Search

Taylor bubble/slug flow is a type of multiphase flow that is predominant in many natural and industrial applications. A thorough understanding of two phase flows and void fraction measurement is es...

Hydrogen peroxide is a green propellant used in nanosatellites for micro-propulsion. The flow pattern and concentration of hydrogen peroxide decide the thrust produced in such micro-thrusters in which the thrust is of the order of milli-Newton. A mini/micro-fluidic cross-sectional geometry can dramatically vary the fluid flow characteristics, particularly for a capillary-driven flow in such devices. In the present work, experiments are carried out in a mini-square channel of 50 × 2 × 2 mm size and thickness of 0.5 mm with air–hydrogen peroxide as two-phase flow fluids. Bubble and slug flow regimes formed during the flow are recorded using a PROMON high-speed camera. An infrared transceiver circuit is used for identifying the flow regimes. COMSOL Multiphysics package is used to develop a numerical model. The developed numerical model is validated with the experiments by comparing the signal behaviour. The shape effects of the square, circular, and triangular channel on IR transceiver irradiation during two-phase flow are detailed. The effects of dimensional ratio of the test section on IR transceiver irradiation are discussed. The attenuation behaviour of the hydrogen peroxide fluid (6, 30, and 50% concentration) on IR transceiver irradiation during two-phase flow is presented.

Stamping process is an important sheet metal forming process used in domestic and automotive components. In this process, blank material is converted into the desired complicated shape by punching process.Stamping includes a process such as punching using a punch or ram, blanking, embossing, bending, flanging, and coining.Cost minimisation ,less time consumption, increase in efficiency are very important in the recent manufacturing industry. Today simulation techniques are used to analyse the performing of dies, processes and billets prior to real timeimplementation. Simulations enable us to find out the common defects such as tears, wrinkles, and material thinning. Finite element analysis (FEA) is the method of simulating the process of sheet metal forming to determine various behaviour of the sheet metal and helps us to find out whether it will produce parts free of defects such as fracture or wrinkling. Sheet metal forming is a popularly used metal working process. In this paper stamping process is analysed numerically using a simulation software package LSTC – LSDYNA. A three dimensional thermo-mechanically coupled stamping model is analysed and its validations are presented. The analysis data from the numerical simulation helps in understanding the real-time mechanism of sheet metal forming process.There areonly few works were reported on numerical analysis of warm stamping of AA6061 such as load requirement, blank holder pressure, stress-strain analysis.This work is based on study the deformation behaviour of sheet metal, flow stress analysis, contact pressure and punch velocity.

Study of two phase flow regimes in a mini/micro channel finds its applications in micro-fluidic devices such as micro heat exchangers owing to its large heat transfer. Such systems have large surface to volume ratio. The present work detail the results obtained for bubbly and slug flow regimes formed in a T-junction for an air water mixture. Experiments are performed in two different tubes with internal diameters of 0.6mm and 2.5mm having a length of 100mm. Image processing techniques are employed using MATLAB software. The data will be helpful in designing fluid flow mini/micro channels commonly used in thermal MEMS.

Multiphase flow occurs in variety of applications in Industries and in nature. One of the most important subcategory of multiphase flow is gas-liquid flows predominantly found in evaporators, condensers, micro-reactors, cryogenic engines and in compact heat exchangers. In the present study, air-water two phase flows in a 4.7mm inner diameter glass tube with 0.3mm thickness is characterized using an IR transceiver and a headphone jack. The output of the IR receiver is sent to the laptop using a 3.5mm headphone jack. The novelty in the present work is that this eliminates the need for a dedicated micro-controller/ DAQ system to process the data. A simple program written in python is used to process the input of the mic and provide amplitude and frequency information which identifies the flow regime. High-Speed Images captured simultaneously are used to validate the output obtained using the headphone jack.

