Numerical simulation of heat transfer performance of spiral wound heat exchanger under sloshing condition.

LNG floating production storage and offloading (FPSO) unit is a new type of floating production unit developed for offshore natural gas fields. It performs the functions of natural gas extraction, pretreatment, liquefaction, and storage. In this study, the heat transfer characteristics of a spiral-wound heat exchanger were studied using numerical simulations, which provides a basis for equipment selection and structural optimization of spiral-wound heat exchangers. The main research contents and conclusions are as follows. Under land-based simulation conditions, the heat transfer coefficient of the shell side of the spiral-wound heat exchanger decreases with an increase in the winding angle of the heat exchange tube, decreases with an increase in the spacing of the heat exchange tube, and increases with an increase in the outer diameter of the heat exchange tube. When the winding angle increased from 5° to 8°, the heat transfer coefficient decreased by 6.70%. The heat transfer coefficient of the shell side decreased by 13.21% when the heat exchange tube spacing increased from 14 to 17 mm. The heat transfer coefficient of the shell side increased by 22.89% when the outer diameter of the heat exchange tube increased from 9 to 12 mm. When the sloshing angle is constant, the heat transfer coefficient of the spiral-wound heat exchanger decreases with an increase in the winding angle and spacing of the heat exchange tubes, and increases with an increase in the outer diameter of the heat exchange tubes. When the structural parameters of the heat exchanger are constant, the heat transfer coefficient decreases as the sloshing angle increases. When the sloshing angle was less than 3°, the sloshing promoted heat transfer on the shell side. When the sloshing angle was higher than 7°, the heat transfer effect of the shell side deteriorated considerably, which weakened the heat transfer performance of the heat exchanger. When the sloshing period is constant, the heat transfer coefficient of the wound heat exchanger decreases with an increase in the winding angle and spacing of the heat exchange tubes, and increases with an increase in the outer diameter of the heat exchange tubes. When the structural parameters of the heat exchanger are constant, the heat transfer coefficient increases with sloshing period. When the sloshing period was greater than 15 s, the influence of sloshing on the heat transfer on the shell side of the heat exchanger was relatively weak.

Influence of Sloshing Conditions on the Pressure Drop and Heat Transfer of a Single-Layer Spiral-Wound LNG Heat Exchanger.

In this study, the results and experimental data under static conditions are verified based on a calculation method. The deviation is controlled within 10%, which verifies the reliability of the experimental data. It is found that pitching has the most obvious influence on heat transfer. Through an analysis of the heat transfer coefficient on the shell side and the friction pressure drop along the path, the variation under rocking conditions is obtained.

Experimental Study on the Effect of Pitch Sloshing on the Heat Transfer and Pressure Drop of an LNG Spiral-Wound Heat Exchanger.

With the development and utilization of offshore liquefied natural gas, it is increasingly important to study the influence of the heat transfer performance of a spiral-wound heat exchanger under sloshing conditions. This study focused on the effects of different sloshing amplitudes and sloshing periods on the heat transfer and pressure drop performance of a heat exchanger. Through experimental research, the results showed that the fluctuation of the UA (U is the heat transfer coefficient; A is the heat exchange area) value first increased and then decreased with an increase in the sloshing amplitude. The UA value increased by 12.92% and decreased by 42.03% compared to the static value at 3 and 9°, respectively. The fluctuation in the UA value first decreased and then increased with an increase in the sloshing period. The UA value decreased by 36.66% and increased by 10.82% slowly compared to the static value when the sloshing period was 6 and 20 s, respectively. Based on this, a mathematical model of heat transfer under the condition of pitch sloshing was established.

Experimental Study on the Slugging Characteristics of Gas-Liquid Slug Flow in Horizontal Pipes.

This study investigates the slugging characteristics of the gas-liquid slug flow interface in horizontal pipes. Using air and water as the experimental media, an experimental system was established using double-parallel conductance probes in a pipe with an inner diameter of 5 cm. By capturing the transient development process of the gas-liquid interface, the slugging characteristics of the gas-liquid two-phase flow interface in different flow regions were revealed. The results show that the value of gas-phase superficial velocity has an important influence on the shape and development of the interface wave during the slugging process. When the gravity wave generated during the slugging process can propagate upstream, the slugging phenomenon is periodic, and when the gravity wave cannot propagate upstream, the slugging phenomenon is random. The experiment verified the correctness of the interface instability theory and the liquid slug stability theory, and clarified the definitions of h o and h s. In addition, the paper analyzed the influence of gas-liquid velocity on slugging distance, h o and h s, and liquid slug frequency.

Rotational speed sensor based on the magnetoelectric effect of composite FeSiB/Pb(Zr,Ti)O3.

This paper proposes a rotational speed sensor based on the magnetoelectric coupling effect. The sensor is composed of a permanent magnet array and a magnetoelectric composite FeSiB/Pb(Zr,Ti)O3. The permanent magnet array rotates with the gear to provide a stable sinusoidal alternating magnetic field in its surrounding space, which is simulated and analyzed by using the finite element simulation software. Based on the magnetoelectric coupling effect, the composite FeSiB/Pb(Zr,Ti)O3 senses the magnetic field information and transforms it into electrical information so as to realize the rotating speed measurement. The experiments of sensing distance and linearity are carried out. The proposed sensor is compared and verified by a coil sensor. The results show that the proposed speed sensor has good linearity in the speed measured range, and the sensing distance can reach 15 mm. At the same time, it can be used for low-speed measurement. This kind of speed sensor has broad application prospects in the field of rotational speed measurement.