Qualification: 
Ph.D, M.Tech
vr_rajesh@cb.amrita.edu

Dr. Rajesh V. R. currently serves as Assistant Professor at the Department of Mechanical Engineering, School of Engineering, Coimbatore Campus. His areas of research include Solar Thermal Energy Conversion Systems and Utilisation; Solar PV Hybrid Systems.

Publications

Publication Type: Conference Paper

Year of Publication Title

2018

B. Ragavi, V. R. Rajesh, and Isha, T. B., “Determination of Step Angle for Tracking the Sun Position of any Location”, in 2018 4th International Conference on Electrical Energy Systems (ICEES), Chennai, India, 2018.[Abstract]


solar energy is an abundant source of energy available in almost all parts of the world. It provides both heat and light energy. Light energy is converted to electricity by photovoltaic module. The energy conversion is maximum only when the solar panel is kept perpendicular to the sun rays. For this, solar position over the sky is calculated by considering the varying altitude and azimuth angle of the sun at any time of a location and the results of these solar angles are observed from the solar tracking program developed in MATLAB (.m file) and the step angle is computed for both the axes according to which the solar panel is to be tilted automatically to track the sun and kept perpendicular to the sun rays to make the incident angle almost zero. This is used to design a solar tracking system on both the axes and thereby increasing the performance compared to a fixed tilt photovoltaic module.

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2018

D. Sharma and V. R. Rajesh, “Modeling and Design of a Flat Plate Solar Collector with Closed Air Circulation for Drying Spices”, in Proceedings of the 4th International Conference on Electrical Energy Systems, ICEES 2018, Chennai, India, 2018, pp. 352-357.[Abstract]


The current work is confined to design and modeling of a flat plate solar collector for drying of spices. This paper highlights the collector design for drying of cardamom. Based on the cardamom moisture content, the collector dimensions are estimated. A single cover flat plate solar collector with selective coating and forced convection is designed with closed loop circulation of air. Using energy balance equations, the theoretical model of the collector is developed. The collector dimensions are found to be 2.1m2 from simulation for 10 kg of cardamom. The maximum temperature obtained at the absorber surface is 68 °C and the temperature of air at the collector output is 55 °C which is safe for cardamom drying. The analysis of variation of collector outlet temperature and efficiency with respect to solar irradiance are done and presented. © 2018 IEEE.

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2018

P. S. Sreekanth and V. R. Rajesh, “Comparative study of energy storage elements in solar still”, in Proceedings of 2017 International Conference on Innovations in Information, Embedded and Communication Systems, ICIIECS 2017, Coimbatore, India, 2018, vol. 2018-January, pp. 1-5.[Abstract]


The efficiency for a passive single-slope type solar still used for desalination and distillation is very low. Most of the available methods are either very costly or very slow in the rate of production. Many studies were conducted to improve the rate of production from the still. In this proposed work, a study on thermal storage elements like pieces of aluminum sheet and galvanized iron sheet with sponge cubes have been performed along with a comparison to the normal plain basin with only sponges. The study is further extended to know the enhancements in efficiency with preheating of the inlet water. In water scarce area, this could be really helpful because of the increased rate and reduced cost of production. A cost analysis has also been carried out to determine the payback period for the proposed system. © 2017 IEEE.

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Publication Type: Journal Article

Year of Publication Title

2017

V. R. Rajesh and Kuzhiveli, B. T., “Comparative analysis of linear motor geometries for Stirling coolers”, IOP Conference Series: Materials Science and Engineering, vol. 278, p. 012042, 2017.[Abstract]


