New approach to estimation of thermal conductivity coefficient for underground pipeline forming a thawing halo in permafrost

Abstract

Practice of northern oil pipelines operation shows that operating modes of pipelines in permafrost are practically incomputable. The fact of surrounding soil thawing changes the conditions of heat transfer so drastically that conventional methods of non-isothermal pipelines calculation prove to be inapplicable both in the cases of thawing and freezing soils. Analysis of data obtained during the experimental study of physical model has shown that, depending on the phase state of soil moisture and the type of ice formation, thermal conductivity coefficient of frozen soil may exceed to twice the coefficient of thawed soil. The proposed equation for soil thermal conductivity coefficient estimation makes it possible to determine the external heat transfer and to calculate the pipeline temperature profile according to conventional method of non-isothermal oil pipelines thermal calculation.