Industrial Crops and Products 22 (2005) 249–255 Rheology of bio-edible oils according to several rheological models and its potential as hydraulic fluid W.B. Wan Nik a, ∗ , F.N. Ani b , H.H. Masjuki c , S.G. Eng Giap a a Faculty of Science and Technology, Kolej Universiti Sains Dan Teknologi Malaysia, Mengabang Telipot, 21030 Kuala Terengganu, Malaysia b Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia c Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia Received 13 May 2004; accepted 19 January 2005 Abstract Today’s concern of protecting the environment has encouraged the research and the use of environmental friendly products. Bio-edible oils are potential energy transport media in hydraulic and lubricating systems. The use of bio-edible or vegetable oils as hydraulic fluid would help to minimize hazardous pollution caused by accidental spillage, lower disposal costs of the used fluid, and help the user industry to comply with environmental safety regulations. In order to successfully use these oils, an understanding of the oil properties is necessary in order to overcome the possible failures or obstacles that might occur in real operating conditions. Rheological property is one of the most important parameters and for this reason this parameter was investigated. The present work evaluates the temperature and shear rate effects of food grade oils that include palm, coconut, canola, corn and sunflower oils. A couette-type viscometer was used to determine the flow behavior of the oils at different temperatures and discrete shear rates that are ranged 40–100 ◦ C and 3–100rpm, respectively. Various empirical models such as Ostwald de-Waele, Cross, Carreau, Herschel–Bulkley and Arrhenius-type relationship were used to evaluate the experimental data. The influence of shear rate and temperature on the variation of viscosity was clearly observed but temperature has more significant influence. Interpretations of rheological models indicate that these food grade oils belong to pseudo-plastic category. The palm and sunflower oils are highly stable in terms of shear rate and temperature, respectively. The overall results suggest the potential substitution of food grade oils as an energy transport media. © 2005 Elsevier B.V. All rights reserved. Keywords: Rheology; Temperature; Viscosity; Vegetable oil; Lubricants; Hydraulic fluid ∗ Corresponding author. Tel.: +60 9 6683342; fax: +60 9 6694660. E-mail address: niksani@kustem.edu.my (W.B. Wan Nik). 1. Introduction Rheology is a field which tends to combine con- tinuum mechanics with ideas obtained by considering the microstructure of the fluid under study. Rheological properties play a major role in describing heat transfer 0926-6690/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2005.01.005