Nowadays, due to continuous growth of the computational capacity, there is tendency to perform complex numerical simulations, which are highly interesting to compare with analytical estimations and experimental investigations. The analysis of the evaporation rate of liquefied natural gas (LNG) from the closed cargo tank with valve has been studied by means of numerical simulation based on the finite volume method. The numerical models have developed for a different environment conditions for the case of real gas. Additionally, the heat transfer mechanisms within the closed cargo tank are considered the calculation results are presented and compared with known experimental data in this work.
During the sea passage the evaporation of the LNG from the tank is taking place. That happens due to particularity of energy transport within the tank's isolation. Liquefied methane is transported at a temperature about the boiling point TCH4 = −163◦ C; however the temperature outside of the tank is equal to the ambient temperature. During the transportation the ambient temperature changes according to the region when the cargo moves (Amid, 2016).
According to the different data sources the average ambient temperature is defined as:
For the whole world, excluding Alaska the air temperature is given in the range (at 5 knot) from −18° to +40◦ C;
For Alaska the air temperature is given in the range (at 5 knot) form -29◦ to +10◦ C.
The ambient temperature in this work is taken in the range from −20◦
C to +40◦ C, (Amid, 2016). The transported system should sustain the total vapor pressure of cargo or to hold on the pressure within the cargo below the specified pressure. The vessels for the methane transporting must keep this condition as least 21 days. There are several ways to provide a stable work of this system: liquefaction of steam combustion in a boiler or catalytic preheater, the use of steam as a fuel, a combination of these methods.