Numerical study on shell-side shear flow and heat transfer in a spiral wound heat exchanger under onshore/offshore conditions

Given that studies on shell-side shear flow and heat transfer characteristics in spiral wound heat exchangers (SWHEs) used in floating liquefied natural gas (FLNG) systems are still scarce, a mathematical-physical model was established based on the two-fluid thermal phase change model, incorporating a modified mean diameter of the dispersed phase. According to the results under onshore conditions with operating pressure ranging from 0.2 to 0.6 MPa, mass flux ranging from 40 to 100 kg/(m²·s), heat flux ranging from 2,000 to 8,000 W/m², and vapor quality ranging from 0.3 to 0.9, respectively, the shell-side frictional pressure drop gradient increased with decreasing operating pressure and increasing mass flux and vapor quality. The effect of the heat flux was negligible and could be ignored. The offshore conditions significantly increased the proportion of shear flow on the SWHE shell side. Therefore, the effects of the rolling and operating parameters on the shear flow were investigated with rolling amplitudes and periods of 5–15° and 5–15 s, respectively. Consequently, the flow and heat transfer characteristics of the shell-side shear flow exhibited sinusoidal periodic fluctuations owing to the influence of the rolling motion, and their fluctuation periods were approximately equal to the rolling period. Within the allowable operating range, a higher mass flux could not only effectively resist the influence of the rolling motion but also maintain the heat exchanger performance at a higher level while delaying the adverse drying of the heat exchange tube wall. Additionally, Aunan's correlation was proven to exhibit good adaptability for calculating the frictional pressure drop gradient of shear flow under both onshore and offshore conditions. These results provide guidance for the design and operation of FLNG SWHEs.