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Sweetpotato (<i>Ipomoea batatas</i>) is a popular vegetable across the world. It is a staple food item of many countries in South America, Africa and Asia where the population depends on the crop as an important source of energy and essential nutrients like vitamins A and C, calcium, iron and copper. It is also a very popular crop in North America. Deep fat frying is one of the favourite processing methods for sweetpotato. The method is fast and the finished product is desired for its unique flavour and taste. <p>The main objective of this study was to establish analogy between convective heat and mass transfer during frying. The accurate estimation of the coefficients for both phenomena is challenging. During frying, the rate of heat transfer from the oil to the food surface is largely controlled by the convective heat transfer coefficient. This heat transfer coefficient is dependent on the interaction between the temperature gradient and the drying rate in a frying process. The temperature gradient and the drying rate in turn partly depend on the thermophysical properties of the product. In this study, thermophysical properties of sweetpotato were studied and modeled as a function of moisture content and temperature. The properties of interest are specific heat capacity, thermal conductivity, thermal diffusivity and density. A designed deep fat frying experiment of sweetpotato was carried out under four different oil temperatures (150, 160, 170 and 180°C) and using three different sample sizes (defined as ratio of diameter to thickness (D/L: 2.5, 3.5 and 4.0). Convective heat transfer coefficients under these frying conditions were estimated and computer simulation based on finite element modeling technique was used to determine convective mass transfer coefficients. Correlation between heat transfer coefficient and mass transfer coefficient were investigated with reliable statistical tool. Effects of sample size, oil temperature and frying time on heat and mass transfer were also studied. <p>Specific heat, thermal conductivity and thermal diffusivity of sweetpotato were all found to increase with increase in temperature and moisture content. Density decreased with increase in moisture content. Maximum heat transfer coefficient reached during sweetpotato frying was in the range of 700-850 W/m2.°C. Heat transfer coefficient of sample during frying increased with increase in frying oil temperature but decreased with increase in sample size. Same trend for heat transfer coefficient was observed for effects of oil temperature and sample size on mass transfer coefficient. Maximum mass transfer coefficient reached during sweetpotato frying was in the range of 4×10-6 to 7.2×10-6 kg/m2.s. No general relationship was established between heat transfer coefficient and mass transfer coefficient during frying but a relationship was established between maximum heat transfer coefficient and maximum mass transfer coefficient. A trend was also observed between maximum heat transfer coefficient and the corresponding mass transfer coefficient at that point.

Micro-channels are believed to open up the prospect of precise control of fluid flow and chemical reactions. The capillary effect can be used to pump fluids in micro-channels and the flow generated can dissolve chemicals previously deposited on the walls of the channel. In this work, numerical and experimental approaches have been developed to investigate the wall mass transfer rate generated by capillary driven flows (CD-Flow). The purpose of this work is to analyze the wall mass transfer rates generated by a CD-Flow in a micro-channel. The results have implications in the optimization and design of devices for biological assays. The correlation for Sherwood number, Reynolds number, contact angle and time is reported. This correlation can be a useful tool for design purposes of microfluidic devices that work with fast heterogeneous reaction and have capillary driven flow as passive pumping system. The numerical results have been confirmed by the experimental results. / La perspectiva del uso de micro-canales para el control preciso del flujo y de las reacciones químicas está ampliamente aceptada. Considerando que el efecto de las tensiones superficiales en la micro-escala es significativo, el bombeo pasivo basado en el uso de la tensión superficial para los Lab-on-a-chip resulta ser el método más eficaz.El propósito de este trabajo es analizar la transferencia de masa en la pared en un campo dinámico de un flujo impulsado por capilaridad. Los resultados permitirán mejorar el diseño y optimizar los dispositivos para ensayos biológicos. Se presenta una correlación entre el número de Sherwood, el número de Reynolds, el ángulo de contacto y el tiempo. La correlación puede ser una herramienta útil en el diseño de dispositivos microfluídicos que trabajen con una reacción rápida y heterogénea y usen el bombeo pasivo impulsado por el flujo capilar. Los resultados numéricos han sido confirmados por los resultados experimentales.

