Influence of twist ratio of twisted tape turbulator on thermal and second law efficiency of spiral tube

Abstract

This study aims to determine the effects of a spirally coiled tube paired with a twisted tape turbulator. The tube was maintained at a constant wall temperature, and the flow was considered to be turbulent. Effect of different flow rates has been studied in which the Reynolds number was ranging between 6000 and 52,000. The Reynolds number and twist angle of twisted tape are the main variables whose influence has been assessed on the heat transfer characteristics. It was observed that the twisted tape may totally change the hydrodynamics behavior of fluid in the spiral tube affecting both pressure drop and heat transfer. As a result of adding twisted tape the pressure drop ratio raised from 1.88 to 2.19 and the Nusselt number raised from 1.03 to 1.115. In order to evaluate both the heat transfer enhancement as a desired phenomenon and the pressure drop as an undesired phenomenon, the performance evaluation criteria (PEC) has also been studied. The amount of 0.868 was the highest PEC amount achieved through this method which indicates that the method has positive effect in enhancing the heat transfer characteristics. In order to better evaluate the proposed method, the White-Shamsundar efficiency has also been evaluated which considers both of the first and second law of thermodynamics simultaneously and reports the data based on both efficiencies of the first and second laws of thermodynamics.

Keywords

• Spiral tube
• Heat transfer
• Twisted tape
• White-Shamsundar (ηW−S) efficiency