GENERALIZED CORRELATION FQR VISCOSITY OF BINARY EUTECTICS

摘要

Heat and mass transfer plays an important role during phase transformation process involving phase change materials. These processes are greatly influenced by thermophysical properties of the material, such as, viscosity, density, thermal conductivity etc. Viscosity is one of the prime factors which controls the crystal growth rate during crystallization/cooling process of the phase change material. It directs the movement of convection currents arising due to concentration gradient, near the interface of the growing crystal.Eutecties are the compounds having sharp transition temperatures corresponding to specific composition and do not suffer from phase segregation, a major problem in incongruent and semi-congruent melting salt hydrates. The viscometric behavior of the following five binary eutecties in the temperature range of 313-363 K has been studied:Mg(NO3)_2.6H_2O- NH_4NO_3; MgNO_3.6H_2O-MgCl_2.6H_2O; CO(NH_2)_2~- NH_4NO_3; CO(NH_2)_2-NH_4Br and CH_3CONH_2-NaBrAn empirical correlation between reduced viscosity and reduced temperature for molten binary eutecties showing Arrhenius behavior above their melting points has been reported. The correlation predicts the temperature dependence of the eutectic viscosity to within ±6%. Consistency tests for viscosity data using reduced parameters have been reported. The empirical correlation developed from this study predicts very well,the viscosity of the molten eutecties and salt hydrates to within ±6% of the experimental values.