FREEZING TIME PREDICTIONS OF BURIED PIPES - A 3-D TRANSIENT SIMULATION

Heat transfer from a buried pipe carrying a flowing liquid is analysed using a 3-dimensional geometry, transient modelling and numerical met hods. The pipe is buried horizontally in soil whose initial surface te mperature is assumed to be below that of the bulk soil and the pipe, a nd also below the freezing temperature of the liquid. The problem is s olved using string-intersected-boundaries and a three-level alternatin g-direction-implicit finite-difference method. It is possible to predi ct the time taken for the fluid anywhere in the pipe to fall to its fr eezing point. The minimum burial depth needed so that the pipe does no t freeze is also predicted. The simulation was run on an ordinary main frame computer with very small computation times. The package develope d can be used by designers such as pipeline, plant and water distribut ion engineers.