Rectangular Micro Research Articles

Influence of Rectangular Micro Inserts and Micro Chambers Heat Transfer Characteristics of Microchannel Heat Exchanger

This decade's smaller gadgets have made heat removal in electronics and microprocessors increasingly crucial necessitating the use of micro channel heat exchangers (MCHEs). The current study investigates the MCHE performance improvement through micro chambers and rectangular inserts with varying orientations (angle of insert: 0˚, 45˚, and 90˚). Experimental and numerical studies are conducted in a laminar environment, with Reynolds number varying from 74 to 446. Simulation of fluid flow and heat transfer is accomplished through Finite Volume Method. Thermal performance indicators, fluid flow parameters, pressure drop, friction factor, are used to evaluate and quantify the efficiency of MCHEs. It is shown that inserting two rectangles at 90° angle can achieve the ideal heat transfer coefficient. As a result, compared to the MCHE-MCDCI with various orientations of 0°, 45°, and 90°, respectively, the increase in Nu is 12.21%, 23.42%, and 37.10%, respectively. The rectangular insert at an angle of 90 in an MCHE caused the highest pressure loss. In contrast with MCHE-MCDCI. The pressure drop at 0˚, 45˚, and 90˚ increases by 13.26%, 37.94%, and 52.70%, respectively. When compared with double cylindrical inserts, MCHEs with rectangular inserts that are orientated at an angle of 90 degrees produced the greatest PEC.

Optimizing inset-fed rectangular micro strip patch antenna by improved particle swarm optimization and simulated annealing

ABSTRACT The recent wireless communication systems require high gain, lightweight, low profile, and simple antenna structures to ensure high efficiency and reliability. The existing microstrip patch antenna (MPA) design approaches attain low gain and high return loss. To solve this issue, the geometric dimensions of the antenna should be optimized. The improved Particle Swarm Optimization (PSO) algorithm which is the combination of PSO and simulated annealing (SA) approach (PSO-SA) is employed in this paper to optimize the width and length of the inset-fed rectangular microstrip patch antennas for Ku-band and C-band applications. The inputs to the proposed algorithm such as substrate height, dielectric constant, and resonant frequency and outputs are optimized for width and height. The return loss and gain of the antenna are considered for the fitness function. To calculate the fitness value, the Feedforward Neural Network (FNN) is employed in the PSO-SA approach. The design and optimization of the proposed MPA are implemented in MATLAB software. The performance of the optimally designed antenna with the proposed approach is evaluated in terms of the radiation pattern, return loss, Voltage Standing Wave Ratio (VSWR), gain, computation time, directivity, and convergence speed.

Numerical study of the optimization of the thermal and flow characteristics of a collector design of microchannels with two inlets and outlets, containing a nanofluid and a water-based fluid

The effect of aluminum microchannel geometry on the flow properties of water and Al2O3–H2O nanofluid was studied numerically using CFD. For this purpose, we studied three cases of three different shapes of microchannels, the first case is rectangular micro channels, and in the second case, we added obstacles to the bottom and top walls of the microchannels. In the last case, we gradually decreased the hydraulic diameter of the channels at a distance of 2L/3 from the outlet of the microchannel. The channels have two inlets and one outlet. There is also a continuous flow heat source at the bottom of the channels. In this study, the Reynolds number varied from 300 to 600 for the two inlets. We also used water and a nanofluid with a low volume concentration of nanoparticles (2%). We considered that the fluid temperature at the inlet of the microchannels changes from 293 K to 300 K. We relied on the finite volume method with the SIMPLE algorithm in the calculation method. According to the results obtained from this study, the effect of changing the value of the Rayleigh number at the two entrances of the channel was observed on the temperature and velocity of the fluid and on the heat exchange inside the channels in the three cases. We also found that difference of the average of the Nusselt number between the nanofluid and the basic one in the three cases at Re =600 is 1.15, 1.74, and 1.57, respectively. In addition, we found that the shape of the studied micro channels has an effect on the friction factor and thermal resistance.

Effect of the global electroneutrality condition on electromigration Taylor-Aris dispersion in a microcapillary with finite Debye layer thickness.

