Correlation Between Dynamic Viscosity and Temperature for Vegetable oil

This article presents the exponential dependence of the dynamic viscosity of temperature for a vegetable oil. In this article I studied coconut oil at temperatures between 40 and 1000C. The coconut oil studied at temperatures between 40 and 1000C and shear rates between 3 and 120 s-1 using a Haake VT 550 Viscotester used with the HV1 viscosity sensor. The exponential dependence is given by the formula (7). By fitting we determined the values of the parameters η0, A and B at different shear speeds. The correlation coefficients have values close to the unit with the lowest value being at the shear rate 17.87 s-1 of 0.9615.


INTRODUCTION
Alternative equations of two constant, three constant and multi-constant forms were proposed by some researchers to describe the dependence of dynamic viscosity of liquids on temperature. Simple form of two constant was proposed by De Guzman and Abramovic 1,2 . Three-constant forms were used and proposed in Vogel study, Andrade study, Noureddini study and in Abramovic study [2][3][4][5] .
Multi-constant forms were proposed in several studies by Thorpe 6 , Noureddini 5 and Daubert [5][6][7] . A polynomial or exponential dependence between temperature and dynamic viscosity of vegetable oil were proposed in Stanciu study 8 .
The effect of temperature on dynamic viscosity of vegetable oil has been studied by several studies [1][2][3][4][5]8 . These studies proposed two, three and multi-constant formula to describe this temperature dependence. Simple formulas of two-constant were proposed to describe the effect of temperature on dynamic viscosity. These are given by: Where η is the dynamic viscosity in cP, T is the temperature in K, A and B are constants 1,4,9,10 .

Brief Communication
Three-constant formulas were used to represent the dynamic viscosity as a function of temperature, which are: Where η is the dynamic viscosity in Pa, s and T is the temperature in Kelvin. A, B, C and D are constants 2,11-14 .
These are represented in the following equations: Where η is the dynamic viscosity in Pa.s in equation (6) and in cP in equation (7). T is the temperature in Kelvin. A, B, C and D are constants [15][16][17]8,9 .
The objective of this article is to find a dependence relation of the dynamic viscosity as a function of temperature for the coconut oil. By fitting the experimental curves we found the relation (7) that shows the dependence of the dynamic viscosity as a function of temperature at all the shear speeds at which the oil was studied.

MATERIAL AND METHODS
Types of coconut oil used in this paper are produced of Secom in Romania. The coconut oil studied at temperatures between 40 and 100 0 C and shear rates between 3 and 120 s -1 using a Haake VT 550 Viscotester used with the HV 1 viscosity sensor (University of Bucharest). The accuracy of the temperature was ± 0.1 o C. Figures 1-8 show the exponential decrease in dynamic viscosity with temperature at the shear rates at which the oil was studied. The program Origin 6.0 was used to determine constants for coconut oil.

RESULTS AND DISCUSSION
The exponential dependence of the dynamic temperature viscosity is described by equation (7) which has the form: Where η 0 and B they are constant and are different depending on the shear rate.
Parameters A, B and η 0 depend on the working conditions, the type of oil, and the shear speeds.
The values of the constants and η 0 and B and the correlation coefficients are included in Table 1. The value of η 0 decreases with the increase of the shear speed and at high shear speeds the decrease is smaller between 6.6084 and 6.1180. Parameter A has a maximum value of 1107.9796 at the shear rate 120 s -1 and a minimum value of 80.5137 at the shear rate 17.87 s -1 . Parameter B decreases with increasing shear speed and has a minimum value of 8.6595 at shear speed 120 s -1 .
The correlation coefficients have values close to the unit with the lowest value being at the shear rate 17.87 s -1 of 0.9615.

CONCLUSION
This article presents the study coconut oil at temperatures between 40 and 100 0 C. We found the exponential relation (7) of the dependence of the dynamic temperature viscosity at the shear rates between 3.3 s -1 and 120 s -1 . The correlation coefficients have values close to the unit with the lowest value being at the shear rate 17.87 s -1 of 0.9615.