Methods for reducing heat losses from flat plate solar collectors: Phase III. Final report, May 1, 1977-January 31, 1979

The present study extends earlier studies by examining the effect of the emissivities of both the absorber plate and the glass cover on the honeycomb's ability to suppress free convection, and on the radiative and conductive heat transfer which takes place across the honeycomb in the absence of free convection. By means of heat transfer measurements on ten Mylar honeycombs, this study has shown that the effect of the above emissivities on the suppression of convection by the honeycomb is slight, and can probably be ignored. On the other hand, the measurements also showed that the effect of these emissivities on the non-convective heat transfer is substantial, but not nearly so large as would have been predicted by existing theories. To explain this latter result theories were developed which take into account the important coupling (ignored by previous theories) between the conductive and radiative modes of heat transfer. These new theories predict the measured heat transfer rates to with about +-15%, depending on the emissivities. The results of this study have direct application to evaluating solar collectors which combine a selective surface with a honeycomb

Single component white-OLEDs derived from tris(β-diketonato) europium(iii) complexes bearing the large bite angle N^N 2-(4-thiazolyl)benzimidazole ligand

Two new organo-europium complexes (OEuCs) [Eu(tfac)3(TB-Im)] (Eu1) [Eu(hfac)3(TB-Im)] (Eu2) incorporating fluorinated (hexafluoroacetylacetone; Hhfaa) or hemi-fluorinated (trifluoroacetylacetone; Htfac) β-diketones together with the large bite angle N^N ligand (2-(4-thiazolyl)benzimidazole; TB-Im) have been synthesized and characterized. The structure of the complexes has been established by single crystal X-ray diffraction (SC-XRD) analysis and shows that the coordination sphere is composed of a EuO6N2 core (octacoordinated). Continuous shape measures (CShMs) revealed that the geometry around Eu(III) is trigonal dodecahedral with approximate D2d-symmetry. Efficient red emission is observed for both the complexes in solution with a fairly large photoluminescence quantum yield (PLQY (QLEu) = 39.00–47.00%). Furthermore, by utilizing the experimental photoluminescence (PL) data and theoretical modelling employing density functional theory (DFT) in conjunction with LUMPAC, energy transfer (ET) and back energy transfer rates were calculated, and an ET mechanism for the sensitized PL is proposed and discussed in detail. Finally, the complexes were used as an emitting layer (EML) to fabricate 20 organic light emitting diodes (OLEDs) by varying the doping concentration. Interestingly, both the complex-based OLEDs at 4 wt% doping concentration display white electroluminescence (EL) with the brightness (B) = 100.5–364.1 cd m−2 at very low turn-on voltage (Vturn-on) = 3.9–4.6 V. The overall electroluminescence performance of Eu1 and Eu2 is higher than that of the reported europium based single component white-OLEDs

Furnishing Amine-Functionalized Metal–Organic Frameworks with the β-Amidoketone Group by Postsynthetic Modification

The post-synthetic modification (PSM) of amino-functionalized MOFs to those bearing pendant β-amidoketone arms using diketene is herein reported. Three unique MOF families demonstrate the scope of this transformation, which is both atom-economical and yields high conversions. In each case, crystallinity was retained, and instances of exceptional solid-state ordering were observed in the PSM products, which has allowed detailed crystallographic characterization in multiple instances

Natural convection heat transfer from arrays of isothermal triangular fins in air

Measurements of the heat transfer to air by natural convection from arrays of isothermal triangular fins on a vertical base plate are reported for several array geometries, for a large range of Rayleigh number, and for two orientations (vertical fins and horizontal fins). The data are believed to be the first available for this important geometry. A single equation is provided that correlates the measured Nusselt numbers for the vertical orientation with an rms error of 4.8 percent. The horizontal fin orientation was shown to have inferior heat transfer performance.On fait \ue9tat ici des mesures du transfert de la chaleur \ue0 l?air par convection naturelle \ue0 partir d?ensembles de capteurs \ue0 ailettes triangulaires isothermes sur une platine verticale, pr\ue9sentant plusieurs g\ue9om\ue9tries diff\ue9rentes de capteur, pour une gamme \ue9tendue de nombres de Rayleigh et pour deux (2) orientations distinctes (ailettes verticales et ailettes horizontales). On croit que les donn\ue9es sont les premi\ue8res disponibles pour cette g\ue9om\ue9trie importante. Une \ue9quation unique est fournie, qui \ue9tablit une corr\ue9lation entre les nombres de Nusselt mesur\ue9s pour l?orientation verticale, avec une erreur quadratique moyenne de 4,8 %. L?orientation horizontale des ailettes s?est av\ue9r\ue9e offrir une performance de transfert de chaleur inf\ue9rieure.Peer reviewed: YesNRC publication: Ye