Abstract
SummaryWe measured the heat flux, temperature distribution and water content of an unsaturated Ando soil under a constant temperature gradient and reduced air pressure to investigate the mechanism of latent heat transfer in the soil and its relationship to the distribution and circulation of soil water. As the air pressure decreased, the heat flux increased for the soil samples with an initial volumetric water content (θini) greater than 0.30 m3 m−3, but did not change for θini less than 0.20. While the temperature gradient of the sample did not change for θini greater than 0.30 m3 m−3, it did increase on the hotter side of the sample and decreased on the colder side for θini less than 0.20. The water content did not change, and a homogeneous distribution of water content was observed for θini greater than 0.30 m3 m−3. For θini less than 0.20, the water content decreased on the hotter side and increased on the colder side, forming a large water content gradient. The large transfer of latent heat was caused by the circulation of water vapour and liquid water, which resulted in the homogeneous water distribution. We concluded that the soil functions as a heat pipe through a series of micro‐heat pipes centred on the soil pores. Our experimental results will help to explain the transfer mechanism of latent heat in soil as a heat pipe phenomenon.
Published Version
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