In the present work, experiments are done to understand the distribution of liquid film in Taylor flows occurring in small circular mini channels using laser-induced fluorescence. Gas–liquid Taylor flow is generated in 3 different channels of inner diameter 1.5, 2.1 and 3.1 mm to understand the effect of flow parameters and nature of forces on the liquid film thickness. Rhodamine-B, a fluorescent dye is mixed with water, the primary phase in the two-phase mixture and is excited by a pointed laser beam of wavelength 531 nm. The liquid film thickness with the excited fluorescent dye emits light at 610 nm which is captured using a CMOS high-speed camera. A long pass filter is used to filter the reflected laser light before being captured by the CMOS sensor camera. Subsequently, the image obtained is processed with a set of image processing techniques to determine the liquid film thickness. Different slug shapes are obtained for various combinations of flow velocities and are found to depend on the Bond number. Further, it is also found from the experiments that asymmetry in the flow regime is found to depend on the capillary forces acting on the flow and it increases with the capillary number. The film thickness is also found to vary across the air slug length and its distribution along the flow length is also presented.

The production of mono-dispersed spherical and non-spherical polymer beads and capsules using micro-fluidics requires precise control of dispersed phase which are distributed in a continuous phase. The prediction of two phase or three phase flow patterns in the mini/micro channels finds its application in production process of such spherical polymers. In the present work a numerical model based flow analysis is done for creation of the spherical/non spherical dispersed air bubbles in a continuous liquid phase. The results are validated with experiments done in a similar liquid–gas flow experiments carried out in a glass mini channel of size 2.05 mm. The flow regime is recorded with a high speed camera. The volume of fluid model in ANSYS Fluent software is used to predict the flow pattern details numerically. The model can be effectively used for predicting the size behavior in such spherical/non-spherical polymer bead production.

Multiphase flows play a vital role in many industrial and naturally occurring processes. Recent trend of miniaturization in mini/micro fluid reactors, compact heat exchangers and micro thrusters requires a thorough knowledge on multiphase flow phenomena in mini/micro channels. The present work is focused on the effect irradiation behavior of infrared rays (IR) during gas liquid two phase flow consisting of thin liquid films inside a mini channel. The influence of size and shape of the slug regime and liquid film thickness on IR rays is analyzed with COMSOL Multi physics package. Experiments are carried out in a 2.5 mm diameter borosilicate glass tube with wall thickness of 0.3 mm. The refraction and transmittance behavior of IR rays on slug and bubbly flow is studied by analyzing the Current-time output of an IR photodiode kept at different angles with the test section. The results are found to be in good agreement with experimental image processing technique and COMSOL results. The results obtained will be useful for designing of IR sensor arrays sensitive to multiphase flows. It can also be used for measurement of liquid film thickness with proper calibration.

Microreaction technologies are employed in various applications like space propulsion, atomization, drug delivery and in lab-on-chip applications. Mixing index measurement in micro reactors is essential to assess the performance of the proposed micro mixer. A major roadblock in the design of a micromixer is its assessment and determination of mixing index during the operation due to the complex flow characteristics and mass transfer that occur during the mixing of fluids or reactants. Sensor design is thus vital in analyzing the performance of micro mixers during operation. Infrared sensing is a versatile flow visualization technique which has been effectively used previously to characterize two phase flows in conventional macro channels. The present work develops a robust multiphysics simulation framework and provides a comprehensive characterization of an infrared sensor to perform online assessment of micromixers during their operation. This study considers the case of an optimized passive micromixer described in several literatures and models the microfluidic mixing between silica nanoparticles and distilled water at various concentrations. Further coupling was done by applying the physics of ray optics to understand the performance of an infrared sensor. The variation in infrared sensor output with the mixing index is presented based on the multiphysics coupling. With this analysis, the characteristic output of an infrared sensor can be inferred for any practical microfluidic mixing and microreactor application, thus helping the instrumentation design for online performance assessment of micromixers.

Over 80% of the world’s people with visual impairment are living in countries which are financially dire. And over 50% of them are above the age of 50 years. The need for a system or of technology that would enable this sector of people to perceive the world in much the same way as the rest of us is imminent. The article presents a novel way to eliminate the use of data acquisition system (DAQ) systems/micro-controllers by incorporating a headphone jack. With the aid of a headphone jack, a cost-effective wearable ultrasonic module that would enable people with visual impairment to virtually see is implemented. Unlike conventional walking canes or its derivatives that do not offer effective feedback, the ingenuity in the proposed module is that it offers audible feedback to the user. The ultrasonic sensor is coupled with the headphone jack and the output of the sensor is relayed to the earphones with the help of a free mobile app (Mic To Speaker). This substantially reduces the cost of the module (since no DAQs/micro-controllers are used) and the processing needed as well.

