Attic radiant barrier systems: A sensitivity analysis of performance parameters

During the past seven years, the Florida Solar Energy Center (FSEC) has conducted extensive experimental research on radiant barrier systems (RBS). This paper presents recent research on the development of mathematical attic models and results from a sensitivity analysis of RBS performance parameters. Two levels of modelling capability have been developed. A very simplified model based on ASHRAE procedures is used to study the sensitivity of RBS performance parameters, and a very detailed finite-element model is used to study highly complex phenomena, including moisture adsorption and desorption in attics. The speed of the simple model allows a large range of attic parameters to be studied quickly, and the finite-element model provides a detailed understanding of combined heat and moisture transport in attics. This paper concentrates on the sensitivity analysis of attic RBS performance parameters using the simplified model. The development of the model is described, and results of the analyses are presented and discussed. Results from the finite-element model are also presented and compared with measurements from a test attic to illustrate the effects of moisture adsorption and desorption in common attics. The simplified steady-state model shows excellent agreement with measured steady-state data when thermal stratification of the attic air is modelled. Results of the sensitivity analysis using this model show that the radiant barrier surface emittance and the attic ventilation inlet air temperature are the most sensitive performance parameters for attic radiant barrier systems. The detailed, finite-element model shows that moisture sorption phenomena can have significant effects in attics. The daily temperature extremes in attics are significant, and they induce a moisture flux at the surfaces of the materials bounding the air zone(s). If this moisture flux is not accounted for in detail (i.e. with fully coupled heat and moisture transport equations) inaccurate surface temperature predictions are likely to occur.     

Mechanical properties of high temperature cyanate ester/BMI blend composites

A new Schiff base functionalized dicyanate ester was synthesized and the monomer was characterized by FTIR, ¹H-NMR, ¹³C-NMR and elemental analysis techniques. This prepared dicyanate ester with catalyst was then blended with BMI resin at different ratios by solution technique. The composites were made by impregnating the fibers with the blend solution followed by curing at various time-temperature schedules. The mechanical properties of the blend composites were tested. The fiber volume fraction of the composites were found to be in the range 41 ± 3%. The mechanical properties such as tensile modulus (32–35 GPa), flexural modulus (56–59 GPa) and Mode I fracture toughness (G_IC = 104–136 J/m²) and impact response (1,121–1,218 J/m) were found to increase with increasing cyanate ester content in the Cy/BMI blends. From the DMA study it was observed that as the cyanate content increases from 3 to 9% in the blend the tan δ value increases from 0.112 to 0.126 and the storage modulus decreases from 24,750 to 22,870 MPa indicating that the crosslink density of the blends decreases. The SEM analysis shows the absence of phase separation. Moisture absorption and chemical resistance of the blend composites increase with increasing cyanate content. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Multivariate polynomial fit: Decay heat removal system and pectin degrading Fe3O4‐SiO2 nanobiocatalyst activity

Herein, multivariate Lagrange''s interpolation polynomial (MLIP) and multivariate least square (MLS) methods are used to derive linear and higher‐order polynomials for two varied applications. (1) For an effective fabrication of Pectin degrading Fe₃O₄‐SiO₂ Nanobiocatalyst activity (IU/mg). Here, the three parameters namely: pH value, pectinase loading and temperature as independent variables are optimized for the maximal of anobiocatalyst activity as a dependent variable. (2) For a passive system reliability estimation of decay heat removal (DHR) of a nuclear power plant. The success criteria of the system depend on three types temperature that do not exceed their respective design safety limits and are considered as dependent variables and 14 significant parameters were used as independent variables. Statistically, the validation of these multivariate polynomials are done by testing of hypothesis. Comparative study of the proposed approach gives significance results in the first application have the optimum conditions for maximum activity using linear MLIP method is: 58.64 with pH = 4, pL = 250 and Temp = 4°C. The maximum activity using second order MLIP method is 59.825 and method of MLS is 59.8249 with the optimized values of an independent variables pH = 4, pL = 300 and Temp = 8°C depicted in Table 1. In DHR system, the significance results are obtained and depicted in Table 2.     

Preparation,characterization, and functional analysis of zinc oxide nanoparticle-coated cotton fabric for antibacterial efficacy

Nanotechnology is an emerging interdisciplinary technology and nanostructures capable of enhancing the physical properties of conventional textiles in areas such as antimicrobial properties, water repellence, soil resistance, antistatic, anti-infrared and flame-retardant properties, dye ability, color fastness, and strength of textile materials. The studies were carried out in order to fine tune the preparation of zinc oxide nanoparticles (NPs) for special applications. Soluble starch (stabilizing agent), zinc nitrate and sodium hydroxide (precursors) were used for the preparation of zinc oxide NPs by wet chemical method. The synthesized NPs were coated on cotton fabric (plain weave), and the antibacterial property of the treated fabric was analyzed. Fourier transform infrared spectroscopic analysis, scanning electron microscopy, and physical and chemical characterization were employed to determine the phase and morphology of the final nanoparticle-coated fabric. The results indicated that 2% zinc oxide nanoparticle (200 nm) -coated fabric have high antibacterial efficiency (99.9% against Staphylococcus aureus and 80% against Escherichia coli) and upon washing the coated fabric (five hand washes), the antibacterial activity was found to be 98% against S. aureus and 75% against Escherichia coli.     

