Comparison of heat transfer characteristics of a heat exchanger with straight helical tube and a heat exchanger with coiled flow reverser

Vertical shell and coiled tube heat exchangers are an important aspect of numerous industrial processes and are renowned for their high heat transfer efficiency, versatility, compact design, easy manufacturability and maintenance. As a novel technique, a coiled flow reverser was used to enhance the thermal performance of shell and coiled tube heat exchangers. Therefore, the impact of employing a coiled flow reverser on the heat transfer characteristics and pressure drop in a counter-current shell and tube heat exchanger is investigated using both numerical and experimental approaches. The results are compared to a straight helical coiled tube heat exchanger. The numerical simulations were carried out by employing computational fluid dynamics (CFD) techniques, and the SIMPLE scheme was implemented through the second-order upwind discretization method. The laboratory device used for experimentation features a shell with an inner diameter of 15 cm, and the coil pitch and coil diameter of both coiled tubes are set at 3 cm and 12.1 cm, respectively. Results reveal that the overall heat transfer coefficient of the heat exchanger with a coiled flow reverser is 39.5 % to 49.9 % higher than that of the heat exchanger with a straight helical tube. The effectiveness ratio of the heat exchanger with coiled flow reverser to the straight helical tube heat exchanger ranges from 1.254 to 1.379. Optimal results are observed at a cold flow rate of 6 LPM and a hot flow rate of 1 LPM for both heat exchangers. Additionally, the coiled flow reverser enhances heat transfer performance at the cost of increased pressure drop. Numerical results are in good agreement with experimental findings, establishing the reliability of the study.