Gas- Liquid flows are by far the most important type of multiphase flow. This can be attributed to the wide range of industrial applications that the gas-liquid flow is discerned in. Popular examples of Gas-liquid flows are oil-gas mixtures, evaporators, boilers, condensers, refrigeration and cryogenics. The measurement of the liquid film thickness in two phase flows is prominent in various heat and mass transfer applications such as in boilers. To determine the thin film thickness is the aim of this study. A glass tube of diameter 4.7 mm is used for conducting the experiment and a laser pointer is used to obtain an image pattern on the screen. Using the principles of Optics, a method has been proposed to determine the thin film thickness and also to characterize the different types of flow. The thin film thickness obtained in the proposed method is validated using Image Processing.

Two-phase flow measurement is important in process and chemical industries. In the present work, a measurement technique for the characterization of two-phase flows using a laser and an arrangement of the photodiodes is proposed and tested. Two-phase flow experiments were carried out in 1.80, 3.14, and 4.68-mm-diameter glass tubes. A high-speed camera was used to analyze the various optical patterns formed by a stationary laser beam on a screen during bubbly, slug, and stratified flows, which have been discussed in detail in Navisa et al. (2015). Photodiodes are arranged on the screen based on high-speed camera recordings. A procedure is demonstrated to calculate the flow regime velocity and length based on the photodiode outputs. The designed nonintrusive instrumentation determines the two-phase flow parameters in real time for flow in optically transparent mini channels. The accuracy of the measurement technique and the limitations are also discussed.

The simultaneous flow of two different phases is referred to as two phase flow. In the present study, a technique is developed for the identification of Air-Water two phase flow regimes using Infrared sensor. Experiments were done in a 4.7 mm borosilicate glass tube with a wall thickness of 0.3 mm. An Infrared (IR) emitter is used to send IR rays continuously. This IR ray is refracted by passing through the glass tube and the flowing medium. The refraction results in variation in current flowing through the IR receiver which is recorded online using data acquisition system. Bubbly, Slug and Stratified flow regimes were identified from the variation in current. Computational Fluid Dynamics (CFD) modeling of two phase flow inside the tube of same dimension was done using Volume of Fluids (VOF) method. Numerical simulations were carried out in Fluent 2D for the same superficial liquid and gas velocities as in the experiments. The results of the IR sensor and the Volume of Fluids method were compared with high speed photography of the two phase flow patterns. The flow patterns identified using IR sensor are in good agreement with the results of VOF method and high speed videography.

The study of bubble column reactors has its significance in applications such as multiphase reactors, aerators and in industrial waste-water treatment. Extensive works has been done in studying the hydrodynamics of a single gas bubble flowing through stationary liquid phase. The natural breakup of bubble during its motion has been studied in the past. In the Part I of the present work, hydrodynamics of an air bubble after its artificial splitting using a stainless steel mesh is experimentally studied using image processing and high speed photography. The significance of bubble splitting is that it increases the surface area of contact between stationery and moving fluid which in turn increases the rate of reaction desired during the process. The motion of the bubble is captured during its release and after splitting using High-Speed Camera. The velocity, area and diameter of the bubble before and after splitting are calculated by applying Image processing technique on the high speed photograph. The splitting of the bubble is found to vary with the superficial gaseous velocity. The splitting of bubbles into two bubbles of nearly equal size is considered and its hydrodynamic characteristics are studied.

Results from numerical investigation of laminar natural convection inside a differentially heated square enclosure with a thin baffle attached to the cold wall are reported. The effect of the baffles on the flow and temperature fields were analyzed for baffle lengths equal to 20, 35 and 50 percent of the width of the enclosure, attached at three locations for Ra = 104, 105, 106 and Pr = 0.707. The presence of a baffle on the cold right wall affects the strength of the clockwise rotating primary vortex. Reduced flow and heat transfer are observed. Longer the baffle more pronounced the effect on the flow field. Secondary convection cells are seen between the baffle and the bottom wall for certain cases. Reduction in average Nusselt Number is observed on the cold wall with the baffle than the hot wall.

