Influence of the addition of aluminium nanoparticles on thermo-rheological properties of hydroxyl-terminated polybutadiene-based composite propellant and empirical modelling

The heat transfer performance and entropy analysis are done in a compact loop heat pipe (CLHP) with Al₂O₃/water and Ag/water nanofluid. A compact loop heat pipe having a flat square evaporator with dimensions of 34 mm (L)?×?34 mm (W)?×?19 mm (H) has been fabricated and tested for the heat load ranging from 30 to 500 W. The experimental tests are conducted by keeping the CLHP in the vertical orientation with distilled water, silver (Ag)/water and aluminium oxide (Al₂O₃)/water nanofluid having low volume concentrations of (0.09% and 0.12%). The effect of wall and vapour temperature, evaporator and condenser heat transfer coefficient, thermal resistance on the applied heat loads is experimentally investigated and compared. The experimental results showed that the evaporator thermal resistance is reduced by 34.70% and 20.21%, respectively, for 0.12 vol% of Ag, Al₂O₃ nanoparticles when compared with that of the distilled water. For the same volume concentrations of Ag, Al₂O₃ nanoparticles, an enhancement of 34.52%, 23.7%, 39.27% and 30.8%, respectively, observed for the convective heat transfer coefficients at the evaporator and condenser. The entropy is also reduced by 19.08% and 11.58% when Ag and Al₂O₃ nanofluids are used as the operating fluid. From the experimental tests, it is found that the addition of small amount of Ag nanoparticles in the working fluid enhanced the operating range by 15% when compared with that of Al₂O₃/water nanofluid without the occurrence of any dry-out conditions.

     

Reactive Extraction of Citric Acid Using Tri-n-octylamine in Nontoxic Natural Diluents: Part 1—Equilibrium Studies from Aqueous Solutions

Use of cheap, nontoxic, and selective solvents could economically provide a solution to the recovery of carboxylic acids produced by the bioroute. In this regard in the present paper, reactive extraction of citric acid was studied. Problems encompassing the recovery of the acid ([H₃A] _aq ^o ?=?0.1?C0.8) was solved by using tertiary amine (tri-n-octylamine, TOA) in natural diluents (rice bran oil, sunflower oil, soybean oil, and sesame oil). TOA was very effective in removal of acid providing distribution coefficient (D) as high as 18.51 (E%?=?95?%), 12.82 (E%?=?93?%), 15.09 (E%?=?94?%), and 16.28 (E%?=?94?%) when used with rice bran oil, sunflower oil, soybean oil, and sesame oil, respectively. Overall extraction constants and association numbers for TOA + rice bran oil, TOA + sunflower oil, TOA + soybean oil, and TOA + sesame oil were evaluated to be 35.48 (mol/l)^?1.46, 29.79 (mol/l)^?1.30, 33.79 (mol/l)^?1.51, and 37.64 (mol/l)^?1.65 and 1.46, 1.30, 1.51, and 1.65, respectively. Specific equilibrium complexation constants (K _E(n/m)) were also predicted using mathematical modeling.     

Effect of binary extractants and modifier–diluents systems on equilbria of propionic acid extraction

Propionic acid is an important carboxylic acid widely used in chemical industries. The recovery from aqueous waste streams and fermentation broth is of research interest. Extraction of carboxylic acids by reactive extraction using extractant-diluent, mixed extractants in diluents and extractants in mixed diluents etc. are emerging areas of study. With this aim reactive extraction of propionic acid was carried out to study: (i) effect of binary extractants (tri-n-octylamine(TOA):tri-n-butylphosphate (TBP), TOA:Aliquat 336 and TBP:Aliquat 336), (ii) effect of modifier (1-decanol) in different diluents (kerosene, n-octane, n-heptane, petroleum ether, butyl acetate, MIBK, 2-octanol, dodecanol, hexane) and (iii) effect of phase volume. Improved extractions using binary extractants and binary diluents were observed. Since liquid–liquid extraction is dependent on effect of modifier concentration, effect of phase volume, presence of single or binary extractants and binary diluents, the study will be useful in the design of reactive extraction process for propionic acid recovery.     

Efficacy of natural oils and conventional chemicals in the physical extraction of 4-hydroxybenzoic acid from aqueous solution

4-hydroxybenzoic acid (4-HBA) is a phenolcarboxylic acid and a valuable chemical with various pharmacological properties and a wide range of industrial applications. The present work is envisioned to retrieve 4-HBA from aqueous solution through physical extraction using natural oils (mustard oil, sunflower oil and soyabean oil) and chemicals (MIBK and 1-octanol) as solvent. The experimental evaluation of extraction equilibrium using aforesaid solvents is reported in the form of distribution coefficient (K_D), extraction efficiency (E_P %), partition coefficient (P) and dimerization constant (D). The results were analysed using several physicochemical aspects of the solvents utilized, such as the solvent polarity parameter, dielectric constant, and dipole moment. Further, the comparison of these extraction results was made with the results of our previous study which was with the solvents sesame oil, canola oil, benzene, toluene and p-ether. The results may be arranged in the increasing order with respect to average K_D and average E_P % for natural oils as canola oil (0.23, 18.85%) < mustard oil (0.25, 20.45%) < sunflower oil (0.27, 21.00%) < soyabean oil (0.34, 25.06%) < sesame oil (0.49, 33.24%) and for chemicals as benzene (0.08, 7.5%) < toluene (0.09, 8.25%) < p-ether (0.09, 8.32%) < MIBK (2.55, 71.41%) < 1-octanol (5.01, 83.01%).