Thermal-hydraulic performance of printed circuit heat exchangers with various channel shapes under rolling conditions

Abstract

The floating liquefied natural gas (LNG) facilities are located in deep oceans, where the harsh ocean conditions cause the facilities to sway and tilt. The rolling conditions in floating LNG systems affect the uniformity of gas–liquid distribution in heat exchangers. Thermal and hydraulic performances of printed circuit heat exchangers (PCHEs) with straight, zigzag, and trapezoidal channels are investigated under static and rolling conditions. The results reveal that all channels enhance heat transfer near the pseudo-critical point of LNG at a rolling period of 2 s and a rolling amplitude of 15°. The Nusselt number for the PCHE with a zigzag channel increases by 32.2% and 72.5% compared to those with straight and trapezoidal channels. The highest increase in comprehensive performance is obtained for the zigzag channel with an evaluation index of 1.23 under the rolling condition. Compared with under the static condition, the Nusselt number and Fanning friction factor for the zigzag channel increase by 12% and 28% under the rolling condition. The thermal performance is weakened by the nonuniform flow velocity and improved by the enhancement of flow turbulence. The thermal–hydraulic performance increases with the rolling period from 1 s to 3 s and the rolling amplitude from 15° to 45°. The maximum improvement of 65.3% and 97.2% in Nusselt number and Fanning friction factors is observed at a rolling period of 1 s and a rolling amplitude of 45°. The methods to suppress the deterioration of heat transfer in microfluidic channels under rolling conditions are proposed to satisfy the requirement of LNG with low-resistance and high-efficiency microfluidic structure.