Abstract: Debris flows surge downslope carrying destructive energy and can result in long runout distances. Structural mitigation is commonly installed along the flow path to impede debris flow mobility and protect downstream facilities. An array of baffles is a structural countermeasure frequently designed using empirical methods or prescribed to impede debris flow; nonetheless, its influence on reducing mobility is not well understood. A 5-m-long flume model is used to conduct a series of tests to systematically study the effects of varying baffle height, number of rows, spacing between rows, and degree of transverse blockage on mobility. Froude scaling is adopted to characterize initial upstream conditions. Debris runout, overflow, and frontal velocity reduction resulting from each baffle configuration used are examined. Experimental results reveal that it is imperative to adopt baffle heights taller than the approach flow depth (h) in order to suppress overflow and reduce runout. Adopting 1.5 h-tall baffles can reduce runout and peak overflow depth by 19 and 20 % compared to short baffles (0.75 h), respectively. A single row of baffles is ineffective in reducing frontal debris velocity, whereas increasing the array to three rows leads to 65 % reduction in runout and up to 57 % reduction in frontal velocity. Increasing spacing between successive rows from 0.25w to 0.5w can reduce runout by up to 37 %.

Abstract: The heat exchangers have a widespread use in industrial, transportation as well as domestic applications such as thermal power plants, means of transport, air conditioning and heating systems, electronic equipment and space vehicles. The key objectives of this article are to provide an overview of the published works that are relevant to the tube banks heat exchangers. A review of available and display that the heat transfer and pressure drop characteristics of the heat exchanger rely on many parameters. Such parameters as follows: external fluid velocity, tube configuration (in-line/staggered, series), tubes rows, tube spacing, fin spacing, shape of tubes, etc. The review also shows the finned and un-finned tube configurations heat exchangers. The important correlations for thermofluids in tube banks heat exchangers also discussed. The optimum spacing of tube-to-tube and fin-to-fin with fixed size (i.e., area, volume) with the maximum overall heat conductance (heat transfer rate) were summarized in this review. In addition, the few studies show the effect of tube diameter in a circular shape compared with elliptic tube shape. Overall, the heat transfer coefficient and pressure drop increases with increasing fluid velocity regardless the arrangement and shape of the tube. In the meantime, the other shape of tubes (such as flat or flattened) for finned and un-finned with the optimum design needs more research and investigation due to have lesser air-side pressure drop and improved air-side heat transfer coefficients. They have putted some the significant conclusions from this review.

Abstract: Channelized debris flows surge downslope in mountainous regions and have large impact forces. Arrays of debris flow baffles are frequently positioned in front of rigid barriers to engage torrents a...

Abstract: The turbulence promoters are widely used to enhance the performance of rectangular channel which were used for turbine blade passage cooling. In the present study, the influence of design parameters of the V down perforated baffle roughened rectangular channel on the heat transfer and friction factor was investigated using RSM and ANN. The quadratic model generated by RSM is used to predict the performance parameters, i.e. Nusselt number and friction factor with reasonably good accuracy. The optimum values of the design parameters of the V down perforated baffle roughened rectangular channel are relative roughness pitch of 2.6, relative roughness height of 0.33, open area ratio of 18% and Reynolds number of 18,500, in the desirable range of the order of 0.95. The training of the experimental data is carried out using 4-10-2 neural network and the predicted values are compared with the experimental values and found deviation in the range of ±10% among predicted and experimental values. The comparison of predicted values by RSM and ANN with the experimental values was carried out for each run of experiment and it was observed that the RSM predicted values are in accord with the experimental values in the uncertainty range of ±5%.