In this work, the electromigration dispersion (EMD) due to the charged electrolytes in microchannels is considered without using the thin electrical double layer assumption. The electrokinetic flow and transport of ions are actuated within a rectangular micro-/nanochannel having a negative surface charge density under the influence of an external electric field. Due to the local variation of the conductivity and the nonvalidity of the electroneutrality condition, the local electric field varies as a function of the solute concentration, wall surface charge density, valency, and Debye layer length. The resulting electrokinetic flow due to the external electric field drives the fluid along with the charged species, where the Taylor-Aris dispersion separates the solutes into their different constituents. The local concentration dependence of the electric field leads to the formation of concentration profiles that are slightly asymmetric with respect to the standard Gaussian distribution. Including a finite Debye layer thickness has an effect on the advection of the species as well as the diffusion of the species. It is found that in cases where Debye layers are thicker, the species advects faster within the microchannel. This might give valuable insights into the nature of the EMD. Our model aims to predict the evolution of ionic concentration at all positions within the channel. A study of the higher-order statistics in skewness and kurtosis has also been conducted to obtain a better understanding of the idealized model consisting of a buffer solution.

An improved Mini Antenna Designed at 60GHZ for a New Generation Mobile Phone

Five-generation (5G) communication systems are being required to meet the needs of small, high-speed, and big bandwidth systems [2]. This paper simulates and designs a 60GHZ rectangular micro strip patch antenna. The proposed antenna resonates at 60GHZ with a return loss of -32.126 dB, efficiency of 87.7119%, and gain of 6.96485 dBi. The patch is 2.726 x 2.364 x 0.125 mm. The radiating patch and the 50Ω micro strip feed line are matched using an iset feed transmission line approach. A Roger RT Duroid 5880 substrate, with a height of 0.125mm and a dielectric constant of 2.20 and a loss tangent of 0.0009, was selected in the design. The Advanced Design System (ADS) was used to compute the antenna's parameters and evaluate the results of simulations.

Experimental investigation of forced convective heat transfer and fluid flow in a mini heat pipe with rectangular micro grooves

In the present study, the convective heat transfer coefficient of water in a laminar flow regime under constant inlet temperature conditions inside a flat mini heat pipe was investigated ex-perimentally. Heat flux ranged from 20-50W and various horizontal heat sink temperatures (operating temperature) ranged from 15-35°C with liquid flow rate (3.563E-8 m3/sec) used during the experiments. The rectangular microchannels performance is evaluated in terms of the temperature profile, heat transfer coefficient, Nusselt number and thermal resistance. The results emphasized that the mini heat pipe temperature gradients are less than the tempera-ture of the copper plate and the heat resistance gradually decreases to its lowest value when the heat flux value reaches its highest value if it does not exceed the capillary limits. The data also demonstrated that the coefficient of heat transfer in the condensation zone is lower than in the evaporation zone at different heat sink temperatures. The augmentation rate for the flat mini heat pipe thermal conductivity reached about 240% at a heat load 30W for the positions of thermosyphon and horizontal, while the rate of increase in the case of the anti-gravity situ-ation at a heat load 30W reaches 210%, then the improvement percentage begins to decrease to 200%. A generalized regression equation is developed for the estimation of the Nusselt number valid for water in a flat mini heat pipe.

Stainless steel bipolar plates with rectangular micro channels by additive manufacturing: Effect channel width on fuel cell performance

AbstractStainless steel bipolar plates (BPs) fabricated using innovative additive manufacturing techniques can improve fuel cell performance and reduce costs. A high current density can be obtained using a low‐cost membrane electrode assembly (MEA) with low platinum (Pt) loading at the anode, along with BPs with rectangular micro channels. Three types of BPs of serpentine flow field are designed after varying the width of the rectangular channel. Two types of MEAs are used. First is 0.12 mg cm−2 Pt loading at anode, and the second is 0.50 mg cm−2. Wherein MEA with Pt loading at 0.12 mg cm−2 is used, a high current density is obtained as the channel width decreases. The BP with 300 µm channels has a current density of 1.205 A cm−2, which is higher by 31.4% than that of BP with 500 µm channels and higher by 70.2% than that of the BP with 940 µm channels. However, when the MEA with Pt loading at 0.50 mg cm−2 is applied to the test, the opposite results are obtained: As the channel width becomes narrow, the current density decreases. In the long‐term operation, a similar trend in the current density as that of the short‐term operation is observed.

