Shahrir Abdullah

Reducing Entropy Generation in MHD Fluid Flow over Open Parallel Microchannels Embedded in a Micropatterned Permeable Surface

The present study examines embedded open parallel microchannels within a micropatterned permeable surface for reducing entropy generation in MHD fluid flow in microscale systems. A local similarity solution for the transformed governing equations is obtained. The governing partial differential equations along with the boundary conditions are first cast into a dimensionless form and then the reduced ordinary differential equations are solved numerically via the Dormand-Prince pair and shooting method. The dimensionless entropy generation number is formulated by an integral of the local rate of entropy generation along the width of the surface based on an equal number of microchannels and no-slip gaps interspersed between those microchannels. Finally, the entropy generation numbers, as well as the Bejan number, are investigated. It is seen that surface-embedded microchannels can successfully reduce entropy generation in the presence of an applied magnetic field.

Entropy Generation Analysis of Open Parallel Microchannels Embedded Within a Permeable Continuous Moving Surface: Application to Magnetohydrodynamics (MHD)

This paper presents a new design of open parallel microchannels embedded within a permeable continuous moving surface due to reduction of exergy losses in magnetohydrodynamic (MHD) flow at a prescribed surface temperature (PST). The entropy generation number is formulated by an integral of the local rate of entropy generation along the width of the surface based on an equal number of microchannels and no-slip gaps interspersed between those microchannels. The velocity, the temperature, the velocity gradient and the temperature gradient adjacent to the wall are substituted into this equation resulting from the momentum and energy equations obtained numerically by an explicit Runge-Kutta (4, 5) formula, the Dormand-Prince pair and shooting method. The entropy generation number, as well as the Bejan number, for various values of the involved parameters of the problem are also presented and discussed in detail.

The Combustion and Performance of a Converted Direct Injection Compressed Natural Gas Engine using Spark Plug Fuel Injector

Compressed natural gas (CNG) has been widely used as alternatives to gasoline and diesel in automotive engines. It is a very promising alternative fuel due to many reasons including adaptability to those engines, low in cost, and low emission levels. Unfortunately, when converting to CNG, engines usually suffer from reduced power and limited engine speed. These are due to volumetric loss and slower flame speed. Direct injection (DI) can mitigate these problems by injecting CNG after the intake valve closes, thus increasing volumetric efficiency. In addition, the high pressure gas jet can enhance the turbulence in the cylinder which is beneficial to the mixing and burning. However, conversion to direct fuel injection (DFI) requires a costly modification to the cylinder head to accommodate the direct injector and also can involve piston crown adjustment. This paper discusses a new alternative to converting to DFI using a device called Spark Plug Fuel Injector (SPFI). It is a combination of a fuel injector and a spark plug which fits into the engine block through the existing spark plug hole. With SPFI, conversion to DFI is simple, cheap and requires no modification to the original structure of the engine, except minor calibration to the ECU. The SPFI was installed on a 0.5 liter single cylinder engine and run at 1100 rpm, WOT and stoichiometric air-fuel ratio. Results showed that engine running with SPFI gained the advantage of significant increased volumetric efficiency, faster burning rate, higher output power and improved fuel conversion efficiency compared to port injection operation in the expense of reduced effective compression ratio.

Comparing the Effects of Hydrogen Addition on Performance and Exhaust Emission in a Spark Ignition Fueled with Gasoline and CNG

With the concern of the foreseen reduction in fossil fuel resources and stringent environmental constraints, the demand of improving internal combustion (IC) engine efficiency and emissions has become more and more pressing. Hydrogen has been proved to be a promising renewable energy that can be used on IC engines. In this paper an evaluation and assessment of numerical and experimental investigations on performance and exhaust emission with hydrogen added to a spark ignited gasoline engine fuelled with gasoline and natural gas are performed. The experimental results showed that thermal efficiency, combustion performance, NOx emissions improved with the increase of hydrogen addition level. The HC and CO emissions first decrease with the increasing hydrogen enrichment level, but when hydrogen energy fraction exceeds 12.44%, it begins to increase again at idle and stoichiometric conditions. Numerical results showed that there is an increase in engine efficiency only if Maximum Brake Torque (MBT) spark advance is used for each fuel. Moreover, an economic analysis has been carried out to determine the optimum percentage of hydrogen in such blends, showing percent increments by using these fuels about between 10 and 34%.

Detection of Defects in Natural Composite Materials Using Thermal Imaging Technique

Abstract Nowadays, non-destructive testing (NDT) is frequently replacing destructive techniques in determining the properties of materials. In this study, defects in Kenaf/epoxy composite materials were detected using an inyyfrared (IR) thermal imaging technique, which is one of the most practical non-destructive techniques currently applied. Kenaf bast fibres were used to fabricate composite materials with epoxy resin as a binding material. The composites were manufactured using a manual lay-up process. The thermography analysis of the IR camera were verified by optical microscope and scanning electron microscope (SEM) investigations. The defect detection accuracy of this technology is 95%.