Abstract: Enhancement of heat transfer in the solar air heater ducts can be achieved by several means like using baffles, fins, ribs and groves. Until now, various attempts have been made to investigate the effects of these geometries on the enhancement of the heat transfer rate; however it is achieved at the cost of the increase in the pressure drop across the surfaces on which these elements are mounted. This paper is an attempt to summarize and conclude the investigations involving the use of small height elements and surface protrusions on absorber plate and channel walls as artificial roughness elements of various geometries and its effect on heat transfer and friction factor through experiments. It also summarizes the various correlations which have been developed for Nusselt number (Nu) and Friction factor ( f ) and reported in the previous investigations. The comparative study has been done to understand the results of these investigations for solar air heaters with different roughness elements on its absorber surface.

Abstract: Raceway pond is the most widely used for large scale microalgae culture. In the present study, the Particle Image Velocimetry technology was used to validate the reliability of the computational fluid dynamics simulation model for raceway pond. In order to increase the mixing degree and decrease the power consumption, novel mixers called sloping baffles and flow deflectors were combined in the raceway pond. The hydrodynamic characteristics of four types of raceway ponds (traditional raceway, raceway fitted with flow deflectors, raceway fitted with sloping baffles, raceway fitted with both flow deflectors and sloping baffles) were simulated by computational fluid dynamics. The results showed that the raceway pond fitted with sloping baffles and flow deflectors reduced the power consumption by 10%, increased the average velocity by 6.8%, promoted the velocity along the light attenuation direction by 93% and significantly eliminated the dead zone compared with the traditional raceway pond at the condition of rotation speed of paddlewheel of 20 rpm. Lastly, cultivation of Chlorella pyrenoidosa experiments was conducted, and the results indicated that the combination of sloping baffles and flow deflectors can significantly improve the productivity of microalgae.

Abstract: Rotating Packed Beds (RPBs) are novel reactors used for intensification of mass transfer and mixing since they provide adjustable centrifugal force to simulate high gravity. In this work, in order to analyze and optimize fluid flow in RPBs, a three-dimensional single-phase flow was simulated and validated with previous experimental data. The results show that pressure drop increases with an increasing gas flow rate and rotation speed, and reveal the distribution of total pressure and velocity magnitude. A RPB with radial gas inlet, one of the generic types of RPBs, which is widely applied in the chemical industry but has poor gas distribution on the surface of packing, was optimized using various baffles. The width, distance, shape, and opening porosity of the baffles were examined by adopting a criterion, and their effect on gas distribution was illustrated. Finally, a possible optimum structure of the RPB was formulated under optimal operational conditions.

Abstract: A headphone apparatus with selectable sound admission is described including an earphone apparatus. The earphone apparatus includes a housing being shaped to substantially cover an ear of a wearer when the headphone apparatus is worn, a sound emitting component within the housing, a baffle member formed of a flexible, sound-insulating material in the form of an open-ended tube having an outer open end and an inner open end with a central axis through the tube, the baffle member has an open arrangement with the tube providing an open channel and a closed arrangement in which the baffle member is twisted about the central axis to form a closed neck in the baffle member thereby preventing sound from transmission through the tube, and an operating mechanism for operating switching of the baffle member between the open and closed arrangements.

Abstract: This study attempts to simulate the flow and heat transfer in shell-and-tube heat exchanger with helical baffles. The effects of geometrical parameters (i.e., helix angle and baffle pitch) on the convective heat transfer and pressure drop have been investigated. The results indicate that application of helical baffles results in almost uniform distribution of temperature and pressure. Furthermore, both convective heat transfer and pressure drop increase by decreasing the helix angle and baffle pitch. In order to find optimum helix angle and baffles overlapping, two-objective optimization was performed, in which neural network was applied to obtain the objective functions. By performing optimization, 38 optimal cases were obtained. After finding the optimal cases, the compromise programming technique was utilized in order to facilitate the decision making process for selection among the optimal points. When importance of heat transfer and pressure drop is considered to be similar, using helical baffles with low overlapping (i.e., high baffle pitch) and low helix angle is suggested, while in case which heat transfer is regarded to be more important than pressure drop, application of helical baffles with high overlapping and low helix angle is recommended.