Efficacy of incorporating PCMs into the commercial wall on the energy-saving annual thermal analysis

Journal of Thermal Analysis and Calorimetry - In this study, the efficacy of incorporating phase change material (PCM) into the building walls on the annual heat transfer reduction is examined....     

Applications of surfactant-modified clays to synthetic organic chemistry

Two triphase catalysts (SLL) have been developed for organic phase-aqueous phase reactions catalyzed by suitable modified clay (solid phase). These triphase catalysts have been applied to nucleophilic displacement on activated (benzylic) as well as unactivated organic halides and provide a convenient and effective method of preparation of the corresponding products. Other useful transformations to, which these triphase catalysts have been successfully applied are the synthesis of 9,9-dichloro bicyclo[6.1.0]nonane, O-alkylation and C-alkylation of β-naphthol.     

Overcoming acid–base copolymer neutralization using mesoporous carbon and its catalytic activity in the tandem deacetalization–Knoevenagel condensation reaction

Research on Chemical Intermediates - Acid–base copolymer materials are of considerable interest because of their fundamental implications for acid–base bifunctional catalysis...     

Fast and Efficient Nitration of Salicylic Acid and Some Other Aromatic Compounds over H_3PO_4/TiO_2-ZrO_2 Using Nitric Acid

TiO₂‐ZrO₂ (1/1)‐surf with Ti and Zr molar ratio of 1/1 was prepared with surfactant through a sol‐gel method. The optimum experimental condition was investigated for nitration of salicylic acid. Then, a number of nitration reactions were carried out with a variety of aromatic compounds in the optimum condition. The 25 wt% H₃PO₄/TiO₂‐ZrO₂ (1/1)‐surf catalyst showed good selectivity and yield in a short time for the nitration of salicylic acid and some other aromatic compounds.     

Numerical study of dynamic thermal conductivity of nanofluid in the forced convective heat transfer

In this work, forced convective heat transfer of nanofluid in the developing laminar flow (entrance region) in a circular tube is considered. The nanofluid thermal conductivity, as an important parameter, is considered as two parts: static and dynamic part. Simulated results show that the dynamic part of nanofluid thermal conductivity due to the Brownian motion has a minor effect on the heat transfer coefficients, on the other hand, static part of thermal conductivity including nanolayer around nanoparticle has an important role in heat transfer.     

Constructal multi-scale structure of PCM-based heat sinks

This paper inquires the effectiveness of a PCM-based heat sink as a reliable solution to portable electronic devices. This sink is composed of a PCM with low thermal conductivity and fins to boost its conductivity. The optimization is subjected to fixed heat sink volume filled with PCM between vertical equidistant fins. New fins are installed in the unheated space existing in each enclosure which is not involved in thermal distribution from vertical fins to the PCM. Based on the same principle, new fins generations are augmented stepwise to the multi-scale structure. The steps of adding fins will continue up to the point that the objective function reaches its maximal value, i.e., maximizing the longest safe operation time without allowing the electronics to reach the critical temperature. The results indicate that in each length of the enclosure, the optimum volume fraction and the best fins distance values exist in which the heat sink performance becomes maximum, and adding more fins lowers the performance of the heat sink. Increasing the enclosure’s length by \(2^{n}\) does not change them. For an enclosure with constant length, the optimal number of steps for adding fins within the enclosure is a function of the fin thickness. The results indicate that increasing the thickness changes the optimal number of adding fins inside the enclosure (normally a decrease). As the fin thickness is lowered, there will be a higher effect by adding vertical fins in the enclosure. Numerical simulations cover the Rayleigh number range \(2\times 10^{5}\le \hbox {Ra}_{\mathrm{H}} \le 2.7\times 10^{8}\), where H is the heat sink height.     

Pd-poly(N-vinyl-2-pyrrolidone)/KIT-6 nanocomposite: Preparation,structural study,and catalytic activity

The Pd-poly(N-vinyl-2-pyrrolidone)/KIT-6 nanocomposite was prepared by an in situ polymerization method and used as an efficient heterogeneous catalyst for C–C bond formation through the Heck coupling reaction of aryl iodides, bromides and chlorides with styrene. The physical and chemical properties of the catalyst were characterized by XRD, BET, FT-IR, TGA, UV-Vis and TEM techniques. The reactions were performed in methanol-water as solvent and the products were obtained in high yield and purity after a simple work-up. The stability of the nanocomposite catalyst was excellent and could be reused 8 times without much loss of activity in the Heck coupling reaction.     

Synthesis and characterization of P4VP/SBA-15 composite by in situ polymerization

Abstract  

Poly(4-vinylpyridine)/SBA-15 (P4VP/SBA-15) composites with various amounts of SBA-15 were prepared and characterized. The physical and chemical properties of P4VP/SBA-15 were investigated by XRD, BET, FT-IR, TGA, and SEM techniques. The catalytic performance of each material was determined for the Knoevenagel condensation reaction between carbonyl compounds and ethyl cyanoacetate in the presence of water as a solvent. The effects of reaction temperature, the amount of catalyst, amount of support, solvent, and the amount of benzoyl peroxide during the synthesis of P4VP/SBA-15 were investigated, as well as the recyclability of the heterogeneous composite. The catalyst used for this synthetically useful transformation showed a considerable level of reusability as well as very good activity. This reaction occurred rapidly when water was used as a solvent, so we assume it to be a green reaction.     

A review on the properties,preparation, models and stability of hybrid nanofluids to optimize energy consumption

Journal of Thermal Analysis and Calorimetry - These days, the importance of energy consumption has led scientists to optimize thermal devices. One of the solutions proposed for this purpose is...     

Evaluation of a tube equipped with different inserts: competition between improvements in heat transfer versus increase in pressure drop

Journal of Thermal Analysis and Calorimetry - This study evaluated the efficacy of different inserts incorporation into the simple tube on the rate of improvement in heat transfer as well as the...