bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of secondary injection on the performance of over-expanded single expansion ramp nozzle
Authors: Shanmugaraj Gopinath , Muruga Lal Jeyan J V , Singh Vijay Kumar
Published: March 2020

Scramjets with Single expansion ramp nozzle (SERN) is one of the most promising candidates for an airframe integrated hypersonic vehicle propulsion system. So, studying the performance of the SERN at various flight conditions is very important to improve the overall performance of the propulsion system. The main problem with a SERN is, it tends to exhibit poor performance characteristics at the over-expanded or off-design operating conditions. So, to improve the performance of the SERN at off-design conditions, the present numerical study focuses on using various secondary injection techniques on the cowl and ramp surfaces. The freestream Mach number considered for the current study is 3, and the corresponding nozzle pressure ratio (NPR) for the SERN is 20. The effects of injection pressure, location, and angle on the axial thrust force and normal force are parametrically studied. It is found that the introduction of secondary injection significantly affects the pressure distribution over the cowl and ramp surface. This change in pressure distribution directly reflects on the magnitude of the normal force and axial thrust force generated by the SERN. The secondary injection also influences the shock pattern of the main nozzle flow.
A review on Aerodynamic performance of NACA Airfoil for various Reynolds number
Authors: Mathew Bilji C , Thakan Amit , Muruga Lal Jeyan J V
Published: March 2020

Morphing and shape shifting technologies offer a wide range of applications in airplane design and are complicated to operate effectively with current existing methods. Variable camber wings is a innovative control surface technology designed as aero elastic wing shaping control device which minimizes drag throughout its flight envelope and increases performance in different flight conditions which leads to corresponding increase in airplane flight efficiency. In order to achieve these results one has to rely on different flight actuator configurations and techniques to achieve variable camber mechanism. Variable camber can be achieved span vice or chord wise on an aerofoil where a slight variation in thickness changes lift coefficient. Variable camber wing is a flexible structure that changes its shape profile at different aerodynamic load these types of wings are tested under different load conditions and Reynolds number in wind tunnel facility to have a detailed study on the performance. In this paper an attempt has been made to cover all the shape shifting and morphing wing technologies and compare the results and discuss the possibility of adaption of such technology in aerospace industry.
Review on influence of radiating and aerodynamic shock at hypersonic vehicle
Authors: Balaji R , Muruga Lal Jeyan J V , Singh Vijay Kumar
Published: March 2020

Hypersonic vehicles are going to play a huge role in the upcoming years. As the vehicle has to attain the hypervelocity flow front at the leading edge of the vehicle, need to be strong enough to withstand the effect of the shock wave and radiating waves. Aerodynamic design and the velocity range decide the aerodynamic heating rate of the vehicles. It is known whenever the flow field and the radiation are coupling one another that make the shock layer region complex to analyse. In general inside the developed shock layer, heat flux variation is maximum that enhance the heat transfer. Technically in practice the ability to alter the heat transfer rate of the outer skull depends on the aerodynamically design. To achieve and maintain the hypervelocity region minimizing and or sustaining the aerodynamic heating is necessary. To achieve that regression study on those mentioned three parameter is mandatory. In this review, design and cooling method of different types of hypersonic vehicles taken, and the possible ways to reduce the intensity of shock waves are discussed.
A Critical Review on the Application of Computational Fluid Dynamics in Centrifugal Turbomachines
Authors: Nilugal Manjunath L , Vasudeva Karanth K , Madhwesh N
Published: March 2020

Centrifugal turbomachines are the popular type of power absorbing machines especially used in many industrial applications. In these devices the energy from the rotating impeller is transferred to the fluid to increase its pressure energy. The flow phenomena in these machines is very complex because of the presence of adverse pressure gradients in the flow passages. The level of complexity of turbomachinery flow fields is directly influenced by flow-path geometry and component blade geometry. Hence there is a dire need of advanced flow modelling techniques to understand and capture the fluid characteristics in these flow devices. To design such flow domains, advanced Computational Fluid Dynamics (CFD) tools are required that are capable of accurately modelling the complex flows encountered in turbomachinery applications. These models reflect the full three-dimensional, turbulent, transonic, and often unsteady nature of the actual flows. In addition, they must allow analyses to be performed in reasonable amounts of time that can be accommodated within a typical design cycle. With the development of fast and validated numerical methods, and the continuous improvement in clock speed of computer processors, highly complex problems are now being solved using CFD methods even more economically and quickly. This article focusses the efficacy of CFD tools in turbomachinery applications and various parametric methodologies pertaining to efficiency improvement of turbomachines in detail.
Numerical analysis of micro-channel heat sink using ethylene glycol based nanofluid in case of electronics cooling
Authors: Bhuvad Sushant S , Patel A K , Rajput S P S
Published: March 2020

