Synthesis and characterization of supported sugar catalyst by dip coating method

Sugar catalyst is a novel solid acid catalyst with reactivity comparable to that of sulphuric acid in biodiesel production. However, the fine powder form of sugar catalyst with the non-porous structure might cause large pressure drop in a packed bed reactor due to low bed porosity, affecting the reaction conversion especially in gas phase reaction. Furthermore, higher pressure drop requires higher electrical energy to drive the fluid through. Increasing the particle size is anticipated to be able to overcome the pressure drop matter. Hence, a deposition of sugar catalyst on larger particle materials was studied. Three types of materials were used for this investigation namely aluminum, silica and clay. The deposition was done via dip-coating method. The materials were characterized for their total acidity, thermal stability, functional groups, surface area, and element composition. The total acidity for SCDCAl, SCDCSi, and SCDCCl were 0.9 mmol/g, 0.2 mmol/g, and 0.4 mmol/g, respectively. The ratio of char deposited on SCDCAl, SCDCSi and SCDCCl were 0.9 g of support/g of carbon, 0.040 g of support/g of carbon, and 0.014 g of support/g of carbon respectively. FTIR and EDX analyses were carried out to determine the presence of active sites of the catalysis by identifying the functional groups such as –COOH, -OH, -SO3H. The results showed that –SO3H was detected on the surface of synthesized catalysts, except for SCDCC1.The pore size of SCDCAl, SCDCSi and SCDCCl were classified as macropores because the average diameter were greater than 50nm.. The catalysts were stable up to 400 °C. The results showed that the dip- coating method could deposit sugar catalyst on aluminum, silica, and clay at low total acidity concentration

Performance of the direct evaporative cooler (DEC) operating in a hot and humid region of Sabah Malaysia

In the last decade, energy consumption for air conditioning applications has been dramatically rising because of the growing global population and increasing comfort demand. Consequently, direct evaporative cooling (DEC) technology is emerging as an alternative to vapour compression air conditioners due to its lower environmental impacts, less energy consumption, and lower operating costs. This paper aims to evaluate the efficiency of direct evaporators in hot, humid environments like Malaysia. Inlet and outlet temperatures, saturation efficiency, cooling capability, and feasibility index are all used to evaluate results. The cooling medium was a rectangular honeycomb cooling pad with a length of 34 cm, a width of 25 cm, and a thickness of 3.5 cm. The temperature and humidity during the analysis were between 31 and 35oC and 47.5 and 65.5%, respectively. The results showed that the air output temperature varied between 28.4°C and 31.7°C, while the cooling capacity between 0.29 kW and 0.64 kW as well as the saturation efficiency between 46% to 80% could be achieved. The result also showed a feasibility index between 19 to 24. Due to the high value of the feasibility index, this evaporative cooling does not work well in the territory of Malaysia. A direct evaporative cooler may be made to work in humid places like Malaysia by drying the air before the evaporative process using the desiccant dehumidification concept

Performance analysis of a solar heat collector through experimental and CFD investigation

In order to attain maximum efficiency in a solar drying system, continuous effort is made to the key component of solar dryer – solar heat collector (SHC). This research aimed to evaluate the thermal performance of SHC with different flow configuration in the air passage, namely single-pass (S-SHC) and multiple-pass (M-SHC), under natural convection (average air velocity = 0.2 m/s). In order to study the flow and heat transfer characteristics across the SHC, performance analysis was carried out by Computational Fluid Dynamic (CFD) simulation and later validated by experimental results. From the simulation model, the collector outlet temperature and efficiency of M-SHC at maximum solar radiation were 67.4 °C and 10.04%, respectively with percentage error of 8.6% and 17.79% to the experimental results. The presence of recirculation region indicated extended drying air residence time in the M-SHC, resulting in high temperature growth from 8.8% to 12.1% across the air passage compared to S-SHC. In addition, heat transfer enhancement in M-SHC was achieved by compensating radiation heat loss observed in S-SHC through the modification of airflow configuration. Both experimental and theoretical analysis in this study showed that the proposed enhancement significantly improved the performance of SHC having air passage made from recycled aluminum cans