Heat transfer enhancement using combined microchannel with vertical rectangular micro fins

This paper focuses on the numerical optimisation of a combined hybrid microchannel heat sink with rectangular solid fins. The axial length and volume are fixed, and external structure is allowed to vary. The simulation was performed on an elemental unit cell of the microchannel heat sink . The purpose of the optimisation is to discover an optimal geometric arrangement in internal and external configurations that minimises peak temperature in the microchannel heat sink. A high-density uniform heat flux of 250 W/cm2 is assumed to be dissipated on the bottom wall of the unit cell by microelectronics circuit boards devices. Computational fluid dynamic code was used to discretized the fluid domain and solve a set of governing equations. The influence of hydraulic diameter, external structural shape and fluid velocity on peak temperature and global thermal resistance, is discussed. Coolant or water of Reynolds number range 400 to 500 in a forced convection laminar flow is introduced through the inlet of the computational domain to remove the heat at the bottom of the rectangular block microchannel. The results show that when the fluid velocity is increased from 9.8 to 12.3 m/s across the axial length of the micro heat sink, more heat is removed from the bottom of the combined heat sink. The results revealed that the pump power increased by 37.1% in combined microchannels with fins and from by 27.2% in finless micro heat sink. The result of the study is validated with what is documented in open literature for a traditional micro heat sink with circular flow channel and the trends agree.

Experiment study on heat transfer enhancement of micro heat pipe PV/T by Reynolds number improvement

The rapid performance improvement of photovoltaic/thermal (PV/T) implies great potential application to various aspects of society. The previously developed micro heat pipe PV/T by our team has shown favorable cogeneration of electricity and heat in cold regions, while it is badly needed to improve its comprehensive performance by enhancement of heat transfer. For same working fluid as HCFC141b in micro heat pipe, higher Reynolds Number (Re) theoretically means better heat transfer. Therefore, two available micro heat pipes were developed with trapezoidal cross section and rectangular cross section respectively while with same cross section area and applied in two micro heat pipe PV/T systems. Subsequent experiment study testifies that the rectangular micro heat pipe PV/T of higher theoretical Re verily shows more favorable performance than the trapezoidal micro heat pipe PV/T when they are at 45° inclination angle. Deducting power consumption of circulating pump, the average electrical efficiency of rectangular micro heat pipe PV/T system is 12.4%, while that of trapezoidal micro heat pipe PV/T system is 11.9%. Moreover, the thermal efficiency, total energy power, and total energy efficiency of rectangular micro heat pipe PV/T system are respectively 28.1%, 472.3 W, and 40.5%, which are 10.1%, 119.8 W, and 10.8% higher than those of trapezoidal micro heat pipe PV/T system. The results are significant and valuable for the application of micro heat pipe PV/T in cold regions.

Effect of evaporation and condensation section length ratio on thermal performance of aluminum flat plate heat pipe with different micro grooved wicks

The length of the evaporation or condensation section has a significant impact on conventional heat pipe or copper flat heat pipe heat transfer performance. Based on this demand, a novel concept of the length ratio of evaporation and condensation section (LREC) of the flat plate micro grooved heat pipe (FPMHP) was proposed and the effect of the LRECs on the thermal performance of aluminum-based FPMHP with different micro grooved wicks was experimentally investigated for the first time. The experiment explored the effects of nine different LRECs on the thermal performance of FPMHP with the same section size, filling mass, rectangular and triangular micro grooved wicks installed at 90°, a constantly increasing input heat flux, and forced air cooling. The findings demonstrate that rectangular micro grooved wick flat heat pipe (FPMHP-r) and triangular grooved wick flat heat pipe (FPMHP-t) have the shortest startup times when LREC is 1.0, with FPMHP-r starting 70 s sooner than FPMHP-t. When 0.8 ≤ LREC ≤ 1.25, the heat transfer performance of FPMHP-t and FPMHP-r is excellent, better than performance when LREC < 0.8 or LREC > 1.25, and the LREC is recommended to be 0.8 ∼ 1.25 in practical applications. The optimal LREC value of aluminum-based FPMHP is 1.0, which can maximizes the heat transfer performance. Under the same conditions, the heat transfer performance of FPMHP-r is better than FPMHP-t, flat heat pipe wicks with high permeability, low porosity and effective pore radius should be designed in practice. The results can provide a theoretical basis for the design and optimization of aluminum-based FPMHP application.

Improved Design of W-band Slot Array Antenna Based on Rectangular Micro Coaxial Line

Improved Design of W-band Slot Array Antenna Based on Rectangular Micro Coaxial Line

Analysis of Deformation of Thermoplastics by Using Thermomechanical Process

Nano fluidics has been a major field of research for application in areas like single molecule detection. Most of the research efforts have been concentrated in developing novel nano channel fabrication techniques. Most of these fabrication techniques developed are either expensive or time consuming.NA novel, low-cost fabrication technique to generate sub-micrometer wide channels in thermoplastic chips with potential application in single molecule detection is demonstrated. A custom, mechanical rig was designed, fabricated and optimized to produce a predefined thermo-mechanical deformation in thermo-plastic micro channel chips. Rectangular micro channels with different shapes and sizes were deformed using this rig to optimize the initial microchannel dimensions. Low aspect ratio (height: width) channels with smaller initial dimensions exhibit more potential to reach sub-micrometer widths. However, the nano channel fabrication consistency was adversely affected by manufacturing and assembly tolerances.