In most of the engineering applications unnecessary heat is produced. Fins are extended surface which are used to enhance heat transfer rate from a surface by increasing the area exposed to convection. The addition of fin increases the surface area and this forms an economical solution for increasing the efficiency and the performance of the device. In the present study a comparative analysis is made between an array of hollow pin fins in upward facing and sideward facing arrangement under natural convection. The model is numerically investigated using commercial CFD code ANSYS FLUENT©. The fin outer diameter (12mm) and fin height (50mm) are kept constant. The parameters varied are the internal diameter of the fins and the heat laod. The results show that the sideward fins have lower base plate temperature as expected due to buoyancy effects. However hot spots are identified in the case of sideward facing fins which will affect the heat transfer characteristics when compared to upward facing hollow cylindrical pin fins.

Braking system is important in any automobile. It is essential to decelerate the vehicle and stop it. Friction braking system is widely used system of braking. It makes use of frictional force to safely retard the vehicle. The temperature of the brake pad (stator) and disc (rotor) increases because of frictional force between them. Higher temperatures may lead to fading of brakes resulting in its failure. This paper briefly reviews published works on studying the wear and thermal characteristics of brake pads and on various available brake cooling methods. The microstructural changes in the brake pads are analyzed and reason for enhanced wear at higher temperatures is traced out. The various test results obtained using microscope (SEM), Friction assessment screening tests (FAST), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) are described in brief. A description of the available methods of enhancing the brake cooling and decreasing the wear rate is discussed. This work will be useful in planning further research in this important area of automotive field.

The present work deals with the use of CFD analysis and the validation of the experimental work carried out on the artificial splitting of an air bubble in a bubble column reactor. In Part I of this work, artificial splitting of bubble in a bubble column rector is experimentally studied by using a high speed camera. Image processing technique was used to identify bubble size and bubble velocity. In present work CFD simulations are carried out using ANSYS FLUENT software using Volume of Fluids (VOF) method. VOF is based on a surface tracking technique applied to a fixed Eulerian space. The phase fraction in physical quantities that can be used to distinguish the distribution of gas hold up in a bubble Column reactor. The numerical study of splitting of bubble into two bubbles of nearly equal size is considered. In the bubble column reactor, the liquid phase is stationary and gas flow rate in it is varied. The superficial gas flow rates are 10 lph, 15 lph, 20 lph and 25 lph. The characteristics of bubble after splitting which include its shape, size and velocity for various gas flow rates mentioned above are studied numerically and are compared with experimental results. These hydrodynamic characteristics play a pivotal role in the reactions occurring between the liquid and gas phases in the bubble column reactor.

With the fast depletion of the conventional energy resources and the amount of pollution it is creating, the entire world is looking for an alternative non-conventional and a renewable energy to lessen the dependency on the conventional energy resources. In this scenario, utilizing solar energy which is abundant in nature is gaining high attention. One way of utilizing solar energy is by using solar photovoltaic cells which convert light energy into electrical energy, but they are too costly and less efficient. Many techniques are being developed to reduce the cost and improve the efficiency in harnessing solar energy. Sun tracking technique is one of the methods to increase the efficiency of solar cells. The present work is focused on providing a microcontroller based automatic two-axis sun tracker using Photodiodes as sensors to track sun. The system is assisted with a manual control through LabVIEW (Graphical User friendly Interface) to aid during bad weather conditions.

Two phase flow regime identification and void fraction measurement is an area of considerable interest because of its wide applications in process industries. The principle involved in dielectric measurement is that the two phase flow regime is characterized by the changes in effective permittivity of the two phase fluid mixture. In the present work, a pair of parallel copper electrodes on the two sides of a glass tube acts as a dielectric sensor. As the void fraction in the glass tube changes, the effective permittivity of the medium changes. This causes a variation in the capacitance value across the electrodes. A standard IC, Oscillator 555 is employed as a tool to generate a rectangular wave. The variation in dielectric constant is analyzed based on the change in time period of the trough (T0) of the rectangular wave that is recorded online by a data acquisition system. Experiments were performed in a 4.7mm diameter tube with air-water, air-palmolein oil two phase fluids to study the variation in dielectric constant which is indicated as a change in time period of trough. The effect of conductivity of water on the capacitance variation is examined with water having Total dissolved solids (TDS) which is a measure of movable ions in the range 10-4000ppm (16?S/cm-6.3mS/cm). The novelty in the present work is the determination of changes in capacitance value based on the change in time of trough of the rectangular wave. The technique does not require amplification or a filtering circuit, thereby leading to a precise identification of two phase flow regime. � 2015.

