The present paper presents the contribution on the performance enhancement study of a regenerative Ljongstrom type air preheater. The experimental analyses are carried out to study the performance enhancement of the system by regular artificial roughening of the heat transfer elements using pin-shaped turbulators (promoters). An experimental test rig is designed and fabricated to simulate the transient operation of the rotary air-preheat system. To study the hydraulic and thermal processes and their combined influences on the system performance, the friction factor and the convection heat transfer coefficient, with and without the turbulators, were evaluated from experimental measurements. The investigations have been carried out under various designs and operational conditions. The results were obtained and presented for Reynolds number in the range of 0.93 � 105 to 2.35 � 105 in the thermal discharge period and 0.58 � 105 to 1.8 � 10 5 in the thermal charging period. The roughening effect was also investigated by varying the pin pitch to pin height ratio, P/e; additionally, the effect of the thermal elements numbers in the working section was considered. The artificial roughening by the pins enhanced the performance of the rotary air preheater, and best results have been achieved at P/e=10. © 2010 WIT Press.