The Study of Magnetic Field Effect on Two-Phase Liquid-Gas Ferrofluid Flow inside the Microchannel for Spacecraft Applications

Abstract

The transport of the ferrofluid under the influence of the magnetic field has been investigated in this work. Two experimental approaches are presented in this report, (i) pressure, velocity and deposition measurements of an isothermal ferrofluid flow inside the transparent capillary tube under the influence of magnetic field, and (ii) thermal characteristics of the ferrofluid flow in the preheated stainless steel capillary tube, under the effect of the magnetic field. On the basis of the above study, a conceptual design model of the magnetic nanofluid cooling device for space application is discussed.

First part of this project presents the study of the transport of two-phase Ferrofluid liquid-gas slug flow inside a transparent capillary tube and under the influence of external magnetic field. The uniform magnetic field (250G) is generated by two separated electromagnets located along the horizontal axis of the capillary tube having an internal diameter of 2.5mm. The Ferrofluid is flowing with a constant Reynolds number of Re=36. Measurements were made using pressure transducers and a CCD camera. Recorded images were processed using in-house MATLAB image processing tool. Liquid slug front velocity is measured for three aspect ratios (L/D) of 20, 16 and 8 respectively. It was observed that when slug flow travels through two magnets, its velocity is significantly affected and depends on liquid slug length. The dynamics of slug flow will depend on the interaction of the Ferrofluid with the magnetic field. The velocity profile of slug front is similar for all the aspect ratio when they pass through the first magnetic field. However, their significant changes in the velocity profile is observed when slugs reach the second magnet. Experiment was also conducted to analyze the deposition of the Ferrofluid slug in the case of no magnet, steady magnet and alternating magnetic field. It is observed with that the deposition was maximum in the case of the alternating magnetic, compared to the constant and no magnetic field.

The second part focuses on the effect of the uniform magnetic field on the convection heat transfer characteristic of a ferrofluid flow inside the preheated stainless-steel capillary tube. The ferrofluid travels through the heated capillary tube having an internal diameter of 1.5 mm. For a constant Reynolds number of Re=36, and a uniform magnetic field of 700 G, heat flux is quantified using temperature measurements. Joule heating is applied to increase the tube’s temperature. Infrared thermography was used to measure the tube’s surface temperature. Fluid inlet and outlet temperature were measured using two K-type thermocouples. Thermal images were recorded using an IR camera, and processed using Fluke Software. The experimental results are validated using a theoretical model. Comparison of Nusselt number with and without magnetic field is characterized. The present study reported that when the fluid passes under the influence of external magnetic field, the surface temperature of the tube decreases corresponding to a significant increase in Nusselt number. The maximum of 50 % increment in heat transfer is observed for an optimum condition.

Date of Award	Dec 2022
Original language	American English
Supervisor	Afshin Goharzadeh (Supervisor)