Total Mass Flow Research Articles

Theoretical research on suppression ratio of dynamic gas lock for extreme ultraviolet lithography contamination control

Dynamic gas lock (DGL) is an important technology for contamination control of extreme ultraviolet (EUV) lithography. DGL prevents contamination diffusion from the dirty compartment into the clean one and allows passage of EUV light between compartments. A number of DGL structures have been proposed for EUV scanners. The suppression ratio is the key index of DGL, but there are few theoretical studies on it. Using the Péclet number to represent the suppression ratio just ignores the variable cross section of DGL and the effect of the total mass flow. A new suppression ratio formula is derived here based on the convection-diffusion equation, including the constant and variable cross section of DGL. In order to verify the theoretical calculation, an experiment is carried out on a self-developed DGL device, obtaining the gas flow utilization and suppression ratio of various mass flows. The results show that the suppression ratio increases exponentially with mass flow, which is consistent with the theoretical expectation. At the same time, the important influence of the convection segment has also been demonstrated. It is concluded that the theoretical approach can well predict the suppression ratio and provide structural design guidance for DGL, which has an important practical application value.

Research on Intelligent Distribution of Liquid Flow Rate in Embedded Channels for Cooling 3D Multi-Core Chips.

A numerical simulation model of embedded liquid microchannels for cooling 3D multi-core chips is established. For the thermal management problem when the operating power of a chip changes dynamically, an intelligent method combining BP neural network and genetic algorithm is used for distribution optimization of coolant flow under the condition with a fixed total mass flow rate. Firstly, a sample point dataset containing temperature field information is obtained by numerical calculation of convective heat transfer, and the constructed BP neural network is trained using these data. The “working condition–flow distribution–temperature” mapping relationship is predicted by the BP neural network. The genetic algorithm is further used to optimize the optimal flow distribution strategy to adapt to the dynamic change of power. Compared with the commonly used uniform flow distribution method, the intelligently optimized nonuniform flow distribution method can further reduce the temperature of the chip and improve the temperature uniformity of the chip.

Cyclic coupling mechanisms in a novel turbo-piston combined cycle engine concept for heavy vehicle applications

A novel concept of the turbo-piston combined cycle (TPCC) engine was proposed to perfectly satisfy the complex and multiple performance requirements of many heavy vehicles. It has a unique function of free mode (cycle) switching between three operating modes, which are the diesel engine (DE), the turboshaft engine (TE), and the DE–TE cyclic combined modes. The cyclic coupling between the baseline DE and TE cycles in the combined mode was supposed to help improve the performances of the two baseline engines simultaneously, and prototype experiments confirmed the feasibility and effects of this assumption. However, the cyclic coupling mechanisms in the combined cycle that are crucial for the R&D of the TPCC engine remain unclear. This study mainly focuses on investigating the fundamentals of the cyclic coupling mechanisms and impacts in the combined cycle of the TPCC engine via theoretical (ideal) thermodynamic cycle modeling analysis and one-dimensional (1-D) cycle modeling simulation. The results mainly show that from theoretical thermodynamic analysis, the TPCC engine’s cyclic coupling can significantly improve the specific net work of the combined cycle and even exceed the sum of the isolated DE and TE cycles, and only the temperature increase ratio parameter of the TE cycle can generate a tradeoff influence between the specific net work and the theoretical thermal efficiency of the combined cycle. In addition, from the 1-D cycle simulation, the performance of the baseline DE cycle in the combined cycle is dramatically improved by the baseline TE in terms of its high intake pressure and exhaust pressure conditions, and the operating process of baseline TE is simultaneously improved by the baseline DE in terms of its intake suction and exhaust-mixing effects. Based on certain simulation cases, the intake mass flow rates of the baseline DE and TE (i.e., the total intake mass flow rate of the combined cycle) are respectively increased by 150% and 1.1%, and their power outputs are respectively increased by 8.5% and 3.1%. Further, the brake specific fuel consumption rate (BSFC) of the baseline DE and TE respectively decreases by 8.0% and 2.9%, and the operating point of the baseline TE on the turbomachinery performance maps is slightly moved to the more efficient and higher performance area. This investigation is consistent with experimental results on cyclic coupling effects, and it can provide a timely and preliminarily understanding of the TPCC engine’s fundamentals.

