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re: formula for indirect solar radiation
18 dec 1999
tim dierauf mentioned:
>"heating and cooling of buildings, design for efficiency", by jan kreider
>and ari rabl, mcgraw-hill, inc., 1994.
hey, nice book, tim! i just got a copy (about $100), based on your
recommendation and found table a2.3 on page 786, "average thermal
properties of soils," which lists
density specific heat heat cap by volume
10^3 kg/m^3 10^3 j/kgc 10^6 j/m^3-c
northway fine sand 2.76 0.824 2.274
northway sand 2.74 0.774 2.121
northway silt loam 2.70 0.736 1.987
chena river gravel 2.70 0.811 2.190
fairbanks silt loam 2.70 0.765 2.066
graded ottowa sand 2.65 0.686 1.818
lowell sand 2.67 0.786 2.099
crushed quartz 2.65 0.795 2.107
crushed granite 2.67 0.728 1.944
averages 2.69 0.767 2.067
the average heat capacity by volume corresponds to 30.8 btu/ft^3-f.
maybe this will soften toby's brain to the point that he starts
believing his own experiments and stops spreading his misbelief that
dirt holds as much heat as water (about 64 btu/ft^3-f) by volume :-)
btw, the average soil thermal conductance was 1.6 w/mc.
nick
from another nice new $100 book, "greenhouses--advanced technology
for protected horticulture" by joe j. hanan (crc press, 1998,
isbn 0-8493-1698-7):
a passive system such as solar tubes (fig. 4-49) provides a gain
of several degrees over a house without heating... 25 cm pe tubes
with 0.2 mm wall thickness and lengths up to 30 m are laid between
rows and filled with water... in some instances a black foil is
laid under the tube, or the tubes are placed with a space between
them to form a container for the plant row...
the ends of the tubes are raised "not more than 0.5 m" to contain
the water...
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