Rectangular Channel Research Articles

Study on the instability of FC-72 vapor–liquid interface in a rectangular channel under different gravity conditions

Study on the instability of FC-72 vapor–liquid interface in a rectangular channel under different gravity conditions

Efficient Microfluidic Particle Separation Using Inertial Pre-Focusing and Pre-Separation Structures Without Sheath Flow

Abstract This study introduces an innovative microfluidic particle separation technique that integrates inertial focusing with deterministic lateral displacement (DLD) on a single chip, significantly enhancing the efficiency of particle separation. This new method completes flow rate matching through a designed pre-focusing and pre-separation inertial structure, avoiding the use of sheath flow. The process involves a sequence of channels: a rectangular channel, a contraction-expansion array (CEA), a lateral separation channel, and another rectangular channel. This three-stage inertial method shortens the focusing channel length and reduces the pressure on subsequent separation stages, streamlining the separation process. It has been demonstrated to separate 20 μm particles from a mixture containing both 10 μm and 20 μm particles with remarkable precision. The technique achieves a 100% separation efficiency, ensuring all target particles are correctly isolated, and a 96.1% separation purity, indicating that the isolated particles are almost entirely free from contaminants. By eliminating the need for sheath flow, this method simplifies the apparatus and reduces operational complexity, offering significant advantages over traditional particle separation techniques. The high efficiency and purity levels achieved by this method highlight its potential for a wide range of applications in fields requiring precise particle separation, such as medical diagnostics, environmental monitoring, and industrial processing.

Modeling and manufacturing of solar modules of different designs for energy supply of biogas plant

The article presents a description of the modeling and manufacturing of solar modules of photovoltaic, thermal and photovoltaic thermal designs intended to supply energy to a biogas plant intended for the production of biohydrogen and biomethane. Mathematical modeling of the photovoltaic module was carried out and the calculated temperature of the photovoltaic converters was determined, and also the photovoltaic module was manufactured using the process of sealing the photovoltaic converters with a two-component polysiloxane compound. Mathematical modeling of a solar thermal collector with water radiators in the form of a round copper tube, an oval copper tube, as well as a rectangular water cooling channel (“water jacket”) was also carried out, in which pressure losses and the amount of water heating were assessed. The distances between the rectangular channels of the water-cooling radiator for uniform heat removal were determined, and mathematical modeling of the thermal state of a solar thermal collector with a semicircular cross-section of the water-cooling radiator channel was carried out, after which the solar thermal collector was manufactured. Mathematical modeling of the total displacements of the components of a photovoltaic thermal module, the values of which do not exceed acceptable limits, was carried out, after which a photovoltaic thermal module was manufactured using the process of sealing photovoltaic converters with a two-component polysiloxane compound.

Mechanistic Insights into Effects of Perforation Direction on Thermal Hydraulic Performance of Ribs in a Rectangular Cooling Channel

Mechanistic Insights into Effects of Perforation Direction on Thermal Hydraulic Performance of Ribs in a Rectangular Cooling Channel

Experimental study on the effect of tube surface modifications and in-channel baffle plates on falling film evaporator heat transfer properties for sever cabinets

To effectively alleviate the high energy consumption associated with traditional cooling strategies in data centers, this research synoptically designs an innovative and energy-efficient integrated structure combining a falling film evaporator with a cabinet. An experimental setup with a water film tube in a rectangular channel is constructed, and the impacts of liquid film temperature, spray density, and inlet air Reynolds number on heat transfer properties in the cases of the tube's surface structure modifications and baffle plates presence in the channel are explored, respectively. Two significant findings that enable low energy consumption-oriented cooling strategy development are derived. (1) Decreasing the spray density can reduce energy consumption when liquid film integrity is maintained. Upon quadrupling the inlet spray density for the smooth and finned tubes, the heat transfer rate and heat transfer coefficient between the tubes and airflow in the baffled and unbaffled channels only increase by 23.1 to 29.9% and 18.6 to 28.3%, respectively. (2) The tube surface modifications and baffles presence can significantly improve the heat transfer performance. The performance evaluation criterion between the airflow and finned tube in the channel with baffles is 2.5–4.0 times higher than those between the airflow and smooth tube in the baffle-free channel.