Time-dependent heat transfer analysis of ellipsoidal protruded microchannel with multiple pulsating jets

Comparing with continuous jets inside microchannel, the heat removal capacity is enhanced by introducing protrusions or pulsating jets individually. Therefore, the preferred heat transfer enhancement and satisfactory thermal performance are investigated after taking both advantages of unsteady properties and ellipsoid protrusions simultaneously in this work. Especially, phase difference, Δφ, as a pivotal parameter, is applied in multiple pulsating jets. The total mass flow rate in microchannel, temperature fluctuation on heated wall, thermal and flow resistance are therefore varied. The largest fluctuation of mass flow rate is achieved when the phase difference between each adjacent jet inlets at Δφ = 0∙π, while the smallest at 0.75∙π, and the temperature distribution of the target wall correspondingly fluctuates. The heat transfer enhancement is most prominent at 0.75∙π. The increment in heat transfer is close to that of flow resistance at Δφ = 0.50∙π, 0.75∙π and 1∙π. The thermal performance TP firstly increases and then decreases with Δφ, and reaches the maximum value at 0.75∙π. Furthermore, due to the phase difference, each jet becomes the one with the highest velocity among all jets periodically, weakening adverse effect of cross flow and suppressing the drift phenomenon effectively. This is exactly the mechanism for heat transfer enhancement of unsteady multiple jets with velocity phase difference in ellipsoid protrusion microchannel.

Generation of ash particles from different lube oil mists

Ash and soot particles are generated during engine combustion and are deposited in particulate filters. In order to understand the basic processes that occur in a particulate filter during the filtration process the particles have to be generated quickly and replicably. In this study, fundamental investigations are conducted on the generation of ash particles independently of an engine to produce a defined aerosol. The formation of ash particles from engine oils with differences in sulfate ash content (SAC; 0.7%, 2.6%, 4.5%) as well as the variation of process parameters (oil temperature, nozzle volume flow) are investigated. The ash particles are produced by nebulizing engine oil and a subsequent thermal conversion in a furnace. The SAC of the oil does influence the ash particles that are generated. With the increase of the SAC, the ash mass flow and the number weighted median diameter increase. Raising the nozzle volume flow as well as the oil temperature leads to an increase in total number concentration and mass flow of the ash particles. The number median diameter of the oil mist and ash particles decrease with the increase of oil temperature and nozzle volume flow. For the fast loading of a particulate filter, the SAC of the oil should be 4.5%. The oil temperature and nozzle volume flow should be set at 30 °C and 6 L·min−1. In conclusion, the ash generation method can be used for the rapid loading of a particulate filter.

Intake Manifold Flow Study using Numerical Method with all Runners Opened

Intake manifolds have to be designed to improve engine performance by avoiding the phenomena like inter-cylinder robbery of charge, inertia of the flow in the individual branch pipes, resonance of the air masses in the pipes and the Helmholtz effect. The objective of work is to predict and analyze the flow through intake manifold of four cylinder spark ignition engine. One of the important factors is air flow inside the intake manifold; the ideal intake manifold distributes flow evenly to the piston valves. The structural analysis has been conducted to decide the thickness and material that is suitable for intake manifold to withstand bursting pressure. Three-dimensional inlet manifold was modeled in ANSYS workbench and numerically analyzed by using the commercially available FLUENT software to study the pressure, velocity and flow characteristics inside the runner. The steady state analysis has been carried out for three for All runners open, The predicted results of total pressure loss and total outlet mass flow were discussed. Inlet pipe and plenum connection creates a back step geometry which causes more total pressure loss due to flow recirculation in conventional model. Tapering the geometry is causing more inlet mass flow due to reduction in total pressure loss in the plenum chamber.