Trucks are heavy load vehicles used mainly for commercial transport operations. There are several classes of heavy duty commercial vehicles classified based on the weight loaded. More than 50% of the engine output power in such trucks is utilized to overcome the drag. Drag force in automobiles is the resistance offered by air on vehicles at higher speeds. Class 8 trucks suffer higher drag when compared to other classes. In the present work, a numerical model is developed using a commercial code ANSYS FLUENT to predict the drag coefficient value. The effects of gap width and cab front radius with a constant fairing is analysed using the numerical model developed. A Class 8 model truck with minimal drag coefficient having constant fairing and optimized gap width between the trailer and cab is proposed.

Hydrogen peroxide is a chemical compound which is commonly used as a disinfectant at lower concentrations. The chemical is called as a green propellant for space applications. Water and oxygen are the products after self-decomposition of the compound at higher concentrations. The reaction rate at lower concentrations can be enhanced by using catalysts for faster reaction rates. In the present study, an experimental analysis of the reaction rate of hydrogen peroxide (6% by volume) with silver catalyst for varying flow rates is detailed. Reaction takes place in a long cylindrical borosilicate glass tube of diameter 2.50 mm. Separation of product mixture takes place in an enlarged tube of diameter 5.50 mm. Various two phase flow patterns formed after decomposition reactions are identified by images captured using high speed camera. Length of oxygen slug formed after catalytic reaction is measured by employing Image processing techniques.

Mini/micro nozzles are used in digital propulsion systems for generating milli/micro thrust. Such systems are used in satellites for precise control and positioning. The measurement of milli thrust which is of the order of few Newton requires specialized measuring systems. In the present work, a force sensing resistor (FSR) is used to measure such low valued thrust. A commercially available FSR is calibrated using standard weights. The FSR response to added loads is recorded using a NI-DAQ (National Instruments - Data Acquisition) system and signals are analyzed using LabView package in a desktop. The calibrated values match well with the standard charts and percentage of error is calculated. The thrust produced by the fabricated nozzle setup is measured using FSR in the same arrangement and compared with the analytical equations. The measured values are in good agreement with analytical results.

Hydrogen peroxide is a monopropellant which is called as a green fuel. It is used in micro propulsion devices for controlling and maneuvering of nano satellites. The concentration of hydrogen peroxide decides the thrust produced in such mini/micro thrusters where the thrust is of the order of few newtons. This paper focuses on the detection of concentration of hydrogen peroxide based on the change in the optical property, the refractive index. An experiment has been done for three different concentrations of hydrogen peroxide. Distilled water was taken as a base reference for the plot. The test liquid was made to flow through a glass tube, and the refractive index was measured using an IR transceiver setup. The values obtained using NI-cDAQ for various concentrations are compared. These concentration variations detected by the sensor is accurate and precise. The sensor will be cost effective when compared to the ones available commercially.

The 3D printer is a three-dimensional prototyping machine which fabricates desired shape by layer over layer material deposition. The printer's extruder should be at its homing position before any deposition process begins. Also keeping the deposition process within the specified limits of movement is very vital. The precise positioning of the extruder can be done using limit switches. This paper focuses on using a hall sensor as a limit switches and comparing its advantages over conventionally used intrusive sensors (mechanical switches). If the movement of the extruder is not within the given workspace, undesirable dimensional changes may happen in the end product. Conventionally the positioning is done by using mechanical switches which may undergo wear and need a regular replacement. The limit switch is an electromagnetic device which restricts the movement of the extruder outside the permissible limit. The limit switch detects the motion of the machine parts and sends feedback to the controller which in turn control the machine. When compared to a opto switch, the device is relatively cheap with all the desired characteristics including no wear

High Speed brushless DC (BLDC) motors are commonly used in quad-copter rotors, drones and in radio controlled systems. Micro controllers are commonly used to control such BLDC motors. However programming a micro controller requires understanding of an assembly language and the limited memory space available in a micro controller limits its use for various applications. Raspberry PI is a single board computer which operates at 5V. It has very wide applications in the area of robotics and automation. In this work, the control of a BLDC motor using a Raspberry pi system is detailed. Programming is done using Python language. PWM technique is adopted for programming to control the Electronic speed controller which in turn activates BLDC with power from LiPo batteries.

