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In this present study, periodically positioned triangular shaped ribs having a round top corner at the bottom with groove positioned on the top side of the plate is analyzed at laminar flow conditions. The numerical results obtained for the heated plate with rib-groove geometry are compared with that of the flat plate kept under similar conditions. At lower air flow velocity, the Nusselt number of the flat plate improved from 400 to 1407 with the provision of triangular ribs-groove arrangement in it. Similarly, it improved from 850 to 6420 at higher air flow velocity with triangular ribs-groove arrangement. Higher Nusselt number values leads to a higher heat transfer coefficient values. Therefore, the triangular ribs-groove geometry gives an enhanced rate of heat transfer with minimum pressure drop. The study shows that irrespective of geometry, the rate of heat transfer is relying on fluid (air in this present case) flow velocity over heated plate, fluid flow contact with the heated plate and surface area of the heated plate.

Purpose This paper aims to compare the performance, emission and combustion characteristics of E20 biodiesel with diesel-water emulsion and eucalyptus water emulsion. Design/methodology/approach This research expounds the trans-esterification process apparently. Various biodiesel blends were made to go through the trans-esterification process to make it suitable for feeding them into the low heat rejection (LHR) engine. E20 biodiesel – 20% of eucalyptus oil by volume with diesel was chosen to carry out the research as it was found to be the best blend with diesel. The volume of water content in diesel water emulsions was varied by 5, 10 and 15% in DWM1 (Diesel Water Mixture1), DWM2 (Diesel Water Mixture2) and DWM3 (Diesel Water Mixture3), respectively. Similarly, the volume of water content in eucalyptus water emulsions was varied with emulsification ratio of E20 biodiesel. Partially stabilized zirconia was coated over top surface of the piston and valve facing of the LHR engine. Findings From the researches carried out, DWM3 (Diesel Water Mixture3) was found to be superior when compared with other diesel-water emulsions in LHR engine. The overall efficiency was found to be higher for EWM3 than other biofuels tested the in LHR engine. Originality/value This investigational experiment can be further extended to multi-cylinder engine and to improve the cetane number, Di ethyl ester (DEE) fuel additives can be added.

Performance of Savonius vertical axis wind turbine can be increased by incorporating end plates, deflector plates, curtains, shielding, guide vanes etc in their designs. However, multi-staging of conventional VAWT rotors could be a viable proposition in terms of improvement of power output. Numerical analysis involving three bucket Savonius turbines are not available in the open domain. The objective of the present numerical investigation is to study the flow and pressure distribution patterns in the two-stage three bucket Savonius vertical axis wind turbine. The performance of SVAWT is based on the maximum difference in pressure between the upstream and downstream of the turbine. Velocity vector plots shows the energy transfer occurring from the fluid to the blade within the flow field in the upstream and downstream of the turbine. The trail of the wake left behind the SVAWT was observed in the downstream of the turbine. It is observed that eddies in large scale are present around the turbine flow field.

The study aimed to compare the performance of R1234yf and R134a refrigeration systems based on Coefficient of Performance (COP) vs. time, refrigeration effect vs. time, compressor work vs. time and discharge temperature vs. time. The R1234yf has been proposed as the better alternative to R134a. However, the results suggest that both systems have advantages and disadvantages, making it difficult to justify the suitability of R1234yf over R134a. The performances were analysed at different heat loads ranging from 0W, 600W, 800W, 1000W and 1200W. The results show that highest performance was recorded at 1200W heat load. In addition, there were significant differences between the two systems. The discharge temperature for R1234yf was about 9% higher than R134a. Similarly, R134a performed better regarding compressor work vs. time. Respectively, R134a performed better in COP vs. time and refrigeration effects vs. time. There was a significant difference in the refrigeration effects and COP for the two systems. Also, the differences in COP and refrigeration effects increased with the heat loads. The lower COP in the R1234yf suggested that it could consume a lot of energy and thus making it unsustainable. The study concluded that the efficiency of the two systems varies; therefore, having a system that is a mixture of the two can help improve refrigeration efficiency and reduce pollution. However, further exploration of the two systems is needed to determine their efficiencies under different conditions before making a conclusive recommendation. The selected system should have minimal effects on the environment and produce the highest refrigeration effects within a short time.

