Microchannel Walls Research Articles

Thermal and hydraulic performance of Al alloy-based 3D printed triangular microchannel heatsink governed by rough walls with graphene and alumina nanofluids as working liquid

Microchannel heat sinks (MCHS) are known for providing enhanced cooling performance but their fabrication requires complex and multi-step processes. The recent development of additive manufacturing has enabled the fabrication of state-of-art monolithic structures that had been impossible to build using conventional methods. In this work, a monolithic cross-flow triangular cross-section MCHS was fabricated from aluminum alloy (AlSi10Mg) using the Direct Metal Laser Sintering (DMLS) process. The microchannel wall surface roughness was measured and the cross-section shrinkage of the microchannels was compared with the initial design hydraulic diameter of 500 µm–1000 µm. The MCHS with an initial design hydraulic diameter of 750 µm possessed a relative wall surface roughness, R a of 7.7%. The triangular cross-section hydraulic diameter underwent a shrinkage of 15.2% and 5.3% in terms of the reduction in angle between adjacent side alloys. Experiments were conducted for Reynolds numbers between 50 and 275 with nanofluids containing graphene and Al2O3 nanoparticles in water/water +10% ethylene glycol; these were compared with their respective base fluids. The Poiseuille number indicated that flow was laminar developed with base fluid and laminar developing with nanofluid as coolant. Despite providing the lowest thermal resistance, the graphene nanoparticles in water created the greatest pressure drop leading to a reduced performance coefficient. Al2O3 nanoparticles in water/water +10% ethylene glycol were found to have 7.7% and 20% better performance coefficients than their respective base fluids.

Influence of Curvature on Cell Motility and Morphology during Cancer Migration in Confined Microchannels.

Microchannels often serve as highways for cancer migration, and their topology largely determines the migration efficiency. Curvature, a topological parameter in biological systems, has recently been reported to be efficient in guiding cell polarization and migration. Curvature varies widely along curved microchannels, while its influence on cell migration remains elusive. Here, we recapitulated the curved microchannels, as observed in clinical tumor tissues with hydrogels, and studied how cancer cells respond to curvature. We found that cells bend more significantly in a larger curvature and exhibit less spreading as well as lower motility. The underlying mechanism is probably based on the hindrance of the movement of cytoskeletal molecules at the curved microchannel walls. Collectively, our results demonstrated that the accelerated actin retrograde flow rate under local curvature has an effective negative regulation on cell motility and morphology, leading to shortened and bent cell morphologies as well as hampered cell migration efficiency.

Thermo-capillarity of immiscible binary fluids within serpentine micro-confinements

The thermocapillary flow of multiple liquid layers over contoured substrates finds applications in many industrial phenomena via micro-electromechanical systems/nano-electromechanical systems devices. This study theoretically explores the thermocapillary transport of binary-liquid layers in a wavy microchannel with serpentine wall profiles. Sinusoidal profiles are considered for the microchannel walls' temperature and surface topology. Patterned slip conditions at the walls are also accounted for in the analysis to make the problem more realistic. We semi-analytically solve the energy and momentum equations to understand the system's thermal and hydrodynamic characteristics for the limiting conditions of Ma, Re, and Ca. The leading- and higher-order solutions of the temperature and flow field are separately shown to demonstrate the advection terms' contribution to the transport equations. The circulatory flow obtained due to periodic thermal stimuli can be used to enhance the mixing efficiency of the system. We also present how the parameters like phase difference between the thermal stimulus, relative thermal conductivity, and relative film thickness ratio of the liquid layers can be altered to control the flow characteristics to obtain the most potent thermocapillary effect.

Inertial migration of polymer micelles in a square microchannel.