In the devices like laptops, microprocessors, the electric circuits generate heat while performing work which necessitates the use of fins. In the present work, the heat transfer characteristics of hollow cylindrical pin fin array on a vertical rectangular base plate is studied using commercial CFD code ANSYS FLUENTⒸ. The hollow cylindrical pin fins are arranged inline. The heat transfer augmentation is studied for different parameters such as inner radius, outer radius, height of the fins and number of pin fins. The base plate is supplied with a constant heat flux in the range of 20–500 W. The base plate dimensions are kept constant. The base plate temperature is predicted using Artificial Neural Network (ANN) by training the network based on the results of numerical simulation. The trained ANN is used to analyse the fin in terms of enhanced heat transfer and weight reduction when compared to solid pin fin. Optimization of the hollow cylindrical pin fin parameters to obtain maximum heat transfer from the base plate is carried out using Genetic Algorithm (GA) applied on the trained neural network. The analysis using the numerical simulation and neural network shows that the hollow fins provide an increased heat transfer and a weight reduction of about 90% when compared to solid cylindrical pin fins.

A passive micromixer with obstacles in the form of deformable baffles is examined numerically. The model deploys an Arbitrary Lagrangian-Eulerian framework with Fluid-structure interaction coupled with a diffusion–advection model. Numerical analysis is carried out in the Reynolds number [Re] range of 0.01≤Re≤300. The objective of the present study is to enhance mixing between two component flow streams in a microchannel encompassing a deformable baffle. In the present work, the baffle deforms only due to the dynamic force of fluids. No external forces are applied. To exemplify the effectiveness of the present design, water and a suspension of curcumin drug loaded nanoparticles are taken as two fluids. Mixing index based on the variance of the local concentration of the suspension is employed to appraise the mixing performance of the micromixer. The introduction of the deformable baffle in a micromixer proliferates the mixing performance with minimal pressure drop over the tested Reynolds number range.

The present work presents experimental results of subcooled flow boiling heat transfer phenomena in minichannels. The experiments were conducted with high surface tension liquid (water), which clearly indicates that inertial effects are important for both momentum and thermal transport in minichannels. The test section is a horizontal AISI 316 stainless-steel minitube with internal diameter of 1.13 mm with uniform heated length of 250 mm and the tube is heated by AC electric current. The variation in wall temperature and pressure drop gives an indication of the different boiling regions along the axis of the horizontal tube. Based on sudden oscillations of the pressure drop and wall temperature, onset of nucleate boiling (ONB) is identified in the tube. During ONB, pressure drop and the fluctuations of fluid outlet temperature are observed near the exit of the test section. Predictive models for ONB were evaluated and Kandlikar's ONB model was found to agree well with the present data. Comparisons of experimental heat transfer coefficient in the subcooled boiling regime with the existing correlations are also presented. � 2015 Copyright Taylor and Francis Group, LLC.

Flow mal-distribution is defined as the non-uniform fluid flow distribution among the parallel channels having a common header. Flow mal-distribution is present in every header channel assembly. This mal-distribution has a significant effect on the performance of the heat exchanger by increasing the pressure drop and affecting the heat transfer characteristics. However, in designing a heat exchanger, a uniform flow distribution in each channel is assumed. The present work attempts to reduce the flow mal-distribution in a cross flow heat exchanger. A numerical analysis is done using a commercial code ANSYS FLUENT 3D and the results are validated experimentally. A parametric study is done by changing the size of the channels within the heat exchanger so as to reduce the flow mal-distribution. The effect of varying channel size on flow mal-distribution and pressure drop across the heat exchanger is studied and a geometry with reduced flow mal-distribution is found.

