Method of Reducing Energy Consumption for Heating Frost-Susceptible Soil around Chilled Underground Pipeline

This article is devoted to the calculation and optimization of the engineering protection of cold underground condensate pipelines using heat-tracing cable in frost-susceptible soils in Western Siberia. The method for stress–strain state calculation of a pipeline in frost-susceptible soils has been developed. The dependence of maximal stresses in the pipeline wall on the linear heat-generation rate of the heat-tracing cable in the case of a constant heating mode has been derived. The dependence shows a monotonic decrease of maximum displacement of the pipeline and stresses in the pipeline wall with an increase of the linear heat-generation rate. The influence of a startup delay of the heat-tracing cable to the stress–strain state of the pipeline has been numerically investigated. The use of heating mode with delayed startup reduces the electrical energy consumption by 35.4% for considered pipeline comparing a constant heating mode due to fast soil freezing around a pipeline at the initial stage. The effect of energy saving depends on the linear heat-generation rate of the heat-tracing cable. For the considered pipeline, heat-tracing cable with a minimum permissible linear heat-generation rate of 1 W · m⁻¹ and 3.5 years startup delay provides maximum energy savings.