Inlet Volumetric Flow Research Articles

Removal of toluene vapour using agro-waste as biofilter media

Biodegradation of toluene vapour was investigated in a laboratory scale biofilter packed with cylindrical pieces of yellow-gram ( Cajanus cajan) stalk. Inlet concentrations and volumetric flow rates of toluene were varied from 2.56 to 34.73 g/m 3 and 0.18 to 0.24 m 3/h, respectively. The steady state was achieved within seven days and the degradation of toluene followed an exponential behaviour with time. Elimination capacity increased and tended towards a constant value but removal efficiency decreased with increase in inlet toluene loading. Depending upon loading rate, the process was either mass transfer or reaction-controlled.

Methodology for Predicting Oxygen Transport on an Intravenous Membrane Oxygenator Combining Computational and Analytical Models

A computational methodology for accurately predicting flow and oxygen-transport characteristics and performance of an intravenous membrane oxygenator (IMO) device is developed, tested, and validated. This methodology uses extensive numerical simulations of three-dimensional computational models to determine flow-mixing characteristics and oxygen-transfer performance, and analytical models to indirectly validate numerical predictions with experimental data, using both blood and water as working fluids. Direct numerical simulations for IMO stationary and pulsating balloons predict flow field and oxygen transport performance in response to changes in the device length, number of and balloon pulsation frequency. Multifiber models are used to investigate interfiber interference and length effects for a stationary balloon whereas a single fiber model is used to analyze the effect of balloon pulsations on velocity and oxygen concentration fields and to evaluate oxygen transfer rates. An analytical lumped model is developed and validated by comparing its numerical predictions with experimental data. Numerical results demonstrate that oxygen transfer rates for a stationary balloon regime decrease with increasing number of fibers, independent of the fluid type. The oxygen transfer rate ratio obtained with blood and water is approximately two. Balloon pulsations show an effective and enhanced flow mixing, with time-dependent recirculating flows around the fibers regions which induce higher oxygen transfer rates. The mass transfer rates increase approximately 100% and 80%, with water and blood, respectively, compared with stationary balloon operation. Calculations with combinations of frequency, number of fibers, fiber length and diameter, and inlet volumetric flow rates, agree well with the reported experimental results, and provide a solid comparative base for analysis, predictions, and comparisons with numerical and experimental data.

Transition to Meandering Rivulet Flow in Vertical Parallel-Plate Channels

While there have been many studies of gravity-driven rivulet flow over an external surface, treatment of internal rivulets has been sparse. A notable exception is the analytical and experimental study by Anand and Bejan [1]; they derived an approximate solution for a laminar rivulet developing between two parallel vertical planes and employed it to examine the transition to a meandering flow. For rivulets flowing between closely spaced plates, the velocity becomes slow (i.e., low Reynolds number) and an approximately fully-developed flow at its terminal velocity can be reached in a short distance. Conceptually, this value can be derived from the analysis of Anand and Bejan. However, for cases where the inlet volumetric flow rate Q is sufficiently high that the rivulet becomes wide relative to the plate spacing, a simple treatment can describe the resulting flow.

Optimal cooling system design for the injection molding process

AbstractA computer‐aided optimal design system was developed to improve the performance of a cooling system for injection molding. This was done by minimizing a weighted combination of the uniformity of the part temperature and the cooling time. The CONMIN algorithm was adopted to obtain the optimal design using the special boundary integral formulation and a corresponding design sensitivity analysis formulation. Design variables related to the processing conditions (i.e., inlet coolant temperature and volumetric flow rate of each cooling channel) and mold cooling system design (radius and location of each cooling channel) were considered. Three different optimization strategies are suggested, and three sample problems were solved to demonstrate the efficiency and the usefulness of this optimization procedure.

Optimum design of injection molding cooling system via boundary element method

The cooling stage is the very critical and most time consuming stage of the injection molding process, thus it cleary affects both the productivity and the part quality. Even through there are several commercialized package programs available in the injection molding industry to analyze the cooling performance of the injection molding coling stage, optimization of the cooling system has npt yet been accomplished in the literature due to the difficulty in the sensitivity analysis. However, it would be greatly desirable for the mold cooling system designers to have a computer aided design system for the cooling stage. With this in mind, the present study has successfully developed an interated computer aided design system for the injection molding cooling system. The CAD system utilizes the sensitivity analysis via a Boundary Element Method, which we recently developed, and the well-known CONMIN alforuthm as an optimization technique to minimize a weighted combination (objective function) of the temperature non-uniformity over the part surface and the cooling time related to the productivity with side constranits for the design reality. In the proposed objective function , the weighting parameter between the temperature non-uniiformity abd the cooling time can be adjusted according to user's interest. In this cooling system optimization, various design variable are considered as follows : (i) (design variables related to processing conditions) inlet coolant bulk temperature and volumetric flow rate of each cooling channel, and (ii) (design variables related to mold cooling system design) radius and location of each cooling channel. For this optimum design problem, three different radius and location of each cooling channel. For this optimum design problem, three different strategies are suffested based upon the nature of design variables. Three sample problems were successfully solved to demonstrated the efficiency and the usefulness of the CAD system.

Mathematical Modeling of Epitaxial Silicon Growth in Pancake Chemical Vapor Deposition Reactors

A fundamental understanding of pancake reactors is necessary for the establishment of process‐property relationships in these systems. Here, a mathematical model of the gas flow, transport phenomena, and growth rate profiles of epitaxial silicon in a pancake reactor is presented and the resulting modeling equations are solved. Two‐dimensional conservation equations of momentum, energy, and mass developed in cylindrical coordinates along with appropriate boundary conditions are solved numerically with finite element methods. Streamlines of the gas flow in the reactor show that the shearing force of the inlet flow yields a recirculation zone inside the reactor and a separation point on the susceptor. As the inlet volumetric flow rate increases, the gas flow direction over the susceptor changes from inwards to outwards, resulting in another reverse circulating flow above the susceptor. The temperature and concentration profiles obtained show that steeper thermal and concentration boundary layers develop above the susceptor at higher volumetric flow rates. Under the assumption of a first‐order deposition reaction on the substrate, growth rate profiles are calculated along the radial direction. The effects of total gas mixture flow rates, magnitude of the deposition rate constant, susceptor temperature, and thermal diffusion upon growth rate profiles are investigated. The agreement between observed and predicted growth rates at various temperatures is seen to be satisfactory.

Jet Breakup and Mixing Throat Lengths for the Liquid Jet Gas Pump

Gas compression with a liquid jet occurs isothermally and hence with minimum work. Performance characteristics of the liquid jet gas pump (efficiency and compression ratio versus inlet volumetric flow ratio) are predicted accurately by a one-dimensional analysis providing the mixing zone remains in the throat. Jet breakup was investigated to enable prediction of required throat length and to improve efficiency. Effects of throat length, nozzle contour and spacing, nozzle-throat area ratio (0.15 to 0.45), jet velocity and suction pressure were investigated. Optimum throat lengths were found; corresponding efficiencies exceed 40 percent. Two jet breakup flow regimes were found: impact and jet disintegration. For the impact regime, jet breakup length-depends on inlet velocity ratio, jet Reynolds number and nozzle-to-throat area ratio. Optimum throat lengths were found to be an empirical function of nozzle-to-throat area ratio and ranged from 12 to 32 throat dia. These results, coupled with the one-dimensional model, permit design of efficient liquid jet gas pumps.