Qualification: 
M.Tech
vr_rajesh@cb.amrita.edu

Rajesh V. R. currently serves as Assistant Professor at the Department of Mechanical Engineering, School of Engineering, Coimbatore Campus. His areas of research include Energy Conversion and Power Plant Engineering.

Publications

Publication Type: Journal Article

Year of Conference Publication Type Title

2017

Journal Article

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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2017

Journal Article

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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2016

Journal Article

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, 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

Journal Article

K. K. Chaithanya, Rajesh, V. R., 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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2015

Journal Article

G. R. Krishnan, Venkatesan, V., Nayak, P., Yadav, A. K., and Rajesh, V. R., “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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Publication Type: Conference Paper

Year of Conference Publication Type Title

2016

Conference Paper

S. Salim and Rajesh, V. R., “Thermodynamic Analysis of Aqua-Ammonia based Miniaturized Vapour Absorption Refrigeration System utilizing Solar Thermal Energy”, in International Conference on Advanced Engineering and Technology for Sustainable Development, Karpagam College of Engineering, Coimbatore, 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

Conference Paper

G. Krishnan, V. Vignesh, ,, kumar, A., and Rajesh, V. R., “Comparative Analysis of a Solar Flat Plate Collector with a Modified Profile”, in National Conference on Recent Trends in Mechanical Engineering with Green Energy and Robotics, Nehru Institute of Engineering & Technology, Coimbatore, 2015.

2014

Conference Paper

R. Jayaram, Xavier, D. P., Ramaswamy, M., and Rajesh, V. R., “Optimization of regenerator in a Stirling cycle cryocooler, considering thermal inertia effects”, in International Conference on Environment and Energy, Jawaharlal Nehru Technological University(JNTU) Hyderabad, 2014.

Publication Type: Conference Proceedings

Year of Conference Publication Type Title

2014

Conference Proceedings

V. R. Rajesh and Kuzhiveli, B. T., “Comparative Analysis of Flexure Springs for a Stirling Cryocooler”, International Conference on Energy, Environment, Materials and Safety (ICEEMS-'14). CUSAT, Kerala, 2014.

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