The process of oil-water displacement is one of the key technologies in offshore underwater tank.When hot oil is contacting the normal-temperature water,the interracial heat transfer should be investigated as the heat loss may result in wax precipitation and solidification which will reduce the flowing of oil and thus affect the process.As for the numerical simulation of heat transfer,the calculation is costly as the underwater tank is usually large and the displacement period is long.A high precision computing method would greatly reduce the mesh scale.Therefore,this research is performed to establish a high precision computing solver.Based on volume of fluid (VOF),a new form of energy equation is proposed.This equation is derived from temperature equation and the variable internal energy per volume is used.This variable is additive and has a close relationship with volume fraction.With algorithm implantation to OpenFOAM,two non-isothermal VOF solvers are established corresponding to temperature equation and the new equation respectively.After an analytical solution is built,the two solvers are compared.The solver based on the new equation presents far more accurate results than the solver based on temperature equation.An energy weighted scheme is more reasonable than a linear temperature distribution for the mixture phase.