Experimental study of a triple spirally coiled tube heat exchanger thermo-fluid characteristics

Abstract

In the present article, the thermal and hydrodynamic characteristics of a new design heat exchanger called a triple spirally coiled tube heat exchanger (TSCTHE) are experimentally conducted and compared with a double spirally coiled tube heat exchanger (DSCTHE) as a particular reference. The new design was created by adding a third tube to a DSCTHE. The study carried out under consideration of turbulent fluid to fluid heat transfer condition. The research aims to present the TSCTHE thermo-hydraulic characteristics with different operating and design parameters. The experiments were carried out at four water inlet temperatures from 50°C to 80°C, four flow arrangements include parallel, counter, counter-parallel, and parallel-counter flow patterns with three coil inclination angles from 0° to 90°. The experimental runs applied at Dean number ranged from 500 to 6,500 corresponding to Reynolds number from 3000 to 37,000. The results obtained that the TSCTHE presents a significant enhancement of the Nusselt number compared to DSCTHE by 94.8% and 82.8% for both counter and parallel flow patterns, respectively. Also, the Nusselt number enhancement occurs with decreasing the hot water inlet temperature from 80°C to 50°C by 40%, while the increment in pumping power is approximately neglected. Moreover, the highest values of Nusselt number occurred at counter flow patterns compared to other flow arrangements. In addition, the higher performance index was recorded at higher coil inclination angle of 90°. New correlations to predict the Nusselt number of hot water, friction factor, effectiveness, and performance index were presented.