Energy and exergy analysis of spiral turns in optimum design spiral plate heat exchangers

Abstract

AbstractThe present study investigates exergy analysis of optimal designed spiral plate heat exchangers (SPHEs) based on energy criteria. A new design algorithm is developed to obtain a higher overall heat transfer coefficient and more compact SPHE by (1) maintaining the geometric aspect ratio (GAR), (2) enhancing channel pressure drops, and (3) minimizing the total costs. Mathematical modeling of spiral turns of designed SPHEs as a hypothetical network of heat exchangers (HEs), and implementation of energy balance equations contribute to the determination of channel temperature distributions. In the second part of the study, two new dimensionless energy‐based numbers have been introduced besides thermal effectiveness, temperature difference number, and modified temperature difference number. These two newly defined dimensionless numbers can add to the exergy evaluation in channels. To reach the set goals, several studies are conducted in different cases of single‐phase counter‐current SPHEs. First, temperature distribution obtained from the mathematical modeling was validated with computational fluid dynamics simulation results, which shows less than 5% deviation in dimensionless temperature distribution. Afterward, results of energy‐based criteria were assessed by thermal effectiveness correlation of counter‐current HEs. Second, comparing the new algorithm with other algorithms highlights the key role of GAR, pressure drop, and economic factors. The results show the highest enhancement in the relative heat rate capacity per volume of the newly designed SPHE, up to 54%, in comparison with other designs. Finally, analysis of various designed SPHEs and their channels confirms the reliability of newly defined criteria and temperature distribution significance in performance and irreversibility evaluation of spiral turns. Nevertheless, results show contradictions in total exergy loss number for SPHEs with larger and smaller than 12 spiral turns in numbers