Effect of storage period on provitamin-A carotenoids retention in biofortified maize hybrids

Vitamin A-rich maize hybrids provide sustainable solutions to malnutrition. However, significant loss of carotenoids during storage reduces its efficacy. Grains of nine sub-tropically adapted crtRB1-based biofortified hybrids along with six normal hybrids were stored under conventional storage for five months. PVAC (β-carotene and β-cryptoxanthin) among crtRB1-based hybrids degraded from initial level of 18.77 to 3.24 µg g⁻¹, while NPVAC (lutein and zeaxanthin) reduced to 10.79 µg g⁻¹ from 19.00 µg g⁻¹ during storage. Among PVAC, β-cryptoxanthin (21.8%) possessed more stability than β-carotene (16.4%). For NPVAC, lutein (61.2%) showed the highest retention than zeaxanthin (50.4%). Majority of the PVAC loss occurred within first three months of storage. Retention for PVAC among crtRB1-based hybrids varied from 14% to 23% indicating the role of favourable genetic factors. APQH1, APQH7 and APH2 were the promising hybrids with higher retention (>20%) of PVAC. This is the first report on identification of provitamin A-rich crtRB1-based biofortified maize hybrids with higher retention during sub-tropical storage.     

Advance electrochemical oxidation of fipronil contaminated wastewater by graphite anodes and sorbent nano hydroxyapatite

Degradation of C₁₂H₄Cl₂F₆N₄OS phenylpyrazole insecticide (Fipronil) by advance electrochemical oxidation in aqueous water solution was studied. The process efficiency was figured based on the COD, chloride, and fluoride reduction from fipronil. Further, we tried to highlight the importance of nano-hydroxyapatite (n-Hap) as a cost-effective nano sorbent for removal of fluoride from fipronil. From the advance electrochemical oxidation experiment, it was found that the COD removal was 79%, chloride 52%, and fluoride 80%. The intermediate of fipronil compounds was examined by GC-MS. The final results conclude that advance electrochemical oxidation process was effective for removal of fipronil synthetic wastewater.     

Investigations on structural, optical and electrochemical properties of blue luminescence SnO2 nanoparticles

A simple solution approach has been developed to synthesis SnO₂ nanoparticles using polyethylene glycol as stabilizer. X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), UV–Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the nanoparticles. XRD, HR-TEM and AFM indicate that the SnO₂ nanoparticles correspond to tetragonal crystal structure with size ranges below Bohr’s exciton radius. UV–Vis absorption spectrum showed band gap exhibiting a 1.3 eV shift from that of bulk SnO₂ structures. The blue emission owing to transition of an electron from conduction band to deeply trapped hole in SnO₂ nanoparticles was analyzed using PL spectroscopy. The charge transfer capability had been investigated using CV and EIS in different electrolytes. A detailed exploration on confinement effect that occurred in SnO₂ nanoparticles, mechanism behind visible emission and electron transfer mechanism in different electrolyte was discussed.     

Experimental investigation of Al2O3/8YSZ and CeO2/8YSZ plasma sprayed thermal barrier coating on diesel engine

In this research work, aluminium oxide/yttria stabilized zirconia (20%Al₂O₃/80%8YSZ) and ceria/yttria stabilized zirconia (20%CeO₂/80%8YSZ) were coated through atmospheric plasma spray technique (APS) as thermal barrier coating (TBC) over CoNiCrAlY bond coat on aluminium alloy (Al-13%Si) substrate piston crown material and their thermal cycling behavior were studied experimentally. Thermal cycle test of both samples were conducted at 800?°C. Microstructural, phase and elemental analysis of the TBC coatings were experimentally investigated. The performance, combustion and emission characteristics of Al₂O₃/8YSZ, CeO₂/8YSZ TBC coated and uncoated standard diesel engine were experimentally investigated. The test results revealed that CeO₂/8YSZ based TBC has an excellent thermal cycling behavior in comparison to the Al₂O₃/8YSZ based TBC. The spallation of the Al₂O₃/8YSZ TBC occurred mainly due to the formation of thermally grown oxide (TGO), and growth of residual stresses at top coating and bond coating interface. The experimental results also revealed that the increase of brake thermal efficiency and reduction of specific fuel consumption for both TBC coated engine. Further reduction of HC, CO and smoke and increase of NOx emission were recorded for both TBC coated engine compared to the standard diesel engine.