Chapter 11, Problem 11.69P

A liquefied natural gas (LNG) regasification facilityutilizes a vertical heat exchanger or vaporizer that consists of a shell with a single-pass tube bundle used toconvert the fuel to its vapor form for subsequent delivery through a land-based pipeline. Pressurized LNG isoff-loaded from an oceangoing tanker to the bottom ofthe vaporizer at $T_{c,i}=-155°C$ and ${\stackrel{\dot{}}{m}}_{LNG}=150\text{ kg/s}$ flows through the shell. The pressurized LNG has a vaporization temperature of $T_f=-75°C$ and specificheat $c_{p,l}=4200\text{J/kg}\cdot \text{K}$ . The specific heat of the vaporized natural gas is $c_{p,v}=2210\text{J/kg}\cdot \text{K}$ while the gashas a latent heat of vaporization of $h_{fg}=575\text{ kJ/kg}$ .The LNG is heated with seawater flowing throughthe tubes, also introduced at the bottom of the vaporizer, that is available at $T_{h,i}=20°C$ with a specific heatof $c_{p,SW}=3985\text{J/kg}\cdot \text{K}$ . If the gas is to leave the vaporizer at $T_{c,o}=8°C$ and the seawater is to exit the device at $T_{h,o}=10°C$ , determine the required vaporizer heat transfer area. Hint: Divide the vaporizer into three sections,as shown in the schematic, with $U_A=150{\text{ W/m}}^2\cdot \text{K}$ , $U_B=260{\text{ W/m}}^2\cdot \text{K}$ and $U_C=40{\text{ W/m}}^2\cdot \text{K}$ .