Increasing Inlet Flow Rate Research Articles

Numerical investigation of dynamic gas–liquid separator by population balance model

Dynamic gas–liquid separator (DGLS) can efficiently separate gas and liquid phases and are widely used in aerospace, chemical, and petroleum engineering. The energy loss and separation efficiency within the DGLS are studied through the combination of numerical simulations and experiments. Three-dimensional transient Reynolds-Averaged Navier–Stokes equations were solved to analyze the fluid dynamics within the DGLS. The bubble aggregation and breakup in oil were simulated by using the population balance model. Experimental data were meticulously compared with numerical results to validate the accuracy and reliability of the numerical methods. The findings revealed a direct correlation between the inlet flow rate and various performance metrics of the DGLS. Specifically, as the inlet flow rate increased, the energy loss within the DGLS escalated, resulting in higher power consumption. The degassing rate of the DGLS exhibited a decreasing trend with increasing inlet flow rate, while the de-oiling rate showed an inverse relationship. The optimal performance of the separator was observed at an inlet flow rate of 140 m3·d−1, with ηg* and ηl* reaching 0.94 and 0.99, respectively. The relationship between the Qo and the η* and Po was fitted by a second-order polynomial. Moreover, the rotational speed of the DGLS demonstrated a positive correlation with energy consumption, accompanied by an increase in power output. However, the separation efficiency of the DGLS exhibited a non-linear relationship with rotational speed, peaking at a specific value before marginally declining. The optimization of degassing and dewatering rates occurred at a rotational speed of 2500 r·min−1. These findings underscore the importance of carefully adjusting operational parameters to achieve optimal performance and energy efficiency within DGLS.

Revealing interactions between the operating parameters of protonic ceramic electrolysis cell: A modelling study

Protonic ceramic electrolysis cell (PCEC) is a clean and sustainable technology for hydrogen production. To provide a comprehensive understanding of the effects of various parameters on the performance of PCEC, a framework is proposed to combine the 2D numerical model with One-Factor-At-a-Time (OFAT) and Design of Experiments (DOE) methods. DOE is a simple but effective method to gain deep insight into the effect of different factors on the response variable using a small number of cases. In the OFAT result, a peak optimal Faradaic efficiency (FE) of 82% is found at 600 °C and a current density of 0.4 A cm−2. The FE increases with the increasing inlet flow rate, while the temperature gradient reduces continuously. It is also found that if the inlet steam mole fraction increases by 5%, the FE can be increased by at least 0.25%. DOE results demonstrate the most important factors are the anodic inlet steam molar fraction and anodic inlet flow rate. Additionally, the interaction effects between them are also found to be significant. Noteworthy, regression models derived from DOE results also demonstrate potential capabilities as surrogate models for 2D numerical model. Therefore, DOE is a powerful tool that can draw rigorous conclusions while saving a lot of computational resources. Overall, this study provides deep insights into the interaction effects of different parameters. The framework proposed in this study can be applied to guide future PCEC design optimization.

Metal fins efficacy on stepped solar still performance: An experimental study

In recent years, significant attention has been paid to the investigation of parameters associated with the absorber surface of stepped solar stills, aiming to enhance their performance. In this study, metal fins have been employed on the absorber surface to increase the absorption of radiant energy. The experiment's input variables included the inlet flow rate (100, 150, and 200 ml/min), number of fins (1, 2, and 3 fins on each step), angle of fins (−30°, 0°, and +30°), height of fins (1, 2, and 3 fins on each step), and material of the fins (copper, aluminum, and galvanized steel). 27 main experiments were designed with the help of design of experiments. Results showed that productivity decreased and increased with increasing inlet flow rates and fin numbers, respectively. In addition, the +30° fin had the best results compared to other angles, and freshwater productivity decreased with increasing fin height. Also, copper fins performed better than other fins. Finally, compared to the stepped solar still without fins, a 171 % increase in efficiency was seen in the optimal mode, which had three copper fins with a height of 3 cm, an angle of +30°, and an inlet flow rate of 100 ml/min.

