Investigation of exergy efficiency in shell and helically coiled tube heat exchangers

•A correlations is proposed for calculating the exergy efficiency.•The efficiency decreases linearly with increase of the fluids dimensionless inlet temperature difference (RT).•The coil which has the maximum number of turns (N) and minimum diameter (dc) is more efficient.

This study presents exergy analysis for forced convection heat transfer in shell and helically coiled tube heat exchangers. The effect of operational and geometrical parameters on the exergy efficiency was investigated. Water is selected as the working fluid of both sides. Results show that, the efficiency decreases linearly with the increase of the fluids dimensionless inlet temperature difference. Based on the results, a correlation was developed to predict the efficiency for wide range of mass flow rates ratio (0.1