Sweetpotato (<i>Ipomoea batatas</i>) is a popular vegetable across the world. It is a staple food item of many countries in South America, Africa and Asia where the population depends on the crop as an important source of energy and essential nutrients like vitamins A and C, calcium, iron and copper. It is also a very popular crop in North America. Deep fat frying is one of the favourite processing methods for sweetpotato. The method is fast and the finished product is desired for its unique flavour and taste. <p>The main objective of this study was to establish analogy between convective heat and mass transfer during frying. The accurate estimation of the coefficients for both phenomena is challenging. During frying, the rate of heat transfer from the oil to the food surface is largely controlled by the convective heat transfer coefficient. This heat transfer coefficient is dependent on the interaction between the temperature gradient and the drying rate in a frying process. The temperature gradient and the drying rate in turn partly depend on the thermophysical properties of the product. In this study, thermophysical properties of sweetpotato were studied and modeled as a function of moisture content and temperature. The properties of interest are specific heat capacity, thermal conductivity, thermal diffusivity and density. A designed deep fat frying experiment of sweetpotato was carried out under four different oil temperatures (150, 160, 170 and 180°C) and using three different sample sizes (defined as ratio of diameter to thickness (D/L: 2.5, 3.5 and 4.0). Convective heat transfer coefficients under these frying conditions were estimated and computer simulation based on finite element modeling technique was used to determine convective mass transfer coefficients. Correlation between heat transfer coefficient and mass transfer coefficient were investigated with reliable statistical tool. Effects of sample size, oil temperature and frying time on heat and mass transfer were also studied. <p>Specific heat, thermal conductivity and thermal diffusivity of sweetpotato were all found to increase with increase in temperature and moisture content. Density decreased with increase in moisture content. Maximum heat transfer coefficient reached during sweetpotato frying was in the range of 700-850 W/m2.°C. Heat transfer coefficient of sample during frying increased with increase in frying oil temperature but decreased with increase in sample size. Same trend for heat transfer coefficient was observed for effects of oil temperature and sample size on mass transfer coefficient. Maximum mass transfer coefficient reached during sweetpotato frying was in the range of 4×10-6 to 7.2×10-6 kg/m2.s. No general relationship was established between heat transfer coefficient and mass transfer coefficient during frying but a relationship was established between maximum heat transfer coefficient and maximum mass transfer coefficient. A trend was also observed between maximum heat transfer coefficient and the corresponding mass transfer coefficient at that point.

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Falling film absorption process is studied for the simulation of the absorber of the absorption solar cooling system. In this study, we use different absorbents such as lithium chloride aqueous solution, and mixed solutions of lithium and calcium chloride aqueous solution, and water is the refrigerent. We also discuss the effects of various parameters of the absorbents such as the solution flow rate (the Reynolds number), the solution inlet temperature and the absorber vapor pressure. The results of the present study can provide the design reference for the absorption solar cooling systems.

The Copper Creek thrust fault in the southern Appalachians places Cambrian over Ordovician sedimentary strata. The fault accommodated displacement of 15-20 km at 100-180 °C. Along the hanging wall-footwall contact, microstructures within a ~2 cm thick calcite and shale shear zone suggest that calcite, not shale, controlled the rheology of the shear zone rocks. While shale deformed brittley, plasticity-induced fracturing in calcite resulted in ultrafine-grained (<1.0 μm) fault rocks that deformed by grain boundary sliding (GBS) accommodated primarily by diffusion creep, suggesting low flow stresses. Optical and electron microscopy of samples from a transect across the footwall shale into the shear zone, shows the evolution of rheology within the shear zone. Sedimentary laminations 1 cm below the shear zone are cut by minor faults, stylolites, and fault-parallel and perpendicular calcite veins. At vein intersections, calcite grain size is reduced (to ~0.3 μm), and microstructures include inter-and-intragranular fractures, four-grain junctions, and interpenetrating boundaries. Porosity rises to 6 percent from <1 percent in coarse (25 μm) areas of calcite veins. In coarse-grained calcite, trails of voids follow twin boundaries, and voids occur at twin-twin and twin-grain boundary intersections. At the shear zone-footwall contact, a 350 μm thick calcite band contains coarseand ultrafine-grained layers. Ultrafine-grained (~0.34 μm) layers contain microstructures similar to those at vein intersections in the footwall and display no lattice-preferred orientation (LPO). Coarse-grained layers cross-cut grain-boundary alignments in the ultrafine-grained layers; coarse grains display twins and a strong LPO. Within the shear zone, ultrafine-grained calcite-aggregate clasts and shale clasts (5-350 μm) lie within an ultrafine-grained calcite (<0.31 μm) and shale matrix. Ultrafinegrained calcite (<0.31 μm) forms an interconnected network around the matrix shale. Calcite vein microstructures suggest veins continued to form during deformation. Fractures at twin-twin and twin-grain boundary intersections suggest grain size reduction by plasticity-induced fracturing, resulting in <1 μm grains. Interpenetrating boundaries, four-grain junctions, and no LPO indicate the ultrafine-grained calcite deformed by viscous grain boundary sliding. The evolution of the ultrafine-grain shear zone rocks by a combination of plastic and brittle processes and the deformation of the interconnected network of ultrafine-grained calcite by viscous GBS enabled a large displacement along a narrow fault zone.