Experimental study of strong imbibition in microcapillaries representing pore/throat characteristics of tight rocks

Imbibition pervasively exists in many industrial processes and is fundamental in developing unconventional resources in tight formations. Micromodels have been widely used as powerful tools for real-time observations of imbibition dynamics to support numerical modeling developments and understanding of macroscopic patterns. However, the inherent limitation of 2D micromodels in presenting 3D features in the pores/throats of tight rocks may reduce the reliability of the microfluidic results. Here, we quantitively investigate imbibition dynamics in single pore geometries that consider 2D pore-scale characteristics of tight rocks with an etching depth higher than the critical geometric criteria for including 3D features. We discuss the experimental data based on varying parameters, such as five pore shapes, a wide range of pore-throat aspect ratios (6.25 to 100), two typical throat widths (3 and 8 μm), and local capillary numbers (10-6 to 10-4). The results show that the wetting phase saturations increase linearly with the increasing inlet flow rate, consistent with previous findings in cores and 2.5D micromodels, but only in macropores. Snap-offs are found when the moved meniscus front pressure is higher than the critical capillary pressure of snap-off. An etching depth higher than the critical geometric criteria is necessary but insufficient to mimic imbibition dynamics in tight rocks by 2D micromodels with a pattern that the most pore-throat aspect ratios are less than 30 at a strong imbibition condition.

Effects of Particle Diameter and Inlet Flow Rate on Gas-Solid Flow Patterns of Fluidized Bed.

The complex multiscale characteristics of particle flow are notoriously difficult to predict. In this study, the evolution process of bubbles and the variation of bed height were investigated by conducting high-speed photographic experiments to verify the reliability of numerical simulations. The gas-solid flow characteristics of bubbling fluidized beds with different particle diameters and inlet flow rates were systematically investigated by coupling computational fluid dynamics (CFD) and discrete element method (DEM). The results show that the fluidization in the fluidized bed will change from bubbling fluidization to turbulent fluidization and finally to slugging fluidization, and the conversion process is related to the particle diameter and inlet flow rate. The characteristic peak is positively correlated with the inlet flow rate, but the frequency corresponding to the characteristic peak is constant. The time required for the Lacey mixing index (LMI) to reach 0.75 decreases with increasing inlet flow rate; at the same diameter, the inlet flow rate is positively correlated with the peak of the average transient velocity; and as the diameter increases, the distribution of the average transient velocity curve changes from "M" to linear. The results of the study can provide theoretical guidance for particle flow characteristics in biomass fluidized beds.

Application of hydrocyclone in chemical precipitation

ABSTRACT This study demonstrates the use of hydrocyclone as a thickener to precipitate sulfate ions from wastewater. Simulated wastewater containing different concentrations of sodium sulfate (100–400 mg L−1) dissolved in distilled water was prepared. Lime was added as the precipitating agent. Different flow rates of the feed (3–11 L min−1) were used for two split ratios (0.1, 0.9). The results showed that increasing inlet flow rate, initial concentration, and split ratio enhanced the separation by concentrating sulfate ions in the underflow. Design Of Experiments was performed to determine the most effective factor on the response (underflow concentration) and to assign the optimum operating conditions. The effect was in the order: inlet flow rate, initial concentration, and split ratio. The quadratics of the factors also affected the separation in the order (inlet flow rate)2, (inlet flow rate) × (split ratio), (inlet flow rate) × (initial concentration). The optimum (maximum) value of the underflow concentration of sulfate ions was 856.538 mg L−1 at the optimum operating conditions (11 L min−1 inlet flow rate, 400 mg L−1 initial concentration, and 0.9 split ratio). The experimental value at the optimum operating conditions was 932 mg L−1 including 8% error. The process was applied on a real wastewater taken from a tile factory. The results confirmed the experimental results in that the pollutant was concentrated in the underflow. It was concluded that using hydrocyclone as a thickener was feasible to separate sulfate ions from wastewater. Also, the separation using hydrocyclone could be integrated with another technique such as electrocoagulation or ion exchange to recover sulfur as an attempt toward sustainable development requisites.