Isothermal transport of a near-critical binary fluid mixture through a capillary tube with the preferential adsorption

We study isothermal transport of a binary fluid mixture, which lies in the homogeneous phase near the demixing critical point, through a capillary tube. A short-range interaction is assumed between each mixture component and the tube's wall surface, which usually attracts one component more than the other. The resulting preferential adsorption becomes significant owing to large osmotic susceptibility. The mixture flowing out of the tube is rich in the preferred component when flow is driven by the pressure difference between the reservoirs. When flow is driven by the mass-fraction difference, the total mass flow occurs in the presence of the preferential adsorption. These phenomena can be regarded as cross-effects linked by the reciprocal relation. The latter implies that diffusioosmosis arises from the free energy of the bulk of the mixture not involving the surface potential, unlike usual diffusioosmosis far from the critical point. We also study these phenomena numerically by using the hydrodynamics based on the coarse-grained free-energy functional, which was previously obtained to reveal near-critical static properties, and using material constants that were previously obtained in some experimental studies. Influence of the critical enhancement of the transport coefficients is found to be negligible because of off-critical composition in the tube. It is also shown that the conductance, or the total mass flow rate under a given mass-fraction difference, can change non-monotonically with the temperature. The change is well expected to be large enough to be detected experimentally.

Pharmaceutical compound removal using down-flow fixed bed filters with powder activated carbon: A novel configuration

Emerging contaminants (ECs) are generating concern among the population, as they can cause adverse effects in aquatic biota. Based on new information for ECs and their potential impact on ecosystems, measures are being promoted among wastewater quality regulatory entities. Thus, the objective of this research was to develop an efficient technology to remove two recalcitrant pollutants, carbamazepine (Cbz) and sildenafil (Sil). A fixed bed adsorption column with powder activated carbon (PAC) uniformly distributed among sand at a ratio of 1:50 was designed to generate porosity and stability for the adsorbent material. This design was initially studied at laboratory to evaluate its operational capacity and the behavior of the compounds. It was determined that the Sil was efficiently removed, while the Cbz reached saturation after 25 days of continuous operation, defining it as the limiting pollutant. Then a pilot plant was evaluated, with a total bed height, PAC mass, contact time, surface rate and working flow of 20 cm, 40 g, 40 min, 0.4 cm3/(cm2.min) and 30 mL/min, respectively; in which removal efficiencies greater than 90% were achieved. The useful life, capacity and speed adsorption of the column were determined by simulating and analyzing the breakdown curves. It was concluded that using this technology, the adverse effects produced by these pollutants on water resources, can be mitigated. This is the first work wherein a downflow fixed bed column with PAC has been operated under continuous flow. The system can be operated without the need to incorporate additional procedures to separate PAC.

Reducing the operational fluctuation via splitting CO2 transcritical power cycle in engine waste heat recovery

CO2 power cycle has been considered a promising technology to recover the engine waste heat at a fixed condition. Nevertheless, the large variation of engine conditions may bring about the operational fluctuation, which is reflected on the system performance deterioration. In this study, a splitting CO2 power cycle layout is proposed and optimized from the point of both design and off-design phases to match the large-fluctuated engine conditions. The mass flow through different heat exchangers can be adjusted when the engine heat sources are altered, which means that a higher system degree of freedom can be achieved. Results showed that the system operational fluctuation could be reduced effectively when the operation parameters were deviated from the design phase. Specifically, the total mass flow rate decreased apparently when the engine speed and torque decreased, whereas a moderate decrease was found in the splitting layout thanks to the flexible mass flow through each splitting branch. In addition, the deviation fluctuation of pressure ratio was also reduced especially at higher engine conditions. Average improvements of 12.2%, 17.5% and 8.5% in net generated power, exhaust utilization and exergy efficiency could be achieved, respectively. And the minimum brake specific fuel consumption could be improved by 5.5%.

A Method of Quantifying Refrigerant Distribution in a Two-Pass Micro-Channel Evaporator