Braking system is one of the important systems in Automobiles. It is essential to decelerate the vehicle and stop it when essential. The temperature of the brake pad (stator) and disc (rotor) increases because of frictional force between them. Higher temperatures may lead to brake fading or failure of braking system. In the present study droplet cooling of commercially available Brake pad is analyzed with surface temperatures in the range of 80°C - 150°C. The brake pad material analyzed is a composite material with Fe2O3, BaO, CaO, SiO2, SO3 and MgO as major constituents. The percentage of the constituents are found using Scanning Electron Microscope (SEM). The brake pad is artificially heated using cartridge heater and a fixed volume of water is dropped on to the brake pad surface using a syringe pump. The characteristics of droplet on the surface of the brake pad are recorded using a High speed camera. The temperature is measured continuously using a K type thermocouple and is recorded using an online data acquisition system. The characteristic of droplet enhanced cooling is presented.

The study of evaporation of water droplets over horizontal heated surfaces is an intense area of research because of its wide application in various fields of heat transfer. The characterization of the behavior of water droplets is important in studying the cooling effects produced over impinging surfaces. The present study focuses on analyzing the shape and size of the droplets by applying image processing techniques. In the present work, a fixed volume of single water droplet is made to impinge on a horizontal Aluminium surface using a designed microcontroller based syringe pump. The formation and the dynamics of bubbles are recorded using a high speed camera. Image processing technique is used to determine the droplet parameters such as contact angle, spreading radius and to study the shape of the droplet. The surface temperature is measured using a Thermocouple connected to an online Data acquisition system. The effect of the characteristics of droplet on the decrease in surface temperature can be seen from the temperature – time graph and the processed photographs taken using high speed camera. The decrease in base plate temperature is found to be depending on the behavior and the properties of the droplet.

Fins are extended surfaces provided to enhance the heat transfer rate of a system. Several attempts have been made in the past to augment the heat transfer rate by using fins of various geometries. In the present study an array of rectangular fins with closed top, standing on a vertical base is analysed under natural convection conditions using commercial CFD code ANSYS FLUENT©. The numerical model is validated with the available experimental results for fins with open top under natural convection conditions. The plate fin heat sink is analysed for a constant heat duty of 60 W. The height, thickness and length of the fins are taken to be constant throughout the analysis. A detailed study is carried out to examine the dependency of the base plate temperature on the thickness of the closed top and on the number of fins. It is concluded based on the analysis that heat fins with closed top are found to have a decreased base plate temperature compared to the conventional rectangular fins.

Surface Micromachining is an important method of fabricating microfluidic systems and devices. The difficulty in microfluidics lies in the introduction of fluids into the micro channels in precise quantities. In the present article, a syringe pump controlled by an Intel 8051 based microcontroller has been designed. The designed single infusion syringe pump is based on a lead screw mechanism. The design is simulated using Simulink toolbox in Matlab and the volumetric flow rate is calculated for a given input. The inputs are dimensions of the syringe and viscosity of the operating fluid. Based on the inputs, a step delay is assigned to actuate a 12 V stepper motor. The designed syringe pump is tested with water at different flow rates. The pressure drop due to friction at various interfaces introduces an error that leads to a decrease in actual flow rate compared to the desired flow rate. The error function is calculated using curve fitting techniques based on the difference in the experimental and actual flow. The error function is also included in the algorithm to obtain a precise flow rate

Quad rotors are vertical takeoff and landing systems (VTOL) which are most commonly used in surveillance, search and rescue operations, aerial photography and in automated applications. Ready to fly (RTF) quadcopter systems are now available in markets which are primarily used for various civilian applications in such a way that even a beginner without any knowledge of such systems can operate on it. The objective of the present work differs from such RTF systems. The paper focuses on assembling a quadcopter system using standard components and flying it in a stabilized manner using manual control. The stabilized flight data is acquired using a standard DAQ which is an integral part of the flying system. In part II of this work the data acquired as voltage signals which are the input to the four motors which control the flight are given as input for a mathematical model developed using MATLAB Simulink. The results of experiments carried in Part I is compared with the model developed in Part II. The logged data could be used to study the stabilization process of the flight controller which is a primary requirement for automation of the system without relying on a manual control. This will be a source for future work for complete automation of a stable flight quadcopter. The data logged during flight time is presented.

