TABLE OF CONTENTS Predicting the flow temperature and pressure changes has become increasingly important for use in both the design and the operation of flow transmission pipelines. It is therefore imperative to develop appropriate methods capable of predicting these parameters for multiphase pipelines (Mokhatab, 2006a). A simplified flowchart of a suitable computing algorithm is shown in Figure 3-6. This algorithm calculates pressure and temperature along the pipeline by iteratively converging on pressure and temperature for each sequential "segment" of the pipeline. The algorithm converges on temperature in the outer loop and pressure in the inner loop because robustness and computational speed are obtained when converging on the least sensitive variable first (Brill and Beggs, 1991).
The pipeline segment length should be chosen such that the fluid properties do not change significantly in the segment. More segments are recommended for accurate calculations for a system where fluid properties can change drastically over short distances. Often, best results are obtained when separate segments (with the maximum segment length less than about 10% of total line length) are used for up, down, and horizontal segments of the pipeline (Brill and Beggs, 1991).
Prediction of the pipeline temperature profile can be accomplished by coupling the pressure gradient and enthalpy gradient equations as follows (Brill and Beggs, 1991).
where ? H is enthalpy change in the calculation segment, Btu/lb m; V M is velocity of the fluid, ft/sec;