Miniaturization of Microstrip Patch Antenna for Biomedical Applications

In this study, a novel quad-band antenna for biomedical applications was designed, fabricated and analyzed. Biomedical application defines the use of antenna in detecting cancerous cells and its cure using hyperthermia. In this research paper, a rectangular micro strip patch antenna is modified with the circular and pentagonal shapes of negative media (Metamaterial). Antenna was reduced in size and ameliorated to operate on multiple frequency bands. Ameliorated antenna is operating at 1GHz also, which is the substantial operating frequency of cancer detecting tissues. Inclusion of metamaterial increased the bandwidth of and subsequently ameliorate the size of the proposed antenna.

Local flow patterns distribution during flow boiling in a micro channel array

The main aim of this study is to experimentally investigate two-phase flow patterns during flow boiling of R245fa in a micro channel array. The array consists of 10 rectangular micro channels connected in parallel, each having a hydraulic diameter of 1 mm. Base area of the channels is 14.5 x 180 mm. Micro channels without and with 0.5 mm wide inlet restrictions are examined to determine their influence on the flow. Four two-phase flow patterns are observed using a high-speed camera: bubbly, slug, churn-annular and annular flows. Two former are grouped together as intermittent flow, and two latter as annular flow. In the paper a special focus is put on the determination of the transition vapor quality corresponding to the change from intermittent to annular flow as well as how it is influenced by heat flux, mass flux and saturation temperature. Tested heat flux ranges from 30 to 50 kW/m2, mass flux from 400 to 1000 kg/m2s, examined saturation temperatures are 49, 63 and 82 °C and inlet subcooling varies between 13 and 19.4 K. It was found that transition vapor quality increases at lower mass flux, higher heat flux or saturation temperature. Coupling data on two-phase flow patterns with the data from our previous study on heat transfer (Halon et al., 2022) shows that flow patterns do not determine the dominant heat transfer mechanism. Intermittent flow occurs both in forced convection and nucleate boiling dominated zones, and annular flow, typically associated with the domination of forced convection, accompanies nucleate boiling dominated heat exchange. Micro channels with restrictions exhibit similar behavior, but transition vapor qualities shift to higher values. Comparison with four recognized models for transition vapor quality shows that it is best predicted by the model of Costa-Patry and Thome (2013) with MAPE of 47.9% calculated for both studied geometries.

Effect of rectangular micro cavity on pool boiling heat transfer on heating surface via the lattice boltzmann method

Effect of rectangular micro cavity on pool boiling heat transfer on heating surface via the lattice boltzmann method

Predicting Cutting Force and Primary Shear Behavior in Micro-Textured Tools Assisted Machining of AISI 630: Numerical Modeling and Taguchi Analysis.

The cutting tool heats up during the cutting of high-performance super alloys and it negatively affects the life of the cutting tool. Improved tool life can enhance both the machinability and sustainability of the cutting process. To improve the tool life preferably cutting fluids are utilized. However, the majority of cutting fluids are non-biodegradable in nature and pose harmful threats to the environment. It has been established in the metal cutting literature that introducing microgrooves at the cutting tool rake face can significantly reduce the coefficient of friction (COF). Reduction in the COF promotes anti-adhesive behavior that improves the tool life. The current study numerically investigates the orthogonal cutting process of AISI 630 Stainless Steel using different micro grooved cutting tools. Results of the numerical simulations point to the positive influence of micro grooves on tool life. The results of the main effects found that the cutting temperature was decreased by approximately 10% and 7% with rectangular and triangular micro grooved tools, respectively. Over machining performance indicated that rectangular micro groove tools provided comparatively better performance.