Confinement induced three-dimensional trajectories of microswimmers in rectangular channels

Confinement induced three-dimensional trajectories of microswimmers in rectangular channels

Experimental and numerical study of flow boiling in a vertical upward narrow rectangular channel under low heat flux

This article experimentally and numerically investigates the flow boiling in a vertical upward narrow rectangular channel under low heat flux. VOF model for interface tracking and the phase-change Lee model are coupled to build a numerical model of a channel with a scale of 1200 mm × 250 mm × 2.75 mm. The temperature, velocity and phase distribution in the channel are obtained at different heights The bubble movement is analyzed and the two-phase flow regimes are classified. Furthermore, the local characteristic of flow boiling heat transfer along the channel and the effect of the bubble regimes on the heat transfer are studied. The results indicate that saturated nucleate boiling is the dominant boiling form under low heat flux.

Heat Enhancement in a Short Air Channel with Solid and Permeable Baffles

Heat transfer enhancement to turbulent air flow in a short rectangular constant-wall temperature channel fitted with either solid or permeable baffles were numerically studied based on COMSOL® simulations. The number of used baffles (1 to 7), Reynolds number (10000, 20000, and 30000), and baffle permeability (1 × 10−11 to 1 × 10−6) were investigated. Operations under turbulent flow conditions were considered, which has not been extensively studied. The average temperature of air at the channel exit and the pressure drop along the channel were obtained via simulation for different cases. For solid baffles, the heat transfer enhancement parameter ranged from 0.30 to 0.35 due to the high friction, while for permeable baffles, it ranged from 1 to 35 as the permeability and number of baffles increased. This is due to the heat-transfer-area increase and pressure-drop reduction when the flow passes through the permeable baffles. For permeable baffles, a minimum heat exchanger temperature approach of 10 K was achieved with minimal pressure drop at a permeability of approximately 4 × 10−8 when using 4–6 permeable baffles. Accordingly, the results demonstrated that using four permeable baffles with a permeability of approximately 4 × 10−8 m 2 is optimal from thermal, economical, and mechanical viewpoints.

Effects of using a finned cylindrical cooler in the nano-enhanced cooling channel on the exergetic performance of a PV/TEG-coupled system

ABSTRACT In this study, three different nano-enhanced channel models were integrated into the 3D photovoltaic (PV)/thermoelectric generator (TEG) system and the effect of the channel models on the PV/TEG system performance was examined. The flat rectangular channel, Model 1 while the cylindrical and fin-reinforced cylindrical object accommodated in the flat rectangular channel are defined as Model 2 and Model 3, respectively. A comparison of water and ternary nanofluid with various nanoparticle (solid particle volume fraction between 0.01 and 0.03) loading was performed in each channel model. In addition, impacts of cooling fluids at different inlet temperatures (Tg between 25°C and 12.5°C) were considered in the simulations. Among different cooling channels, lowest PV cell temperature and the highest PV output power were obtained in Model 3. The highest PV power (0.51 W) was obtained with Model 3 with ternary nanofluid (%3 volume fraction) at Tg = 12.5°C. This value is is 3.66% and 4.03% higher than Model 2 and Model 1, respectively. Under the same conditions, TEG output power reached its highest value with Model 2 and it was followed by Model 1 and Model 3, respectively. With the reinforcement of fins to the cylindrical object, an improvement in thermal performance was achieved, but a decrease in total output power was observed.

Fog collection on wettability-mixed patterned surfaces inspired by multiple biological structures

Fog collection has become one of the effective means to solving water scarcity. Wettability-mixed patterned surfaces exhibit great potential in fog collection. In this article, the desert beetle, honeycomb structures and cactus spines served as an inspiration in the proposal of a bionic pattern of honeycomb and cactus spine coupling (BPHCSC) that can efficiently collect fog. First, a superhydrophobic (SHB) surface was successfully prepared on the surface of 5052 Al alloy through combined electrochemical etching with fluorosilane modification. Subsequently, laser etching technology was used in the precise etching of a superhydrophilic BPHCSC on the SHB surface. Compared with the fog collection efficiencies of a single SHB surface and the honeycomb-like wettability-mixed patterned surface composed of rectangular channels, that of the prepared BPHCSC surface increased by approximately 23.5% and 4.27%, respectively. In addition, a thorough exploration was conducted on the effects of factors, such as the distance between the sample surface and the fog outlet, tilt angle and the number of laser etchings, on fog collection efficiency. This study provides a new idea for fog collection and exhibits a broad application potential in fields, such as microfluidic systems, droplet manipulation and cell screening.