Using a hybrid simulation approach that combines a lattice-Boltzmann method for fluid flow and a molecular dynamics model for polymers, we investigate the inertial migration of star-like and crew-cut polymer micelles in a square microchannel. It is found that they exhibit two types of equilibrium positions, which shift further away from the center of the microchannel when the Reynolds number (Re) increases, as can be observed for soft particles. What differs from the behaviors of soft particles is that here, the blockage ratio is no longer the decisive factor. When the sizes are the same, the star-like micelles are always relatively closer to the microchannel wall as they gradually transition from spherical to disc-like with the increase of Re. In comparison, the crew-cut micelles are only transformed into an ellipsoid. Conversely, when the hydrophobic core sizes are the same, the equilibrium position of the star-like micelles becomes closer to that of the crew-cut micelles. Our results demonstrate that for polymer micelles with a core-shell structure, the equilibrium position is no longer solely determined by their overall dimensions but depends on the core and shell's specific dimensions, especially the hydrophobic core size. This finding opens up a new approach for achieving the separation of micelles in inertial migration.

On-chip light sheet illumination for nanoparticle tracking in microfluidic channels.

A simple and inexpensive method is presented to efficiently integrate light sheet illumination in a microfluidic chip for dark-field microscopic tracking and sizing of nanoparticles. The basic idea is to insert an optical fiber inside a polydimethylsiloxane (PDMS) elastomer microfluidic chip and use it as a cylindrical lens. The optical fiber is in this case no longer seen as only an optical waveguide but as a ready-made micro-optical component that is inexpensive and easy to source. Upon insertion, the optical fiber stretches the PDMS microchannel walls, which has two effects. The first effect is to tone down the intrinsic ripples in the PDMS that would otherwise create inhomogeneities in the light sheet illumination. The second effect is to remove any obliqueness of the channel wall and constrain it to be strictly perpendicular to the propagation of the illumination, avoiding the formation of a prismatic diopter. Through calculations, numerical simulations and measurements, we show that the optimal configuration consists in creating a slowly converging light sheet so that its axial thickness is almost uniform along the tracked area. The corresponding thickness was estimated at 12 μm, or 10 times the depth of field of the optical system. This leads to an at least six-fold increase in the signal-to-noise ratio compared to the case without the cylindrical lens. This original light-sheet configuration is used to track and size spherical gold nanoparticles with diameters of 80 nm and 50 nm.

A multiscale analytical-numerical method for the coupled heat and mass transfer in the extended meniscus region considering thin-film evaporation in microchannels

A Computational Fluid Dynamics (CFD) framework is established to investigate the microscale transport phenomena in the evaporating extended meniscus region formed in rectangular microchannels. A wide range of microchannel widths (W = 1 to 250 µm) and wall superheats (ΔT = 0.01 to 5.0 K) are considered. Prior to performing CFD simulations, it is first necessary to employ thin-film evaporation modeling based on an augmented Young–Laplace model and kinetic-theory based model for the evaporating mass flux across curved surfaces to find the exact shape of the liquid-vapor interface along with disjoining and capillary pressure distributions. Two widely-used methods for the determination of boundary conditions (BCs) at the beginning of the thin-film region (i.e., setting δ0″ = 0 and finding δ0′ by the far-field BC or setting δ0′ = 0 and finding δ0″ by the far-field BC), where δ is film thickness, are thoroughly examined and the first approach is recommended because of its better convergence and ease of implementation in the thin-film evaporation model. Then, the two-dimensional domain of the extended meniscus is generated and discretized to simulate the evaporating liquid flow through the UDF programming in ANSYS Fluent. The developed framework is shown to be a simple yet powerful and practical method for accurately predicting the evaporation mass and heat fluxes from extended menisci in microchannels. The CFD simulation results indicate that the previous one-dimensional models which represent the state of the art in the literature in the field are not able to predict the rate of evaporative heat transfer from the extended meniscus in microchannels with an acceptable degree of accuracy. Based on the CFD simulations results, a multiple regression analysis is employed to establish several simple thermal resistance correlations. The correlations can be straightforwardly integrated into macroscale mathematical models of micro and miniature heat pipes for analyzing their thermal characteristics.

Stopping Microfluidic Flow.

