Numerical investigation of the thermohydraulic performance of double-pipe heat exchangers under ocean motions

Abstract

In this paper, the finite volume method was used to numerically study the heat transfer and flow of double-pipe heat exchangers (DPHE) under static and ocean motion conditions. The ocean motion is simplified as a harmonic oscillation with the center of the DPHE as the axis of rotation. In addition the flow direction and the inlet Reynolds number, the effects of amplitude and period ontal heat transfer coefficient, pump power and thermal performance factor were also analyzed quantitatively. The results showed that as the heat exchanger oscillates, the total heat transfer coefficient, and pump power exhibit a periodic change and the period is half of the oscillating period of the heat exchanger. The total heat transfer coefficients for all oscillating DPHE are higher compared to static conditions, reaching a maximum improvement of 9.84% at low Reynolds numbers. The total heat transfer coefficient and pump power of DPHE under oscillation are significantly regular, positively correlated with amplitude and negatively correlated with period. When the amplitude exceeds 0.5 rad/s, the oscillatory condition has thermal performance improvement for the oscillating DPHE with the inner tube with low Reynolds number and the outer tube with high Reynolds number. In the optimum condition, the thermal performance of the inner and outer tubes is improved by 5.01% and 1.48%, respectively. The thermal performance coefficient of DPHE hardly changed when the period exceeded 5 seconds. The results herein provide a theoretical basis for predicting the development of offshore double-pipe heat exchange equipment.