Sharif Digital Repository

In common solar stills, a portion of the produced vapor undesirably condenses on the sidewalls and runs down to be mixed with saline water in the basin. This results in lower distillate output of the system. The aim of this study was to improve the condensation process of a solar still without complicating its structure to collect the water condensed on sidewalls. The proposed solar still was made of two containers nested one inside the other such that the smaller container, containing saline water, fitted easily into the larger container. There was a thin gap between the two in which condensed liquid on sidewalls, ran down and was collected from the bottom of the larger container. The... 

In this study, ferrofluid droplet formation from a nozzle in the presence of a non-uniform Pulse-Width Modulated (PWM) magnetic field with different angles was studied experimentally. A Drop-on-Demand platform was introduced and three different regimes of droplet formation were observed. The regime map of the droplet formation was presented. A new type of droplet formation evolution was observed in which the droplet is formed while it is swinging around the nozzle, and the satellite droplet is not generated in this regime. The effects of five important parameters including magnetic flux density, applied magnetic frequency, duty cycle, distance between the nozzle and the center of the upper... 

Magnetically actuated droplet manipulation offers a promising tool for biomedical and engineering applications, such as drug delivery, biochemistry, sample handling in lab-on-chip devices and tissue engineering. In this study, characteristics of an adjustable alternating magnetic field generated by a magnetic coil for droplet manipulation was investigated which enables more control on droplet transport, and it can be considered as a suitable alternative for moving magnets or an array of micro-coils. By adjusting the magnetic flux density, the duty cycle and applied magnetic frequency, the manipulation of water-based ferrofluid droplets with a bio-compatible surfactant for different volumes... 

Numerous applications in engineering and biotechnology have attracted the attention of many researchers to the analysis of underlying physical phenomena during the droplet pinch-off. In this study, the neck evolution during the formation of a ferrofluid droplet from a capillary is investigated under two types of magnetic field for a drop-on-demand system. The two types are steady and Pulse-Width Modulated (PWM) magnetic fields. First, under steady magnetic field, the necking process is studied for different values of magnetic Bond number and various angles between magnetic coil centerline and gravity. Subsequently, self-similar behavior in the vicinity of the detachment moment is observed.... 

Micro-magnetofluidics offers a promising tool to regulate the drop formation process with versatile applications in engineering and biomedicine. In the present study, on-demand ferrofluid drop generation at a T-junction is investigated utilizing a magnetic pulse. Also, a novel method for ferrofluid droplet formation is introduced using a non-uniform Pulse-Width Modulation (PWM) magnetic field. A novel mechanism of drop generation named “beating regime” was seen for the first time in which the ferrofluid moves back and forth before the breakup. The effect of the magnetic induction, continuous phase flow rate, duty cycle, and applied frequency on the generation frequency and drop diameter was... 

The magnetic actuation of ferrofluid droplets offers an inspiring tool in widespread engineering and biological applications. In this study, the dynamics of ferrofluid droplet generation with a Drop-on-Demand feature under a non-uniform magnetic field is investigated by multiscale numerical modeling. Langevin equation is assumed for ferrofluid magnetic susceptibility due to the strong applied magnetic field. Large and small computational domains are considered. In the larger domain, the magnetic field is obtained by solving Maxwell equations. In the smaller domain, a coupling of continuity, Navier Stokes, two-phase flow, and Maxwell equations are solved by utilizing the magnetic field...