Reciprocating wear behavior of mild steel carburized using Na₂CO₃-NaCl

The surface of the mild steel carburized using Na2CO3–NaCl was dominated by retained austenite. Towards the core, the amount of austenite reduced while the amount of martensite increased. Increasing the duration of the carburization resulted in higher peak hardness and case depth. It also increased the amount of cementite in the grain boundaries and the austenite grains size, rendering the steel more susceptible to cracking. The superior wear resistance of the martensite, as compared to the austenite, could be attributed to its high cracking and adhesive wear resistance owing to its high hardness and tendency to form oxides. The friction was governed by the wear mechanism and the type of microstructure at the worn scar sliding on the carbide ball

Merekabentuk dan menganalisa sistem penyejukan permukaan bagi meningkatkan kecekapan fotovoltaik

Di samping dapat menjanakan tenaga elektrik, solar fotovoltaik (‘Phtovoltaic’ - PV) mempunyai potensi besar sebagai sumber tenaga boleh diperbaharui. Semasa solar PV berada pada suhu yang optimum, kecekapan solar PV menukarkan tenaga haba kepada tenaga elektrik berlaku secara konsisten. Namun, kecekapannya akan berkurang sekiranya suhu panel PV meningkat. Satu kajian dijalankan bagi meningkatkan kecekapan solar PV dengan merekabentuk sistem penyejukan pada solar PV yang dinamakan Hibrid Fotovoltaik/Termal (PV/T) sistem solar. Objektif rekabentuk ini ialah bagi menyejukkan panel PV dan mengkaji kesan sistem penyejukan ke atas prestasi solar PV di mana air dialirkan di permukaan atas modul PV untuk menyejukkannya. Dengan sistem ini, tenaga elektrik dan tenaga haba dapat dijanakan secara serentak. Sistem ini diuji di bawah pancaran sinaran matahari (radiasi) pada keamatan purata 676.28 W/m2. Dua set PV diuji serentak iaitu panel PV tanpa penyejuk dan panel PV terma dengan aliran air bagi membandingkan kecekapan dan penghasilan kuasa keluaran maksimum. Hasil daripada ujikaji diplotkan pada graf dan hasil penelitian mendapati kecekapan PV dapat ditingkatkan sebanyak 23.07% dengan menggunakan sistem penyejukan aliran air. Kuasa keluaranmaksimum oleh panel fotovoltaik terma aliran air dapat ditingkatkan sebanyak 11.99 W berbanding dengan panel fotovolta tanpa penyejuk. Suhu purata pada permukaan atas panel fotovolta dapat diturunkan sebanyak 28.42%. Faktor pengisi, FF yang dikira untuk PV tersebut ialah 0.78. Prestasi panel PV tersebut berada dalam keadaan memuaskan kerana faktor pengisi piawai fotovolta adalah di antara 0.7 dan 0.85. Beberapa cadangan penambahbaikan telah dikemukan pada pengakhiran laporan penyelidikan ini. Di sini boleh disimpulkan bahawa kecekapan solar PV menukarkan tenaga haba kepada tenaga elektrik berada pada tahap yang baik sekiranya solar PV mempunyai suhu yang rendah dan begitu juga sebaliknya

The effect of air velocity on the performance of the direct evaporative cooling system

This experimental study aimed to determine the effect of airflow velocity on the performance of a direct evaporative cooling system. Rectangular-shaped honeycomb cooling pads with a length of 34 cm, a width of 25 cm, and a thickness of 3.5 cm are used as cooling media. The main parameters of the study are low air velocity (2.3 ms−1), medium (3.2 ms−1), and high velocity (3.7 ms−1). The data collected include dry bulb temperature, wet bulb temperature, output air temperature, input and output air velocity, input and output humidity, and solar radiation. These data are used to determine saturation efficiency, cooling capacity, temperature decreases, and feasibility index. The experimental results are presented in the form of tables and graphs and analysed based on existing theories. The results showed that the evaporative cooling system could produce output temperatures up to 27.5°C with input 31.4°C at low airspeed, 27.97°C with input 31.47°C at medium speed, and 27.7°C with input 31.30°C at high air speed. It was concluded that a low airflow rate would add to the cooling efficiency, and the higher the airflow rate, the lower the cooling efficiency. The results showed that evaporative cooling is achievable with a feasibility index of 19.89 ≤ F*≤ 20.67. The results also affirmed that cooling capability is higher where the feasibility indexes are comparatively low

