Improvement performance of the double-concentric pipes heat exchanger using twisted tape insertions and nanofluids TiO2/TermoXT 32

Abstract

The purpose of this study is to observe the effect on the performance of a double pipe-concentric heat exchanger as the effect of the addition of twisted tape insertions and nanofluids TiO2/TermoXT 32 as the working fluid. Experiments were carried out on a test rig that consists of two pipes with an inner pipe diameter of 38.1 mm for the inside pipe and inner pipe diameter of 75.2 mm for the outside pipe. The working fluid, nanofluids, were constantly flowed and maintained at a low temperature of 20°C. The flow rate was varied at 10 LPM; 12 LPM; 14 LPM; 16 LPM; 18 LPM; and 20 LPM. Twisted tape insertions which are used in the experiment were made of Aluminum and have three variations of twist ratio which are 7.35; 5.25; and 4.72. The nanofluids TiO2/TermoXT 32 has 3 volume fraction variations of 0% (base fluid); 0.1%; and 0.3%. The results showed that the addition of twisted tape insertions led to the increased heat transfer rate. This increment was indicated by the increase of Nusselt number for each measurement planning. The increase of Reynolds number was followed by the increase of heat transfer rate. Moreover, the increasing volume fraction of nanofluids TiO2/TermoXT 32 also influenced the performance of heat exchanger. The highest heat transfer rate was demonstrated by the highest Nusselt number that observed on the twist ratio of 4.72 and Reynolds number of 20 LPM. On top of that, the volume fraction of 0.3% also produced the optimal Nusselt number. The experiments showed the best-operating conditions were found in the specification of 0.3% nanofluids volume fraction with 4.72 twisted tape ratio.