ABSTRACT

For the convenience of the cargo oil offloading process, the high-viscosity crude oil in oil tankers needs to be heated and insulated to keep the cargo oil temperature above the freezing point. The thermodynamics associated with the oil heating/insulation process needs to be well understood for optimization, especially when the oil tanker is subjected to a global motion, exciting oil sloshing inside the cargo tank. This paper presents an experimental study characterizing the heat transfer of the sloshing oil. In the experiment, a side tank of a VLCC (very large crude carrier) is considered as a prototype, and a 1/40 model is built following the Froude and Grashof similarity. The model is placed in a 6 DoF sloshing platform, which exciting periodic roll motion to simplified the wave-excited motion in the real scenario. The time histories of temperature at various monitoring points are measured. The results show that the conduction and convection are the dominated factors including the heat transfer when the oil is subjected to a sloshing condition. The characteristics of the temperature variation show different features at different locations and during different stage of the process; within the range of the consideration, larger motion angle and shorter exciting period results in more violent oil sloshing in the tank and, consequently, more significant effects on the heat transfer; as the sloshing becomes more significant, compared with the lower sloshing intensity, there is stronger forced convection above the heating coil. Forced convection makes the variation of oil temperature in the area above the heating coil more severe. Overall, the sloshing significantly influences the temperature distribution and causes a regional difference in the temperature characteristics. The experiment expects to provide a useful reference for guiding the oil heating/insulation process.

INTRODUCTION

Due to the high freezing point of crude oil, when oil tankers transport cargo oil in a low-temperature environment, once the cargo oil has solidified, it is not easy to unload. So, the cargo oil needs to be heated and insulated to ensure fluidity. At present, to prevent this from happening on ships, cargo oil is often overheated, which increase the transportation cost of cargo oil. In the current research on the heating process of cargo oil, cargo oil is mostly under a static environment. However, due to the influence of external wind and waves, cargo oil is always sloshing. Still, few related papers have been published on the effects of oil sloshing on the characteristics of temperature during the cargo oil heating process.

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