A cross-comparison of three stop-flow configurations-such as low-pressure (LSF), high-pressure open-circuit (OC-HSF), and high-pressure short-circuit (SC-HSF) stop-flow-is presented to rapidly bring a high velocity flow O(m s-1) within a microchannel to a standstill O(µm s-1). The performance of three stop-flow configurations is assessed by measuring residual flow velocities within microchannels having three orders of magnitude different flow resistances. The LSF configuration outperforms the OC-HSF and SC-HSF configurations within a high flow resistance microchannel and results in a residual velocity of <10µms-1. The OC-HSF configuration results in a residual velocity of <150µms-1 within a low flow resistance microchannel. The SC-HSF configuration results in a residual velocity of <200µms-1 across the three orders-of-magnitude different flow resistance microchannels, and <100µms-1 for the low flow resistance channel. It is hypothesized that residual velocity results from compliance in fluidic circuits, which is further investigated by varying the elasticity of microchannel walls and connecting tubing. A numerical model is developed to estimate the expanded volumes of the compliant microchannel and connecting tubings under a pressure gradient and to calculate the distance traveled by the sample fluid. A comparison of the numerically and experimentally obtained traveling distances confirms the hypothesis that the residual velocities are an outcome of the compliance in the fluidic circuit.

Scrutiny of MHD impact on Carreau Yasuda (CY) fluid flow over a heated wall of the uniform micro-channel

The Carreau-Yasuda model is a useful rheological tool for describing complex fluid flow behavior, especially those involving non-Newtonian fluids. This is significant because it allows for a more accurate depiction of fluids with non-linear connections between shear stress and shear rate. This research aimed to examine the effects of slip on the peristaltic transport of a magnetized Carreau–Yasuda (CY) fluid in a uniform channel where the fluid characteristics change at a heated wall. Non-dimensionalization of the governing equations was achieved by assuming a large wavelength and a low Reynolds number and then solving the resulting coupled equations with appropriate boundary conditions and mathematical "ND Solve" methods. This research looked into the two extremes of shear rate-dependent fluid behavior: shear-thinning (a decrease in viscosity with increasing shear rate) and shear-thickening (an increase in viscosity with increasing shear rate). The model can also predict Newtonian and Carreau fluid behaviors. Critical parameters such as velocity, temperature, concentration, skin friction coefficient, Nusselt number, and Sherwood number were displayed visually and tabulated in the study's results. In addition, the study used the stream function method to investigate the peristaltic motion of the bolus, uncovering that magnetic effects can decrease bolus size due to their substantial influence on apparent viscosity, with shear-thinning behavior proving more influential than shear-thickening behavior. The study further clarifies the dynamic fluctuations in fluid viscosity in response to increasing shear stress, which sheds light on the viscoelastic nature of shear-dependent behavior in a uniform microchannel using the Carreau–Yasuda fluid.

Gravity-driven flow control in a fully integrated microfluidic cartridge for molecular point-of-care testing.

Molecular point-of-care testing (POCT) system is crucial for the timely prevention and control of infectious diseases. We recently proposed a gravity-driven microfluidic cartridge for molecular POCT detection, without the need for external sources or actuators, demonstrating the advantages in terms of the reduced cartridge size and low development costs. How to achieve precise control of liquid flow behavior is challenging for the gravity-driven cartridge. In this work, we explored the underlying mechanism of flow control in the cartridge and offered optimized solutions for our cartridge design to achieve precise control of dynamic flow rates and enhance pumping efficiency significantly. Through the computational fluid dynamics simulations, we demonstrated that adopting an asymptotic contraction chamber geometry design and a closed-loop air flow channel design with the cartridge inlet can facilitate stable laminar flow of the liquid in our microfluidic cartridge, enabling precise control of flow velocity. We further optimized the microchannel diameter and the contact angle of the liquid with the microchannel wall. The effectiveness of the optimized cartridge for POCT detection was well validated by the accurate detection of the human papillomavirus type 16 virus in the 120 clinical swab samples.

Enhancing heat transfer in microchannels: A systematic evaluation of crescent-like fin and wall geometries with secondary flow

Recent developments in additive manufacturing processes, coupled with the demands of modern microelectronics, have spurred research in heat sinks at the micro-scale. The present study introduces microchannel designs resembling crescent-like walls and fins inside a coolant-based heat sink to enhance its thermal performance. Three different microchannel designs, namely the crescent-like fin design (CF design), the crescent-like wall design (CW design), and the crescent-like wall design with secondary flow (CWSF design) have been proposed and evaluated for their ability to transfer heat while maintaining a low pressure drop penalty. Furthermore, these geometries were tested with different inlet–outlet configurations. The paper investigates flow profile, pressure drop, and temperature profiles for a wide range of flow rates and explores certain hydrodynamic phenomena, such as the Coanda effect and vortex formation generated by the network of convex and concave surfaces that induce flow disruption, thus increasing the potential for enhanced thermal performance. Velocity and temperature maldistribution analyses have also been included to compare the stress distribution around the microchannel walls, highlighting the relative potential for structural failure. The findings suggest that incorporating secondary flow passages inside the crescent-like walls would result in a 28–51% reduction in pressure drop, indicating the potential to meet the thermal management needs of modern microchips. The main objective of the paper is to study how varying the attributes of crescent-like geometries affects the flow profile and thermal performance of a heat sink. The study aligns with the requirements of modern microchips, such as the 13th Gen Intel® Core™ processor, and serves as a guideline for the manufacturing of microchannel heat sinks with crescent-like morphologies.

Electrokinetic Effect of a Two-Liquid Interface within a Slit Microchannel.

This paper presents an investigation of the electrokinetic effect at a two-liquid (immiscible liquid-aqueous solution) interface within a slit microchannel using a three-dimensional (3D) numerical model, with a particular focus on the impact of the surface ζ-potential and liquid phase height on the interface electrokinetic velocity. The findings indicate that the direction of the interface movement depends on the ζ-potentials at the two-liquid interface and the microchannel wall. When the absolute value of the negative ζ-potential at the interface is smaller than that at the wall, the interface moves toward the negative pole of the applied direct current (DC) electric field; conversely, it moves in the opposite direction. The velocity of interface motion decreases as the height of the aqueous phase and the dynamic viscosity ratio between the immiscible liquid and the aqueous solution increase. Conversely, the velocity increases with an elevation in the height of the immiscible liquid phase and the DC electric field intensity. This study holds significant importance in elucidating the patterns of change in fluid interface electrokinetic effects and their potential applications in manipulating and separating particulate pollutants within water systems.

Thermal performance of microchannel heat sink integrated with porous medium, slip coefficient and phase change material and machine learning approach

In this study, the thermal performance (TP) of the microchannel heat sink (MCHS) under the influence of the slip coefficient on the microchannel wall, the use of porous medium (PM) and phase change material (PCM), and the changes in the geometrical parameters and the shape of the microchannel have been discussed. The flow and energy equations were solved using the finite volume method. The validation of the melting process, slip coefficient, and porous medium with the previous literature demonstrate the high accuracy of the numerical solution, with the difference between the results being <8 %. The results indicate that using a wavy microchannel can improve TP by approximately10.6 % and 5 % compared to smooth and converging microchannels. Additionally, using non-Newtonian fluids with a power characteristic of 0.53 leads to improved TP about 2.8 % by reducing shear stress compared to Newtonian fluids. Furthermore, the presence of slip on the microchannel wall influences the flow pattern, resulting in reduced convection resistance and improved TP about 3.2–3.8 %. The highest TP was observed at a slip coefficient of 0.00001. Incorporating PM in the microchannel (either in the center or around it) can enhance TP by approximately 8–15 % compared to the base state, with greater improvements observed when PM is placed around the microchannel. The type of PM material and the porosity coefficient significantly impact TP. Varying the cross-sectional shape of the microchannel (square, rhombus, and triangle) has a substantial effect on improving TP compared to a circular cross-section, with the highest TP (with a 71 % increase) observed in microchannels with a square cross-section. Lastly, the use of PCM and PM on the active surface leads to a significant TP improvement of over 80 % compared to the base state. Using the Group Method of Data Handling algorithm, thermal resistance was estimated with an R-square value of 0.94 to validate the available data.

Mixed Convection of Cu–H2O Nanofluid in a Darcy–Forchheimer Porous Medium Microchannel with Thermal Radiation and Convective Heating

Heat transfer and convective flow of Cu–H2O nanofluid in a microchannel with thermal radiation has many attributes in engineering, industries, and biomedical sciences including cooling of electronics, drug delivery, cancer therapy, optics, missiles, satellites, and lubricants. Therefore, this paper aims to investigate the hydrodynamical behaviors and heat transfer characteristics of Cu–H2O nanofluid through a porous medium microchannel with thermal radiation and convective heating. The highly non-linear partial differential equations that govern the momentum and energy equations are formulated, non-dimensionalized, transformed into ordinary differential equations and solved numerically via the fourth order Runge-Kutta integration scheme. Consequently, the numerical simulation reveals that the nanofluid velocity and temperature profiles show a rising pattern with increasing values of the pressure gradient parameter, variable viscosity parameter, Darcy number, thermal Grashof number and Eckert number. The temperature profile escalates with the Prandtl number however it diminishes with the Biot number, Forchheimer number, suction/injection Reynolds number and nanoparticles volume fraction. Furthermore, the thermal radiation parameter indicates a retarding effect on the temperature profile and hence, radiation quite effectively controls the microchannel temperature distribution which plays a significant role in cooling the flow transport system. The skin friction coefficient at both microchannel walls indicates a rising pattern with the suction/injection Reynolds number, thermal Grashof number, Eckert number and Darcy number. Moreover, at both microchannel walls the heat transfer rate enhances for large values of the suction/injection Reynolds number, thermal Grashof number, Eckert number, variable viscosity parameter and Darcy number whereas it decreases with the thermal radiation parameter, Forchheimer number and nanoparticles volume fraction. The Biot number reveals an opposite effect on the heat transfer rate at the left and right walls of the microvhannel.

Cattaneo-Christov heat-mass flux model on mixed convection of Casson nanofluid in a porous medium microchannel with thermal radiation and chemical reaction

This article presents mixed convection of radiating and reacting Casson nanofluid in microchannel filed with a saturated porous medium with Cattaneo-Christov heat-mass flux model. The Buongiorno’s nanofluid flow model is used to study the effects of the Brownian motion and the thermophoresis whereas the Darcy-Forchheimer model is considered to examine the nanofluid and porous medium interaction. Thereafter, the highly nonlinear system of equations for momentum, energy and concentration are formulated and solved numerically by utilizing the Runge-Kutta-Fehlberg integration scheme with shooting technique. Consequently, the numerical simulation indicates that the Casson fluid parameter and the variable viscosity parameter play a great role in escalating the velocity field and temperature profile however chemical reaction, porous medium, radiation, thermal relaxation time and convective heating control over the temperature profile. Besides, an increase in the thermal relaxation time causes more transfer of heat from the hot microchannel wall to the fluid and thus, fluid temperature distribution is higher for Hence, the Cattaneo-Christov heat flux model is constructive in cooling process as compared to that of the classical Fourier’s law of heat conduction. Furthermore, heat and mass transfer rates are enhancing because of the thermal radiation and solutal Grashof number at both sides of the microchannel walls. Also, the current findings are compared with that of the existing literature and a sound agreement was established.

Tuning Molecular Orientation Responses of Microfluidic Liquid Crystal Dispersions to Colloid and Polymer Flows.

