

Articles
by
R. Velraj 
Total Records (
2 ) for
R. Velraj 





K. Senthil Manikandan
,
G. Kumaresan
,
R. Velraj
and
S. Iniyan


This study suggests a theoretical performance study of an existing solar Parabolic Trough Collector (PTC). A study of the trough thermal analysis is necessary to evaluate the performance of a PTC. The parametric study of the existing PTC makes use of the mass flow rate, the concentration ratio, the different Heat Transfer Fluid (HTF), the solar insolation and the heat removal factor. The results showed that the efficiency of PTC decreases for various mass flow rates and HTF, as the inlet fluid temperature increases. This is because the radiation losses increased as the collector temperature increases. It is also observed that the useful energy from the PTC decreases for various concentration ratios and insolation, as the inlet fluid temperature increases. 





G. Kumaresan
,
R. Velraj
and
S. Iniyan


The aim of this study was to investigate the thermal properties of DMannitol as a Phase Change Material (PCM) for latent heat storage system. Heat absorbed by DMannitol causes it to undergo a change from the solid to the liquid phase and this heat is stored as the latent heat of fusion. The stored energy can then be retrieved at a later time for various applications. The melting point and enthalpy of the fusion of DMannitol are important properties and these were determined by Differential Scanning Calorimetry (DSC) measurements. Melting was found to begin at 162.15°C and attained a peak at 167.8°C while the enthalpy of fusion was found to be 326.8 J g^{1} for 10°C min^{1}. Furthermore the change in melting temperature and enthalpy of fusion for different heating rates were studied experimentally by DSC. DMannitol’s thermal stability was studied using the TGDTG (thermogravimetryderivative thermogravimetry) and TGDTA (thermogravimetrydifferential thermal analysis) curves. The TGDTG curves revealed that thermal decomposition began at 300.15°C. The DTA curve had a sharp endothermic peak at 169.2°C followed by a broad exothermic one at 297°C. The curves showed that DMannitol decomposes in one prominent mass loss stage. The measurement of latent heat (enthalpy of fusion), melting point and decomposition point showed that DMannitol with a latent heat 326.8 kJ kg^{1} and melting temperature 167.8°C is the most suitable PCM candidate for medium temperature applications because of a large temperature difference of 132°C between its melting point and decomposition temperature. 





