A review of the thermal performance parameters of box type solar cookers and identification of their correlations

One of the many thermal performance parameters such as efficiency, cooking power, figures of merit etc. are used to evaluate a solar cooker (including box type) based on test procedures which are non-identical. In the absence of an interrelation between the different performance parameters, it is very difficult to compare the cookers’ performance reported by different researchers and establish the criteria required for selection of a cooker which can accomplish cooking successfully and satisfactorily. In this review paper, some of the performance parameters and the related test procedures have been reviewed for box type solar cooker. Further an attempt has been made to identify common links between the different performance parameters in terms of a few objective parameters. This provides an enabling tool to the researchers to compare and correlate the different performance parameters. Three such objective parameters have been identified for box type solar cookers.     

Achieving the Best Yield in Glycolipid Biosurfactant Preparation by Selecting the Proper Carbon/Nitrogen Ratio

Pseudomonas aeruginosa RS29, the native biosurfactant-producing strain isolated from the oil fields of Assam, India was used to investigate the influence of the carbon nitrogen ratio on production of the biosurfactant. The biosurfactant producing ability of the strain was measured based on surface tension (ST) reduction of the culture medium and the emulsification (E24) index. Production was greatly influenced by the sources of nitrogen and carbon as well as the carbon to nitrogen (C/N) ratio. Sodium nitrate was the best nitrogen source and the water miscible carbon source, glycerol was observed as the best carbon source for maximum biosurfactant production. The C/N ratio 12.5 allowed the maximum production of biosurfactant by the RS29 strain. At this C/N ratio, 55 % ST of the culture medium was reduced by the produced biosurfactant. Concentrations of crude and rhamnolipid biosurfactant obtained at this particular C/N ratio were 5.6 and 0.8 g/l respectively. The RS29 strain was novel as it was able to produce a sufficient amount of biosurfactant utilizing a much lower amount of the water miscible carbon source, glycerol. Extraction of the biosurfactant by a chloroform–methanol (2:1) mixture was the best method to obtain the highest biosurfactant from the culture medium of the strain. The biosurfactant was confirmed as a mixture of mono and di-rhamnolipid congeners, Rha–C₁₀–C₁₀–CH₃ being the most abundant one. The biosurfactant was a good foaming and emulsifying agent.