The design of ECU has been created, which allows in the process of growing halide crystals to create in the growth and annealing zones, respectively, the high-gradient and low-gradient temperature regions necessary for each of the processes. The mathematical study of the influence of the processes of hydrodynamics, heat and mass transfer inside ECU, between ECU and the crystallization apparatus, is considered. For numerical calculations, the Navier-Stokes equation, the Menter differential k-ω turbulence model SST, the modified Stefan-Boltzmann law, the Fourier law are used. To describe the mechanism of heat transfer and heat conduction in solids, boundary conditions of the third kind were set. The distribution of the axial temperature gradient inside the carbon-graphite heat unit was studied. The mode of flow of the refrigerant inside the cooling jacket was determined. The radiative heat transfer between the surfaces, and the mechanisms of heat transfer and heat conduction in solids were studied.