Numerical simulation of flow and heat transfer for a 3 in. (0.075m) diameter liquid encapsulant full float zone (LEFZ) growth of single-crystal GaAs was conducted using the finite-element method. Convective and conductive heat transfers, radiative heat transfer between diffuse surfaces and the Navier–Stokes equations for both melt and encapsulant as well as the interface position are all combined and solved simultaneously. The effect of the thickness of encapsulant, rotation rate of crystal and feed rod on the flow and heat transfer as well as on the growing and melting interface shape were investigated.