Experimental investigation on the pressure drop and heat transfer characteristics of a recuperator with offset strip fins for a micro gas turbine

In this study, the pressure drop and heat transfer characteristics of a recuperator with offset strip fins for a micro gas turbine were experimentally investigated in the high-temperature range. A unit recuperator with offset strip fins was fabricated using furnace-brazing technology in vacuum atmosphere. Experiments were conducted by varying the mass flow rate and inlet temperature of the hot air stream in the range of 1.5−4 g/s and 250−500 °C, respectively. Based on the experimental data, the total pressure drop results measured at high temperature were much larger than those in ambient-temperature condition, and we showed that the inlet pressure of each air stream should be measured to correctly figure out the pressure drop characteristics of the recuperator in the high-temperature range. Furthermore, the effectiveness was almost constant regardless of the inlet temperature of the hot air stream, which means that the fluid mean temperature variation hardly affected the effectiveness of the recuperator. Two types of analytical models were proposed to predict the pressure drop and the effectiveness of the fabricated recuperator and the model prediction results were also compared with the experimental data. The comparison with the experimental data showed that the results from the simple model may lead to incorrect results for the thermal efficiency of the micro gas turbine because the recuperator effectiveness was overestimated and the pressure drop of the recuperator was underestimated. On the other hand, the modified model proposed in the present work successfully estimated the pressure drop and heat transfer characteristics of the fabricated recuperator with offset strip fins for a micro gas turbine.