Energetic analysis of an air handling unit combined with enthalpy air-to-air heat exchanger

The energetic analysis of an air handling unit (AHU) combined with an enthalpy air-to-air heat exchanger has been studied to improve the first law thermodynamic efficiency. The energy balance equations for enthalpy air-to-air heat exchanger, conditioned space, heating coil, cooling coil and mixing box have been performed and solved based on a program developed in Engineering Equation Solver. The results showed that using an enthalpy air-to-air heat exchanger leads to energy recovery which in turn decreased the total required AHU power. The effect of using an enthalpy air-to-air heat exchanger on recovered energy in hot and humid ambient is more than the cold and dry one. Using the enthalpy air-to-air heat exchanger, the cooling coil load decreases by 28.27%, which in turn increases the first law efficiency by 32.8%.

     

Heat transfer characteristics of a two-phase closed thermosyphon using different working fluids

In this paper, an enhanced FORTRAN code was combined with the EES software to predict the vapor flow thermal resistance effects on the heat transfer characteristics of a two- phase closed thermosyphon (TPCT). Different refrigerants such as water, ammonia, R-11, R-22 and R-134a were tested. Also an enhanced time integration scheme was recommended for solving the governing equations in FORTRAN code.     

Electron transport properties of boron nitride fullerene B24N24 doped with lithium atom: first-principles calculations

The transport properties of Li@B₂₄N₂₄ metallofullerene bridging two Au contacts are studied with a combined density functional theory and the non-equilibrium Green’s-function technique. Our calculated results show that the conductance of Li@B₂₄N₂₄ nanocage is generally higher than that of the undoped B₂₄N₂₄ molecule. We calculated the current–voltage characteristics for positive and negative bias voltages. It was found that due to presence of Li in B₂₄N₂₄ nanocage, a novel negative differential resistance (NDR) phenomenon is observed. Furthermore, the transmission coefficients of the Li@B₂₄N₂₄ metallofullerene at various external biases are analyzed and it indicates that the broadening of the transmission coefficient spectrum with increasing of the external biases confirms the NDR behavior at the I–V characteristic.     

Frames and bases in tensor products of Hilbert spaces and Hilbert <Emphasis Type="Italic">C</Emphasis>*-modules

In this article, we study tensor product of Hilbert C*-modules and Hilbert spaces. We show that if E is a Hilbert A-module and F is a Hilbert B-module, then tensor product of frames (orthonormal bases) for E and F produce frames (orthonormal bases) for Hilbert A ⊗ B-module E ⊗ F, and we get more results. For Hilbert spaces H and K, we study tensor product of frames of subspaces for H and K, tensor product of resolutions of the identities of H and K, and tensor product of frame representations for H and K.     

Investigation of the reaction of dithiocarbamic Acid salts with aromatic aldehydes

A reaction of dithiocarbamic acid salts with carbonyl compounds was investigated for the first time in the presence of BF(3)·OEt(2). The reaction is temperature dependent and gives gem-bis(dithiocarbamates) at 35-45 °C as a molecule with high equivalents of dithiocarbamate groups. At lower temperatures (15-20 °C), the 2-iminium-1,3-dithietane is obtained as the only product. The structure of a 2-iminium-1,3-dithietane was accomplished by X-ray crystallographic analysis.     

A novel polymeric catalyst for the one-pot synthesis of xanthene derivatives under solvent-free conditions

A simple, efficient, and environmentally benign route was developed for the preparation of 14-aryl or alkyl-14H-dibenzo[a,j]xanthene, 1,8-dioxo-octahydroxanthene and 12-aryl??8,9,10,12-tetrahydrobenzo[a]xanthene-11-ones from condensation of various aldehydes with (i) ??-naphthol, (ii) cyclic 1,3-dicarbonyl compounds and (iii) ??-naphthol and cyclic 1,3-dicarbonyl compounds, using novel polymeric catalyst [poly(AMPS-co-AA)] under solvent-free conditions. Use of easily available catalyst, shorter reaction times, better yields, simplicity of the reaction, heterogeneous system, and easy work-up are the advantages of the present method.     

Recognition of \text {PSL}(2,p) by order and some information on its character degrees where p is a prime

Let \(G\) be a finite group and \(\text {cd}(G)\) be the set of irreducible character degrees of \(G\) . In this paper we prove that if \(p\) is a prime number, then the simple group \(\text {PSL}(2,p)\) is uniquely determined by its order and some information about its character degrees. In fact we prove that if \(G\) is a finite group such that (i) \(|G|=|\text {PSL}(2,p)|\) , (ii) \(p\in \text {cd}(G)\) , (iii) \(\text {cd}(G)\) has an even integer, and (iv) there does not exist any element \(a\in \text {cd}(G)\) such that \(2p\mid a\) , then \(G\cong \text {PSL}(2,p)\) . As a consequence of our result we get that \(\text {PSL}(2,p)\) is uniquely determined by its order and the largest and the second largest character degrees.