A high-efficiency mini-hydrocyclone for microplastic separation from water via air flotation

A mini-hydrocyclone was designed to remove microplastics from water through air flotation. The hydrocyclone geometry parameters were optimized through the combination of the orthogonal design method and numerical simulation. The performance of the optimized mini-hydrocyclone was experimentally evaluated. The experimental and numerical underflow pressure drop results showed a consistent trend in the considered flow range. The separation efficiency increased with increasing inlet flow rate, but increased, and then decreased, with the flow split ratio. The separation performance of microplastic in the entire size range could be improved through the injection of air bubbles into the water. The separation efficiency enhancement ranged from 5 % to 15 % within a split ratio range of 0.04 to 0.23. The separation efficiency increased rapidly with a low flow rate of air injection and remained high (> 92 %) with a further increase in the air flow rate. The concentration ratios of the hydrocyclone were all >7.8 owing to low flow split ratios. The maximum concentration ratio reached 9.7 at a feed flow rate of 0.45 m3/h, a split ratio of 0.1 and an air holdup of 5.4 %. The results demonstrated that the designed hydrocyclone with injected microbubbles can achieve high separation efficiency and concentration rate at the same time. The air flotation-induced increase in grade efficiency was mainly due to the density reduction effect of MP–bubble agglomerates, and the volume expansion effect was relatively small. The cyclonic air flotation technology can be applied to small-scale water treatment, such as separating microplastics in a washing machine.

Sand coated with graphene oxide-PVA matrix for aqueous Pb2+ adsorption: Insights from optimization and modeling of batch and continuous flow studies

In the present study, a composite of graphene oxide-polyvinyl alcohol coated sand (GO-PVA@sand) was prepared and examined for adsorption of aqueous Lead ion (Pb2+) in batch and fixed-bed columns. The characterization of GO-PVA@sand revealed that GO-sheets were randomly immobilized into the PVA-matrix and formed a stable complex surrounding sands particles. And hence, preventing leaching of GO from the GO-PVA@sand and avoiding agglomeration of GO-PVA@sand inside the column that leads to no column chocking. The adsorption of Pb2+ onto GO-PVA@sand was endothermic in nature, attained equilibrium in ≤ 45 min, followed the pseudo-second-order kinetics, and the Langmuir adsorption isotherm with the maximum adsorption capacity of 8.25 mg/g. Moreover, the fixed-bed column study revealed that the adsorption capacity (qeq) decreased from 7.4 to 7.0 mg/g by increasing inlet flow rate from 5 to 15 mL/min because of drop in the contact time between Pb2+ and GO-PVA@sand. In contrast, the qeq increased from 7.2 to 7.6 mg/g, with an increase of bed-height from 2 to 6 cm, due to greater contact time and surface exposure. Besides increasing inlet concentration from 20 to 40 mg/L, the qeq increased from 7.2 to 8.0 mg/g, apparently because of the presence of a higher mass driving force. To understand the potential for process scale-up, breakthrough modeling was performed and found that the Thomas and Yoon-Nelson model best described the adsorption behavior. The post-adsorption characterization of GO-PVA@sand showed Pb2+ adsorbed through ion-exchange, cation-π, electrostatic interaction, and hydrogen bonding. The regeneration and reuse potential of the GO-PVA@sand up-to five adsorption-desorption cycles, signify its relevance in low-cost continuous water treatment.

Investigation of optimal design and separation performance of the hydrocyclone with a vorticose involute-line diversion feeding body

As an important transport channel for multi-phase flow, the feeding body imposes significant effects on the formation of granularity layer and pre-separation of particles. In a conventional feeding body, particles are generally under a turbulent state and intensively collide with the wall surface, thereby leading to the decline in particle separation precision. In this study, a novel hydrocyclone with a vorticose involute-line diversion feeding body was designed, and meanwhile the feeding body was optimized in structure. By means of numerical analysis, the inner flow field and particle separation performance were examined. It was found that using the novel structure of the feeding body can effectively reduce the inner turbulence in the hydrocyclone, accompanied with the enhancement of flow field stability and particle separation precision. Compared with the conventional hydrocyclone, the content of fine particles in the overflow can be enhanced by 32.68% while that in the underflow can be reduced by 43.17% using the novel feeding body. To be specific, the quality efficiency and quantity efficiency of the novel hydrocyclone were 15.66% and 14.87% higher than that of the conventional hydrocyclone, respectively, exhibiting remarkable improvement. Finally, the effect of inlet flow rate on the separation performance of the novel hydrocyclone was investigated. Results show that fine particles moved gradually outwards with the increasing inlet flow rate, accompanied with gradually increasing content of fine particles in the underflow and the decline in the mass of coarse particles. The cutting capability can also be enhanced with the increase of the inlet flow rate. At an inlet flow rate of 4.1055 L/min, the separation precision reached a peak. The present conclusion can offer insightful guidance for the further development of novel hydrocyclones.