As size of Integrated circuit is goes on decreasing and number of elements per chip increases, the heat dissipation per unit area of IC increases. Therefore, nanofluid forced convection cooling using an micro-channel heat sink is introduced as new research topic for efficient cooling of IC devices. In this manuscript, ethylene glycol base nanofluid has been studied by using five different oxide nanoparticles including Al2O3, TiO2, CuO, SiO2 and ZnO and varying their concentration from 0 to 10% volume fraction. Single phase model has been considered in simulation analysis using ANSYS Fluent 13.0 software and the results obtained from simulation have been validated with previous experimental and simulation work. Furthermore, several aspects of parameters such as local thermal resistance, pumping power and local heat transfer coefficient are presented in below manuscript. From the result it is analysed that ethylene glycol base nanofluid increases the heat transfer parameters very effectively. Further, as concentration of nanoparticle sis increases the convective heat transfer coefficient and pumping power increases. Also, CuO-EG nanofluid cooled electronics devices more efficiently compared to other nanofluid which are considered in this study.
CFD analysis on the effect of radiation and inlet gas temperature on porous media solar heater
Authors: Warghat Ketan V , Sathish Kumar D , Jayavel S
Published: March 2020

The effect of porosity on flow and thermal characteristics is significant. Fluid flow through porous media has many practical relevance such as agriculture, engineering, bio-medical, etc. applications. In the present study, flow of gas and through solar heater is simulated and the heat transfer characteristics are studied. Two-dimensional numerical simulations are carried using ANSYS-Fluent. Velocity of gas at the inlet is varied from 0.005 to 0.5 m/s and passed through the porous media with porosity value of 0.7. Results are presented in the form of pressure variation, velocity variation and temperature variation.
Energy Management with Bi-Directional Converters in DC Microgrids
Authors: Sreeramulu Mahesh G , Puskar Aman , Murali Krishna P. , Rajashekhar S.
Published: March 2020

The application of Bi-Directional converter has been well notified in Electric Vehicles and the energy flow between the Grid-2-Vehicle and Vehicle-2-Grid are flexible, reliable, efficient and with reduced number of hardware components as compared with conventional DC-DC converters. Using these benefits, the Bi-Directional Converters are used in the DC Microgrids to charge the storage elements in the grid connection mode and to discharge the storage elements in the islanded mode of operation. In this paper, the balanced energy flow between the Storage Elements (Charging Mode) and DC loads (Discharging Mode) using Bi-Directional Converters with Fuzzy control technique is proposed. With this system, the Demand Response objectives like minimization of energy cost and awareness to the social welfare are achieved. The proposed Bi-Directional Converters system is developed using MATLAB-Simulink software and the energy flow between the battery and utility grid or DC load waveforms are shown.
Comparative fatigue life estimations of Marine Propeller by using FSI
Authors: Vijayanandh R , Venkatesan K , Senthil Kumar M , Raj Kumar G , Jagadeeshwaran P. , Raj Kumar R
Published: March 2020

Generally, inward and outward effects are huge and prime in the rotating components. Based on the working environments of a rotor, the complexity is increased furthermore. In this work also deals the same problem, which is fatigue life estimation of marine propeller for different materials under given Ocean environments by using Ansys Fluent 16.2. The conceptual design of the Marine propeller is modelled with the help of CATIA. Fatigue life estimation on the rotor is key and complex output of this work, advanced methodology is mandatory for computation therefore Fluid-Solid Interaction (FSI) technique is used as advanced numerical simulation. Fluid properties such as density and operating pressure are used to define the Ocean environment in the Ansys Fluent 16.2. In the case of structural simulation, the existing materials such as Aluminium alloy and Stainless Steel are used for fatigue life estimation. Finally, the fatigue life estimation of marine propeller is extended for Composite material to compare the life of a rotor.
Circuitry parameter analysis of piezoelectric materials for micro energy harvesting
Authors: Manoj R M , Sudheer Reddy J
Published: March 2020

Energy scavenging using piezoelectric materials is conventional and reliable method of energy harvesting in case of wireless sensor application. The mechanical stress or strain caused on the piezoelectric material leads to generation of voltage which in turn can be used for storage in batteries. This article deals with simulation of circular piezoelectric transducer using COMSOL software and the comparison of various parameters with respect to the structure is studied, also the experiment is conducted to compare the voltage values generated by piezoelectric transducers in different circuitry connections. This data signifies the efficiency and adaptability of piezoelectric transducers for various applications.
Enhancement of Heat Transfer in Perforated Circular Finned-Tube Heat Exchangers: A Numerical Investigation
Authors: Rai Ankur , Bhuvad Sushant S , Sarviya R M
Published: March 2020

The effects of employing perforations of circular shape in circular finned-tube heat exchangers (CFTHEs) are numerically investigated in the present study using Computational Fluid Dynamics (CFD) software. Simulations performed on the validated CFD model shows considerable increase in the Average Nusselt Number for perforated circular finned-tube heat exchangers (PCFTHEs) as compared to their solid counterpart, with only a slight increase in Euler Number for 10,000 ≤ Re ≤ 50,000. Diameter of perforations (dp
) is kept equal to 6mm and optimum range of number of perforations per fin (np
) by analysis is found to be 16 to 20. For this range, the performance of PCFTHEs improves with the increase in number of perforations per fin. The maximum increase in Average Nusselt Number is 24% for dp
= 6mm and np
= 20 at Re = 10,000. The minimum increase in Average Nusselt Number is 3% for dp
= 6mm and np
= 14 at Re = 40,000. This increase in Average Nusselt Number on introducing perforations is due to (i) flow of localized air jets through the perforations, and (ii) reduction in recirculation region caused by the separation of flow. This improvement in the performance of CFTHEs on introducing perforations is achieved with the maximum and minimum reduction in weight of 41% and 29% respectively.
Study of circulation ratio for natural circulation in water-tube boiler at different operating conditions.
Authors: Elgandelwar Atul M , Jha R S , Lele Mandar M
Published: March 2020