Compared to rotary motor driven Stirling coolers, linear motor coolers are characterized by small volume and long life, making them more suitable for space and military applications. The motor design and operational characteristics have a direct effect on the operation of the cooler. In this perspective, ample scope exists in understanding the behavioural description of linear motor systems. In the present work, the authors compare and analyze different moving magnet linear motor geometries to finalize the most favourable one for Stirling coolers. The required axial force in the linear motors is generated by the interaction of magnetic fields of a current carrying coil and that of a permanent magnet. The compact size, commercial availability of permanent magnets and low weight requirement of the system are quite a few constraints for the design. The finite element analysis performed using Maxwell software serves as the basic tool to analyze the magnet movement, flux distribution in the air gap and the magnetic saturation levels on the core. A number of material combinations are investigated for core before finalizing the design. The effect of varying the core geometry on the flux produced in the air gap is also analyzed. The electromagnetic analysis of the motor indicates that the permanent magnet height ought to be taken in such a way that it is under the influence of electromagnetic field of current carrying coil as well as the outer core in the balanced position. This is necessary so that sufficient amount of thrust force is developed by efficient utilisation of the air gap flux density. Also, the outer core ends need to be designed to facilitate enough room for the magnet movement under the operating conditions.

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2017

V. R. Rajesh and Biju, T. K., “Effect of Geometrical Parameters on the Performance of Linear Motor for a Stirling Cooler”, International Journal of Air-Conditioning and Refrigeration, 2017.[Abstract]


Stirling coolers are becoming more popular in the area of remote sensing and space applications because of their inherent characteristics, viz., long life, high reliability, less weight, etc. In order to have a good onboard performance, the selection of the compressor drive system is crucial. The current development is to replace the conventional crank-driven compressor with a linear motor-driven compressor. Linear motors are simple devices in which axial forces are generated by current flowing in a magnetic field. This paper explores the possibility of employing various combinations of components and their materials for the design of linear drive system. The analysis includes material selection, electromagnetic design and comparison of different configurations in order to meet the stringent operating requirements of the cooler. The compactness of the Stirling cooler is influenced by the available permanent magnet dimensions, the coil winding and the shape of the outer core. Various material combinations were simulated and compared before finalizing the motor geometry. The effect of an increase in magnet height on the flux density of the air gap was studied and the magnetic saturation levels of the inner and outer core were analyzed. The influence of radial air gap on the thrust force was compared for the different configurations. The present study helps in choosing a linear motor with appropriate materials and geometry in the development of a Stirling cooler. © 2017 World Scientific Publishing Company

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2017

V. R. Rajesh and Kuzhiveli, B. T., “Modelling and Failure Analysis of Flexure Springs for a Stirling Cryocooler”, Journal of Engineering Science and Technology, vol. 12, pp. 888-897, 2017.[Abstract]


In the range of milliwatt to a few watts cooling capacity, Stirling cycle and pulse tube coolers are most suitable for producing cryogenic temperatures owing to their eco-friendliness, high efficiency, cooling capacity to mass ratio etc. The compressor of a Stirling cooler is powered by a linear motor. The power piston of the cooler is held in position and moves to and fro with the support of so called flexure springs or flexure bearings. Flexures avoid direct contact between moving parts of the compressor of the cooler. Thus, if designed adequately to withstand fatigue, flexure bearings can easily outlast rolling element bearings and slider bearings. In this work, a computational analysis is used to study the performance of flexure spring by varying the geometrical parameters. Three of the most common spring materials namely, SS304, beryllium copper and spring steel are considered for analysis. The analysis was made by varying the parameters like spiral sweep angle, slot width, number of spirals and disc thickness. The influence of each of these parameters on the fatigue life of the spring has been investigated. The results suggest that flexure springs of three spiral arms would be the ideal choice for the selected cryocooler. The variation of stress developed with respect to different design parameters and fatigue damage factor are presented graphically. © School of Engineering, Taylor’s University.

