Numerical investigation on flow pattern transformation and heat transfer characteristics of two-phase flow boiling in the shell side of LNG spiral wound heat exchanger

Abstract

The flow pattern transformation and heat transfer characteristics of refrigerant flow in the shell side of LNG spiral wound heat exchangers (SWHEs) have a significant influence on the performance of SWHEs. A numerical model was developed to predict the flow pattern and heat transfer characteristics of two-phase flow boiling in the shell side of SWHEs. In the model, a submodel for simulating flow pattern was developed by employing Volume of Fluid combined with a Continuous Surface Force (VOF-CSF model), and a submodel for the mass transfer rate was developed; the forces and the heat and mass transfer rates were introduced into the control equations as the source terms. The experimental validation of the model shows that, the deviation of heat transfer coefficient is within ±20%, and the predicted flow patterns are consistent with those observed ones. Based on the proposed model, the flow pattern maps were developed, and the flow pattern transformation principles and heat transfer characteristics in SWHE shell side under different conditions were analyzed. The maximum heat transfer coefficient for SWHE shell side is enhanced by 10.5% as the longitude tube pitch increases from 1 mm to 3 mm, and reduced by 8.9% as the tube diameter decreases from 12 mm to 8 mm.