The basic objective of the paper is to identify the desired circulation ratio for the natural circulation of water tube boilers in different operating conditions. This requires the basic study of heat flux and the mode of the boiling heat transfer, and the phenomenon like departure from nucleate boiling and tube overheating. The parameters, which need to be studied are heat flux, pressure, dryness fraction, void fraction, liquid velocity and their impact on the required circulation ratio. For a natural circulation boiler, the circulation ratio is one of the most important design parameters as the other design parameter like critical heat flux and skin temperature are mainly derived from the circulation ratio. The required circulation ratio can vary with the boiler pressure, liquid velocity and maximum heat flux. This study is intended to provide input for the safe and optimum design of a natural circulation boiler.
Heat transfer studies for infrared radiation assisted curing in polymer composites
Authors: Uday M , KiranKumar P
Published: March 2020

Conventional materials are replaced by polymer composites in every field due to its wide applications and its ease to custom make the required properties for the purpose it is designated for. Structural applications require higher strength, and this is achieved only by better curing of polymer composites during its processing. Elevated temperature curing helps to improve cross linking of polymers. In this regard infrared radiation curing is one of the methods adopted in the recent days for elevated temperature curing of polymer composites. It is one of the efficient ways of curing polymer matrix composites. In this paper Infrared radiation heat transfer studies of polymer composite is reviewed and compared its efficiency with the hot air or conventional curing method. Further modelling is carried out to prove the efficacy of the same.
Convection heat transfer in a porous medium saturated with an Oldroyd B fluid - A Review
Authors: Prema S , Shankar B M , Seetharamu K N
Published: March 2020

In this review paper, the important milestones in model studies such as Darcy and Brinkman on heat transfer through porous medium were summarized. Mathematical expressions pertaining to models were studied to understand the response of theaOldroyd B fluid flowing through aaporous medium with a finite element boundary conditions. Research papers on Linear stretched sheet and circular tube flow models gave the clear picture of the extent of work carried out by the heat transfer researchers. Handful of verticals are identified as research gaps which still remains unexplored. Hence Provides an opportunity to carryout in-depth analysis for complete understanding of heat transfer thorough a Oldroyd B fluid filled porous media.
A review on performance study of finned tube heat exchanger
Authors: Basavarajappa S , Manavendra G , Prakash S B
Published: March 2020

The plate Fin-and-tube heat exchangers are one of the most common type of heat exchangers that are widely used in variety industrial applications like space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, aerospace industry and sewage treatment. It is very important to reduce the size, weight and enhance the heat transfer rate of heat exchanger. Fin-and-tube heat exchangers with different geometry and orientations are used to improve the thermal performance. The purpose of this paper is to provide an overview of research works carried out to improve the thermal performance of a heat exchanger by using different parameters like type of fins, orientation, shapes and locations. This review is to help understand how every mentioned parameters influences on improvement of thermal performance.
Heat transfer enhancement in concentric tube heat exchanger with tangential injection and twisted tape inserts
Authors: Warghat Ketan V , Jagdale H D
Published: March 2020

Heat exchanger has many engineering applications such as air conditioning, chemical reactor and refrigeration systems, etc. The performance of this industries mainly depends on the performance of heat exchanger. So, to increase the performance of heat exchanger many techniques have been investigated on enhancement of heat transfer rate and decrease the size and cost of the heat exchangers. In most of applications and key areas like power plants, process & chemical industries uses surface enhancement methods. Present work mainly emphasis on the both passive and active methods of heat transfer enhancement. In this work, to enhance the heat transfer rate with the help of twisted tape insert in passive method in which aluminium twisted tapes are used. In the active method fluid is injected in annulus space to generate turbulence through tangential injectors. There are six injectors are used to generate turbulence. Water is used as a working fluid in both types of heat exchanger. From the experiment it shows that, as Reynolds number increases heat transfer coefficient also increases
Temperature Cross in Three-Fluid Cryogenic Heat Exchangers
Authors: Krishna V , Seetharamu K N , Spoorthi S , Akshobhya  , Sukruth R , Manoj M , Murali Prashanth , Bharadwaj Prerak , Nayak Subhash
Published: March 2020

