A distributed-parameter model for LNG spiral wound heat exchanger based on graph theory

For the purpose of designing LNG spiral wound heat exchanger, a distributed-parameter model is proposed in this paper. In the distributed-parameter model, the governing equations are established layer by layer instead of tube by tube to reduce the complexity of heat transfer calculation and improve the computation speed; a graph theory based method is proposed to describe the flexible flow circuits of different liquefaction processes, and an equivalent flow resistance is employed to replace the nonlinear equations to describe the mass flow rate distribution through flow circuits. An alternating iteration algorithm of heat transfer and pressure drop is proposed to quickly solve the equations of the distributed-parameter model. The presented model is validated by a practical application case and the results show that the predicted heat exchange capacity and outlet temperature of LNG agree well with the experimental data.