The influence of the flow rate ratio on plug hydrodynamics is investigated experimentally in a rectangular T-junction microchannel under different conditions, where water plugs are dispersed in a silicone oil carrier phase. The study examines plug length, generation frequency, velocity, and shape. The results show that the resultant forces at the junction, characterised by the two-phase capillary number CaTP, predominantly govern all plug characteristics. Under constant CaTP, the plug length increases linearly with the flow rate ratio, while the generation frequency remains within the range of 41–55 Hz. Plug velocity is primarily controlled by the liquid film thickness, which varies with the flow rate ratio, whereas plug shape is only weakly influenced by this parameter. These findings enhance understanding of two-phase plug flow in microchannels and provide valuable insights for controlling plug flow regimes in microelectronic cooling applications.

With recent advances in semiconductor technology, conventional cooling methods and standard coolants are no longer adequate to manage electronic chips’ enormous heat generation. Therefore, innovative cooling solutions are required to maintain these devices at optimum operating temperatures. Taylor flow in microchannels is an effective technique that allows excellent mixing of two fluids, which is crucial for heat transfer. A 3D numerical analysis of the heat transfer performance of liquid-liquid Taylor flow in a rectangular microchannel was carried out by ANYSY Fluent. Water droplets were dispersed in either ethylene or propylene glycol, with the interface between the two fluids captured using the Volume of Fluid method. For optimal computational time, two symmetries in the XY and XZ planes are considered. Furthermore, mesh size refinement was performed in the near-wall region to capture the liquid film. An analysis of the effect of plug/slug length and liquid film thickness is conducted with initially constant thermo-physical properties. This assumption was considered to analyse the heat transfer process and determine the most critical parameter affecting heat transfer performance. A user-defined function is then implemented in ANSYS Fluent to examine the effect of working fluids temperature-dependent viscosity change on the heat transfer rate. Conjugate heat transfer and axial conduction are also examined, as these two factors can significantly affect the thermal behaviour inside the microchannel and enable the achievement of realistic and accurate results. The results reveal that Taylor liquid-liquid flow can increase the heat transfer rate by up to 440% over single-phase flow. It was also found that the temperature-dependent viscosity of the working fluids significantly affects the plug/slug length and liquid film thickness, resulting in a 20.8% improvement in heat transfer rate compared with constant thermo-physical properties. This study will improve the state of knowledge on heat transfer by Taylor flow in microchannels and factors that can influence it, and highlight the significance of this flow pattern in enhancing heat transfer performance over single-phase flow.

A three-dimensional (3D) numerical simulation of a two-phase flow liquid/liquid is performed in a rectangular microchannel with a T-junction. The volume of fluid (VOF) method was used under ANSYS Fluent to capture the interface between the two phases. The dynamic mesh adaptation technique together with the assumption of symmetry plane helps us to reduce the computational cost. The study focuses on the flow patterns and hydrodynamics of plugs. So, the influence of the flow rate ratio q , the capillary number Ca , and the viscosity ratio on the liquid film, the plug/droplet shape, and velocity are examined here. Particularly, the plug/droplet lengths predicted by the simulation show good agreement with the experimental and cor-relation available in the literature. The results revealed six distinct flow patterns by dispersing water in a continuous phase of silicone oil. By decreasing the flow rate ratio as well as the viscosity ratio, the liquid film thickness increases in the corners and side planes. In turn, this greatly impacts the liquid film velocity and the plug velocity. Furthermore, capillary number (based on two-phase flow velocity) is also shown to have a greater impact than viscosity ratio and flow rate ratio on plug shape, with the curvature radii of the tail always larger than the front one.

This work deals with the construction, and the experimentation of a Bi-fluid (air/water) hybrid photovoltaic/thermal solar collector intended for the residential sector. The hybrid PV/T collector consists mainly of à 185Wp mono-crystalline photovoltaic module, a copper radiator for the circulation of water, and a ribbed metal absorber with fins. The copper radiator and the absorber were glued to the backside of the PV module. This structure was mounted in an insulated box with reservation of a rectangular duct for the air circulation between the absorber and the insulation panel of the box. An experimental bench was set up to evaluate the energy performance of the designed collector under real operating conditions. The obtained results showed that the proposed configuration of the bi-fluid PV/T collector both allows the air to be heated to temperatures appropriate for the intended application (space heating) and to recover additional calories by a second fluid (water) at appropriate temperatures (40–45 °C). Hot water can be used for a double purpose; a direct consumption in a building, and to prolong the production of hot air by a simple recirculation of the stored hot water in the radiator. The average of thermal, electrical, and overall energy efficiencies evaluated for this configuration are very important with values of 56.96%, 13.6%, and 94.53%, respectively.

This paper presents the results of a numerical study of a hybrid photovoltaic/thermal (PV/T) solar air collector provided with fins, assisted PV ventilation, and tracking support. This work aims to study the effective influence of the various key elements (fins, assisted PV ventilation, and tracking support) on the thermal and electrical behaviors of a hybrid PV/T air collector. The addition of fins placed in the dynamic air vein aims to improve the evacuated heat from the PV panel. The purpose of the assisted PV ventilation system is to control the flow of air according to the solar radiation incident on the PV panel. A comparison between simulation and experimental was done in order to validate the numerical model developed for this study. The results show that the three elements provided to PV/T collector give interesting results. The outlet air temperature from the solar device (23 °C) is adequate for residential applications (building air conditioning). Electrical, thermal, and overall average efficiencies have reached significant values of around 13.5, 30, and 70%, respectively.