In multi-fluid heat exchangers, local equalization of fluid temperatures occur(s) at certain location(s) within the heat exchanger, depending on the chosen values of the operating condition parameters and design parameters. This is referred to as a ‘temperature cross’ between the concerned fluids. The formation of the temperature cross leads to a situation wherein there is reversal of heat transfer in the heat exchanger section on one side of the cross. A three-fluid cryogenic heat exchanger, involving thermal interaction between all the three-fluids - hot, cold and intermediate - is investigated for the effect of the temperature cross, for the different flow arrangements. Non-dimensional governing equations are formulated to account for ambient heat-in-leak and longitudinal wall conduction and solved using finite element method. An algorithm, using MATLAB, has been used to determine the position of the temperature cross. The variation of the temperature cross is investigated for varying values of the Thermal Resistance Ratio between intermediate-cold fluids and hot-cold fluids (H1).
Effects of injection pressure on performance and exhaust emissions of CIDI diesel fuelled with synthesized biodiesel (fish oil and honge oil)
Authors: Tilak S R , Nayeem Ahmed M , Anil Kumar B N , Yogish H
Published: March 2020

To assess the emissions and performance of a test engine fueled by biodiesel - blends made from mixed fish oil extracted from processing by-products with honge oil in equal proportions. The experimental investigation was utilized to examine the effects of injection pressures on compression ignition engine testing and correlation of these effects the biodiesel blends. Consequently, commercial diesel fuel intermingled with various concentrations of fish-oil biodiesel with B0, B10, B20, B30, B40 and B50 were utilized for the test engine. Compared to B0, the average decline in brake power of the methyl esters was reduced proportionally with the biodiesel ratio in the fuel blends. The brake specific fuel consumption (BSFC) and oxides of nitrogen emissions improved together with a decline in hydrocarbons and carbon monoxide emissions as the proportion of biodiesel rises. As injection pressure increases, the brake power increases for all kinds of fuels tested.
A review on thermal barrier coating for diesel engine and its characteristics studies
Authors: Rohini A , Prema S
Published: March 2020

Thermal Barrier Coating (TBC) on diesel engine performance was studied with a purpose of improving the thermal efficiency by decreasing Specific fuel consumption (SFC) and reducing exhaust emissions. This review paper gives a comparison of a standard diesel engine over a Low heat rejection engine. The experimental results from the various researchers show a gradual improvement in efficiency and specific fuel consumption rate. Higher operating temperature in combustion chamber gives higher efficiency which by using temperature resistant materials. Yttria-stabilized zirconia (YSZ) ceramic, ZrO2, Al2O3, Aluminium titanium are the coatings used on piston crown, cylinder liners, valves by adopting plasma spray technique. The results of LHR engine shows that, NOx emission is increased, whereas the efficiency and SFC are closer to standard engines at Low loads and noticeable improvements are seen at higher loads.
Thermal analysis of natural gas as an alternative fuel for gasoline engine
Authors: Ravichandra R , Rajesha S , Sang C C
Published: March 2020

Transport sector is one of the highly emerging industries which consume a million barrels of petroleum fuels like gasoline and diesel per day. Consequently, petroleum fuels are getting exhausted day-by-day. Energy supply for growing demand from the transport sector would be difficult to combat in the near future. This crisis has led to the avenue for alternative fuels to be one of the solutions. Compressed Natural Gas (CNG) has been successfully used as one of the alternative fuel worldwide. However, the design features of the gasoline operated engines are facing certain issue related to performance, consistency and reliability of the engine when it was switched to CNG as prime fuel. Distinct researchers have worked on the issue to find an appropriate solution. In the current work, the thermal behaviour of engine and its effect on engine cooling mechanism is considered as part of the study to analyse the effect of applying CNG as prime fuel on a gasoline operated engine.
Experimental investigation on thermal characterization of gasoline-ethanol blends
Authors: Atgur Vinay , Manavendra G , Bala Chaitanya Subba Rao T , Durga Prasad M , Bala Saloman Reddy T , Dheeraj K
Published: March 2020

Petroleum products are now current consumption rate it will be depleting in upcoming decades. Ethanol usage is one of the transport sectors can fulfill the requirement and contribute to mitigating the greenhouse gas emissions of the vehicles. In order to expand the SI engine this can work on 100% ethanol or adding ethanol in petrol and use the blends of that. The intention of this work is to study the thermal characteristics of Gasoline and its E5, E10, E15 ethanol blends. All thermograms of heat flow exhibited at a 350C-2800C temperature range at heating rate of 100C/min in atmospheric air as medium. Transport properties like Thermal conductivity, Specific Heat capacity and Thermal diffusivity are studied using TPS500(s). This study concludes that ethanol blending is the lowest exhaust emissions with considerable improvement in the performance of the Spark Ignition (SI) engine and promising, Ethanol as a future fuel which can be fortunately replace petrol and its depletion problem.
Evaluation of performance and emission characeristics of heterotrophic chlorella protothecoides microalgae biodiesel and its blends with diesel in a direct injection diesel engine.
Authors: Jagadevkumar A P , Pravin V K
Published: March 2020

