An exergy-based thermohydraulic model has been developed to minimize carbon dioxide emissions from heat tracing of oil pipelines. This model determines an optimal fluid flow velocity by balancing the increase in the pipe-to-fluid convection coefficient on the one hand and the increase in pumping power demand on the other. Exergy destruction is considered in both cases, which contradict each other regarding responsibility for carbon dioxide emissions. Electric and hydronic heating are considered. A case study has shown that the optimal solution for the flow velocity at a unit mass flow rate, including varying the pipe diameter, can reduce carbon dioxide emission responsibility by 40%. Considering projections for the completion of new land-based pipeline construction worldwide, the total decarbonization potential of employing the new model is estimated at 0.13 Gton CO2 per year, once new pipeline installations totaling 11,947 km are completed by 2030. The option of replacing online electric power generators at pumping substations with combined heat and power systems, thereby shifting heat tracing from electric cables or mats to thermal power with hydronic heating with heat pipes, thereby using the generated electric power for pumps or compressors, has also been investigated, and it has been shown that a 64% emission saving is possible relative to generator-driven electric power heat tracing.
Birol Kılkış (Fri,) studied this question.