Characterization of a short microchannel device for surface cooling

The development of microchannel devices is expanded widely due to the demand for small scale electronic devices. In order to increase the capability of the electronic devices, high heat transfer performance with low energy consumption cooler is required. This study is focusing on the characterization of new short microchannel for surface cooling purposes with the channel dimension of 800 μm wide, 200 μm length, 100 μm depth and total area of one cm2. Deionized water is used as the transport medium. A map of microchannel characteristics is plotted in term of average thermal resistance, pumping power, power supplied and mass flow rate of the fluid. From this mapping, it is shown that the thermal resistance decreased as the pumping power decreased. The results also show that the heat flux has not affected the value of pumping power. The different for each heat flux value is ranged between 3 to 4 %. The mapping presented in this study provides potential characteristics information and conditions to apply this particular microchannel for surface cooling

Flame propagation and burning rates of methane-air mixtures using schlieren photography

Different methodology have been shown to produce different results for Markstein length and laminar burning velocity of methane-air mixture. This study attempts to determine the aforesaid parameters using the newly developed closed vessel combustion chamber with Schlieren photography. Markstein length and burning rate of methane-air mixture was determined under the initial pressure of 1 atm, temperature range of 298-302K and equivalence ratio range of 0.7-1.3. Experiments were performed in a centrally ignited 29.16L cylindrical constant volume combustion chamber. Ignition energy was set at 25mJ for each experiment. The images of spherically expanding flame were recorded using Schlieren photography technique at a speed of 2000 frame per second. Analysis of the flame area yield flame radii from which the flame speed and stretch rate could be obtained. These parameters would allow the determination of Markstein length and burning rate of the flame. Results show that Markstein length magnitude increases proportionally with equivalence ratio with a magnitude ranging from 0.125cm to 0.245cm. Maximum burning rate occurs at equivalence ratio of 1.1 with a magnitude of 0.366 m/s. Flame of each equivalence ratio also exhibits fluctuation arising from acoustic disturbance. This disturbance becomes more apparent at higher equivalence ratio

Detection of Coalescent Acute Mastoiditis on MRI in Comparison with CT

Purpose Current imaging standard for acute mastoiditis (AM) is contrast-enhanced computed tomography (CT), revealing inflammation-induced bone destruction, whereas magnetic resonance imaging (MRI) outperforms CT in detecting intracranial infection. Our aim was to compare the diagnostic performance of MRI with CT in detecting coalescent AM and see to which extent MRI alone would suffice to diagnose or rule out this condition. Methods The MR images of 32 patients with AM were retrospectively analyzed. Bone destruction was evaluated from T2 turbo spin echo (TSE) and T1 Gd magnetization-prepared rapid acquisition with gradient echo (MPRAGE) images. Intramastoid enhancement and diffusion restriction were evaluated subjectively and intramastoid apparent diffusion coefficient (ADC) values were measured. The MRI findings were compared with contrast-enhanced CT findings of the same patients within 48 & x202f;h of the MR scan. Results Depending on the anatomical subsite, MRI detected definite bone defects with a sensitivity of 100% and a specificity of 54-82%. Exception was the inner cortical table where sensitivity was only 14% and specificity was 76%. Sensitivity for general coalescent mastoiditis remained 100% due to multiple coexisting lesions. The absence of intense enhancement and non-restricted diffusion had a high negative predictive value for coalescent mastoiditis: an intramastoid ADC above 1.2 & x202f;x 10(-3)& x202f;mm(2)/s excluded coalescent mastoiditis with a negative predictive value of 92%. Conclusion The MRI did not miss coalescent mastoiditis but was inferior to CT in direct estimation of bone defects. When enhancement and diffusion characteristics are also considered, MRI enables dividing patients into low, intermediate and high-risk categories with respect to coalescent mastoiditis, where only the intermediate risk group is likely to benefit from additional CT.Peer reviewe

Aluminum toxicity in acid sulfate soil alleviated with biogenic liming composites of blood cockle shell and palm kernel shell

Low crop yield from acid sulfate soil was caused by high concentrations of aluminum and iron in soil. Aluminum ion which cause root injury at root region inhibits the uptake of the nutrients by the root and lead to nutrient deficiency. Ground magnesium limestones can beapplied to overcome this problem but incurred more production cost. Biogenic liming agent from blood cockle shell and/or palm kernel shell are more cost effective and provide the essential element i.e. calcium. This study evaluate phase-association of Al in acid sulfate soil remediated using biogenic composites liming material using selective sequential extraction analysis. Biogenic liming composites were characterized for pH, proximate analysis and elemental composition. High ratio of BCS in composite retained Al in the residual form about 91.33%. Amelioration of soil with 100% PKS did not give significant reduction of the exchangeable Al.Keywords: soil remediation; phytotoxicity; abiotic stress; calcination; alkalinity

Simulation-based Study of Capacitance Values Affected by Various Dielectric Materials and Distances for Low Power Wireless Power Transfer System

