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Evaluation of Theoretically Predicted Thermal Conductivities of Soils under Field and Laboratory Conditions¹

ABSTRACT

In the literature one finds claims that the Philip-deVries model of heat and moisture transfer fails to predict the amounts of water moved by vapor transfer.

In the work reported here an attempt was made to check and verify the predictive capabilities of the deVries, Philip and deVries models for vapor transfer by evaluating the latent heat transfer carried by vapor rather than to account for vapor flow from the usually performed total moisture balance.

It was found that the deVries model predicts quite accurately the transfer of heat by vapor under steady state conditions, but underestimates it under nonsteady state conditions.

The possibility that the assumed diffusive vapor transport should be corrected by including "enhancement factors" so as to incorporate local thermal gradients and mass movement induced vapor transfer, not accounted by the present model is brought up and the nature of the enhancement factors and the implications to field conditions are discussed.

¹ Contribution from the Agricultural Research Organization, The Volcani Center, Bet-Dagan, Israel; and the Dep. of Soil Science and Agricultural Engineering, Univ. of California, Riverside. This report was supported in part by Grant No. AID/ta-G 1141.

² Soil Scientist, Div. of Soil Physics, Institute of Soil & Water, Agric. Res. Organization, The Volcani Center, Bet-Dagan, Box 6, Israel. On sabbatrical leave at the Dep. of Soil Science & Agriculture, Univ. of California, Riverside, CA 92502, USA

Received for publication November 15, 1976. Accepted for publication January 26, 1977.