Investigation of effect of the circular ring turbulators on heat transfer augmentation and fluid flow characteristic of solar air heater

摘要

This study presented effects of the circular ring turbulators (CRTs) having different pitch ratio and hole number on heat transfer augmentation in a new type solar air heater (SAH). The experiments have been performed by varying the parameters, pitch ratio (PR), hole number (N) and Reynolds number (Re) in a range of between 3000 and 7500 under solar radiation heat flux (I). The results obtained using CRTs compared with conventional plain tube. The experimental results have shown a significant enhancement in heat transfer on SAHs with CTRs. According to the experimental results, the higher heat transfer augmentation with CRTs inserted inside the tube in SAHs have been obtained for PR = 2 and N = 2. The best experimental results were found with similar to 229% heat transfer enhancement, similar to 5.8 times friction factor compared to a conventional plain tube and the thermal performance factor (eta) was computed as, similar to 1.83. In addition, statistical correlations for Nu, f and eta were developed. These correlation results illustrated a good agreement with experimental results with +/- 10% deviation. (C) 2016 Elsevier Inc. All rights reserved.