The thermo-fluid and exergy analysis of a shell and twisted helical tube heat exchanger

The present study experimentally investigates a shell and twisted helical tube heat exchanger ( STHTHX ), which employs a twisted helical tube configuration to enhance thermofluid performance under turbulent flow conditions. The effects of the twisted helical coil diameter ( D ), inner Reynolds number ( Re i ), and shell Reynolds number ( Re sh ) on the thermal performance ( η ) and exergy characteristics of the STHTHX are examined and compared with those of a conventional shell and smooth helical tube heat exchanger ( SSHTHX ). The twisted helical tube design is expected to intensify the swirl motion of the fluid and induce additional flow disturbances and improve the thermofluid characteristics. Three test specimens were fabricated and tested with twisted coil diameters ( D ) of 0.095, 0.125, and 0.165 m. The experiments were carried out under counter-flow conditions with inner mass flow rates ( ṁ i ) ranging from 0.033 to 0.181 kg/s, corresponding to Reynolds numbers ( Re i ) from 6.1 × 10 3 to 4.4 × 10 4 in the twisted helical coil, and shell-side mass flow rates ( ṁ sh ) between 0.067 and 0.175 kg/s. This study aims to fill the research gap regarding the thermofluid characteristics and exergy analysis of the STHTHX and to provide experimental guidance for its design and optimization. The results reveal that the STHTHX demonstrated superior thermofluid performance compared to SSHTHX . Reducing the twisted coil diameter from 0.165 to 0.095 m increasing Nuᵢ , and f i by 47.9, and 38.77%, respectively. The STHTHX achieved a maximum η of 2.07 at D = 0.095 m. New correlations are proposed to predict Nuᵢ and f i .