Temperature Analysis of Two-layered Soil, Upper Being Gravel (pebbles) and Lower Being Sandy Soil

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Other Title
  • 上層砂利, 下層砂質土の成層土壌の地温解析
  • ガラス オンシツ ノ ネツ シュウシ コウゾウ ニ カンスル ケンキュウ 2
  • Studies of a heat balance structure for glasshouses (II)
  • ガラス温室の熱収支構造に関する研究 (II)

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The temperature analysis of the floor part of glasshouses composed of two layers (its upper thin layer is gravel) was performed following the previous report on the heat balance structure. As a result, the obtained apparent thermal conductivity of the gravel layer having a large aperture may be a fairly good approximation. It is found that the three conditions may be necessary to give such a reasonable thermal conductivity value, in excess of 20% of, the value of dry sand as follows in addition to absolutely necessary conditions such as known values about the lower layer's, thermal properties.<BR>First, the surroundings for these glasshouses must be comparatively simple. For example, they are non-crop-types and constant intensity of global solar radiation at noon time, because at noon time, in-and outdoor air temperature and surface temperature of the glass is maintained almost constant.<BR>Next, it was estimated that solar radiation is rather diffused extending to a depth corresponding to the size of one gravel when the soil surface layer consisted of gravel of a large diameter. Then, consideration must be given to the temperature analysis of the two layers of soil in which the depth of the zero position of the apparent soil surface should be moved to be equivalent to about one particle of gravel in which the diffusion intensity of the solar radiation in the gravel, layer becomes weak and equivalent to the heat flux in the gravel layer, part of the net radiation estimated by the previous report.<BR>Last, if the value of the heat flux, in other words, the value of the apparent thermal conductivity of the gravel layer is overestimated, to the opposite effect, heat transfer coefficient becomes small. As a result, the apparent thermal conductivity of the gravel layer should be corrected as the computed temperature profile of the surface layer is clearly changed.

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