Experimental investigation of thermal and hydrodynamic performance of different length twisted tape inserts inside an inclined tube flow

In this experimental study, the effect of using different length twisted tape inserts on the thermal and hydrodynamic performance of flow in an 30 degrees inclined tube was investigated experimentally under thermally developing flow conditions. Ranges of the experimental variables examined were: 500 <Re<5000 and 5<Pr<7. The twist ratio is selected as 3 and the length of the insert is 1 m for full-length twisted tape (FLTT) and 0.5 m for short-length twisted tape (SLTT). The Nusselt number and friction factor were determined by using measured heat transfer coefficient and pressure drop for both FLTT and SLTT and compared with the data obtained for the smooth tube. Performance evaluation factor is calculated in the range of 0.9-2.1. The same performance was approximately observed as the turbulence intensity increased. Beside that correlations were developed for Nusselt number and friction factor. Correlation developed for Nusselt number predicted experimental data within +/- 13.9% average deviation. For friction factor, this deviation was determined as +/- 11.9%.