Background: The flow rate distribution in the flat tubes of a micro-channel evaporator is essential for its heat transfer performance. Due to a large number of flat tubes in a microchannel evaporator, the flow rate distribution is often difficult to determine. Objective: An evaporator test rig was constructed to study the quantification of the refrigerant mass flow rate distribution in a two-pass evaporator without destroying its structure. Methods: A heat transfer performance test rig for a two-pass evaporator was utilized. Subcooled refrigerant R134a was pumped into the inlet header, and infrared thermography was used to obtain the cloud map of the wall temperature distribution on the surface of the evaporator. The flow rate distribution in each flat tube was calculated based on an analysis that combines the heat balance between the air side and the refrigerant side with the effectiveness-Number of Transfer Units (ε- NTU) method. Results: The flow rate distribution was found to be in good agreement with the evaporator wall temperature distribution.The difference between the calculated and measured total mass flow rates was less than 15.9%, which proves that the method is simple and effective. And the unevenness of flow rate distribution in the 1st and 2nd pass is 0.13 and 0.32, respectively. Conclusion: This method is simple and effective, and does not destroy the structure of the microchannel evaporator. However, it is only suitable for cases in which there exists a subcooled zone in a pass, and is not applicable to a pass in which the refrigerant is only in a single-phase or a twophase state.

Study of the possibility of high accuracy flow measurements with the pulsed neutron activation method

Abstract The performance of water flow measurements with pulsed neutron activation (PNA) have been investigated in the past few years. In this report the following particular Problems were investigated: (a) the effect of collimation on the time-resolved detector signals; (b) the behavior of the background signal, in order to expedite optimum background elimination from the measured signals; and (c) the properties of water mixing, by measuring the geometrical asymmetry of the activated volume as a function of distance from the source as well as of flow velocity. It was seen that with the flow velocities and Reynolds numbers in the present experiments, the mixing is not perfect. Thus, in general, the PNA method will lead to an underestimation of the mass flow due to the effect of the laminar layer close to the wall whose contribution to the total mass flow will be enhanced. The investigations reported here contribute to the improvement of the accuracy of the method.

Heat Production from Single Fracture Hot Dry Rock, Applications for EGS Reservoir Design

A new analytical solution for the thermal-hydraulic coupling process is derived with a 1-D steady state conductive heat flow in the body of hot rock with perpendicular water flow in the single fracture and transient heat transfer from rock to water. The heat produced from the hot rock via water flow in the idealized single fracture is demonstrated by arithmetic equations. The applicability of the analytical solution is verified by numerical calculations and is limited to conditions with fast water flow rates or high water flux and long fluid pathways. The lifetime of an EGS reservoir in these reference conditions is 23.2 years and is confined by the produced water temperature of 150 °C for commercial utilization. The heat recovery factor is 12.4%. With a power plant capacity of 5 Mw installed, the total area for extracting recoverable heat within the projected lifetime of a fracture surface of 1.58 × 106 m2 was determined. The total mass flow rate of water injected into the large fracture was 57 kg/s. The discussion shows the ability of the model to estimate heat production and reservoir scale.

Development and Use of a Residence Time Distribution (RTD) Model Control Strategy for a Continuous Manufacturing Drug Product Pharmaceutical Process.

Residence-time-distribution (RTD)-based models are key to understanding the mixing dynamics of continuous manufacturing systems. Such models can allow for material traceability throughout the process and can provide the ability for removal of non-conforming material from the finished product. These models have been implemented in continuous pharmaceutical manufacturing mainly for monitoring purposes, not as an integral part of the control strategy and in-process specifications. This paper discusses the steps taken to develop an RTD model design space and how the model was statistically incorporated into the product’s control strategy. To develop the model, experiments were conducted at a range of blender impeller speeds and total system mass flow rates. RTD parameters were optimized for each condition tested using a tank-in-series-type model with a delay. Using the experimental RTD parameters, an equation was derived relating the mean residence time to the operating conditions (i.e., blender impeller speed and mass flow rate). The RTD parameters were used in combination with real-time upstream process data to predict downstream API concentration, where these predictions allowed validation across the entire operating range of the process by comparison to measured tablet assay. The standard in-process control limits for the product were statistically tightened using the validation acceptance criteria. Ultimately, this model and strategy were accepted by regulatory authorities.

