The effect of heat transfer and the role of the surface integration process in crystal growth are analysed quantitatively in terms of a non-isothermal effectiveness factor, defined as the ratio of actual growth rate to the rate that would be obtained if conditions of the supercooled or supersaturated bulk liquid existed at the crystal surface. The expression for simultaneous transfer of mass and heat in the liquid phase in the vicinity of the growing crystal surface is developed. Surface conditions of growing crystals. freely settling in a supercooled or supersaturated liquid, are determined for seven binary systems including organic melts and aqueous solutions of inorganic salts. Organic melt systems and some aqueous systems exhibit effectiveness factors significantly less than unity, indicating that the liquid phase transport phenomena play an important role in crystal growth. As a measure of the contribution of heat transfer, the ratio of the isothermal to the non-isothermal effectiveness factors is introduced.
For both organic and inorganic systems this ratio increases at high concentrations of the crystallizing component and high heats of crystallization.
An empirical criterion for the importance of thermal processes is that the nondimensional group /?., = (k'p,AH/h')(dzX/dT) should be greater than 0.01.