In the present work, the thermal and exergy efficiency of the equilateral triangular duct solar air heater is analytically investigated and its performance is improved by attaching an inclined wire rib over the absorber surface. Using triangular ducts improves the operating flow conditions up to the Reynolds number of 35000. The thermal model of solar air heater is solved by using an iterative procedure by code developed in MATLAB. The analysis considers the roughness parameters that roughness pitch (P)-to-height (e) ratio (P/e) of 4 to 16, roughness height (e)-to-hydraulic diameter (Dh) ratio (e/Dh) of 0.021 to 0.043, and rib inclination angle (α) of 30 to 75°. While increasing the Reynolds number from 2000 to 35000, the inclined rib roughened triangular duct solar air heater thermal performance is increased and attains the maximum value of 83.61% and the effective thermal efficiency of 80.26%. The maximum exergy efficiency of 2.62% is obtained at the Reynolds number value of 1864. It improves the thermal performance by 14.2% as compared with the rectangular rib roughened triangular duct solar air heater. The optimum value of roughness parameters is P/e of 12, e/D of 0.042, and α of 75°. The air heater is useable to attain the temperature rise parameter ranges from 0.001 to 0.03 K·m2/W.