An experimental burner of the heat-recirculating type was constructed and its thermal characteristics were investigated for steady methane/air and low-calorific-fuel/air combustion. Longitudinal temperature distributions of air and burned gas flowing in the passes of the burner were determined by means of both experiments and numerical simulations. Using the heat recirculation rate and the thermal efficiency as criteria for the heat transfer performances of the burner, the optimal design of the burner was examined in terms of a chemical parameter (the equivalence ratio), a fluid-mechanical parameter (the Reynolds number) and a geometrical parameter (the number of passes).