Droplet impingement cooling on flat surfaces finds its applications in spray cooling of hot surfaces, deposition of molten metal on surfaces, plasma coating, cooling of brake pad, turbine blade and in electronic chip cooling. Optimization of such a process requires a thorough understanding of the hydrodynamic process which happens during impingement of the droplet on the surface. Image processing techniques can be employed to understand the process. Image processing is converting an image into digital form and analyzing it, to get an improved image and extracting the desired information from it. The technique is widely used in face detection, remote sensing applications, machine vision and industrial robotics. In the present work an image processing algorithm is developed for a specific surface cooling technique. A hot surface is treated by impinging droplets. The size of the droplets can alter the material characteristics significantly. The objective of the present work is to develop an image processing algorithm to find the droplet dimensions. The variation in radius and height is examined with the help of Matlab software. Edge detection techniques are used to determine the boundaries of the droplet clearly. The algorithm is developed using Matlab toolbox and is capable of measuring droplet height and spreading radius in detail. The advantage of this algorithm is that the technique can be employed to the process in real time.

Continuous and accurate fluid delivery is a real challenge in many of the modern industrial applications such as continuous subcutaneous infusion, micro fluidics, delivery of hydrogel in rapid 3D printing, liquid-liquid micro extraction, etc. In most of the drug delivery systems, drug needs to be injected at a rate even less than a drop per minute. So in order to design such a precise delivery system that ensures continuous flow, there arises a need to employ different mechanisms depending upon the applications. In the present work, rotary to linear converting mechanism using rack and pinion with and without worm wheel for a double acting syringe pump is simulated using Matlab-Simulink toolbox. To have high accuracy in position of the syringe plunger, a 1.8 degree stepper motor is considered as a syringe actuator. The rack and pinion assembly consists of only two members i.e. a toothed rack and a pinion gear. The simulation results show that the designed mechanism is able to deliver the fluid continuously with precise delivery.

Quad copters are VTOL aerial robot systems and has complex dynamics in spite of its simple design. In the present work, a quadcopter of plus configuration is assembled and its flight characteristics are experimentally studied. To stabilize the system during its flight a KK multicopter platform is used. Flight stabilization is done and data of motor input voltage is acquired using a arducopter flight board. The flight dynamics of such a system is briefly explained in Part I of this paper. In this paper the numerical simulation of such a quad copter is done using Matlab Simulink. The work includes motor dynamics and the nonlinearities involved in the governing equations. The voltage data acquired during the flight of the experimental system is given as an input and its motion control analysis is done. The results of the experiments and developed mathematical model are compared. They are fairly in agreement with each other which validate the present model. This is a first step in automating the VTOL aerial robot system avoiding human dependence in any form which will be the scope of future work.

The concurrent flow of two different liquid or gaseous phases is termed as two phase flow. The study of two phase flow is important due to its wide applications in industries. Its applications include cooling, refrigeration, atomization of fuels, chemical processing and cryogenics. Study of two phase flow parameters such as velocity and length of two phase slug flow pattern is significant in analyzing the heat transfer characteristics in the case of refrigeration and chemical process industries. In the present study, a pair of infrared emitter and receivers is used to determine the velocity and the length of a slug type two phase flow. By knowing the distance between the IR pairs and by calculating the time taken using a DAQ, velocity and length can be determined. Image processing and high speed videography technique is used to validate the obtained results.

Rapid mixing in microchannels plays a significant role in chemical, biological and medical analysis fields. Microchannels are widely used for chemical and biochemical reactions because of their high surface to volume ratio. However, the rate of mixing of two or more chemical reagents is less as the flow through the micro-channel is highly laminar. Thus, two reactive fluids are predominantly parallel when they flow along the length of the channel. Generally, obstacles or surface modifications are made in the flow path which induces chaotic advection in the fluids. Considerable amount of research has been done in the past in developing different types of surface modifications to enhance the chaotic mixing. But, the intricate nature of fluid flow phenomenon makes it difficult to design the surface modification suitable to achieve the maximum rapid mixing. The present work aims at designing micromixers with the objective of obtaining rapid mixing with reduced pressure drop. A topology optimization algorithm is illustrated in the present manuscript for the design of optimal micromixer configuration. Finite element based optimization for surface modification of micromixer is developed using porosity of the channel as the control variable. In the present work, the optimisation solver works over two objectives. One is to increase the mixing in the channel and the second is to reduce the pressure drop. Numerical experiments are done to test the algorithm to obtain the optimal surface modification to achieve maximum rapid mixing between the two fluids. The results show that rapid mixing is achieved with the modified topology obtained using the code.