Affiliation:
1. Department of Mechanics, Energy Conversion, Islamic Azad University, Arak Branch, Arak, 3836119131, Iran
2. Department of Mechanical Engineering, Heat and Fluid, University of Kashan, Kashan, Iran, and Islamic Azad University, Arak Branch, Arak, 3836119131, Iran
Abstract
The present study investigates the effects of using a magnetic field on the flow field and heat transfer of ferromagnetic Fe3O4/H2O nanofluid considering two-phase model for nanofluid in heat exchanger equipped with helical ribs. Three methods are employed to enhance the thermal efficiency of heat exchanger, as employing of corrugations, utilizing nanofluid as heat transfer fluid, and employing the magnetic field. The performance evaluation criteria index (PEC) is employed to analyze the thermal-hydraulic characteristics of the heat exchanger. The main aim is to achieve an optimum model with the highest performance evaluation criteria value. Usaging of corrugated heat exchanger or nanofluid can increase the average Nusselt number and friction factor in the tube sharply. Also, it is understood that the presence of a magnetic field has a significant effect on the heat transfer enhancement inside the heat ex-changer. The model with magnetic field of 600 G has the highest Nusselt number ratio among all studied models, which is followed with 400 G, 200 G, and 0 magnetic fields, respectively. Furthermore the effects of different corrugation heights, widths, and pitches have been stud-ied. Finally, usage of the novel corrugated heat exchanger with 14 mm corrugation heights, 9 mm rib width, and 12.5 mm blade pitches filled with nanofluid, and under a magnetic field of 600 G it suggested as the most efficient configuration. Also, at the Reynolds number of 4,000, the highest performance evaluation criteria values are achieved.
Publisher
Journal of Thermal Engineering
Subject
Fluid Flow and Transfer Processes,Energy Engineering and Power Technology,Building and Construction