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2016

K. K. Chaithanya, V. R. Rajesh, and Suresh, R., “Experimental Analysis of Desalination Unit Coupled with Solar Water Lens Concentrator”, IOP Conference Series: Materials Science and Engineering, vol. 149, p. 012182, 2016.[Abstract]


The main problem that the world faces in this scenario is shortage of potable water. Hence this research work rivets to increase the yield of desalination system in an economical way. The integration of solar concentrator and desalination unit can project the desired yield, but the commercially available concentrated solar power technologies (CSP) are not economically viable. So this study proposes a novel method to concentrate ample amount of solar radiation in a cost effective way. Water acting as lens is a highlighted technology initiated in this work, which can be a substitute for CSP systems. And water lens can accelerate the desalination process so as to increase the yield economically. The solar irradiance passing through the water will be concentrated at a focal point, and the concentration depends on curvature of water lens. The experimental analysis of water lens makes use of transparent thin sheet, supported on a metallic structure. The Plano convex shape of water lens is developed by varying the volume of water that is being poured on the transparent thin sheet. From the experimental analysis it is inferred that, as the curvature of water lens increases, solar irradiance can be focused more accurately on to the focus and a higher water temperature is obtained inside the solar still.

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2016

V. R. Rajesh, Harikrishnan, K., Chaithanya, K. K., and Salim, S., “Performance Evaluation of a Solar Desalination System Integrated with a Fresnel Lens Concentrator”, International Journal of Renewable Energy Research, vol. 6, no. 1, pp. 250-253, 2016.[Abstract]


The purpose of this research work is to develop a water desalination unit that could efficiently produce potable water by evaporation and condensation; integrated with a Fresnel lens solar concentrator. The experimental setup consists of a heater tank powered with a Fresnel lens concentrator for pre-heating the water and a desalination unit. The objective of the work is to evaluate the enhancement in the performance of the system and was compared with the existing desalination unit. The study shows that Fresnel lens concentrator alone as pre-heating device can improve the yield of the desalination system up to 30.8 liters with an efficiency of 55%.

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2016

S. Salim and V. R. Rajesh, “Thermodynamic Analysis of Aqua-Ammonia based Miniaturized Vapour Absorption Refrigeration System utilizing Solar Thermal Energy”, International Conference on Advanced Engineering and Technology for Sustainable Development, vol. 11, 2016.[Abstract]


Solar Energy based refrigeration is one of the most promising technology to meet up the hiking demands for cooling applications. Among the two refrigeration cycles, Vapor Compression Refrigeration (VCR) driven by Photovoltaic (PV) system proves to be the most widely used cooling equipment, while the Vapor Absorption Refrigeration (VAR) driven by solar thermal energy is at its infant stages of development and is biased for usage in industrial applications. This work emphasize on the development of a miniaturized model of aqua-ammonia VAR system integrated with solar collector that can be used for small-scale cooling applications. The evaporator capacity is restricted to 0.5 ton of refrigeration (TR). The study is incorporated with theoretical design and evaluation of performance of the system in terms of Coefficient of Performance (COP). The COP estimated for the VAR system is 0.65. And the influence of evaporator temperature on COP is analyzed. © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved.

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2015

G. R. Krishnan, Venkatesan, V., Nayak, P., Yadav, A. K., and V. R. Rajesh, “Performance analysis and thermal modeling of a solar flat plate collector with concave ridged profile”, International Journal of Applied Engineering Research, vol. 10, pp. 29875-29882, 2015.[Abstract]


Solar flat plate collectors are one of the most popular and cost effective ways of trapping the sun’s heat energy for domestic as well as industrial applications. They are relatively cheap, simple in design and highly useful in tropical climatic conditions. Over a period of time various new designs for the solar flat plate collector have come up leading to more efficient collector setups. This paper evaluates the results of an experimental investigation on the performance of a solar flat plate collector when the conventional absorber plate profile is replaced with a concave-ridged profile. It is known theoretically that for the same aperture area the concave-ridged profile will provide larger surface area for the collection of heat energy from incoming solar radiation (insolation) as compared to the conventional flat profile. Further the concave-ridged profile has a larger shape factor with respect to itself than a conventional profile which leads to better entrapment of heat received from solar radiation. A scaled down model of a commercial solar flat plate collector was fabricated and experiments were conducted using both of the above mentioned profiles at the same geographical coordinates. The results of the experimental studies as well as the comparison of collector efficiencies are presented. Thermal analysisof the concave-ridged profile using ANSYS 14.5 was also done in order to study the distribution of temperatures and thermal fluxes within the profile.

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