Reducing heat gain from sheet metal-clad walls by utilizing industrially wasted materials (experimental study)

Buildings' walls are covered to reduce environmental impact and esthetics, and cladding materials vary based on public preference and financial capacity. Metal sheets with glossy surfaces are commonly used, but researchers propose using aluminum sheets and filling gaps with commercial waste materials, like, fabric roll sticks or circular plastic hollow parts. A test room with internal dimensions of 1 × 1 × 2 m used in Baghdad (latitude 33.2° N) was used to study thermal behavior, with a window-type air conditioner providing standard thermal conditions. The air gap attached to the top of the test wall was either left open or closed during the day. Results showed that double-layer bamboo packing preserved 52.1% with a closed-air gap and 49.5% with an open-air gap, but no discernible difference was observed between the two situations.     

Cooling of lithium-ion battery pack using different configurations of flexible baffled channels

The rated temperature and its uniformity of lithium-ion (Li-ion) battery (LIB) pack are the main demands for safe and efficient operation. This paper investigates an air cooling system of a pack of five prismatic LIB's generating considerable heat through discharging energy. The cooling system is a three-dimensional channel with flexible baffles of different arrangements installed on the walls of the channel to lower and regulate the temperature of the batteries. Three arrangements of these baffles are studied, transverse; L-shaped and staggered. The study is formulated as turbulent fluid–structure interaction and solved numerically using the finite elements method. The study was conducted for five spaces between batteries, S = 0, 1, 2, 3 and 4 mm and three different inlet air velocities, U_in = 0.5, 1 and 2 m/s. It was found that the flexible baffles guide the coolant towards the batteries smoothly with less pressure drop and this significantly improves the performance of the battery thermal management system due to the reduction of the maximum temperature and temperature variation as well. The staggered arrangement of the baffles shows the most effective configuration, where the maximum temperature difference between batteries is only 1.85°C for S = 1 mm and U_in = 2 m/s.     

Comparison of β-galactosidase immobilization by entrapment in and adsorption on poly(2-hydroxyethylmethacrylate) membranes

β-Galactosidase was immobilized in/on poly(2-hydroxyethyl methacrylate) (pHEMA) membranes by two different methods: adsorption on Cibacron F3GA derivatized pHEMA membranes (pHEMA-CB), and entrapment in the bulk of the pHEMA membranes. The maximum β-galactosidase adsorption on pHEMA-CB membranes was obtained as 95·6μgcm^-2 in 2·0mgcm^-3 enzyme solution. The adsorption phenomena appeared to follow a typical Langmuir isotherm. In the entrapment, an increase in β-galactosidase loading resulted in a consistent increase in membrane activity from 3·3×10^-2 to 17·8×10^-2Ucm^-2 pHEMA membranes. The K_m values for both immobilized β-galactosidase (adsorbed 0·32mM and entrapped 0·81mM ) were higher than that of the free enzyme (0·26mM ). The optimum reaction temperature of the adsorbed enzyme was 5°C higher than that of both the free and the entrapped enzyme. The optimum reaction pH was 7·5 for free and both immobilized preparations. After 15 successive uses the retained activity of the adsorbed and the entrapped enzymes was 80% and 95%, respectively. The storage stability of the enzyme was found to increase upon immobilization. ©1997 SCI     

New generation polymeric nanospheres for catalase immobilization

Monosize poly(2‐hydroxyethyl methacrylate‐co‐N‐methacryloly‐L ‐histidinemethylester) [mon‐poly(HEMA‐MAH)] nanospheres were prepared via surfactant‐free emulsion polymerization method. L ‐Histidine groups of the mon‐poly(HEMA‐MAH) nanospheres were chelated with Fe³⁺ ions. Mon‐poly(HEMA‐MAH) nanospheres were characterized by Fourier transform infrared spectroscopy, proton NMR, and scanning electron microscopy. Particle size of the mon‐poly(HEMA‐MAH) nanospheres was measured by Zeta Sizer. Elemental analysis of MAH for nitrogen was estimated as 0.94 mmol/g polymer. The catalase immobilized onto the mon‐poly(HEMA‐MAH)–Fe³⁺ nanospheres resulted in increasing the enzyme stability with time. Optimum operational temperature for both immobilized preparations was the same, and the temperature profiles of the immobilized preparations were significantly broader. It was observed that enzyme could be repeatedly adsorbed and desorbed on the mon‐poly(HEMA‐MAH)–Fe³⁺ nanospheres without loss of adsorption capacity or enzymic activity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical and Thermal Properties of Thermoset–Graphene Nanocomposites

Graphene has resulted in significant research effort to generate polymer nanocomposites with improved mechanical, thermal as electrical properties as compared to pure polymers. A large number of studies have been undertaken using different graphene derivatives, filler loadings, synthesis methods, and so on to obtain optimum filler dispersion as well as filler–matrix interactions, which are crucial for achieving significant enhancement in the properties, especially at low filler fraction. This review summarizes the mechanical and thermal properties of numerous studies carried out for the property enhancements of commercially relevant thermosetting materials such as epoxy, polyurethane, natural rubber, melamine formaldehyde, phenol formaldehyde, silicones, vinyl ester, cyanate ester, and unsaturated polyester resin.

