Performance assessment of the automotive heat exchanger with twisted tape for thermoelectric based waste heat recovery

Abstract

Waste heat recovery in automobiles is a practical technique to reduce emissions and fuel consumption. The extent of waste heat recovery is directly proportional to the efficiency of the heat exchanger. However, the change in internal geometry has become a convenient method to extract the maximum heat from the exhaust heat exchanger while producing a minimum pressure drop. In the current study, the performance of the exhaust heat exchanger with twisted ribs has been studied for the six different operating points of the diesel engine. Three distinct geometric parameters of twisted tape i.e., pitch ratio, twist ratio, and tilt angle have been studied in detail. Experiments were repeated for various geometric parameters to arrive at the best specification of the twisted tape. The results show that the pitch ratio of 8, twist ratio of 4, and the tilt angle of 60° yield the highest power output. The results obtained were compared with the internal flat heat exchanger. It has been observed that the system equipped with a twisted rib produces more net power than the smooth surface system. Moreover, a comparison of fuel consumption with the commonly used alternator has been performed and the proposed system has the potential to improve the BSFC by 0.65%.