Reliable prediction of peak cladding temperature during top reflooding processes: A neural network-based perception-interaction approach

The reliable prediction of peek cladding temperature is crucial for heat transfer and reactor security when large break loss of coolant accident (LBLOCA) happens. This study proposes a neural network-based Perception-Interaction system to effectively predict and monitor the peak cladding temperature during reflooding phase after LOCA. The system employs a narrow rectangular channel for conducting top reflooding experiments, wherein the peak temperature is predicted by the Back Propagation Neural Network (BPNN) algorithm. The system’s primary objective is to accurately predict the peak cladding temperature of various test conditions. First, the special Counter-Current Flow Limitation (CCFL) phenomenon is identified based on the different heat exchange patterns inside the test section. Then the experimental data is collected by LabVIEW and calculated by MATLAB to accurately predict the quench velocity and peak temperature at a specific location by conducting various test conditions. The final experiment results indicate that the built Perception-Interaction system in this article has a high prediction accuracy, with a relative error within 2% between the predicted peak temperatures and actual temperatures.

Enhancement of cooling process of hot blocks mounted inside a horizontal channel using flexible baffles — Alternative arrangement

In this paper, two heated blocks and three flexible baffles that are alternately placed on the upper and bottom sides of a rectangular channel are used to replicate the transient heat and air movement. The novelty of this research is the use of flexible baffles to destruct the thermal boundary layer with maintaining little pressure drop, and thus reducing the required pumping capacity. The finite thickness blocks are subject to a constant heat flux, while the baffles are very thin and deforms depending on the strength of the flow of coolant (air). Finite element method with arbitrary Lagrangian–Eulerian approach is used for solving such deforming domain problem. The problem is inspected transiently by varying the dimensionless time (τ=0.0 to 10) and two salient parameters which are Reynolds number Re=10−500, and baffle elasticity parameter E=105−108. Results show that the flexibility feature of the baffles contributes not only in directing the coolant towards the hot blocks, but also contributes in reducing the skin friction and pressure drop through the channel. At Re=150, the skin friction and pressure drop of the flexible baffles are 13.2% and 16.5%, respectively lesser than the rigid baffles. The improvement of Nusselt number with flexibility parameter is marginal and within a limited low Reynolds number, where the maximal improvement is about 3.4% at Re=150.

Flow birefringence of cellulose nanocrystal suspensions in three-dimensional flow fields: revisiting the stress-optic law

This study systematically investigates the flow birefringence of cellulose nanocrystal (CNC) suspensions. The aim is to clarify the importance of the stress component along the camera’s optical axis in the stress-optic law (SOL), which describes the relationship between birefringence, the retardation of transmitted polarized light, and the stress field. More than 100 datasets pertaining to the retardation of CNC suspensions (concentrations of 0.1, 0.3, 0.5, and 1.0 wt%) in a laminar flow field within a rectangular channel (aspect ratios of 0.1, 1, and 3) are systematically obtained. The measured retardation data are compared with the predictions given by the conventional SOL excluding the stress component along the camera’s optical axis and by the SOL including these components as second-order terms (2nd-order SOL). The results show that the 2nd-order SOL gives a significantly better agreement with the measurements. Based on the 2nd-order SOL, the retardation at the center of the channel, where the effect of the stress component along the camera’s optical axis is most pronounced, is predicted to be proportional to the square of the flow rate, which agrees with the experimental data. The results confirm the importance of considering the stress component along the camera’s optical axis in the flow birefringence of CNC suspensions at high flow rates, even for quasi-two-dimensional channel flow.

Numerical analysis of fluid flow and heat transfer characteristics in single crystal diamond microchannels with ribs and secondary channels

To meet the heat dissipation requirements of high-frequency and high-power electronic devices, single crystal diamond microchannels (SCD-MC) with secondary channels and rib combinations are proposed. The fluid flow and heat transfer characteristics in SCD-MC with various secondary channels and rectangular rib combinations are investigated through numerical simulations. The comprehensive performance and energy saving effect of the microchannel were evaluated by analyzing the factor of merit and entropy generation performance. The results show that the SCD-MC with secondary channels and rib combinations enhance fluid disturbance and increase the solid–liquid contact area, significantly improving heat transfer. When Reynolds number (Re) is 586, compared with the straight microchannel, the average temperature at the bottom of the SCD-MC with rectangular secondary channels and rectangular rib (Case 5) is reduced by 4.8 K, the heat transfer coefficient is increased by 209.8 %, and the factor of merit is improved by 89.2 %. The entropy generation augmentation number of the Case 5 microchannel was the minimum of 0.52, which has the highest energy saving effect. The factor of merit of the Case 5 microchannel exhibits a tendency to first increase and then decrease with the increase of the relative width of the secondary channel (Ψ), the relative width of the rib (Φ), and the relative position of the rib (Π). At Re = 586, Ψ = 0.933, Φ = 0.667, and Π = 0.5, the factor of merit of the Case 5 microchannel is 2.08, indicating the highest comprehensive performance. This finding provides new ideas and methods for the design and application of microchannel thermal management.