     

Suppression of 3D mobility of carrier and superconductivity by Y substitution in Cu0.5Tl0.5Ba2(Ca2−xYx)Cu3O10−δ samples

Bulk Cu_0.5Tl_0.5Ba₂(Ca_2−xY_x)Cu₃O_10−δ superconductor ceramic samples were synthesized by the conventional solid-state method and characterized by X-ray diffraction, dc-resistivity, ac-susceptibility and Fourier Transform Infrared spectroscopy. The main purpose of this study was to investigate the role of charge carriers and the effect of Y substitution at Ca sites in between the CuO₂ planes on superconductivity. The superconducting properties are suppressed by Y substitution at Ca sites in between the CuO₂ planes of Cu_0.5Tl_0.5Ba₂(Ca_2−xY_x)Cu₃O_10−δ samples. It is most likely that Y³⁺ may create correlated domains in between the CuO₂ planes and localizes the carriers, which lowers the diamagnetic screening and suppresses the superconductivity. Therefore, cationic substitution reduces the three dimensional (3D) mobility of carriers, resulting in the reduction of the Fermi vector and velocity of the carriers, which in turn suppresses the superconducting properties of the material.     

Ag/PEPC/NiPc/ZnO/Ag thin film capacitive and resistive humidity sensors

In this study, thin film of blended poly-N-epoxypropylcarbazole (PEPC) (25 wt.%), nickel phthalocyanine (NiPc) (50 wt.%) and ZnO nano-powder (25 wt.%) in benzene (5 wt.%) was spin-coated on a glass substrate with silver electrodes to produce a surface-type Ag/PEPC/NiPc/ZnO/Ag capacitive and resistive sensor. The sensor with two different PEPC/NiPc/ZnO films thicknesses (330 nm and 400 nm) were fabricated and compared. The effect of humidity on capacitance and resistance of the Ag/PEPC/NiPc/ZnO/Ag sensors were investigated at two frequencies of the applied voltage: 120 Hz and 1 kHz. It was observed that at 120 Hz under humidity of up to 95% RH the capacitance of the sensors increased by 540 times and resistance decreased by 450 times with respect to humidity conditions of 50% RH. It was found that the sensor with thinner semiconducting film (330 nm) was more sensitive than the sensor with a thicker film (400 nm). The sensitivity was improved when the sensor was measured at a lower frequency if compared with a high frequency. It is assumed that the humidity response of the sensors is associated with absorption of water vapors and doping of water molecules in the semiconductors blend layer. This had been proven by the simulation of capacitance-humidity relationship.     

The mechanism of the formation of chloromethyl side groups in vinyl chloride polymerization

Summary The dependence of the content of short branches on the monomer and initiator concentrations in vinyl chloride polymerization has been investigated by infrared examination of polymers reduced with tributyl tin hydride. The branch content increases with decreasing monomer concentration but appears to be independent of the initiator concentration. The findings best fit the mechanism of RIGO et al (1972) involving head-to-head addition followed by migration of the end chlorine atom.     

Application of integrated computational chemistry system to the design of inorganic membranes

Today inorganic membranes attract a lot of interest as a growing field. Main focus of those activities is on the development of membrane materials, which can offer high permselectivities with acceptable high permeances. The need for high permselectivity beyond those limited by Knudsen flow requires the estimation of the factors, which determine the permselectivity. Plausible theoretical models based on physical or chemical reasoning is desirable to guide systematic development efforts for designing next generation inorganic membranes. Here we reviewed our attempts to generate theoretical models based on the molecular dynamics method for this purpose. As a first attempt, simulation was performed at specific conditions where the Knudsen theory can be applied and can be reproduced well by our simulation methodology. Molecular dynamics simulation at 373 K of the permeation of iso- and n-butanes through ZSM-5 type silicalite membrane are presented. After 200 ps of simulation time the permeation of n-butane was observed whereas the permeation of iso-butane was not observed. The calculated permeability of n-butane, which is close to experimental data, is also presented. A study on the affinity membrane for the separation of CO₂ at high temperature is presented and the prospect of permselectivity of CO₂ is demonstrated.     

Dye‐affinity microbeads for removal of phenols and nitrophenols from aquatic systems

Alkali Blue 6B attached poly(2‐hydroxyethyl methacrylate) (PHEMA) microbeads were investigated as dye‐affinity adsorbents for the removal of phenol and nitrophenols (i.e., 2‐nitrophenol, 4‐nitrophenol, and 2,4‐dinitrophenol) from aqueous solutions. PHEMA microbeads were prepared by radical‐suspension polymerization of HEMA in the presence of azobisisobutyronitrile as the initiator. These microbeads with a swelling ratio of 55% and carrying 23.6 μmol Alkali Blue 6B/g polymer were then used in the removal of phenol and nitrophenols from aqueous media. The adsorption was fast in all cases (20‐min equilibrium time). The maximum adsorptions of phenols onto the microbeads carrying Alkali Blue 6B were 145.2 μmol/g for phenol, 87.8 μmol/g for 2,4‐dinitrophenol, 112.6 μmol/g for 4‐nitrophenol, and 104.3 μmol/g for 2‐nitrophenol. The affinity order was phenol > 4‐nitrophenol > 2‐nitrophenol > 2,4‐dinitrophenol. The adsorption of nitrophenols decreased with increasing pH. Desorption of nitrophenols was achieved using a 30% (v/v) methanol solution. The microbeads carrying Alkali Blue 6B are suitable for repeated use for more than five cycles without a noticeable loss of adsorption capacity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2411–2418, 2002