Assessment of energy saving potential of an industrial ethylene cracking furnace using advanced exergy analysis

Steam cracking furnace is a high energy-consuming equipment in the ethylene plant. Reducing the exergy destruction and losses associated with the steam cracking furnace can increase the thermodynamic efficiency of the system and thereby reducing energy penalties. This paper aims to quantitatively evaluate thermodynamic performance of an industrial steam cracking furnace through conventional and advanced exergy analysis in order to assess its energy saving potential. A steady state simulation of an industrial steam cracking furnace with a total feed capacity of 12 t/h was carried out. The simulation was validated by comparing the model prediction results with the industrial data. The conventional exergy analysis shows that the overall exergy efficiency of the steam cracking furnace is found to be 43.43% and the combustion process in the radiation section exhibits the largest exergy destruction followed by the tube reactors in the radiation section. The advanced exergy analysis shows that the combustion process has the highest unavoidable exergy destruction. Moreover, the tube reactors in the radiation section has the highest avoidable exergy destruction, followed by the combustion process and the feed-steam mixture superheater in the convection section. Therefore, there is high energy saving potential in the tube reactors, combustion process and feed-steam mixture superheater. The advanced exergy analysis also indicates that efforts on improving the radiation and convection sections should be dedicated to themselves while the thermodynamic performance of the quench system should be improved by reducing the exergy destruction of other interacting components

Fouling in a steam cracker convection section part 1 : a hybrid CFD-1D model to obtain accurate tube wall temperature profiles

To study fouling in steam cracker convection section tubes, accurate tube wall temperature profiles are needed. In this work, tube wall temperature profiles are calculated using a hybrid model, combining a one-dimensional (1D) process gas side model and a computational fluid dynamics (CFD) flue gas side model. The CFD flue gas side model assures the flue gas side accuracy, accounting for local temperatures, while the 1D process gas side model limits the computational cost. Flow separation in the flue gas side at the upper circumference of each tube suggests the need for a compartmentalized 1D approach. A considerable effect is observed. The hybrid CFD-1D model provides accurate tube wall temperature profiles in a reasonable simulation time, a first step towards simulation-based design of more efficient steam cracker convection sections

Numerical modelling of the temperature distribution in a two-phase closed thermosyphon

Interest in the use of heat pipe technology for heat recovery and energy saving in a vast range of engineering applications has been on the rise in recent years. Heat pipes are playing a more important role in many industrial applications, particularly in improving the thermal performance of heat exchangers and increasing energy savings in applications with commercial use. In this paper, a comprehensive CFD modelling was built to simulate the details of the two-phase flow and heat transfer phenomena during the operation of a wickless heat pipe or thermosyphon, that otherwise could not be visualised by empirical or experimental work. Water was used as the working fluid. The volume of the fluid (VOF) model in ANSYS FLUENT was used for the simulation. The evaporation, condensation and phase change processes in a thermosyphon were dealt with by adding a user-defined function (UDF) to the FLUENT code. The simulation results were compared with experimental measurements at the same condition. The simulation was successful in reproducing the heat and mass transfer processes in a thermosyphon. Good agreement was observed between CFD predicted temperature profiles and experimental temperature data.The Saudi Cultural Bureau in London, the Ministry of Higher Education and the Mechanical Engineering Department, Umm Al-Qura University

Coupling of volume of fluid and level set methods in condensing heat transfer simulations

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this record Additive Manufacturing (AM) is a rapidly developing new technology which allows the manufacture of arbitrarily complex geometries, and which is likely to transform heat exchanger design. To drive this transformation we need to develop computer modelling techniques to model fluid flow, heat exchange and phase change in arbitrarily complex domains, such as can be manufactured using AM. The present work aims to develop a computational fluid dynamics (CFD) model for heat transfer and phase change, robust enough to model compact AM heat exchangers for automotive fuel cell application. The hydrodynamics of the two-phase flow is captured via the Volume Of Fluid (VOF) approach, coupled with a Level Set method in order to capture the sharp interface between liquid and vapour in laminar film condensation. The Stefan problem is used to show the improvement of the interface tracking with LS-VOF against VOF approach. The resulting complete condensation model is applied for the first time for a complex AM geometry and validated against experimental data