+---------------------------------------------------------------------+
|+------+---------------------------+----+----+----+-----+-----+-----+|
|| | | | | | | | ||
|| Pipe | |1/2 |3/4 | 1 |1-1/4|1-1/2| ||
||Inches| Thickness of Covering |inch|inch|inch|inch |inch |Bare ||
|+------+---------------------------+----+----+----+-----+-----+-----+|
|| |B. t. u. per lineal foot | | | | | | ||
|| | per hour |149 |118 | 99 | 86 | 79 | 597 ||
|| |B. t. u. per square foot | | | | | | ||
|| | per hour |240 |190 |161 | 138 | 127 | 959 ||
|| 2 |B. t. u. per square foot | | | | | | ||
|| | per hour per one degree | | | | | | ||
|| | difference in temperature|.770|.613|.519|.445 |.410 |3.198||
|+------+---------------------------+----+----+----+-----+-----+-----+|
|| |B. t. u. per lineal foot | | | | | | ||
|| | per hour |247 |193 |160 | 139 | 123 |1085 ||
|| |B. t. u. per square foot | | | | | | ||
|| | per hour |210 |164 |136 | 118 | 104 | 921 ||
|| 4 |B. t. u. per square foot | | | | | | ||
|| | per hour per one degree | | | | | | ||
|| | difference in temperature|.677|.592|.439|.381 |.335 |2.970||
|+------+---------------------------+----+----+----+-----+-----+-----+|
|| |B. t. u. per lineal foot | | | | | | ||
|| | per hour |352 |269 |221 | 190 | 167 |1555 ||
|| |B. t. u. per square foot | | | | | | ||
|| | per hour |203 |155 |127 | 110 | 96 | 897 ||
|| 6 |B. t. u. per square foot | | | | | | ||
|| | per hour per one degree | | | | | | ||
|| | difference in temperature|.655|.500|.410|.355 |.310 |2.89 ||
|+------+---------------------------+----+----+----+-----+-----+-----+|
|| |B. t. u. per lineal foot | | | | | | ||
|| | per hour |443 |337 |276 | 235 | 207 |1994 ||
|| |B. t. u. per square foot | | | | | | ||
|| | per hour |196 |149 |122 | 104 | 92 | 883 ||
|| 8 |B. t. u. per square foot | | | | | | ||
|| | per hour per one degree | | | | | | ||
|| | difference in temperature|.632|.481|.394|.335 |.297 |2.85 ||
|+------+---------------------------+----+----+----+-----+-----+-----+|
|| |B. t. u. per lineal foot | | | | | | ||
|| | per hour |549 |416 |337 | 287 | 250 |2468 ||
|| |B. t. u. per square foot | | | | | | ||
|| | per hour |195 |148 |120 | 102 | 89 | 877 ||
|| 10 |B. t. u. per square foot | | | | | | ||
|| | per hour per one degree | | | | | | ||
|| | difference in temperature|.629|.477|.387|.329 |.287 |2.83 ||
|+------+---------------------------+----+----+----+-----+-----+-----+|
+---------------------------------------------------------------------+
Covering--Magnesia, canvas covered.
For calculating radiation for pressure and temperature other than 160
pounds, and 60 degrees, use B. t. u. figures for one degree difference.
Radiation from Pipes--The evils of the presence of condensed steam in
piping systems have been thoroughly discussed above and in some of the
previous articles. Condensation resulting from radiation, while it
cannot be wholly obviated, can, by proper installation, be greatly
reduced.
Bare pipe will radiate approximately 3 B. t. u. per hour per square foot
of exposed surface per one degree of difference in temperature between
the steam contained and the external air. This figure may be reduced to
from 0.3 to 0.4 B. t. u. for the same conditions by a 1½ inch insulating
covering. Table 64 gives the radiation losses for bare and covered pipes
with different thicknesses of magnesia covering.
Many experiments have been made as to the relative efficiencies of
different kinds of covering. Table 65 gives some approximately relative
figures based on one inch covering from experiments by Paulding,
Jacobus, Brill and others.