Experimental Investigation of Heat Transfer Enhancement in a Shell and Tube Heat Exchanger Using Twisted Tape Inserts

Shell and tube heat exchangers are widely employed in the oil and gas processing facilities and chemical plants of South South Nigeria, and improvements in their thermal performance have direct economic implications for process energy efficiency and equipment sizing. This study presents an experimental investigation of heat transfer enhancement in a small-scale shell and tube heat exchanger using twisted tape inserts placed in the tube-side flow passages. Inserts of three twist ratios, 2.0, 3.5, and 5.0, were fabricated from 1-millimetre aluminium strip and installed in the inner tubes. Cold water and hot water were used as the tube-side and shell-side working fluids respectively at five flow rate combinations. Nusselt number, friction factor, and thermal performance enhancement factor were calculated from measured temperature and pressure data. Results showed that the lowest twist ratio of 2.0 produced the highest Nusselt number enhancement of 2.4 times over the plain tube baseline but also the highest friction factor penalty of 3.1 times. The twist ratio of 3.5 delivered the best thermal performance enhancement factor of 1.48, indicating a net benefit in heat transfer rate relative to the increased pumping power requirement. Experimental Nusselt number correlations were developed as functions of Reynolds number and twist ratio and showed good agreement with published literature data. The findings support the use of twisted tape inserts as a low-cost retrofit enhancement option for existing heat exchangers. Keywords: heat transfer enhancement, twisted tape inserts, shell and tube heat exchanger, Nusselt number, friction factor.