This investigation concerns performance of a new low-Reynolds version of an explicit algebraic stress model (EASM) for numerical calculation of turbulent forced-convective heat transfer and fluid flow in straight ducts with fully developed conditions. The turbulent heat fluxes are modeled by a SED concept, the GGDH, and the WET methods. New versions of GGDH, WET, and EASM are presented for low Reynolds numbers. However, at high Reynolds numbers, two wall functions are used, one for velocity fields and one for the temperature field. All the models are computed in a general three-dimensional channel. The low-Reynolds version of the models presented is very stable and has been used for Reynolds numbers up to 70,000 with least demanded number of grid points, and without any convergence problem or stability problem.