At present research in biofuels for internal combustion engines received a lot of attention because the fossil fuels are depleting in nature and also due to their exhaust emissions they imposing threats like global warming, acid rain etc on environment. The use of biofuels derived from plant biomass in internal combustion engines can reduce the global warming and other hazards on environment, but the difficulty associated with these fuels is the feed stocks, fertile land requirement for their growth resulting in shortage of fertile land for cultivating food crops. So algae are the best alternative promising biofuel resourc energy. Particularly microalgae are most reliable source of biofuel because they are non edible, and they does not require fertile land for their growth. Hence, Accordingly, in this research work Heterotrophic chlorella prothecoides microalgae biodiesel, diesel and their blends are tested with a DI diesel engine to study the performance and emission characteristics. The experimental study shown that, compared to Petroleum diesel the Heterotrophic chlorella protothecoides microalgae biodiesel produces lesser emissions. Heterotrophic chlorella protothecoides microalgae biodiesel B100 shown a reduction of 2.85,2.89, 3.15, 20, 4.67 and 13.54 % in, torque, brake power, brake thermal efficiency, CO, CO2 and NOx, respectively and an increase of 11.81 and 15.96 % in O2 and bsfc, respectively compared to petroleum diesel.
Effects of adding powdered metals with the solid propellants – A review
Authors: Adharsh Unni A , Kulkarni Rajat , Singh Chanchal , Singh Vishal , Priya Varshini Vasireddi Mouli , Shanmugaraj Gopinath
Published: March 2020

Rocket engines that use solid propellants are widely used in the commercial space flight industry for powering orbital-class launch vehicles and small research rockets. Thrust and the specific impulse developed by a rocket engine are essential properties of a rocket propulsion system, and it specifies the overall performance of a rocket. These properties heavily influenced by the burn-rate properties of the solid propellants. One of the many methods to improve the burn rate of the solid propellant is the addition of metallic powders into the fuel-oxidizer matrix. This technique has been observed to enhance the burn rate of the solid propellants; several studies have concluded the same. On the other hand, these additives result in the release of metal oxides into the atmosphere and lead to a higher amount of environmental pollution. This paper summarizes the effects of adding metals and their concentrations on the burning properties of the solid propellants.
Investigation of bending properties on carbon fiber reinforced polymer matrix composites used for micro wind turbine blades
Authors: Puttaraju D.G , Hanumantharaju H.G. , Shreyas  , Pradeep  , Nuthan
Published: March 2020

Composite is material which is made by two or more constituent material. When these materials are combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure. Metallic materials are most widely used in structure, Automobile industry and in our daily life. Metallic materials also show a good property, but main problem with this is more density which causes heavy weight. This is a big disadvantage in many fields. To overcome the problem metallic materials can be replaced by composite material which has lesser density, less weight, higher stiffness, higher strength and better fatigue resistance. The present study is made on Carbon fiber.

Carbon acts a high performance fiber material. It has highest specific modulus and high specific strength of all reinforcing fiber material. Carbon fiber reinforcement composite is a strong, light and very expensive material. High cost of this material is compensated by its excellent strength to weight ratio. The composite consist of Carbon fiber, epoxy resin namely Ly556 and Hardener 951. This study has been done to study the mechanical properties tensile test, compression test, three point bending test etc to be carried out for better understanding of the carbon fiber composite material. In this study three point bending test is discussed and use of carbon fiber and epoxy resin composite in micro wind turbine blade has been studied.
Studies on the feasibility of adsorption cooling technologies
Authors: Ashok Kumar K , Kapilan N
Published: March 2020

In the current scenario, for majority of the people and industry needs of the globe, cooling processes such as refrigeration as well as air conditioning are important and major requisites. On the other hand, the conventional vapour compression systems require high electrical energy input and employ refrigerants with negative environmental impacts like ozone layer depletion and climate change resulting from the emission of harmful gases such as CO2, Hydro fluorocarbons and Chlorofluorocarbons with the usage of conventional refrigerants. The solar energy being a renewable source is one of the key solutions to pollution problems and can be used to drive the adsorption cooling machines. With the heat source temperature of even 50° C which is obtained from the low grade energy like solar energy or waste heat energy is feasible to run the adsorption refrigeration system to reduce the operating cost. In the present work, a single bed adsorption refrigeration system is developed and tested using working pair as silica gel and water. From the experimental results, it was observed that this system can be used as alternative to the conventional vapour compression refrigeration system to produce cooling effect. However, the performance of the adsorption system studied is lower than the vapour compression refrigeration system.
Effect of parallel plate stack spacing on the performance of thermoacoustic refrigerator in terms of temperature difference using air as a working fluid
Authors: Shivakumara N V , Arya Bheemsha
Published: March 2020

The existing conventional refrigerators are operated by using hazardous refrigerants, which produces CFCs and HCFCs resulting in the depletion of the ozone layer. However, these disadvantages can be overcome using inert gases in the thermoacoustic refrigeration system. The present research involves the effect of the spacing of a parallel plate stack on the performance of the thermoacoustic refrigerator (TAR). TAR is fabricated by using Poly-Vinyl-Chloride (PVC), which is designed for 10W cooling power. Three parallel plate stacks have been used to study the performance of TAR considering different porosity ratios by varying the gap between the parallel plates (0.28 mm, 0.33 mm and 0.38 mm). The parallel plate stacks are fabricated by using aluminium and mylar sheet material, and the working fluid used for the experimental study is zero air. The experiments have been carried out with different drive ratios ranging from 0.6% to 1.6%, with operating frequencies of 200 – 600 Hz. Also, the mean operating pressure used for the experiment is 2 to 10 bar, and the cooling load of 2 to 10W is considered. The temperature difference (ΔT) between the hot heat exchanger and cold heat exchanger is recorded using RTDs and Bruel and Kjaer data acquisition system. Experimental results show that the lowest temperature measured at cold heat exchanger is 1.23 °C by maintaining the hot heat exchanger temperature at about 32 °C. The maximum ΔT of 30.77 °C is achieved.
Urbanization has stronger impacts than regional climate change on wind stilling: a lesson from South Korea
Authors: Chen Xing , Jeong Sujong , Park Hoonyoung , Kim Jinwon , Park Chan-Ryul
Published: March 2020