Capacitive Power Transfer (CPT) system is nowadays getting better attention by some of the researchers who are focusing on wireless power transfer field. This is because of the simplicity, small size, and better reaction towards EMI characteristics of the method. Furthermore, the efficiency of the CPT system is greatly influenced by the coupling capacitances which are varied by distances and permittivity values. Thus, this paper attempts to converge into the effect of several dielectric materials towards capacitance values and also the effect of the capacitive plates’ distances towards the output power. By using Class E circuit configuration and MATLAB Simulink as the simulation software, the results are then explained graphically. From those simulations, the work achieved 90.7% as highest efficiency as compared to the theoretical values

Flameless combustion of propane-air mixture in a laboratory scale burner

In this work, the operational and emission of the laboratory scale burner under the flameless combustion regime using propane is examined. The combustor is equipped with parallel jet burner systems with controlled gas fuel and oxidizer. The combustor consists of several ports that are used to measure temperature variation and analyze gas emission. The atmospheric air was heated by flowing it inside the chamber until the air temperature increased to approximately the auto ignition temperature of the fuel. The furnace under investigation has successfully produced temperature uniformity ratios that are one order of magnitude less than such of the visible flame mode. It is observed that, flameless combustion can be achieved by using propane as a fuel. The value of NOX emission during flameless combustion was reduced of about 70% in average compared to the conventional flame at certain range of equivalence ratio

Carbonization cbn550 effect on tensile properties of composite for marine structure application

The composites have gained commercial success, where strength, stiffness, durability and light weight are required as well as retardant capacity. Improvement has been made such new series of resin such as vinyl ester and epoxy type[1, 2]. However 95% of pleasure vessels and boats under 60 feet today are still made with polyester resin. The main consideration for most composite builders is cost, with performance and more importantly value for money often being a secondary consideration. Therefore, this study investigate the tensile - mechanical effects of mixing carbon black CBN550 with wax and non-wax type resin and manufactured according to fiber orientation of [0°] and [90°]. The 10% CBN550 exhibit highest reading for stress under [90°] fiber orientation and the lowest reading when arranged at [0°] fiber orientation. The preliminary study on CBN550 flammability has indicated the suitability for this study to pursue in. The structural composites samples of 1000 mm by 1000 mm prepared which consist of 10 of composite mats layer in combination of CSM 450 g/m2 and Woven Roving 600 g/m2. The carbon black (CB) volume fraction range from/with 0% to 20% volume fractions. Optical observation revealed the most suitable fraction of CBN550 in wax polyester resin is at 10% and non-wax polyester resin is also at 10%. The fire resistance behaviour of this CBN550 - CSM 450 g/m2 - Woven Roving 600 g/m2 composite (polyester wax) and polyester non wax was investigated previously as per[3]. This results are in line with the finding of the maximum load where the highest reading was recorded by the 10%CBN550 specimen. This study showed that the introduction of carbon black into the resin mixture helps reinforce the matrix materials. The results suggested that CBN550 mixture should attend to next level of experiment investigation such as oxygen content, TG value, microstructure and other mechanical destructive test. The CBN550 could be a suitable candidate for fire retardance application in marine composite structure

The effect of N550 carbon black in polyester resin for fire-retardant application in marine composite

This paper presents the experimental investigation on the influence of N550 carbon black (CBN550) series in polyester resin (wax and non -wax type). The CBN550 was added into polyester resin at different weight percentages with a curing agent. The investigation is mainlyto study the effect on fire retardance application in marine composite structure. The fire-resistant structural composites samples of 1000 mm by 1000 mm prepared which consist of 10 of composite mats layer in combination of CSM 450 g/m2 and Woven Roving 600 g/m2. The carbon black (CB) volume fraction range from/with 0% to 20% volume fractions. Optical observation revealed the most suitable fraction of CBN550 in wax polyester resin is at 10% and non-wax polyester resin is also at 10%. The fire resistance behavior of this CBN550 - CSM 450 g/m2 - Woven Roving 600 g/m2 composite (polyester wax) and polyester non wax was investigated by Fire Test Procedure Code-Resolution A.653 [1]. Though smaller filler size escalates the rheological behavior and values outstandingly at initial reading compare to large particles but it slow down the curing processdue to its small particle size, large surface area and high dispersion rate. Experimental data showed the retardance level has been increased up to 56.66% in non-wax type polyester resin (10%/CBN550) and 30.14% in wax polyester resin (10%/CBN550). The improvement in fire resistance points are due to the presence of CBN550 which acts as a positive additive in both polyester resin wax and non-wax. Filling CBN550 in polyester resin also reduces the cost of theend products.The preliminary results suggested that CBN550should attend to next level of experiment investigation such as oxygen content, TG value, microstructure as well as mechanical destructive test. The CBN550 could be a suitable candidate for fire retardance application in marine composite structure.In conclusion, crystallinity of polyester resin increases with additional of CB particles