Dynamic Simulation and Characteristic Analysis on Freezing Process in Ballast Tanks of Polar LNG Carriers

The ballast tank is a critical system for LNG carriers, ensuring structural safety and stability during navigation. When LNG carriers navigate in polar regions, the ballast tank is prone to freezing, which will reduce the efficiency of ballast water circulation. Furthermore, the freezing process generates frost heaving forces that may damage the walls of the ballast tank, shorten the structure’s service life, and disrupt the ship’s normal operations. Therefore, analyzing the freezing process of ballast tanks is essential. This paper focuses on the ballast tank of a polar LNG carrier as the research subject. It assumes that the ballast water is fresh water with unchanging physical properties and takes into account the environmental conditions in polar regions. A numerical simulation model of the freezing process within the ballast tank is established. This study investigates the influence of various environmental parameters on the freezing process and determines the evolution of ice shape in relation to temperature field changes under different environmental conditions. The results indicate that as the ambient temperature decreases, the rate of temperature reduction at the ballast water level accelerates, resulting in a thicker ice layer formed by freezing. Additionally, as the seawater temperature decreases, the rate of temperature decline in the ballast water at the bulkhead is significantly accelerated, leading to an increased rate of ice shape evolution. Furthermore, a reduction in the height of the ballast water level enhances the heat transfer rate of the ballast water, which markedly increases the degree of freezing in the ballast water.