Metal-Organic Framework: Fabrication of Nano Fluorescent Composite Materials and Treatment of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is a common malignant tumor originating from liver cells, characterized by complex pathogenesis and limited treatment options such as surgery, chemotherapy, and transplantation. Cisplatin, an effective chemotherapeutic agent, disrupts cancer cell DNA but is hindered by side effects and the need for controlled sustained release to optimize efficacy. Metal-organic frameworks (MOFs) have emerged as promising nanocarriers for precise local drug delivery, reducing required doses and mitigating side effects of chemotherapeutic drugs, thus offering a potential avenue for hepatocellular carcinoma (HCC) treatment. In this research, a rectangular channel MOF (Rumgay H, Ferlay J, Martel C, Georges D, Ibrahim AS, Zheng R, Wei W, Lemmens VEPP, Soerjomataram I (2022) Global, regional and national burden of primary liver cancer by subtype. Eur J Cancer 161:108-118) carrier was synthesized using ligand L as the organic linker coordinated with Cu(II) and I(I). The MOF's structure and fluorescence properties were characterized. Additionally, to enhance substrate biocompatibility, composite carrier materials were prepared by incorporating polylactic acid (PLA) with 1, utilized for cisplatin loading. To evaluate the inhibitory effect of PLA-1@cisplatin on HCC, HepG-2 and Huh-7 HCC cell lines were treated with varying concentrations of the drug for 48h, and their cell viability was assessed. The results demonstrated a significant dose-dependent reduction in cell viability of both HepG-2 and Huh-7 cells. To explore the potential inhibitory mechanism of PLA-1@cisplatin on HCC, the mRNA levels of GADD45A and NACC1 in HepG-2 and Huh-7 cells post-treatment were measured. GADD45A expression, initially low in HCC cells, was significantly upregulated after drug treatment, while NACC1, typically highly expressed in HCC, showed a significant decrease in mRNA levels with increasing concentrations of PLA-1@cisplatin. These findings indicate that PLA-1@cisplatin effectively upregulates GADD45A expression and downregulates NACC1 expression. Overall, the developed cisplatin-loaded nanoparticle system holds promise for HCC treatment by reducing chemotherapy side effects and enhancing drug efficacy.

Asymmetrical suction and injection in laminar channels with porous walls: a fixed point approach

The problem of laminar flow in a rectangular channel with a pair of porous walls is considered. The porous walls allow fluid to be injected into or sucked out of the channel at constant velocities normal to the walls; the velocities at each wall are not necessarily of equal magnitude nor symmetrical in direction. In this article, a unique solution to this problem is shown to exist for sufficiently low Reynolds numbers through the application of Banach's fixed point theorem. This serves to further the discussion about the uniqueness of solutions for this problem, whilst also demonstrating the suitability of a fixed point approach to this family of fluid dynamics problems.

Numerical investigation of flow boiling characteristics in narrow rectangular channels using two-fluid Eulerian CFD model covering a wide range of pressures

Narrow channel heat exchange technology is one of the key technologies for the development of integrated small modular reactors (SMR). The ‘wall heat flux partitioning’ (WHFP) model in conjunction with an Eulerian–Eulerian Multiphase Flow (EEMF) method is found to be an important tool for two-phase hydrothermal analysis. In this paper, the accuracy of the EEMF-WHFP method with various sub-models is systemically evaluated over a large database of boiling flows in narrow rectangular channels. Prediction results using a total of 9 model combinations, are compared with data from 22 experimental conditions covering a range of the mass flux of 134.2 to 2200 kgm-2s-1, the inlet fluid subcooling of 7.2 to 74.2 K, the pressure of 0.1 to 14 MPa and the heat flux of 9.54 to 1700 kWm-2 in narrow rectangular channels with gaps of 1.0 to 3.0 mm. The evolution of distributions of void fraction, wall temperature and the net vapor generation (NVG) point along the flow channel is simulated and compared with experimental data. It is found that due to the limitation of the range of applicability of sub-models, certain models produced better prediction results under different pressure ranges than others, and the recommended combinations are given according to the quantitative assessments. In addition, the ability of the model combinations to predict the NVG point, as well as the flow structure and boiling process in narrow channels is investigated. The critical local void fraction near the wall at the NVG point is quantitatively estimated based on numerical results. The research conclusions in this paper can be used in thermal–hydraulic calculations in a wide range of operating pressures covering the applications of compact heat exchangers, flat plate fuels, climbing/falling film plate evaporators and the cooling of microelectronics, among other applications.