Numerical investigation of squeeze film lubrication on bioinspired hexagonal patterned surface

PurposeThis paper aims to investigate the squeeze film lubrication properties of hexagonal patterned surface inspired by the epidermis structure of tree frog’s toe pad and numerically explore the working mechanism of hexagonal micropillar during the acquisition process of high adhesive and friction for wet contacts.Design/methodology/approachA two-dimensional elastohydrodynamic numerical model is employed for the squeezing contacts. The pressure distribution, load carrying capacity and liquid flow rate of the squeeze film are obtained through a simultaneous solution of the two-dimensional Reynolds equation and elasticity deformation equations.FindingsHigher pressure is found to be longitudinally distributed across individual hexagonal pillar, with pressure peak emerging at the center of hexagonal pillar. Expanding the area density and shrinking the channel depth or initial film thickness will improve the magnitude of squeezing pressure. Relatively lower pressure is generated inside interconnected channels, which reduces the load carrying capacity of the squeeze film. Meanwhile, the introduction of microchannel is revealed to downscale the total mass flow rate of squeezing contacts.Originality/valueThis paper provides a good proof for the working mechanism of surface microstructures during the acquisition process of high adhesive and friction for wet contacts.

Numerical investigation on transient thermal performance predictions of phase change material embedded solar air heater

In this work, thermal performance of PCM embedded parallel flow solar air heater employing differential air flow arrangements is predicted using transient computational iterative solution procedure. The present iterative approach is capable of predicting transient temperatures of the complete collector design for 24 h working cycle including sunshine and nocturnal hours. Finite volume method is used employing explicit time marching scheme in a MATLAB code to solve the discretized transient governing differential equations. First Order Upwind advection scheme is applied to predict the air temperatures. Obtained results revealed all possibilities of obtaining significant thermal energy storage in PCM, instant and long thermal backups, and heat gain of air as a function of time of the day and variable air flow rate arrangements. The maximum thermal efficiency of about 63% is obtained at the total mass flow rate of 0.05 kg/s. In addition, air flow rate conditions for the present design are revealed that can provide the outlet air temperature ≥303 K during nocturnal hours. An off sunshine situation is presented that depicts the scope of obtaining the possible instant thermal energy backup. The effect of PCM unit thickness on thermal performance of the collector is also considered in the present work.

Modelling of Methanol Synthesis: Improving Hydrogen Utilisation

Hydrogen is a key component in the methanol (MeOH) synthesis process. It affects both the environmental and economic performance, since renewable hydrogen (usually produced by electrolysis) is the most expensive component of the process. The addition of renewable hydrogen improves the carbon balance of the process but necessitates the planning of a suitable strategy to account for the stochastic nature of renewable energy and the respective costs. For this reason, the focus of this work is the efficient hydrogen utilization in contrast to most of the past literature works that mainly focus on the conversion of the carbonaceous feedstock. Several operating parameters such as the extent of recycling, operating temperature and pressure, stoichiometric number, inlet temperature and total mass flow per tube affect the methanol yield, carbon conversion and hydrogen consumption of the process. The scope of this work is to provide insight on the effect of those parameters on the efficient hydrogen utilisation using a methanol synthesis modelling tool. The findings of this study showed that hydrogen utilisation could be considerably improved if operating at certain conditions. Lower stoichiometric numbers and mass flows per tube, inlet and cooling temperatures up to 510 K and higher operating pressures could reduce the required hydrogen per produced methanol unit. Especially the employment of recycling, could lead to substantial reduction of the associated hydrogen requirements. In particular, recycling 50 % of the residual off-gases could lead to 10 % less fresh hydrogen requirements and 90 % recycling results to 40 % less hydrogen for the production of the same amount of methanol.

Effects of tip-bleed holes on two-pass channel on heat transfer with various aspect ratios

The heat transfer characteristics in 180-degree turn region of two-pass channel with three different aspect ratios were investigated as coolant being extracted through tip-holes. The naphthalene sublimation technique was used for the heat/mass transfer measurements from the internal ceiling surface of the 180-degree turn region. The channel aspect-ratios of 1:1, 2:1, and 5:1 while keeping the same hydraulic diameter were studied. The inlet Reynolds number was set at 10000 that matches an actual land-based gas turbine. The tip-extraction mass flow rate was set at 10% of the total inlet mass flow rate. The experimental results showed that the heat/mass transfer is improved with the coolant extraction from tip-holes for all test cases. The improvement of thermal performance on tip surface is ranged from 10.8% to 67.0% compared to the no coolant extraction cases. The improvement was highest for the case of 1:5 aspect ratio as the extraction helped to minimize the region of local recirculation. The study proved that the tip-hole extraction could be effectively designed to improve the cooling of 180-degree turn region.

