EVALUATION OF HEAT TRANSFER BOUNDARY CONDITIONS FOR CFD MODELING OF A 3D PLATE HEAT EXCHANGER GEOMETRY

In this paper fluid flow and heat transfer are modeled in a corrugated 3D plate heat exchanger geometry with a commercial computational fluid dynamics (CFD) program, Fluent 6.1.22 (Fluent Inc., Lebanon), in order to find out the most realistic heat transfer boundary conditions for a plate heat exchanger. The built-in boundary conditions of Fluent available for this case are Heat flux, Convection and Constant wall temperature. The CFD models are verified with correlations and experimental data obtained by a flat plate test equipment of which parameters can be calculated analytically. Deficiencies are found in all the built-in heat transfer boundary conditions. Heat transfer modeling with CFD in a corrugated plate heat exchanger is problematic because of the assumptions that have to be made when defining the boundary conditions in the complex geometry. The values of the computational parameters have spatial variations and can not be defined explicitly. However, when compared to the experimental correlations in the literature, the Convection boundary condition gives the most realistic results in the case of corrugated plate heat exchanger

Sub-ppb detection of formaldehyde with cantilever enhanced photoacoustic spectroscopy using quantum cascade laser source

Abstract A novel cantilever enhanced photoacoustic spectrometer with mid-infrared quantum cascade laser was applied for selective and sensitive formaldehyde (CH 2 O) gas measurement. The spectrum of formaldehyde was measured from 1,772 to 1,777 cm -1 by tuning the laser with a spectral resolution of 0.018 cm -1 . The band at 1,773.959 cm -1 was selected for data analysis, at which position the laser emitted 47 mW. In univariate measurement, the detection limit (3r, 0.951 s) and the normalized noise equivalent absorption coefficient (3r) for amplitude modulation (AM) were 1.6 ppbv and 7.32 9 10 -10 W cm -1 (Hz) -1/2 and for wavelength modulation (WM) 1.3 ppbv and 6.04 9 10 -10 W cm -1 (Hz) -1/2 . In multivariate measurement, the detection limit (3r) can be as low as 901 pptv (1,773.833-1,774.085 cm -1 , 15 spectral points each 0.951 s) for AM and 623 pptv (1,773.743-1,774.265 cm -1 , 30 spectral points each 0.951 s) for WM. Because measurement time increases in multivariate measurement, its application is justified only when interferents need to be resolved. Potential improvements of the system are discussed

Remoción de plomo presente en soluciones acuosas utilizando biocarbón producido a base de coronta de maíz

Se produjo biocarbón a partir de residuos de coronta de maíz (Zea mays) para remover plomo de soluciones acuosas. La carbonización del residuo se realizó a 600 °C por 2 h a 1 atmosfera de nitrógeno controlada. Se realizaron análisis texturales, morfológicos y estructurales para caracterizar el material. De los datos de la isoterma de adsorción de N2, el material mostró una estructura microporosa de 144,13 m2/g de área superficial. Se realizaron experimentos de adsorción de Pb2+ en equilibrio y cinética, donde los datos de equilibrio se ajustan mejor al modelo de Dubinin-Radushkevich (R2 ≥ 0,990) con capacidad de adsorción máxima de 12,16 mg/g con. Asimismo, para los datos de cinética, el modelo con mejor ajuste fue el de Elovich (R2 ≥ 0,994). Sin embargo, la cinética de adsorción también se ajustó a los modelos de Pseudo-Primer orden (R2 ≥ 0,990) y Pseudo- Segundo orden (R2 ≥ 0,992), con valores de adsorción de 10,54 mg/g y 15,59 mg/g respectivamente. El análisis de la espectrometría de energía dispersiva (EDS), después de las pruebas de adsorción detectaron la presencia de Pb2+ en la estructura del biocarbón. La coronta de maíz tiene un potencial uso para la producción de biocarbón y la remoción de Pb2+, demostrando ser eficiente

Investigation of Sulfonated Graphene Oxide as the Base Material for Novel Proton Exchange Membranes

This work deals with the development of graphene oxide (GO)-based self-assembling membranes as possible innovative proton conductors to be used in polymer electrolyte membrane fuel cells (PEMFCs). Nowadays, the most adopted electrolyte is Chemours’ Nafion; however, it reveals significant deficiencies such as strong dehydration at high temperature and low humidity, which drastically reduces its proton conductivity. The presence of oxygenated moieties in the GO framework makes it suitable for functionalization, which is required to enhance the promising, but insufficient, proton-carrying features of GO. In this study, sulfonic acid groups (–SO3H) that should favor proton transport were introduced in the membrane structure via a reaction between GO and concentrated sulfuric acid. Six acid-to-GO molar ratios were adopted in the synthesis procedure, giving rise to final products with different sulfonation degrees. All the prepared samples were characterized by means of TGA, ATR-FTIR and Raman spectroscopy, temperature-dependent XRD, SEM and EDX, which pointed out morphological and microstructural changes resulting from the functionalization stage, confirming its effectiveness. Regarding functional features, electrochemical impedance spectroscopy (EIS) as well as measurements of ion exchange capacity (IEC) were carried out to describe the behavior of the various samples, with pristine GO and commercial Nafion® 212 used as reference. EIS tests were performed at five different temperatures (20, 40, 60, 80 and 100 °C) under high (95%) and medium (42%) relative humidity conditions. Compared to both GO and Nafion® 212, the sulfonated specimens demonstrate an increase in the number of ion-carrying groups, as proved by both IEC and EIS tests, which reveal the enhanced proton conductivity of these novel membranes. Specifically, an acid-to-GO molar ratio of 10 produces a six-fold improvement of IEC (4.23 meq g-1) with respect to pure GO (0.76 meq g-1), while a maximum eight-fold improvement (5.72 meq g-1) is achieved in SGO-15

Combined Partial Oxidation of Methane to Synthesis Gas and Production of Hydrogen or Carbon Monoxide in a Fluidized Bed using Lattice Oxygen

ISSN:2194-4296ISSN:2194-428

Carbon dioxide: from waste to resource for methanol-based processes

International audienc

Concentration of meat processing industry wastewater by reverse osmosis and anaerobic digestion of the concentrate

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Electronic waste recovery in Finland:consumers’ perceptions towards recycling and re-use of mobile phones

Abstract This paper examines consumers’ awareness and perceptions towards mobile phone recycling and re-use. The results are based on a survey conducted in the city of Oulu, Finland, and analysed in the theoretical framework based on the theories of planned behaviour (TPB) and value-belief-norm (VBN). The findings indicate that consumers’ awareness of the importance and existence of waste recovery system is high; however, awareness has not translated to recycling behaviour. The survey reveals that 55% of respondents have two or more unused mobile phones at homes. The more phones stored at homes, the more often reasons ‘I don’t know where to return’ and/or ‘have not got to do it yet’ were mentioned. This indicates that proximity and the convenience of current waste management system are inadequate in promoting the return of small waste electrical and electronic equipment (WEEE). To facilitate re-use, and the highest level of recovery, consumers will need to be committed to return end-of-use electronics to WEEE collection centres without delays. Further, the supply and demand of refurbished mobile phones do not meet at this moment in Finland due to consumer’s storing habits versus expectations of recent features under guarantee and unrealistic low prizes. The study also points out that, in order to change current storing habits of consumers, there is an explicit need for more information and awareness on mobile phone collection in Finland, especially on regarding retailers’ take-back