Abstract: A gas turbine engine includes an epicyclic gear train that drives a turbo fan. The epicyclic gear train employs a one-piece carrier in which the spaced side walls are interconnected with circumferentially spaced apart mounts to form a unitary structure. Baffles are secured to the carrier near the mounts and provide lubrication passages that spray oil onto the sun gear and/or intermediate gears arranged between the baffles. The baffles can be constructed from a different material than the carrier since the baffles are not structural components in the gear train.

Abstract: The use of turbulators in different forms of ribs, baffles, delta winglets, obstacles, vortex generator, rings and perforated blocks/baffles is an effective way to improve the performance of heat exchangers and solar air heaters. Investigators studied the effect of these turbulators for heat transfer and friction characteristics in air ducts. An attempt has been made in this paper to carry out an extensive literature review of turbulators used to investigate heat transfer augmentation and flow structure in air ducts. Based on the review it is found that perforation in ribs/baffles/blocks and combination of combined rib and delta winglet leads to the better thermo-hydraulic performance. The correlations presented by various investigators, in terms of non-dimensional parameters for heat transfer and friction factor in solar air heaters and heat exchangers have also been presented.

Abstract: The performance characteristics of a solar heater and heat exchangers can be effectively improved by using artificial roughness in different forms, shapes and sizes Artificial roughness is provided in the form of different geometries such as ribs, dimple shape roughness, wire mesh, baffles, delta winglets etc To determine the effect of these geometries on thermal performance of solar heaters and heat exchangers, several experimental and numerical studies have been carried out by various researchers In this paper, an attempt has been made to review various roughness element geometries employed in solar air heaters and heat exchangers in terms of heat transfer, friction factor and flow simulation techniques Correlations developed for heat transfer and friction factor for different roughness geometries by various investigators in solar air heaters are presente

Abstract: Micromixing plays a significant role in microfluidics. Here a passive mixer with triangle baffles embedded in the main channel was designed, fabricated and characterized. Systematic simulations and experiments have been done with the increase of Reynolds number (Re), ranging from 0.1 to 500. All results confirmed the improvement of mixing within a short distance (<6.4 mm). At common flow rate of microfluidics (Re = 1.0), ‘the percentage of mixing’ (ϕ) can be 85.5% by the distance of 6.4 mm, which is 2.48-fold better than that of common Y-mixer. ϕ values of the design containing triangle baffles are 4.75-time at Re of 100 and 8.32-time at Re of 500 better than those of the common Y-mixer at the distance of 6.4 mm, respectively. The mixing effect caused by different apical angle and the number of triangles was also investigated using simulations. The mixing effect was improved with the growth of the apical angle of the triangles from 30 to 150°. Similarly, more triangle baffles lead to better mixing effect. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Abstract: Baffles serve as heat transfer augmentation features in solar air heaters; however, they increase pressure drop in flow channels. Perforated baffles are relatively good heat transfer augmentation features with superior performance over conventional smooth duct solar air heater and as a result find application in some solar air heaters. The exergy method is employed to in determining the roughness parameters, as second law-based exergy analysis is suitable for design of roughened solar air heaters. The exergetic efficiency of V down perforated baffled roughened duct solar air heater is studied analytically, and the results obtained compared with conventional system. Results indicate that high efficiency with optimum V down perforated baffle improves the heat absorption and dissipation potential of a solar air heater. Design plots are prepared to predict the optimum roughness parameter as a function of temperature rise parameter.

Abstract: A novel photocatalytic reactor for wastewater treatment was designed and constructed. The main part of the reactor was an aluminum tube in which 12 stainless steel circular baffles and four quartz tube were placed inside of the reactor like shell and tube heat exchangers. Four UV–C lamps were housed within the space of the quartz tubes. Surface of the baffles was coated with TiO2. A simple method was employed for TiO2 immobilization, while the characterization of the supported photocatalyst was based on the results obtained through performing some common analytical methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), and BET. Phenol was selected as a model pollutant. A solution of a known initial concentration (20, 60, and 100 ppmv) was introduced to the reactor. The reactor also has a recycle flow to make turbulent flow inside of the reactor. The selected recycle flow rate was 7 × 10−5 m3.s−1, while the flow rate of feed was 2.53 × 10−7, 7.56 × 10−7, and 1.26 × 10−6 m3.s−1, respectively. To evaluate performance of the reactor, response surface methodology was employed. A four-factor three-level Box–Behnken design was developed to evaluate the reactor performance for degradation of phenol. Effects of phenol inlet concentration (20–100 ppmv), pH (3–9), liquid flow rate (2.53 × 10−7−1.26 × 10−6 m3.s−1), and TiO2 loading (8.8–17.6 g.m−2) were analyzed with this method. The adjusted R 2 value (0.9936) was in close agreement with that of corresponding R 2 value (0.9961). The maximum predicted degradation of phenol was 75.50 % at the optimum processing conditions (initial phenol concentration of 20 ppmv, pH ∼ 6.41, and flow rate of 2.53 × 10−7 m3.s−1 and catalyst loading of 17.6 g.m−2). Experimental degradation of phenol determined at the optimum conditions was 73.7 %. XRD patterns and SEM images at the optimum conditions revealed that crystal size is approximately 25 nm and TiO2 nanoparticles with visible agglomerates distribute densely and uniformly over the surface of stainless steel substrate. BET specific surface area of immobilized TiO2 was 47.2 and 45.8 m2 g−1 before and after the experiments, respectively. Reduction in TOC content, after steady state condition, showed that maximum phenol decomposition occurred at neutral condition (pH ∼ 6).

