Parameters optimization of intermediate fluid vaporizer based on mixed working fluid

Intermediate Fluid Vaporizer (IFV) is a key heat exchange device for off-shore floating LNG receiving terminals. Based on the heat transfer theory, a coupled heat exchange calculation model for multiple heat exchangers was established, and mixed working fluid was used as an intermediate medium to study the influence of operating parameters on the heat exchange performance of the gasifier. By analyzing the influence of the saturation temperature of the mixed intermediate medium on the heat exchange performance of the vaporizer, combined with the sensitivity analysis of seawater temperature fluctuations, the optimal saturation temperature range of the mixed intermediate medium is 256-265 K. As the total heat exchange area is small and the change is not vulnerable to seawater temperature fluctuation, the IFV will operate more stably under such condition. Thanks to the high heat exchange coefficient of evaporator and condenser, the IFV will have good heat exchange performance. By studying the influence of the temperature drop of seawater in the thermostat on the heat exchange performance of IFV, the temperature drop range of seawater in the thermostat is 0.6–1.2 K. At this time, the UA value of each IFV, i.e., the product of heat exchange thermal coefficient U and heat exchange area A, and heat load both show high volume, the heat flux density is high, the heat exchangers have good heat exchange performance, and the change on the total heat exchange area of IFV is controlled within 10% of the minimum heat transfer area, each heat exchange accounts for 20% to 50%, which is more conducive to improving the stability and adaptability of IFV operation, and the recommended heat load ratio between heat exchangers is 3–7.