Pioneering hybrid heat recovery systems: Thermoelectric generators as insulators and channels boosted by vortex generators

Vortex generators are very effective tools in increasing heat transfer from one region to another, especially by convection, and appear to be a very promising concept to be coupled with heat recovery systems. On the other hand, Thermoelectric Generators (TEGs) are devices able to convert differences in temperature into electrical power using the Seebeck effect, the main advantage being working on high or even low differences in temperature. These TEG modules could be very effective tools in the hybridization of heat recovery systems. In this context, the present paper suggests an innovative system that couples three important energy axes together such as Heat recovery, TEGs, and Vortex generators. The current study employs a TEG in a rectangular channel to analyze the influence of the TEG on the flow and the effect of the effect of flow regime on producing electric power in order to assess the viability of this recently proposed concept. The investigation is conducted by varying the Reynolds number in a range of five values: 1000, 2000, 4000, 7000, and 10,000, applying six different configurations. Consequently, the results show that several factors affect the electrical power generated by TEG such as the emplacement, angle of attack, and absence/presence of vortex generators. On the other side, the heat recovered by the flow is affected by the TEG and Re, where the highest heat recovery is achieved at Re = 10,000 for configuration 4 with electrical power of 7.4 W, and for configuration 5 heat recovered by the flow of 1913 W. Besides, it was concluded that TEGs decreased the losses in both hot and cold sides by 1.42 times.

Anchor chains—A simple low‐cost device to assist passage of small‐bodied mass fish

AbstractAttention has been placed on a variety of barriers that hinder fish passage in modern times. The most prevalent fish barriers were culverts which have negatively impacted waterway connectivity and fish habitats. For small‐bodied mass fish, high barrel velocities and turbulence have reduced fish swimming performance because of their weak swimming capabilities. In the present study, physical testing was conducted under controlled flow conditions to assess the extent and magnitude of turbulence characteristics, secondary flow and low‐velocity zones in a 0.5‐m‐wide box culvert barrel. Two cases were investigated; a reference case consisting of a smooth rectangular channel and a low‐cost design solution to improve upstream fish migration consisting of a single galvanized anchor chain fitted within a smooth rectangular channel. The single anchor chain was positioned towards one corner of the channel to induce asymmetric flow, reducing overall energy losses and enhancing the existing low‐velocity zone in the adjacent channel corner. The anchor chain induced a strong turbulent flow motion away from the anchor chain, characterized by higher Reynolds stress and turbulent kinetic energy, along with a distinct channel flow asymmetry. Conversely, the low‐velocity zone, between the anchor chain and the bottom channel corner, was significantly expanded with reduced longitudinal mean velocities and turbulent scales. Whilst the anchor chain link contributed to some complex localized wake flow, the anchor chain also influenced the distributions of normal turbulent stresses (v'z2 – v'y2), which in turn influenced the location of secondary flow cells. This secondary flow redirected low momentum fluid into the low‐velocity zones, setting the conditions for the favorable upstream passage of small‐bodied mass fish species.

Effect of twisted tapes and surface extensions in enhancing the condensation heat transfer of high-temperature saturated steam in a circumferential rectangular channel

This article numerically investigates the impact of twisted tapes and extended surfaces (fins) on enhancing high-temperature steam flow in a circumferential rectangular channel, akin to the external jacket cavity of a tyre cure press. The passive enhancement techniques for improving the mold warm-up time of the tyre curing process have received limited attention in previous studies, which have primarily focused on enhancing heat transfer in configurations and working conditions typical of heat exchanger applications. The objective of this article is to enhance the condensation heat and mass transfer rate by geometrically modifying the internal flow path of the circumferential rectangular channel, resembling an external jacket cavity of a tyre cure press, using twisted tapes and extended surfaces. Four configurations are simulated: i) conventional circumferential rectangular channel, ii) channel with twisted tapes, iii) channel with surface extension, and iv) channel with both twisted tapes and surface extension. The heat transfer performance of all the modified channel configurations derived from the simulation results is assessed in comparison to the conventional channel. The channel, featuring a design that includes five twisted tapes with a twist ratio of 8 and 54 extended surfaces, records a substantial 36.85% rise in heat flux along with a notable 24% increment in the condensation mass flux. The simulation results are validated using an in-house experimental study. The tyre cure press in the experimental setup is modified to align with the design proposed by the simulation results, and a warm-up study is conducted. The warm-up time for the modified mold to attain the desired temperature is reduced by 33%, with no accompanying increase in steam consumption, compared to the warm-up time for the conventional mold. This significant reduction in mold warm-up time holds immense potential in enhancing the productivity rate, an ongoing requirement of the automobile industry.