Abstract: This paper presents an experimental analysis of a single pass solar air collector with, and without using baffle fin. The heat transfer coefficient between the absorber plate and air can be considerably increased by using artificial roughness on the bottom plate and under the absorber plate of a solar air heater duct. An experimental study has been conducted to investigate the effect of roughness and operating parameters on heat transfer. The investigation has covered the range of Reynolds number Re from 1259 to 2517 depending on types of the configuration of the solar collectors. Based on the experimental data, values of Nusselt number Nu have been determined for different values of configurations and operating parameters. To determine the enhancement in heat transfer and increment in thermal efficiency, the values of Nusselt have been compared with those of smooth duct under similar flow conditions.

Abstract: The effect of the operating parameters on the system hydrodynamics and mixing inside two circulating fluidized bed reactor (CFBR) risers with different ring baffle configurations were investigated using computational fluid dynamics simulations and a 24 factorial experimental design analysis. The operating parameters varied were the gas inlet velocity, and the mass flux, diameter and density of the solid particles, while the response variables were the standard deviation of the solid volume fraction (SVF) in the radial direction (SDSVF-RD) and the average SVF (ASVF). The results from the two CFBR risers with different ring baffle configurations showed a similar trend. The operating parameters that significantly affected the ASVF in both modified CFBR risers were the inlet gas velocity and solid particle mass flux, while those that significantly affected the SDSVF-RD were the inlet gas velocity and the inlet gas velocity–solid particle diameter–solid particle density interaction. For these systems, the lowest and highest ASVF was approximately 0.07 and 0.20, respectively, while the lowest and highest SDSVF-RD was 0.01 and 0.04, respectively. The low variability of the solid particle distribution and the high solid particle concentration will be suitable for chemical reactions. All the obtained results could be explained in terms of the system hydrodynamics. Finally, regression models to predict the mean solid particle concentration and variability of solid particle distribution in the system were obtained.

Abstract: Heat transfer enhancement has been always a significantly interesting topic in order to develop high efficient, low cost, light weight, and small heat exchangers. The energy cost and environmental issue are also encouraging researchers to achieve better performance than the existing designs. Two of the most effective ways to achieve higher heat transfer rate in heat exchangers are using different kinds of inserts and modifying the heat exchanger tubes. There are different kinds of inserts employed in the heat exchanger tubes such as helical/twisted tapes, coiled wires, ribs/fins/baffles, and winglets. This paper presents an overview about the early studies on the improvement of the performance of thermal systems by using different kinds of inserts. Louvered strip insert had better function in backward flow compared to forward one. Modifying the shape of twisted tapes led to a higher efficiency in most of the cases excpet for perforated twisted tape and notched twisted tape. Combination of various inserts and tube with artificial roughness provided promising results. In case of using various propeller types, heat transfer enhancement was dependent on higher number of blades and blade angle and lower pitch ratio.

Abstract: The general principles of mathematical modeling of heat transfer in cross-flow tube heat exchangers with complex flow arrangements that allow the simulation of multipass heat exchangers with many tube rows are presented. The finite-volume method is used to solve the system of differential equations for temperature of the both fluids and the tube wall with appropriate boundary conditions. A numerical model of a multipass steam superheater with 12 passes is presented. The convection and radiation heat transfer on the flue gas side are accounted for. In addition, the deposit layer is assumed to cover the outer surface of the tubes. Comparing the computed and measured steam temperature increase over the entire superheater allows for determining the thermal resistance of the deposits layer on the outer surface of the superheater. The developed modeling technique can especially be used for modeling tube heat exchangers when detailed information on the tube wall temperature distribution is needed.