Wind stilling has been observed in many regions across the Northern Hemisphere; however, the related mechanisms are not well understood. Analyses of the wind speed variations in South Korea during 1993–2015 in this study reveal that the annual-mean surface wind speeds at rural stations have increased by up to 0.41 m s−1 decade−1, while those at urban stations have decreased by up to −0.63 m s−1 decade−1. The local wind speed variations are found to be negatively correlated with the population density at the corresponding observation sites. Gustiness analyses show the increase in local surface roughness due to urbanization can explain the observed negative wind speed trends at urban stations as the urbanization effect overwhelms the positive wind speed trend due to climate change. The observed negative wind speed trend in urban areas are not found in the regional climate model simulations in the Coordinated Regional Climate Downscaling Experiment—East Asia (CORDEX-EA) as these models do not take into account the impact of urbanization on wind variations during the period. This study suggests that urbanization can play an important role in the recent wind stilling in rapidly developing regions such as South Korea. Our results suggest that future climate projections in CORDEX-EA may overestimate wind speeds in urban areas, and that future regional climate projections need to consider the effects of urbanization for a more accurate projection of wind speeds.
Behavior of hybrid Reinforced Concrete Beams made with two types of concrete (Normal Weight and Reactive Powder Concrete)
Authors: Abdullh Kammash Khudhayer Najim , Mseer Ayad Hameed , Alameer Eedan Osama Abd
Published: March 2020

This research confirms the use of finite element modeling using volume 16 ANSYS package to represent the non pre stressed concrete beams reinforced with steel bars, reactive powder concrete beams and hybrid reinforced concrete beams. This work focused on two main purposes: the first one is for economic purpose to check the effects of inclusion of fresh reactive powder concrete with the fresh normal weight concrete beams body at compression and tension stress concentration regions to improve the ultimate load resistance and to control mid span deflection of simply supported beams or any great structural elements. The second purpose is to check effects of using steel fibers with different volume fractions (Vf = 0%, Vf = 1%, Vf = 1.5% and Vf = 2%) in reactive powder concrete beams with fixing all other mechanical properties of concrete to show clearly its effect on controlling of mid span deflection with applied loads or in other words, on beam ductility. The used beam was simple supported reinforced concrete beam with dimensions (110 X 200 X 1500)mm width, height and length, respectively, reinforced with bottom 2 main bars of 12mm diameter and 8mm diameter stirrups spaced at 50mm. Each beam was loaded up-to maximum load which makes failure under the effect of two concentrated parallel loads for beam used as a case study and one central concentrated load for parametric study beams to assign the load and deflection values at beams mid-span locations.

The proposed nonlinear finite element solutions are compared with the experimental data obtained from other researcher [1], which gives a good agreement between the obtained results.

Parametric studies are carried out by using the proved nonlinear ANSYS (version 16) model to investigate the effects of adding expensive RPC with cheap NWC in structural elements bodies to obtain an economic construction material and to reduce weight and volumes especially for great structural elements.
Structural behavior of SCC continuous deep beam strengthening and retrofitting with carbon fiber reinforced polymer strips
Authors: Al-Bdari W J , Al-Bayati Nabeel , Al-Shaarbaf A. S.
Published: March 2020

This study presents an experimental work to investigate the structural behavior of continuous self-compacting concrete (SCC) deep beams strengthened and retrofitted with woven carbon fiber reinforced polymer (CFRP) strips and evaluate their shear capacity. The work includes casting and testing fourteen beams specimens. All tested beams have the same dimensions, the same flexural reinforcement and concrete compressive strength with two continuous span and have been subjected to two-point loads. The test specimens were divided into three groups. The first group including eight beams with minimum ratio of shear reinforcement (ρv= ρh=0.25%) and two parameters considered, shear span to overall depth ratio (a/h) and three different schemes of CFRP strip. The second group including four beams without interior vertical and horizontal shear reinforcement (ρv=ρh=0%) with three different schemes of CFRP strip and control beam. The third group consists of two beams with minimum ratio (ρv= ρh=0.25%) were firstly loaded to 65% of the ultimate load of control beams, after that the loads were released and then retrofitted by CFRP strip by two different schemes. The experimental results show that the specimens with vertical CFRP strips an increase in ultimate strength load by 32.6% and 20% compared to the control beams.
Kinetics and Thermodynamics Studies of Ketalization of Glycerol and Acetone in the Presence of Basolite F300 as Catalyst
Authors: Sulistyo Hary , Perdana Indra , Pratiwi Fatimah Tresna , Hartati Indah
Published: March 2020

