Ravinder Kumar Malhotra

Biodiesel surrogates : Achieving performance demands

Synthesis of surrogate molecules is particularly useful for generating in sight of structural-activity relationships, understanding processes and improving the performance. In order to improve upon the physico-chemical properties of biodiesel, methyl, ethyl, isopropyl and n-butyl esters of beta-branched fatty acid have been synthesized, initiating from beta-branched alcohols. Beta-branched alcohols upon oxidation gave corresponding acids, which were converted to their esters. The synthesized esters have substantially better oxidative stability, exhibited by Rancimat oxidation induction period of more than 24 h. The cloud point of synthesized esters is < -36 degrees C, pour point is < -42 degrees C and CFPP is < -21 degrees C, which is substantially better than fatty acid methyl esters. Besides achieving the objective of better oxidative stability and improved low temperature properties, the synthesized surrogate esters have viscosity in the range of 4.2-4.6 cSt at 40 degrees C, meeting the international diesel and biodiesel standards. The cetane number of synthesized esters is 62-69, which is much better than diesel and biodiesel. The blends of the synthesized esters in diesel at 5% and 10% meet Indian standards of diesel.

Recent Developments in Heat Transfer Fluids Used for Solar Thermal Energy Applications

Solar thermal collectors are emerging as a prime mode of harnessing the solar radiations for generation of alternate energy. Heat transfer fluids (HTFs) are employed for transferring and utilizing the solar heat collected via solar thermal energy collectors. Solar thermal collectors are commonly categorized into low temperature collectors, medium temperature collectors and high temperature collectors. Low temperature solar collectors use phase changing refrigerants and water as heat transfer fluids. Degrading water quality in certain geographic locations and high freezing point is hampering its suitability and hence use of water-glycol mixtures as well as water-based nano fluids are gaining momentum in low temperature solar collector applications. Hydrocarbons like propane, pentane and butane are also used as refrigerants in many cases. HTFs used in medium temperature solar collectors include water, waterglycol mixtures – the emerging “green glycol” i.e., trimethylene glycol and also a whole range of naturally occurring hydrocarbon oils in various compositions such as aromatic oils, naphthenic oils and paraffinic oils in their increasing order of operating temperatures. In some cases, semi-synthetic heat transfer oils have also been reported to be used. HTFs for high temperature solar collectors are a high priority area and extensive investigations and developments are occurring globally. In this category, wide range of molecules starting from water in direct steam generation, air, synthetic hydrocarbon oils, nanofluid compositions, molten salts, molten metals, dense suspension of solid silicon carbide particles etc., are being explored and employed. Among these, synthetic hydrocarbon oils are used as a fluid of choice in majority of high temperature solar collector applications while other HTFs are being used with varying degree of experimental maturity and commercial viability – for maximizing their benefits and minimizing their disadvantages. Present paper reviews the recent developments taking place in the area of heat transfer fluids for harnessing solar thermal energy.

A Study on the Performance of Rolling Oil During Cold Rolling of Stainless Steel Simulating Industrial Condition

The primary role of rolling oil in cold rolling is to reduce friction at the rubbing interface of the work roll and metal sheet surface. The rolling performance as well as cost effectiveness of rolled products is influenced by quality of the rolling oil. Lubricants are required to function under increasingly stressful operating conditions, so it is a challenge to evaluate the product under simulated conditions to improve the customer confidence in its performance.A steel rolling mill customer had requested us to develop a rolling oil to roll stainless steel in a new 3-stand 18-high rolling mill and demonstrate its performance on an experimental set up. The present paper describes the methodology adopted to assess the suitability of a rolling oil for the particular rolling mill. The screening was carried out with a SRV (Schwingungs Reibungs und Verschleisstest, meaning Vibration, friction and Abrasion) tribometer and EHD (Elasto-hydrodynamic) interferometry based film thickness apparatus to assess the frictional and film forming characteristics of the oil under simulated operating conditions. In addition, simulated tests were carried out on a laboratory 2-Hi Experimental rolling mill to find out the specific roll force (rolling force per unit width of the strip being rolled) required to obtain 55–60% cumulative reduction in three passes as desired by the customer for different grades of stainless steel. Based on results obtained in the laboratory mill simulating industrial test conditions, the product was recommended and was accepted by the customer for use in their rolling mill.Copyright