Thermal stability of a vegetable oil-based thermal fluid at high temperature

Abstract

Synthetic and mineral oils are widely used in high temperature processes (above 200°C) as heat transfer fluids or thermal storage materials. Mineral oils are essentially derived from petroleum that is depleting and synthetic oils are expensive. Furthermore, these oils are toxic to the environment. Today, with environmental concerns, vegetable oils have gained considerable interest. Vegetable oils are renewable, environmentally friendly and non-hazardous resources. Refined Jatropha curcas oil, a vegetable oil, has been identified as a possible thermal oil for high temperature applications such as concentrating solar power. The vegetable oil was thermally aged at 210°C for up to 2160 h. The volatile materials were below 5% from 100°C to 300°C. The specific heat capacity remained constant at 2.4 kJ·kg−1·°C−1 and had a density increase of 2%. The viscosity of aged oil at 100°C was quite similar to that of the new oil. The flash point was around 175°C after 2160 h versus 220°C for the new oil. Based on these results, refined Jatropha curcas oil presents real potential as a heat transfer fluid and thermal storage material.