Constructal design for flat plate collector in a solar ocean thermal energy conversion system

<p indent=0mm>Collectors are important components for heat collection in solar ocean thermal energy conversion (OTEC) systems. In the present study, a complex function composed of the linear weighted sum of the seawater outlet temperature and the total consumed pumping power is established. Under the conditions of fixed total volumes of the heat absorption plate and the heat exchange tube, constructal optimization of a flat plate solar collector is conducted by taking the complex function as the optimization objective. The minimum complex function and optimal inner diameter of the heat exchange tube are obtained. The results show that compared with those obtained for the initial design point, the total consumed pumping power and complex function of the solar collector after constructal optimization are reduced by 66.89% and 5.56%, respectively, and the seawater outlet temperature is reduced by 8.9%. This illustrates that although the complex function sacrifices a certain amount of heat transfer performance, the flow performance is greatly improved, as is the overall performance of the flat plate collector. The minimum complex function decreases with increases in the single plate width, solar radiation intensity, seawater outlet temperature, thermal conductivity of the heat absorption plate, and number of collector units, and a decrease in the total seawater mass flow rate. Constructal theory is applied for constructal optimization of the flat plate solar collector, which provides new guidelines for its structural optimization design. This method can be further extended to the optimal designs of solar OTEC systems.

Effect of the Number of Nozzles of Swirl Flow Generator Utilized in Flat Plate Solar Collector: An Entropic Analysis

The numerical model of the pipes of a flat plate solar collector (FPSC) with several nozzles has been investigated in the present study. Indeed, the effect of the number of nozzles of the swirl generator on the entropic characteristics has been evaluated. The nozzles were applied for improving the performance of FPSC. For evaluating the proposed system based on the entropy concept, the effect of injection angle and mass flow rate has been considered. The selected injection angles were 30°, 45°, 60°, and 90°. Also, the total mass flow rates entered from all of the nozzles were 0.2 kg/s, 1 kg/s, and 2 kg/s. The effect of said variables on frictional and thermal entropy generations was analyzed; then, the overall energetic-entropic performance of the system was predicted using several dimensionless parameters including NE, NS, Nu ∗ , and heat transfer improvement (HTI). Moreover, Witte-Shamsundar efficiency ( η W − S ) was applied to pinpoint the efficiency of the system. The highest value of HTI and η W − S was 1.7 and 0.9 that achieved by “single-nozzle; A90-D50-N12.5-M0.2” and “quad-nozzle; A30-D50-N12.5-M2,” respectively.

Study on thermal-hydraulic characteristics of hybrid heat exchangers with interpolated etched plates

The Supercritical carbon dioxide (S-CO2) Brayton cycle can be used to recover the exhaust heat energy of marine diesel engines. The hybrid heat exchanger is one of the potential solutions for heat exchange between flue gas and S-CO2, but there is no good design theory and design method at present. The traditional hybrid heat exchanger has an one-to-one correspondence between the fin and the etched plate. However, under special requirements, it is necessary to insert etched plates in the hybrid heat exchanger to improve the thermalhydraulic characteristics. In this study, four CFD models of the hybrid heat exchangers with interpolated etched plates were established. When the total mass flow rate and the total mass velocity are constant, the thermalhydraulic characteristics of the hybrid heat exchanger are analyzed by Fluent. The results show that regardless of the constant mass flow rate or the constant mass velocity, inserting etched channels into the hybrid heat exchanger will increase the total heat transfer coefficient. When the total mass flow rate of the cold and hot fluids is unchanged, the heat transfer coefficient and pressure drop of the etched channel decrease with the increase of the inserted etched channel. When the total mass velocity of the hybrid heat exchanger is unchanged, the insertion of the etched channel causes the pressure drop and the convective heat transfer coefficient of the fin channel to increase. Meanwhile, the pressure drop and convective heat transfer coefficient of the etched channels are reduced, but the total heat transfer coefficient is increased. The study can provide guidance for the design of the hybrid heat exchangers.