Optimization of SMR process for syngas production through a solar-assisted thermo-chemical reactor with a multi-layered porous core

A two-dimensional steady-state axisymmetric model is developed to analyze the performance of a thermo-chemical porous reactor used for syngas and subsequently hydrogen generation through the steam methane reforming (SMR) process. The finite volume method coupled with kinetics thermo-chemical reaction and local thermal non-equilibrium (LTNE) model with modified P1 approximation is employed to obtain the temperature distribution for both the fluid and porous zones. First, the effects of inlet mass flow rate, inlet steam to methane ratio, porosity, number of pores per inch (PPI), permeability, and reactor length on reactor performance are scrutinized. Next, to optimize the performance of the reactor, an artificial neural network (ANN) is developed to obtain the maximum hydrogen generation rate concerning the effective parameters. Finally, a two-layer porous foam is utilized as the catalyst zone to further improve the performance. Results show that increasing inlet flow rate leads to temperature decline and causes an incomplete reaction. Also, increasing porosity enhances heat absorption at the inlet and decreases radiative heat transfer through the porous foam. At a specified condition (ṁ= 0.25 kg.h−1, XCH4/XH2O = 1/3, and PPI = 10), increasing the porosity from 0.6 to 0.8 has increased hydrogen production by 27 %, while by a further increase of porosity to 0.9, hydrogen production decreased by 3 %. Results indicate up to 164 % increment in the performance of the optimal case compared to the base case. Furthermore, employing the two-layer porous foam with different PPIs could further increase hydrogen production, up to 20 %, and reduced the pressure drop.

Experimental investigation on cryogenic chilldown performance under high-Reynolds number condition and using interior micro-fin structure

Future aerospace vehicle requires a fast propellant fueling and a rapid launching. In the present study, a high-pressure chilldown test platform is established, and two different tube structures, including a straight tube and an interior micro-fin tube, are tested under different inlet Reynolds number (Re) conditions. The test results show that for a typical chilldown case through the straight tube, different boiling mechanisms successively dominate the fluid-wall heat transfer, and inverse annular flow film boiling occupies the maximum proportion of wall temperature decrease. Increasing inlet flow rate could accelerate the chilldown rate, and the time cost in Re=45,000 case is only about 15% of that in Re=5,000 case. For the proposed interior micro-fin tube, the test results verify its excellent performance in improving chilldown rate. Under Re=5,000 condition, the time cost for micro-fin tube case is only about 70 s, which is far less than the time cost by a straight tube case. This astonishing performance is mainly because the micro-fin structure induces a radial velocity component in the inverse annular vapor film. The radial velocity strike acts on the liquid-vapor interface, yielding an interface fluctuation or even a liquid column breakup. Therefore, the liquid phase could contact the tube warm wall earlier, and then a sustained high heat flux gives rise to significant temperature decrease effect throughout the whole chilldown process.

Simulation study on influencing factors of coal low temperature oxidation based on a one-step chemical reaction equation

ABSTRACT Coal spontaneous combustion is one of the important factors affecting coal mine safety production. However, the numerical simulation of coal spontaneous combustion influence factors is mostly carried out by gas concentration, using chemical equation to simulate has higher accuracy. In this paper, a temperature-programmed experiment investigating low-temperature oxidation based on small-scale coal samples was performed, and an one-step chemical reaction equation for coal low-temperature oxidation was established. Then, SIMTEC was used to conduct a numerical simulation of the equation, the simulation results are compared with the experimental results to verify the accuracy of the simulation. Finally, the effects of different porosity, wind speed and heating rate on low temperature oxidation of coal were simulated. The results show that when the temperature is lower than 398.15 K, the O2 consumption rate as well as CO and CH4 production rates change slowly and then change rapidly when the temperature exceeds 398.15 K. The porosity and inlet flow rate of the coal samples were positively correlated with the O2 consumption rate and gas production rate, O2 consumption rate and production rates of CO and CH4 increase with increasing inlet flow rate and decrease with increasing heating rate.

