Radiation at the Outer Surface of Pot and Heat Exchange in Pot Soil

Abstract

The purposes of this paper are to elucidate the distributions of solar radiation and net radiation at the outer surface of a pot, and to determine the quantity of flowed heat in the pot soil in both horizontal and vertical directions.Three different conditions of the surface were prepared using Wagner pot (1/2000a). The outer surfaces of pots were coated with black lacquer, covered with aluminum film, and not covered respectively.Observations were made on August 5 and December 16 in 1978.1) On August 5, the daily amounts of solar radiation calculated directly were the greatest at the east and west side surfaces which were 54% as much as that at the horizontal surface, while those at the south (23%) and north side surfaces (7%) were smaller than those at other surfaces. Its distribution pattern showed a cardioid. On December 16, radiations at the surface of all directions became greater than that of the horizontal surface owing to a low altitude of the sun, especially radiation at the south side surface was 168% as much as that at the horizontal surface.2) Measured solar radiations at sunrise and at sunset differed from those of calculated direct solar radiations. The diurnal variations of solar radiation at all surfaces of pot showed a kind of sine curve. On August 5, the daily amounts of solar radiation at the south and north side surfaces showed 36% and 19% as much as that at the horizontal surface, respectively, while on the west and east side surfaces they were about 40%. These differences among the directions were less than those of calculated direct solar radiation. On December 16, radiations received in most directions at the outer surface of pot were greater than that at the horizontal surface.3) Net radiations at the south side and near middle part on the soil surface of pot had maxima at noon, at the west side surface at 14:00, and at the east side surface at 10:00 on December 16.The diurnal variation of net radiation was small at the north side surface. Radiation at the south side surface of pot coated with black lacquer was the greatest and followed by those at the west and east side surfaces. Net radiation at the south side surface of pot coated with black lacquer was 165% as much as that at a plain pot. The radiation of pot covered with aluminum film was the smallest and half as much as that of pot coated with black lacquer.4) In the diurnal range of flowed heat in the pot soil, there were little differences among all horizontal directions, but in the vertical directions it was the greatest at the south side surface and this tendency was more remarkable on December 16 than on August 5.