Enhancement of Integrated Solar Collector with Spherical Capsules PCM Affected by Additive Aluminum Powder

This research aims to study, analyze, design, and construct a solar air heater combined with an appropriate phase-change material (PCM) unit. This solar air heater is analogous to a collector integrating a thermal storage unit and a solar thermal collector. In this study, such single-pass solar air heater in amalgamation with PCM was constructed, and several tests were conducted on this device. During the experiments for the solar collector with PCM (spherical capsules), the temperature varied between 30°C and 35°C, and the air mass flow rate ranged between 0.03 and 0.09 kg/s. Results confirmed the predicted experimental findings. With the use of paraffin wax-aluminum composite, the thermal storage efficiency of the constructed solar air heater reached a maximum value of 71% at 0.05 kg/s mass flow rate, its charging time decreased by almost 70%, and its cooling rate increased. The thermal storage efficiency of the compound composite was 76.8% at 0.07 kg/s mass flow rate. The results also indicated that the time of charging decreased by almost 60% with the use of paraffin wax-aluminum composite.

The Effect of Injection Timings on Performance and Emissions of Compressed Natural-Gas Direct Injection Engine

This experimental part investigates the effect of injection timing on performance and emissions of homogenous mixture compressed natural-gas direct injection. The engine of 1.6 L capacity, 4 cylinders, spark ignition, and compression ratio of 14 was used. Performance and emission were recorded under wide-open throttle using an engine control system (Rotronics) and the portable exhaust gas analyser (Kane). The engine was tested at speed ranging from 1500 revolutions per minute (RPM) to 4000 RPM with 500 RPM increments. The engine control unit (ECU) was modified using Motec 800. The injection timings investigated were at the end of injection (EOI) 120 bTDC, 180 bTDC, 300 bTDC, and 360 bTDC. Results show high brake power, torque, and BMEP with 120 as compared with the other injection timings. At 4000 RPM the power, torque, and BMEP with 120 were 5% compared to that with 180. Furthermore, it shows low BSFC and high fuel conversion efficiency with 120. With 360, the engine produced less CO and CO2 at higher speeds.

ENHANCEMENT OF HEAT TRANSFER COEFFICIENT MULTI-METALLIC NANOFLUID WITH ANFIS MODELING FOR THERMOPHYSICAL PROPERTIES

Cu and Zn-water nanofluid is a suspension of the Cu and Zn nanoparticles with the size 50 nm in the water base fluid for different volume fractions to enhance its Thermophysical properties. The determination and measuring the enhancement of Thermophysical properties depends on many limitations. Nanoparticles were suspended in a base fluid to prepare a nanofluid. A coated transient hot wire apparatus was calibrated after the building of the all systems. The vibro-viscometer was used to measure the dynamic viscosity. The measured dynamic viscosity and thermal conductivity with all parameters affected on the measurements such as base fluids thermal conductivity, volume factions, and the temperatures of the base fluid were used as input to the Artificial Neural Fuzzy inference system to modeling both dynamic viscosity and thermal conductivity of the nanofluids. Then, the ANFIS modeling equations were used to calculate the enhancement in heat transfer coefficient using CFD software. The heat transfer coefficient was determined for flowing flow in a circular pipe at constant heat flux. It was found that the thermal conductivity of the nanofluid was highly affected by the volume fraction of nanoparticles. A comparison of the thermal conductivity ratio for different volume fractions was undertaken. The heat transfer coefficient of nanofluid was found to be higher than its base fluid. Comparisons of convective heat transfer coefficients for Cu and Zn nanofluids with the other correlation for the nanofluids heat transfer enhancement are presented. Moreover, the flow demonstrates anomalous enhancement in heat transfer nanofluids.

Car Body and Chassis Development of UKM CARevo for Perodua Eco-Challenge 2011

This paper presents the development of the UKM Perodua Eco-Challenge vehicle, CARevo in terms of aesthetic design, novel fabrication of car body and superior chassis design. The objective of the competition was to develop a fuel efficient car which was competent to travel the longest distance using 0.5 liter of RON95 fuel with some rules and regulation verified by the Perodua to be followed. The UKM CARevo was powered by a 660cc fuel injection engine with manual 5-speed transmission with the total of 3450 mm, 1500 mm and 1106 mm for its length, wide and height. Several design such as space frame chassis design, composite bodywork result from fiberglass with resin, aerodynamic design of car body and are the key features that is discussed in this paper.

Underhood Fluid Flow and Thermal Analysis for Passenger Vehicle

The present paper reports a simulation study of the fluid flow and thermal phenomena in the passenger vehicle underhood compartment by analysing velocity magnitude, temperature, radiator heat transfer rate and heat transfer efficiency. Analyses are carried out on a half cut passenger vehicle sample model by using commercial computational fluid dynamics (CFD) software, Star CCM+. Total volume meshes of the model are 24 451 759 cells, and the speed of the car is 0.036, 40, 70, 110, 130 and 213 km/h. Investigation are performed for three dimensional conditions, steady state gas with segregated flow, constant density, turbulence flow, with the use of the Reynolds-Averaged Navier-Stokes model and the K-Epsilon turbulence model. In the thermal analysis, particular attention is given to find hot spot locations under the hood. . High temperature region is observed at the right side of the hood (from the top of view) due primary heat sources from the engine. An air intake at hood is introduced in order to facilitate the airflow to engine room and to remove hot spot to the atmosphere. It is shown that the underhood average temperature decreases by 26.2% and the average airflow velocity at section plane of the centreline increases by 14.5% by adding this air intake.