Abstract
An advanced algorithm has been developed in order to analyze the performance of re-boiling process of crude oil flowing inside reboilers tubes. The proposed model is composed from Heptane fire heater and a tube array. The heat flux produced from burner is transferred to the crude oil flowing inside the tube. The computational model is composed of two phases—Simulation of fire by using Fire Dynamics Simulator software (FDS) version 5.0 and then a nucleate boiling computation of the crude oil. FDS code is formulated based on CFD (Computational Fluid Dynamics) of fire heater. The thermo-physical properties (such as: thermal conductivity, heat capacity, surface tension, viscosity) of the crude oil were estimated by using empirical correlations. The thermal heat transfer to evaporating two-phase crude oil mixture occur by bubble generation at the wall (nucleate boiling) has been calculated by using Chen correlation. It has been assumed that the overall convective heat transfer coefficient is composed from the nucleate boiling convective coefficient and the forced turbulent convective coefficient. The former is calculated by Forster Zuber empirical equation. The latter is computed from the Dittus-Boelter relationship. In order to validate the nucleate boiling heat transfer coefficient, a comparison has been performed to nucleate boiling convective coefficient obtained by Mostinski equation. The relative error between the nucleate boiling convective heat-transfer coefficients is 10.5%. The FDS numerical solution has been carried out by using Large Eddy Simulation (LES) method. This work has been further extended to include also the structural integrity aspects of the reboiler metal pipe by using COMSOL Multiphysics software. It was found out, that the calculated stress is less than the ultimate tensile strength of the AISI 310 Steel alloy.
Highlights
Several works have been written about crude oil boiling
Fire Dynamics Simulation (FDS) output file which contains the Heptane flame simulation data, Stanjan software which evaluates the thermo-physical properties of the burned mixture, COMSOL Multi-physics transient axi-symmetrical model which performs Heat transfer and structural analyses [41], and the main program which calculate the nucleate boiling convective coefficient and the convective coefficient of the external flow
An advanced simulation algorithm has been developed in order to analyze the performance of re-boiling process of crude oil flowing inside reboilers tubes
Summary
Sciance [1] has conducted experiments on nucleate and film saturated pool boiling for several hydrocarbons, such as: methane, ethane at twelve reduced pressures (the ratio between the pressure and the critical pressure). These experiments have been performed between 0.02 (atmospheric pressure) and 0.9 (close to critical pressure). He has been obtained complete burnout flux (critical heat flux) vs reduced pressure curves for each substance. The Critical Heat Flux (CHF) equation derived by Noyes [2] describes these experimental data with reasonable accuracy over the entire pressure range. Zhu [3] has applied Wall-Resolved Large Eddy
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