Papers by Keyword: Condensation

Abstract: The processes model in a flame during the n-alkanes air mixture combustion initiation is proposed, taking into account the supramolecular structures formation possibility in the peroxide clusters form. This approach is justified by the n-alkanes melting temperatures correlation with their autoignition temperatures and anti-knock indexes. The condensation possibility is provided for such high molecular structures. Boiling temperatures values at flame front pressures characteristic were evaluated. To predict the peroxide clusters melting temperatures, a formula developed earlier for the hydrocarbons condensed state was used, which takes into account the length and molecular weight of modeled clusters. Expected peroxide clusters melting temperatures were predicted for conditions of dimeric and tetrameric structures. A linear dependence was used to recalculation the obtained values in boiling temperatures. It is shown that the calculated clusters phase transitions characteristic temperatures can be realized in the flame front preparatory zone. Based on the condensation theory, the flame front thickness and the minimum non-extinguishing sphere radius during ignition were estimated: the obtained data closely coincide with these parameters known values.

Abstract: The study of water condensation phenomena is important in order to evaluate the performance of materials and coatings employed in the fabrication of waste heat recovery units including heat exchangers, heat pipes, condensing economizers and related functional surfaces. Fast evaluation of lab-scale samples is important during research and development of coatings for wetting phenomena under controlled, reproducible, and stable humidity and temperature conditions of both sample and environment. To study these effects, we report on the construction of a lab-scale condensation chamber, along with its evaluation and benchmarking with superhydrophobic coatings on stainless steel using perfluorooctyl silane (PFOTS). A working unit has been successfully fabricated and applied in a highly responsive device capable of recording the condensation performance of flat specimens under controlled conditions. Sample temperature was maintained with 0.10 °C deviation. The humidity response time of the chamber is 17.2 s per degree of RH% while the maximum relative humidity variation is +/- 3.2%RH. The unit successfully delivered valuable data over hydrophillic, hydrophobic and superhydrophobic surfaces. Data useful for studying open research issues such the relationship of contact angle and condensation phenomena.

Abstract: Microstructure fabrication and chemical surface functionalization with low-surface-energy materials are the key steps to achieve hydrophobic surfaces with high water droplet contact angles (CA). In this work we employed wire Electric Discharge Machining (EDM) as a way to induce microstructure topography on stainless steel 304 coupons. The resulting topography was rendered hydrophobic using trichloro-1H,1H,2H,2H-perfluorooctyl silane (PFOTS) via gas phase deposition. The channels created by machining and PFOTS functionalization facilitate water condensation by increasing nucleation sites and enhancing droplet coalescence. The resulting surface is hydrophobic (CA~140^o) in contrast to the bare stainless steel 304, which is hydrophilic (CA~76^o).

Abstract: This study aimed to design a condenser for a special application of condensing the vapor of pyrolysis process of hydrocarbon-based material such as plastic and biomass into liquid form or pyrolytic oil. Numerous condensers have been available in the market. However, a condenser cannot be selected and utilized directly for pyrolysis vapor condensation purposes. Before doing selection, the condenser must be designed first to meet the heat transfer requirements. In this work, the condenser was designed based on thermal analysis and validated with numerous published experimental data and the pyrolytic characteristics from related industry. A theoretical model is formulated for describing condensation of the pyrolysis vapor in the condenser to determine heat transfer requirement and the rate of condensation obtained. The effect of operating parameters such as cooling water rate in liters per minute (LPM) and temperature on the condensation rate was examined through an iterative procedure which rely to the heat transfer rate and the allowed pressure drop in the condenser. In this study, it was obtained that the highest cooling load is obtained when the flow rate of cooling water is 1.95 LPM. It was also obtained that the condenser effectiveness decreased of about 29.3 % with the ranges of cooling flow rate from 1.3 to 2.6 LPM

Abstract: The paper deals with the possibilities of using probabilistic calculation methods for the assessment of structures in building thermal technology and energetics. The subject is particularly the performance of individual probabilistic calculation methods that can be used for this purpose and their basic principles. Following are then examples of these calculations used in practice.

Abstract: The process of silicon carbide producing (SiC) in a resistance furnace is accompanied by moisture movement in the batch. An important consideration is the accounting of moisture transfer in the preparation of the mathematical description of the process. The aim of the article is to improve the existing model of heat and mass transfer in SiC production.

Abstract: This study investigates the possibility of Bose-Einstein condensation (BEC) in 2D-nanoclusters. A ground state equilibrium structure involves the single phonon exchange approximation. At critical temperature, the specific heat, entropy, and free energy of the system can be determined. The results support the existence of BEC in nanoclusters, and they lead to predictions of the behaviour of 2Dmaterials at low temperatures.

Abstract: In this article, we describe the synthesis of polyretherketones (PEK) by the method of acceptor-catalytic polycondensation, using oligoketones with different condensation degree (n = 1, 10, 20), isophthalic and terephthalic acid dichloride hydrides and 2,2-di-(4-hydroxyphenyl)propane. Their properties were also studied

Abstract: Ionic liquids (ILs) are organic salts that have a liquid phase under 100°C. Due to its ionic nature, it has affinity with water as well as organic compounds that make it potential to be developed as solvents with tuneable property. One class of material that possess this property is imidazolium compound which serves as organic cation. Variations of substituents (alkyl or aryl groups) in the parent cation provide several compounds that can be used as medium in various reactions. In this research, the synthesis of several imidazolium based ionic liquids had been performed utilizing Microwave Assisted Organic Synthesis (MAOS) method namely: butyl-methyl imidazolium chloride (BMIM-Cl), Decyl-methyl imidazolium bromide (DMIM-Br), Dodecyl-methyl imidazolium bromide (DDMIM-Br). The ILs were subsequently used as medium in cyclization reactions of diketone to provide an alternative route to flavanon. The structure of the synthesized ILs and the cyclization product were characterized by FT-IR and ¹H-NMR spectroscopy. The yield of the synthesized ILs were moderate (24-87%) while the yield of cyclization reactions was high (99%). The formation of the cyclization product, was clearly indicated by the ¹H-NMR spectrum with the peaks that appear at 6.81 ppm as singlet which corresponded to the proton at the pyranone ring.

Abstract: The main trends and prospects of water resources consumption, as well as existing ways of obtaining fresh drinking water, were analyzed. The design of a vortex condenser of atmospheric moisture has been provided. Its operating principle is based on the organization of free-convective flow under the temperature drop effect and air-cooling to a temperature below the dew point. The designed vortex condenser of atmospheric moisture runs on solar energy and do not require using additional energy sources. The results of numerical simulation of the flow structure in a vortex condenser of atmospheric moisture and experimental data, which confirms the formation of air flow inside the condenser and moisture condensation in its lower part, are presented.