Acetalyzation of glycerol with acetone has been carried out using Basolite F300 as catalyst. Heterogeneous catalysis reaction model was employed and Langmuir Hinshelwood mechanism was simulated and validated to the experimental data. The experiment was conducted at varying temperature (30 – 55°C) with an initial molar ratio of glycerol to acetone of 1:4, agitation speed of 700 rpm and catalyst loading of 1% (w/w glycerol). The agitation speed of 700 rpm was sufficient to neglect the external mass transfer as the rate controlling step.The results showed that glycerol conversion as high as 83.33 % was obtained from one hour reaction time. The glycerol conversion was simulated and the results were compared with experimental data in a temperature range of 30°C to 55°C. From mathematical model, it was found that the pre-exponential factor of 0.0149 min–1 and activation energy of 15.7085 kJ.mole–1. Comparison of experimental data and calculation results showed that the proposed mathematical model was adequately able to approach the experimental data within the temperature range under investigation. Thermodynamics analysis on the ketalization resulted in ΔS°, ΔH° and ΔG° which values were 0.0834 kJ.mole–1 K–1, -29.7176 kJ.mole–1 and -4.8675 kJ.mole–1, respectively.
Modelling of Saltwater Evaporation using WAIV
Authors: Henrietta  , Santoso H , Witono J R
Published: March 2020

Indonesia as a country, which has the second longest coastline in the world, has a big opportunity to improve its salt production. The productivity of salt production in Indonesia from 2011 to 2014 was around 67, 92, 40, and 90 tons/ha/year, respectively. This low productivity was mainly due to the method of salt production used, which was very traditional and depended mainly on the availability of solar energy for evaporation. The longer the dry season was, the higher the salt production would be in that year, and vice versa. Since the performance of evaporation process holds the key to the improvement of productivity of salt production, it is important to study a method that can speed up the evaporation process in the salt production. One of the recent methods that can be used to achieve that purpose is the Wind Aided Intensified Evaporation (WAIV) process. In this study, a model for saltwater evaporation in a WAIV unit using Harbeck equation is proposed. Two set of data for saltwater evaporation in a WAIV unit was extracted from literature. The first set of data was used to obtain the parameters of Harbeck equation by minimizing the sum of error squares of the cumulative evaporation rate in a WAIV unit compared to its model. The second set of data was used to validate the model. It is found that the proposed model can estimate the evaporation rate in a WAIV unit based on the surrounding climate data reasonably well.
Development of Skin Lotion Containing Antioxidant Extract from Coffee Pulp and Study on Its Stability
Authors: Widiputri D I , Wijaya S , Kusumocahyo S P
Published: March 2020

Coffee pulp, a major coffee waste in the coffee industry, has been found to contain bioactive compounds that can provide high antioxidant activity and hence, can be utilized as a natural antioxidant source. One of the beneficial utilizations of coffee pulp extract is its application in skin cosmetics, such as skin lotion. The application of antioxidant on the skin is one way to avoid skin damages and diseases from happening, which can be caused by free radicals generated through ultraviolet (UV) radiation from sunlight. The aim of this study is to apply the coffee pulp extract powder into skin lotion formulation, and to study the phenolic content, antioxidant activity and the stability of the formulated lotions. First, the coffee pulp (CP) was extracted at sample to solvent ratio of 1:10 (w/v) using ethanol/water mixtures at various extraction temperatures and times to obtain the optimum extraction condition. The resulting coffee pulp extract at optimum condition (50°C, 120 minutes) was pulverized into coffee pulp extract powder. The yield of the pulverization was 0.217146 g powder/g CP. The coffee pulp extract powder was then added into skin lotion formulation with four different concentrations (0.125 %, 0.25 %, 0.5 % and 1 % by mass). All coffee pulp skin lotions were found to show good physical stability and considerably higher antioxidant activity (IC50 : 5,805 ppm – 55,776 ppm) compared to commercial lotions (IC50 : 505,018 ppm – 557,218 ppm).
Application of Quantitative Structure-Property Relationship (QSPR) Models for the Predictions of Critical Micelle Concentration of Gemini Imidazolium Surfactants
Authors: Setiawan Ely , Mudasir  , Wijaya Karna
Published: March 2020

The critical micelle concentration (cmc) is important indexes to determine the performance of surfactants quantitatively. In this study, based on the molecular descriptors, which calculated, by Dragon software, were proposed a quantitative structure-property relationship analysis for prediction of cmc of gemini imidazolium surfactants. In the present study, the associative neural networks (ASNN) and multiple linear regression analysis (MLRA) technique were used to interpret the chemical structural functionality (molecular descriptors) against the cmc of gemini imidazolium surfactants. The models were validated rigorously through 5-fold cross-validation. The ASNN method showed to be better than the MLRA method in terms of the internal and the external prediction accuracy with high statistical quality r2 = 0.96, q2 = 0.95, RMSE = 0.08 and MAE = 0.04 respectively. The developed QSPR models are publicly available on the web site at https://ochem.eu/model/11583111 for ASNN model and https://ochem.eu/model/43858671 for MLRA model. These models can be applied to predict the cmc of new gemini imidazolium surfactants.
Effect of Particle Size and Shaking Speed on Enhancing Concentration of Manganese using Shaking Table
Authors: Prasetya Agus , Ahsa Winayu Mutiara , Gustiana Himmah Sekar Eka Ayu , Astuti Widi , Petrus Himawan Tri Bayu Murti
Published: March 2020