An important approach to molecular diagnostics is integrating organized substances that provide complex molecular level responses to introduced chemical and biological agents with conditions that optimize and distinguish such responses. In this respect, liquid crystal dispersions are attractive components of molecular diagnostic tools. This paper analyzes a colloid system, containing a nematic liquid crystal as a dispersed phase, and aqueous surfactant and polymer solutions as the continuous phases. We applied a microfluidic approach for tuning orientation of liquid crystal molecules in picoliter droplets immobilized on microchannel walls. Introduction of surfactant to the aqueous phase was found to proportionally increase the order parameter of liquid crystal molecules in microdroplets. Infusion of polymer solutions into surfactant-mediated microfluidic liquid crystal dispersions increased the order parameter at much lower surfactant concentrations, while further infusion of surfactant solutions randomized the orientation of liquid crystal molecules. These effects were correlated with the adsorption of surfactant molecules on surfaces of microdroplets, stabilizing the effect of a polymer matrix on bound surfactant ions and the formation of insoluble polymer-colloid aggregates, respectively. The revealed molecular behavior of liquid crystal dispersions may contribute to optimized synthesis of responsive liquid crystal dispersions for in-flow molecular diagnostics of polymers and colloids, and the development of functional laboratory-on-chip prototypes.

Pseudopotential Lattice Boltzmann Model for Immiscible Multicomponent Flows in Microchannels

To investigate droplet formation in a microchannel with different walls, simulations were conducted based on a pseudopotential model using the exact difference method force scheme. The variable surface tension was obtained using Laplace’s law, and the static contact angle was estimated using a first-order linear equation of the corresponding control parameter of the model. The droplet motion in microchannels was simulated using our model, and the effects of surface wettability and the Bond number on the droplet motion were investigated. The droplet motion for the intermediate microchannel wall took a significantly shorter time than that for the hydrophilic wall, and the wet length also depended on the contact angle. As the Bond number increased, the wet length of the droplet decreased on the hydrophilic surface. The droplet formation in a T-junction device was also simulated using the proposed model, and the effects of the capillary number and viscosity ratio on droplet formation were discussed in detail, and some empirical correlations between the capillary number and dimensionless droplet length are presented according to different viscosity ratios. The three flow patterns of droplet formation were categorized by the different capillary numbers as the dripping–squeezing, jetting–shearing, and threading regimes. In the dripping–squeezing regime, the droplet volume was nearly independent of the viscosity ratio, but the viscous effect was more prone to occur in the jetting–shearing regime. In the jetting–shearing regime, as the capillary number increased, the effect of the viscosity ratio on droplet formation became more significant.

On‐Demand Inkjet Printed Hydrophilic Coatings for Flow Control in 3D‐Printed Microfluidic Devices Embedded with Organic Electrochemical Transistors

AbstractMicrofluidic surface chemistry can enable control of capillary‐driven flow without the need for bulky external instrumentation. A novel pondered nonhomogeneous coating defines regions with different wetting properties on the microchannel walls. It changes the curvature of the liquid–air meniscus at various channel cross‐sections and consequently leads to different capillary pressures, which is favorable in the strive toward automatic flow control. This is accomplished by the deposition of hydrophilic coatings on the surface of multilevel 3D‐printed (3DP) microfluidic devices via inkjet printing, thereby retaining the surface hydrophilicity for at least 6 months of storage. To the best of our knowledge, this is the first demonstration of capillary flow control in 3DP microfluidics enabled by inkjet printing. The method is used to create “stop” and “delay” valves to enable preprogrammed capillary flow for sequential release of fluids. To demonstrate further utilization in point‐of‐care sensing applications, screen printed organic electrochemical transistors are integrated within the microfluidic chips to sense, sequentially and independently from external actions, chloride anions in the (1–100) × 10−3 m range. The results present a cost‐effective fabrication method of compact, yet comprehensive, all‐printed sensing platforms that allow fast ion detection (&lt;60 s), including the capability of automatic delivery of multiple test solutions.

