A general distributed-parameter model for thermal performance of cold box with parallel plate-fin heat exchangers based on graph theory

For predicting the thermal performance of cold box with parallel plate-fin heat exchangers, a general distributed-parameter model based on graph theory was developed. In the present study, a mathematical description model of cold box based on graph theory was established, capable of describing the connection relations of multiple streams and components in cold box; a distributed-parameter thermal performance model of plate-fin heat exchangers based on approximate analytical method was developed, and the temperature gradients along both axial and transversal directions are reflected; a mass flow rate distribution model of parallel pipelines based on the pressure balance was presented to calculate the flow distribution of multiple streams in pipelines. A tailor-made iteration algorithm using graph-based traversal method was developed to solve the present model. The validation of the proposed model shows that the deviations of the calculated heat capacity and outlet temperature of natural gas from experimental data are -1.9% and +4.35 degrees C, respectively.