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Enabling Low-Emission LNG Systems

LNG process heat-exchanger modelling

In order to estimate the performance of a heat exchanger, several complex conditions have to be included in the evaluation.

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Often the heat-exchanger modelling in process simulations is using hot and warm composite streams with constant heat transfer rate and constant pressure drop ignoring the actual geometry of the heat exchanger. More advanced simulation and rating tools in use generally account for pressure drop and heat transfer characteristics relevant for the geometry in question. However, effects of unequal distribution of two phase flow into the heat exchanger or mass-transfer inside a heat exchanger are not often accounted for. In addition, the static and dynamic stability of a chosen design need to be checked when running on or off the design operation point. To do this, the heat exchanger model needs to take into consideration all physical and geometry effects.

Today, the focus of LNG plant designs is increasingly on space and energy efficiency. Process optimization with such objectives is likely to result in plant conditions where non-ideal effects are present. Hence, it is necessary to incorporate these effects in the models, as they may have an impact on the performance and operational stability of the plant and lead to reduced plant efficiency.

In this project a modelling framework are being developed including the investigation of suitable numerical techniques and solution schemes.

PhD candidate associated with this subproject:
Gunhild A. Reigstad (Completed)
Modelling of two-phase flows in heat exchangers
Supervisor: Professor Tor Ytrehus
Co-Supervisors: Tore Flåtten and Alexandre Morin