Using computational thermofluid dynamics, we calculated the fluid temperature from the enthalpy and mole fractions of chemical species and the inner wall temperature from thermal equilibrium with radiative heat transfer. The fluid and wall temperatures were approximately found using a temporary solution in the iterative part of the polynomial equations. We carried out combustion simulations using Newton's method and the approximate method introduced in this study, and calculated the fluid and wall temperatures. The computed temperatures from both methods agree completely; furthermore, over 20% reduction in computational time compared to current methods was achieved. Therefore, the approximate method is useful for computations concerning steady-state thermofluids, such as those in combustion simulation.