Abstract Reformer, the most important link of fuel cell, is the main set to create the hydrogen. After the fuel passes through the catalytic reaction by reformer, will produce hydrogen and chemical substances, the hydrogen will become the energy to support fuel cell. At the present day, the technology of PEM fuel cell and traditional fuel reformer has already existed, only need to reduce the volume, cost and to promote the efficiency. Catalytic layer, with the construction of microchannel, makes the adequate impact to gas and catalyst to promote the efficiency. This research uses the Lattice Boltzmann method (LBM) to simulate the fluid field and heat-mass transfer of microchannel, to discuss the function influence to the different parameter such as velocity, temperature, channel length, and channel height. The result displays, with the same inlet speed and temperature, by the increasing of the channel length, the amount of hydrogen will raise and residual methanol will reduce. When the channel length is more than 500£gm, the produce rate of hydrogen will not be a big change. If fix the channel length at 500£gm, under the different inlet temperature, while the maximum concentration at inlet, the speed of hydrogen at inlet is not the same. The best inlet speed will increase with the higher temperature. When fix the channel length at 500£gm, raising the altitude to 500£gm, the hydrogen product will not increase, on the contrary, it¡¦ll go down. Keywords¡GFuel cell reformer¡BMicorchannel of hat and mass transfer¡BNumerical simulations

Research is performed to assess the potential of surface moisture evaporative cooling from composite plates as a means of reducing the external temperature of military aircraft. To assess the feasibility of evaporative cooling for this application, a simplified theoretical model of the phenomenon is formulated. The model consists of a flat composite plate at an initial uniform temperature, T0. The plate also possesses an initial moisture (molecular water) content, M0. The plate is oriented vertically and at t=0 s, one surface is exposed to a free stream of air at an elevated temperature. The other surface is exposed to stagnant air at the same temperature as the plate’s initial temperature. The equations associated with energy and mass transport for the model are developed from the conservation laws per the continuum mechanics hypothesis. Constitutive equations and assumptions are introduced to express the two nonlinear partial differential equations in terms of the temperature, T, and the partial density of molecular water, &#961;w. These equations are approximated using a weak form Galerkin finite element formulation and the &#945;–family of time approximation. An algorithm and accompanying computer program written in the Matlab programming language are presented for solving the nonlinear algebraic equations at successive time steps. The Matlab program is used to generate results for plates possessing a variety of initial moisture concentrations, M0, and diffusion coefficients, D. Surface temperature profiles, over time, of moisture bearing specimens are compared with the temperature profiles of dry composite plates. It is evident from the results that M0 and D affect the surface temperature of a moist plate. Surface temperature profiles are shown to decrease with increasing M0 and/or D. In particular, dry and moist specimens are shown to differ in final temperatures by as much as 30°C over a 900 s interval when M0 = 30% and D is on the order of 10–8m2/s (T0 = 25°C, h = 60 W/m2°C, T&#8734; = 90°C).

Mass transfer experiments were conducted to study the thermal performance characteristics of blockages with round and elongated holes, positioned in a 12:1 rectangular channel. Naphthalene sublimation technique was adopted to conduct experiments with four different blockage configurations, flow rates corresponding to Reynolds numbers (based on channel hydraulic diameter) of 7,000 and 17,000, and at three blockage locations. The hole area to channel area ratio for all four blockage configurations was the same at 0.196. The hole width was half the channel height, and the distance between consecutive blockages was twice the channel height. Average heat transfer, local heat (mass) transfer and overall pressure drop results were obtained. The thermal performance for a particular blockage configuration was measured in terms of the heat transfer enhancement and the friction factor ratio. Heat transfer enhancement was measured as a ratio of average Nusselt number on the blockage surface to the Nusselt number for a thermally fully developed turbulent flow in a smooth channel. Results indicate that this ratio ranged between 3.6 and 12.4, while the friction factor ratio varied between 500-1700. The blockage configuration with round holes was found to yield best thermal performance, while the configuration with largest hole elongation was nearly equal in thermal performance. In order to compare different blockage configurations, an average value of upstream and downstream side thermal performances was used. A general downward trend in Nusselt number ratio with elongation of holes was observed on the upstream side and a reverse trend was observed on the downstream side. An upward trend in the Nusselt number ratio with blockage hole elongation on the downstream side of a blockage was primarily due to jet reversal from the downstream blockage and its impingement on the downstream surface of the upstream blockage. Local experiments were performed to compare against the results from average experiments and also to gain insights into the flow behaviour. There was good agreement between the results from local and average mass transfer experiments. The average variation in Nusselt number ratio between local and average mass transfer experiments was about 5.06%.