Aluminium metal matrix composites are generally produced employing stir casting technique. The effect of stirrer blade on stir casting of aluminium composite with 12 wt% SiC, 4 wt% magnesium and 2 wt% copper was observed. The composites were prepared with 6061 base metal using three different design of stirrer blade which created different vortex fluid flow while stirring. Due to high density of SiC particles, it tries to settle in lower part of the molten metal matrix. Hence change in vortex technique by stirrer design modification can have influence on the mechanical and microstructure behaviour of the composites. The aluminium SiC composite are evaluated by mechanical properties and microstructure analysis based on stirrer blade design used while stir casting. The change in blade stirrer shows variation in testing tensile strength and hardness. The optical microstructure and SEM images were observed to analyze the cast structure and reinforcement distribution in the composites. The SiC particles were appeared to distribute along the grain boundaries of the composite and also cast defects were observed. Composite prepared with alternate peddle blade produced best mechanical properties.

An experimental work is carried out on automobile air conditioning test setup. Pure refrigerant R134a is used initially and its thermodynamic characteristics were analysed and then it is compared with the R134a CuO nanorefrigerant. The experiment is conducted by heating the cabin to a temperature of 50ºC by using electric heaters. Temperature uniformity inside the cabin is maintained and by varying the evaporator airflow rates at various compressor speeds. The difference in suction pressure between low, medium and high speed is very small. The discharge temperature of R134a at low speed Td L is 72ºC at 850 rpm, the discharge temperature at the same speed for nanoparticles is 63.7ºC and 58.3ºC. The coefficient of performance of nanorefrigerant is increased by 17% at low speed and 20% at medium speed and 34% at high speed at 1600 rpm when compared with pure R134a.

Because of its superior thermal properties and multiple prospective uses, nanofluids had sparked the interest of investigators. Addition of nanoparticles to refrigerants and lubricants improves thermal characteristics and lowers power wastage. In this paper R134a refrigerant is added with nanoparticle CuO in the concentration of 0.1%v to 0.5%v and its performance is evaluated. The suction pressure of R134a at 32C is 9% higher than R134a+0.1nm and 17% higher than R13a+0.5nm.The discharge temperature of R134a is more than nano refrigerant. Due to this, the power consumption of R134a is more than nano refrigerant. By adding nanoparticles to refrigerant, the power consumption at 28C is 23% less than R134a which shows nanoparticles works normally when mixed with R134a. Due to high thermal conductivity of nanoparticles, the coefficient of performance of R134a is 35% less than R134a+0.1nm and 41% less than R134a+0.5nm.

Desires of materials with lesser weight made wide spread use of alloys based on magnesium in automobiles and aerospace applications in the view of overcoming lower strength of these materials when compared to aluminium, these materials are added with some hard materials like ceramics, metal oxides or natural remaining as a reinforcing phase with a proof for improvement in properties. In the present work AZ31 alloy is strengthened by adding Coconut Shell Ash particles (CSAp) by means of powder metallurgy and the examinations like microstructure, micro hardness, compressive strength and wear are conducted. The ash particles content as reinforcement has not imparted larger variation in the strength and hardness, the wear resistance is increased with the addition of ash particles and the addition of CSAp exceeding 3% leads to crack.

Magnesium based alloys are some of the widely used light weight metals in vehicles and aerospace industries, but these materials are having low strength to weight ratio when compared to aluminium. To enhance their strength to weight ratio, some ceramic materials like carbides and oxides of metals are added as reinforcements. In this work, AZ31 magnesium alloy is reinforced with 1%, 2% and 3% of Groundnut Shell Ash particles (GSAp) through powder metallurgy. Micro hardness and compressive strength are studied and the microstructural analysis is also done. The addition of ash particles as reinforcement has not shown much variation in the strength and hardness. The addition of ash particles of more than 3% leads to crack. The addition of ash particles increases the rate of corrosion.

This paper presents the numerical studies of an irregular surface – a circular dimpled surface with different patterns of dimple arrangement (i.e., inline and staggered) and to identify the one that gives maximum heat transfer rate under laminar flow conditions. The comparative studies are made with a flat plate. The studies are carried out with inlet velocities 1 m/s and 49 m/s at laminar flow regimes. The investigations revealed that heat transfer rate increases as the air flow velocity increases and it decreases as the air flow velocity is decreased. Also, air flow contact with heated plate plays a vital role in heat transfer rate. Based on the study, it is concluded that the heat transfer rate depends on the surface area, air flow velocity and the air flow contact with the heated plate. At air velocities 1 m/s and 49 m/s, the heat transfer rate is highest for the circular dimple with staggered pattern under the laminar flow conditions.