Increased levels of elements or minerals from ore are usually always done in the metallurgical industry. In the present investigation, low grade manganese ores from Kulonprogo, Yogyakarta has investigated by gravity methods using shaking table. In this context, the effect of different process variables such as particle size (-60 + 100 mesh; -100 + 200 mesh and -200 + 270 mesh) and shaking speed (80 rpm, 100 rpm and 120 rpm) was analysed. The table slope and wash water flow rate are a constant variable, which are at 11° and 13 dm3/minute. The interactional effects between different process variables were analysed using contour plot. It was founded that enhancement of the concentration of Mn is more than 5% with the shaking speed condition of 100-120 rpm and the particle size of 0.17 mm. Second order quadratic equations have developed to predict enhancement of Mn concentration using shaking table.
The Effect of Salt-GDL Coagulant and Temperature on Tofu Quality
Authors: Inggrid Maria , Hananjaya Nikolas
Published: March 2020

Soymilk tofu can be coagulated with salts, acid and lactones. The objectives of this investigation was to study the effect of temperature and different coagulant to the quality of tofu; such as protein content, texture, mass and moisture. Soybean was oaked and grinded to produced soymilk. The soymilk was coagulated with two type of mixed coagulant; CaSO4- Glucono delta-lactone (GDL) and MgSO4-GDL, the variation of composition were 0:4, 3:1, 2:2, 1:3, 0:4 at temperature of 70°C and 80°C. The highest protein content was obtained from the tofu with CaSO4-GDL (2:2) and 70°. The results showed that the different in coagulation temperature affect the protein content of tofu. Mass and texture of the tofu increased as the composition of salt coagulant increased. General factorial method was used in this experiment, the result supports that the various composition of coagulant increased significantly (P<0.05) from 111-135 gram and 241-642 gram, respectively for tofu mass and texture. Temperature has significant result to protein content and mass of the tofu.
Thermal Conductivity of Geopolymer with Polypropylene Fiber
Authors: Rastri Utami Felisitas Aprilia , Triwiyono Andreas , Agustini Ni Komang Ayu , Perdana Indra
Published: March 2020

Geopolymer is widely used to replace cement for fire-resistant products. The benefits of geopolymer based on fly ash are cost-effective and easy process production. Lightweight products are needed to minimize dead load for the existing structure. The addition of polypropylene fiber is intended to produce relative lightweight and strong material applied for fire resistance. This research was conducted to obtain thermal conductivity, density, and compressive strength of the geopolymer. The ratio of activator/fly ash (a/f) was varied 40%, 45%, and 50% with addition of polypropylene fibers of 0.5%, 1%, and 1.5% of the fly ash weight. The experimental test was conducted on the 7th day at ambient temperature while concentration of NaOH used in geopolymer synthesis was kept at 10M with a ratio of alkaline activator (Na2SiO3/NaOH) of 2. The test results showed that thermal conductivity (λ) is in a range between 0.19-0.82 W/m.C while the thermal conductivity is less than 1 W/m.C. This indicates that the geopolymer can be applied for thermal insulating material. Geopolymer with polypropylene fiber and a/f 50% can be classified as lightweight material with a density around 1.6283-1.7625 gr/cm3. The ratio of a/f 50% produces a compressive strength ranging from 18.14 MPa to 28.42 MPa.
Valuable Metals Precipitation of Low Grade Nickel Ore Leachate Using Sodium Hydroxide
Authors: Surianti  , Utami A N , Permatasari M A , Bendiyasa I M , Astuti W , Petrus H T B M
Published: March 2020

Nickel metal is widely used in various industries. Nickel sources come from nickel sulfide ores and nickel oxide ores (laterite). Nickel content in laterite ore is 1.5-2.5 % (weight basis), lower than the nickel content in sulfide ores. Indonesia is one of the major nickel producers with laterite nickel ore reserves of 1576 million tons or 15 % of total world reserves. The distribution of laterite nickel in Indonesia is found in several regions such as Maluku, Sulawesi and Papua. However, the low grade nickel processing in Indonesia has not been well established. Thus research on valuable metals extraction from ow grade nickel ore has put some interest to some researchers. In this study, precipitation of valuable metals from low grade nickel leachate was conducted using sodium hydroxide as the precipitation reagent. Nickel ore used in this experiment was obtained from Pomalaa, Southeast Sulawesi. After leaching at optimum condition resulting of about 75 % recovery of nickel using HCl (1 M at 90 °C and stirring for 1 hour), the leachate was then added sodium hydroxide to varied pH of 8, 10, and 12. Along with the pH conditioning, temperature was kept to the value of 55 °C, 70 °C, and 85 °C. The optimum nickel recovery of 83.97 % is obtained at pH 12 and temperature of 85 °C. The residual metals concentration in the solution after precipitation was analyzed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES).