfer film coefficient between the insulated
ond layer of insulation if different than first layer. or bare pipe and air. See Figure 10-170, assume
0.90 and ambient air temperature 70°F
2
2
2
Heat flow per ft of pipe surface q o q s (r s /r o ), Btu/(hr) (ft ) h a h c h r , Btu/(hr) (ft )(°F)