Temperature dependence of thermophysical and rheological properties of seven vegetable oils in view of their use as heat transfer fluids in concentrated solar plants

Abstract

Selecting a heat transfer fluid (HTF) depends on the value of thermophysical parameters. In response to the need for innovative heat transfer fluids in concentrated solar power (CSP) plants, vegetable oil offers a promising solution. The relevant thermophysical properties are density, thermal conductivity and specific heat capacity. Moreover, a rheological property, the dynamic viscosity is also relevant. The objective of this work was to study and compare these properties for seven different vegetable oils (rapeseed, soybean, sunflower, palm, copra, cotton and jatropha) in the temperature range from ambient to 250°C. For all the properties studied, the values evolved with increasing temperature and were influenced by the fatty acid composition of each vegetable oil. Experimental results are compared with those in the literature and are found to be consistent. The temperature dependencies are correlated to temperature using polynomial equations. The correlations presented here may be useful as a database for the selection of innovative heat transfer fluids.