Powder Bed Fusion 3d Printing and Performance of Stainless Steel Bipolar Plate with Rectangular Micro Channels and Ribs

Powder Bed Fusion 3d Printing and Performance of Stainless Steel Bipolar Plate with Rectangular Micro Channels and Ribs

SEMI-ANALYTICAL METHOD FOR UNSTABLE PRESSURE OF 3D FRACTURE NETWORK

Due to the influence of in-situ stress and fracturing technology, the distribution of hydraulic fracture network in highly deviated wells is complex with different inclined directions, different distribution forms and different penetration degrees. In this paper, the fracture surface is discretized into several rectangular micro elements to realize the effective characterization of fracture morphology. The seepage process is divided into two stages: matrix flow to fracture and fracture flow to wellbore. The numerical solution of unsteady seepage in discrete fracture surface is constructed by using finite difference method, and the analytical solution of unsteady seepage in matrix is constructed by combining closed boundary source function and superposition principle. The solution of the unstable pressure of the 3D fracture network is obtained by coupling the numerical solution of flow in fracture and the analytical solution of flow in matrix. Based on the integral mean value theorem, a solution method of point source and special line source instead of surface source is proposed to solve the seepage in matrix. The feasibility and applicable conditions of this method are analyzed, which can ensure the accuracy of the model and improve the calculation efficiency. The research shows that the point source function area fraction method can accurately solve the bottom hole pressure dynamic of 3D pressure fracture network in the matrix, but the calculation is quite inefficient. The point source and special line source approximate surface source method based on the integral mean value theorem can greatly improve the calculation efficiency, and can achieve higher accuracy when the fracture micro element division is more precise (the dimensionless side length of micro element is less than 0.15). Based on this model, the flow regimes and related sensitivity analysis are analyzed. The results show that the fracture conductivity, fracture dip angle, fracture height and fracture interval have great influence on the typical well test curves of highly deviated wells. Fracture dip angle and fracture interval mainly affect the pressure and pressure derivative curve from linear flow to early radial flow, especially when the fracture height is small, the pressure derivative has backflow phenomenon.

Active control of vibrations of piezoelectric‎ rectangular nanocomposite micro plates reinforced with graphene platelet in thermal ambient considering the structural damping

This paper investigates on the active control ‎of vibrations of rectangular nanocomposite micro plates reinforced with graphene platelet bonded with piezoelectric‎ layers in thermal environment regarding the structural damping. The micro plate is subjected to a transverse load. The thermo-mechanical features of the reinforced layers are determined employing the Halpin-Tsai micromechanical model. The first order shear deformation theory is accompanied by the modified couple stress theory to derive the motion equations of the micro plate. The Ritz technique is applied to the governing equations to discretize the equations of motion. In order to active control ‎of vibrations of the micro plate, a closed-loop PD-controller is proposed. For the sake of determination of the transient response, the Newmark- direct integration technique is applied to the discretized governing equations of motion ensuing from the Ritz technique. The present findings are validated with the available data in the literature. A parametric study is established to shed light on the impression of the material length scale parameter, the boundary condition type, the graphene platelet distribution pattern and its weight fraction, and the control gain values on the dynamic response of the micro plate when it is subjected to a pulse-uniformly distributed transverse force. The results illustrate the more effectiveness of the designed PD controller for X-GPL micro plates with four clamped boundaries especially when the size dependency is incorporated into the formulation. Moreover, the PD controller performance boosts up at higher temperatures.

Circularly Polarized Rectangular Micro Strip Patch Antenna Design, Analysis for C Band Applications

Now a days the wireless communication system development requires the low cost, low profile, minimal weight antenna development which is accomplished of continuing great presentation completed a wide frequency range. This forward-looking abilities style has supported into the MSPA (Micro Strip Patch Antenna) plan. In this administrative work presents a working recurrence of 4.85 GHz roundabout polarization rectangular miniature strip fix radio wire is planned and mimicked. The proposed rectangular miniature strip fix reception apparatus is double miniature strip-edge-took care of circularly spellbound miniature strip radio wire. The proposed receiving wire can plan and invigorate Left Hand Circular Polarization (LHCP) and Right Hand Circular Polarization (RHCP) with utilizing cross coupler is straight associated with miniature strip radio wire to get polarization of round. The proposed paper work resonant frequency or operating frequency is 4.85 GHz which is mainly used for satellite communications, full-time satellite TV networks or raw satellite feeds. This operating frequency is the IEEE 802.11a version C band frequency and this C band frequency is also used in Wi-Fi devices and Radio LAN. The proposed roundabout polarization rectangular miniature strip fix receiving wire on FR-4 (Flame Retardant and type 4) epoxy substrate material thickness of substrate is 1.6 mm. The dielectric steady of FR4 epoxy is 4.4. The double miniature strip edge took care of round polarization rectangular miniature strip fix radio wire is planned and reenacted utilizing CSTMWS (Computer Simulation Technology Micro Wave Studio) programming. The thunderous or working recurrence of proposed reception apparatus presents at 4.85 GHz for remote correspondences that gives S boundaries (return misfortune), transmission capacity and radiation example of Gain and directivity.