One Dimensional Numerical Study for Thermal Performance of Intermediate Fluid Vaporizer for Liquefied Natural Gas

A one-dimensional heat transfer model was established for the three typical parts of Intermediate Fluid Vaporizer (IFV), namely, evaporator, condenser and thermolator used to vaporize liquefied natural gas (LNG). Seawater and propane were applied as heat sources and intermediate working fluid respectively for regasification and cold energy recovery of LNG in an IFV system. Based on the energy balance among the evaporator, the condenser and the thermolator, the heat transfer and thermodynamic model was established and the distribution of temperature of all fluids and heat transfer coefficients were predicted. The effects of several parameters, including the inlet temperature of seawater and LNG, the mass flow of seawater and LNG, the pressure of LNG, on the temperature distribution and heat transfer coefficients were conducted. The results show that the heat transfer capacity of evaporator was enhanced greatly by increasing inlet temperature and inlet mass flow rate of seawater and the thermal resistances in the two sides of evaporator were proportionate, and show that the heat transfer coefficient of condenser increases gradually along flow path and the curve exists convex firstly and another concave with the turning point, and also show that the heat transfer capacity of thermolator decreases gradually with the heat transfer coefficient inside tube keeping consistent along with the flow path and the heat transfer coefficient inside tube was much bigger than heat transfer coefficient outside tube. The results show that the main thermal resistance is the heat transfer of nature gas flowing across the outside tube banks for the thermolator and the propane condensing outside tube for the condenser, respectively.