The interaction parameter estimation problem in thermodynamic models is an important requirement and a common task in many areas of chemical engineering because these models form the basis for synthesis, design, optimization and control of process systems. Recently, this problem has been solved using minimization of Gibbs free energy, using global optimization techniques. In this paper, liquid-liquid equilibrium (LLE) data of ternary system (water + alcohol + isopropyl ether) at 298.15 K is experimentally investigated, A newly developed heuristic algorithm, harmony search algorithm (HSA) is applied for solving the liquid-liquid phase equilibrium and estimation of binary interaction parameters of this ternary systems. The results of the proposed method are compared with the results given by other optimisation techniques such as genetic algorithm (GA). In all cases, the obtained solutions using the modified HSA are valuable. (C) 2012 Elsevier B.V. All rights reserved.