Impact of hybrid surfaces on the droplet breakup dynamics in microgravity slug flow: A dynamic contact angle analysis

Microfluidic devices, which enable precise control and manipulation of fluids at the microscale, have revolutionized various fields, including chemical synthesis and space technology. A comprehensive understanding of fluid behavior under diverse conditions, particularly in microgravity, is essential for optimizing the design and performance of these devices. This paper aims to investigate the effects of discontinuous wettability on droplet breakup structures under microgravity conditions using a microchannel wall. The approach we adopt is underpinned by the volume-of-fluid methodology, an efficient technique renowned for its accurate resolution of the fluid interface in a two-phase flow. Furthermore, a modified dynamic contact angle model is employed to precisely predict the shape of the droplet interface at and near the wall. Our comprehensive model considers influential parameters such as slug length and droplet generation frequency, thereby providing crucial insights into their impact on the two-phase interface velocity. Validated against existing literature data, our model explores the impact of various configurations of discontinuous wettability on breakup morphology. Our findings highlight the significance of employing a dynamic contact angle methodology for making accurate predictions of droplet shape, which is influenced by the wall contact angle. Emphasis is placed particularly on the effects of slug length and droplet generation frequency. Notably, we demonstrate that the use of a hybrid surface at the junction section allows for precise control over the shape and size of the daughter droplets, contrasting with the symmetrical division observed on uniformly hydrophilic or superhydrophobic surfaces. This study contributes valuable insights into the complex dynamics of the droplet breakup process, which has profound implications for the design and optimization of microfluidic devices operating under microgravity conditions. Such insights are further poised to augment applications in space exploration, microreactors, and more.

Analysis of factors affecting the performance of a novel micro-channel heat pipe PV-Trombe wall system for space heating

Building energy consumption accounts for about 1/3 of the world's total energy consumption. Photovoltaic Trombe wall (PV-TW) is an effective way to reduce a building's energy consumption, but it still has disadvantages such as low energy efficiency and uneven indoor temperature distribution. To address these issues, a novel system with a PV-TW and a micro-channel heat pipe (MCHP) was initially presented in this research. By cooling the PV cell with both air and refrigerant, the system can reduce its surface temperature and improve its electrical performance. To promote thermal performance and user comfort, an air-cooled condenser is also employed to regulate the room's heat transfer. This paper establishes the system's dynamic mathematical model for winter and theoretically evaluates its performance. Besides, the key factors influencing the system’s performance were examined. In winter, the total power generation and average daily electrical efficiency are 3.12 MJ and 13.52%, respectively, with a maximum indoor temperature of 21.46 °C and a daily average thermal efficiency of 56.76%. The system’s performance is all improved with the incremental change of the factors besides the size of the micro-channel flat tube (MAFT), and the performance is not sensitive to the change of the air channel width. The optimal number and width of the MAFT in the evaporator section are 11 and 45 mm. The indoor air-cooled condenser should have about 10 rows of tubes and an ideal air volume of 540 m3/h. The recommended airflow channel thickness is between 5 cm and 10 cm.

INVESTIGATION OF ARRHENIUS-CONTROLLED CHEMICAL REACTION THROUGH A SUPERHYDROPHOBIC MICROCHANNEL

The consequence of fully developed free convection with Arrhenius-controlled heat flow for a viscous and an electrically-conducting fluid flowing along an isothermally heated vertical parallel plate in a slit micro-channel is presented in this article. One wall had super-hydrophobic slip (SHS) and a temperature spike, while the other did not. A semi-analytical technique (perturbation series) was utilized to analyze the primary equations. The analytical solutions were thoroughly presented, and the functions of the pertinent parameters were illustrated with the help of various plots. It is revealed from this work that the action of chemically reacting factors is noticed to substantially strengthen the fluid movement in the micro-channel for a constant pressure gradient. In the fields of engineering and medicine, it is essential to understand these fluids' characteristics. Due to the lubrication of micro-channel boundary walls where conductivity and viscosity interact with thermos-physical behavior, the outcomes of the current research can substantially enhance the operations of micro-electro-mechanical systems (MEMS) and micro-devices that rely on micro-fabrication processes.