Optical performance of an asymmetric inverted absorber compound parabolic concentrating solar collector

A computer-based numerical model has been developed utilising ray trace techniques, to simulate the optical characteristics of asymmetric inverted absorber line axis compound parabolic concentrating solar collectors (IACPCs). Cognisance is taken of the separate effects of the beam and diffuse properties of the total insolation on the optical performance. Increasing absorber gap height was expected to increase convection heat loss suppression and overall collector performance at the expense of a reduction in optical efficiency. The results are presented as graphical analyses of optical efficiency versus height of absorber gap, reflectivity and, acceptance and ray input angles.     

Boiling local heat transfer enhancement in minichannels using nanofluids

This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance.     

Effect of Some Polymeric Phenolic Antioxidants on the Properties of SBR Vulcanizates

Polymeric antioxidants can be useful in the protection of styrene-butadiene rubber (SBR) against thermal oxidative aging as an alternative to the low molecular weight ones, which migrate out of the rubber articles. Three polymeric compounds were prepared and incorporated into SBR mixes to be evaluated as antioxidants in comparison with the commercial antioxidant, N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD). The rheometric characteristics of the produced SBR mixes were measured and the cure time was determined. The mechanical, swelling, extraction, and compression properties were studied. The results obtained revealed that poly(4-mercaptophenyl)acrylamide has superior effect in the protection of SBR articles against thermal oxidative ageing.     

Initial chilling rate of pre-rigor beef muscles as an indicator of colour of thawed meat

The effect of three rigor temperatures and two muscles of different fibre composition on the colour of thawed meat were determined. Within 45 min post-mortem, m. semitendinosus (ST) and m. biceps femoris (BF) from unstimulated heifer sides were held at 0, 10 and 35°C until they entered rigor. The rate of pH fall was higher at 35°C than at 0 and 10°C; and the pH values were lower (first 12 h post mortem) in the ST than the BF. Hunter L*, a* and b* and the hue angle increased with increasing rigor temperature (P<0.001). The ST was lighter and yellower and had greater hue angle than the BF. Colour parameters were plotted against the rate of muscle cooling in the first hour post mortem and linear regression lines were fitted to the data and equations were derived that gave a good indication of the colour and colour stability of the muscles as meat.     

The recovery of uranium and the lanthanides from phosphate rock

A process is proposed for the treatment of phosphate rock for the recovery of uranium and lanthanides. The process assures the production of phosphatic fertilisers without polluting the environment with radioactive material.     

Crystallisation of impurities from black phosphoric acid at high temperature

Technical phosphoric acid when heated at 180°C in a pressure reactor deposits fluoro-aluminate crystals (Na, Mg) A1 (F, OH)₆.H₂O known as ralstonite, together with minor amounts of sodium fluorosilicate, Na₂SiF₆, and aluminum phosphate, AlH₃ (PO₄)₂^.3 H₂O. Uranium and vanadium in solution do not co-precipitate.     

Effects of pH adjustment with phosphates on attributes and functionalities of normal and high pH beef

Longissimus dorsi muscles from six normal- and six high-ultimate pH bulls were selected for fine mincing and subsequent pH adjustment with acid and alkaline pyrophosphate. Four pH treatments were prepared: initially high remains high (mean of pH 6.37), high becomes normal (5.62); initially normal remains normal (5.65), and normal becomes high (6.21). The addition level of phosphate as P(2)O(5) was the same in all replicates. Before pH adjustment, colour and water holding capacity (WHC) values were strongly affected by higher (initial) pH in expected ways: darker, lower chroma, higher capacity. After pH adjustment, these values were affected only by the final pH, not the initial pH (the pH history). Total protein solubility was likewise affected by final pH but not initial pH. In contrast, the combination high initial pH-high final pH improved sarcoplasmic protein solubility by 20% over the combination normal initial pH-high final pH. Sarcoplasmic protein solubility is an indicator of strain required to fracture cooked batters made from the minced meats; in the event, the rank order of the four treatments for strain-to-fracture matched that of sarcoplasmic protein solubility. Statistically, sarcoplasmic protein solubility and strain-to-fracture were both affected by initial pH (P<0.01) and final pH (P<0.001). However, stress required to fracture cooked batters was entirely controlled by initial pH (P<0.01). In other words, the stress-to-fracture advantage of initially high pH meat was not matched by upward pH adjustment of initially normal pH meat. Emulsion stability, which is better with higher pH meat, was affected by initial and final pH (both P<0.01). Cook yield, like WHC of pH-adjusted raw meat, was more due to final pH than initial pH, similarly cooked batter colour, whereas final pH had a significant effect on quality attributes (generally better when higher). An initially high pH history conferred an enduring advantage on three important batter attributes, stress-to-fracture, strain-to-fracture, and emulsion stability. Therefore, prior exposure of beef to normal pH conditions (pH 5.4-5.7) renders it less useful as a manufacturing grade product.     

Optimal design of a maintainable cold-standby system

This paper considers a framework to optimally design a maintainable cold-standby system. Not only the maintenance policy is to be determined, but also the reliability character of the components will be taken into account. Hence, the mean time to failure of the components and the policy time of good-as-new maintenances are proposed as decision variables. Following probability analyses, the system cost rate and the system availability are formulated as the optimization object and the constraint, respectively. Then, this optimization problem is directly resolved by recognizing its underlying properties. Moreover, the resolving procedure is found to be independent of the failure distributions of the components and the forms of the system cost, which is illustrated through a numerical example. As a conclusion, an exact method is successfully established to minimize the cost rate of a cold-standby system with the given maintenance facility.     

Preparation and characterization of novel bio-composites based on functionalized zeolite and nano-hydroxyapatite for a potential application in bone treatment

Journal of Porous Materials - This work was aiming to design novel bio-composite (BC) materials based on microwave-prepared AuNPs-loaded Zeolite-A (ZA-Au) and nano-hydroxyapatite (HA)....