Plastic straining and concomitant microstructure recrystallization of Ni-Cu alloy in the undercooled condition

Microstructure and microtexture of rapidly solidified undercooled Ni-Cu alloys were investigated. The characteristic undercooling of Ni80Cu20 alloy was determined as 45K, 90K and 160K. Dendrite deformation due to rapid solidification led to strong deformation microtexture. Due to recrystallization upon annealing after recalescence, many subgrains were formed in the microstructure. Further, annealing the quenched alloy at 900℃, new microtextures and subgrains were formed, which was due to recrystallization and dislocation network rearrangement. The results of comparative experiment proved the recrystallization mechanism of the microstructure refinement in the non-equilibrium solidification structure of the undercooled binary alloy

Structural Analysis of Laterally Aerated Moving Bed (LAMB) Dryer by using Robot Structural Analysis (RSA) Professional 2018

The structural design of Laterally Aerated Moving Bed (LAMB) dryer is subjected to buckling effects due to the loads of the paddy bed, self-weight and static pressures by the air blower to overcome the air resistance in the paddy bed, perforated tube and the bed chamber perforated wall. The dryer structural type is a spatial complex structure where the boundary conditions are not very clear, thus the Robot Structural Analysis (RSA) Professional 2018 is used to determine the critical values of loads when the overall structural elements instability occurred to form buckling. The RSA analysed the global buckling of a structure to find the critical coefficient value to be multiply with the case load for the critical buckling load determination. Three different model of dryer structural designs were prepared and analysed by RSA to find the buckling critical coefficient values (αcr), displacements (mm), reactions (N) and moments (Nm). All structural design model was designed with similar type of materials, different sizes and geometrical arrangements. The RSA results within the three structural design models were compared. The structural design model with the best buckling coefficient values with minimum displacement had been selected for the actual LAMB dryer structural construction

Production of carbon via Electrochemical conversion of CO2 in carbonate based Molten Salt

Carbon was successfully deposited on AISI 304 stainless steel rod cathode through electrolysis process in three molten salt mixtures, namely K2CO3-Li2CO3 (mole ratio: 1:1), CaCO3-Li2CO3-LiCl (mole ratio 0.09:0.28:0.63) and CaCO3-CaCl2-KCl-LiCl (mole ratio: 0.13:0.31:0.10:0.45), under CO2 atmospheres as continuous source of carbon. The process were carried out for 1 hour at temperature range 545–585°C and electrolysis voltage of 4.0V to drive the deposition of carbon through electrochemical conversion. EDX analysis on deposited products shown carbon as dominant element (89-98%). SEM revealed carbon with Flakes and grapes aggregation shapes for different salt mixtures. The achieved current efficiency of 83.8%, 80.46% and 92.41% were found in the respective salt mixtures, and energy consumption promotes several ways for efficiency improvement on the electrochemical conversion of CO2

Performance enhancement of a baffle-type solar heat collector through CDF simulation study

The application of solar energy conversion has been extensively utilized as an alternative energy source to generate heat. This approach would be a step towards sustainable energy development particularly in the manufacturing industry with energy-intensive process. In this paper, thermal enhancement on the key component of a solar energy device – solar heat collector (SHC), has been evaluated by proposing a baffle-type SHC with various geometric configuration in the air passage namely longitudinal baffle and transversal baffle. The performance of SHC is evaluated in term of efficiency, temperature distribution, airflow pattern and pressure drop across the collector outlet through Computational Fluid Dynamic (CFD) investigation. It was observed that maximum collector efficiency was achieved in the Longitudinal-SHC (L-SHC), with a value of 46.2 % followed by Transversal-SHC (T-SHC) and without baffles. Maximum drying temperature at the collector outlet was 332.43 K for L-SHC, showing temperature rise of 0.35 % and 4.21 % from T-SHC and without baffles, respectively. The velocity vector indicated that turbulence flow was created in the T-SHC which consequently improved the heat transfer. Whereas in L-SHC, enhancement was achieved through the prolonged heating time in the passage. Considering the thermo-hydraulic performance factor evaluated, these enhancement features had diminished the effect of pressure drop