Investigation on the temperature distribution in the two-phase spider netted microchannel network heat sink with non-uniform heat flux

The considerable increase of the heat flux and chips density on the phased array antenna has brought great challenges to the thermal management. The objective of the work is to explore an effective scheme to achieve ideal uniform temperature distribution and lower maximum temperature with the condition of non-uniform heat flux. Taking into account of the high efficiency of microchannel heat sink and the promising performance of the two-phase flow boiling heat transfer due to its merit in keeping uniform surface temperature, a novel two-phase spider netted microchannel network heat sink is proposed in this paper. Firstly, a three-dimensional fluid-solid-thermal conjugate model is developed to investigate the flow boiling heat transfer performance of the spider-netted microchannel network numerically. During the numerical calculation, a multi-scale meshing generation method is proposed to reduce modeling difficulties on the premise of proper mesh quality. Then, the flow boiling heat transfer experiment is conducted to verify the reasonable of the model and the simulation results. Finally, the flow boiling heat transfer performance in the spider netted microchannel network is compared to the typical straight microchannel network. Results show that the proposed structure yields better flow boiling heat transfer performance with lower thermal resistance and more satisfactory temperature uniformity mainly due to its uniform flow distribution and enhanced vapor movement. It is also found that the temperature uniformity has reached 1.58 °C at heat flux of 100 W/cm2, but it decreases with the increase of heat flux. This situation cannot be effectively solved by means of increasing inlet flow rate. Thus the structure optimization is conducted to enhance the flow boiling heat transfer performance further, and the optimal structure can meet requirements of temperature uniformity within 2 °C at higher heat flux of 150 W/cm2.

SEWAGE PERFORMANCE OF A NEW TYPE OF FLAP FILTER

The drainage performance of a mesh filter determines the water consumption degree of the filter and the efficiency of the next work cycle. Through analysis, we found that the influent flow rate and the sediment content of the influent were important influencing factors. This experiment focused on the drainage time, pressure difference, and cleanliness to investigate the drainage performance of a new type of flap filter. The results showed that with increasing inlet flow rates, the time to discharge the effluent decreased, and the time required for the difference between the primary and secondary sewage pressures to reach a constant level was shorter. The cleanliness and drainage effects were improved. To verify this, we established mathematical models of sewage discharge time, sewage pressure difference, and sewage cleanliness based on the mass conservation law. The results showed that the relative error between the fitting calculation results and the experimental results was small, and the formula fit was over 95%. In the actual work, to achieve efficient sewage discharge under the condition of low sewage discharge and low water consumption, the discharge flow rate was set to 180 m³ h-1, and the sewage discharge time was set to 50 s. Under this condition, the sewage cleanliness reached above 97%.

Implementation of Ion Exchange Processes for Carbon Dioxide Mineralization Using Industrial Waste Streams

Sequestration of CO2 within stable mineral carbonates (e.g., CaCO3) represents an attractive emission reduction strategy because it offers a leakage-free alternative to geological storage of CO2 in an environmentally benign form. However, the pH of aqueous streams equilibrated with gaseous streams containing CO2 (pH < 4) are typically lower than that which is required for carbonate precipitation (pH > 8). Traditionally, alkalinity is provided by a stoichiometric reagent (e.g., NaOH) which renders these processes environmentally hazardous and economically unfeasible. This work investigates the use of regenerable ion-exchange materials to induce alkalinity in CO2-saturated aqueous solutions such that the pH shift required for mineralization occurs without the need for stoichiometric reagents. Na+-H+ exchange isotherms (at [H+] = 10−8–10−1 M) and rates were measured for 13X and 4A zeolites and TP-207 and TP-260 organic exchange resins in batch equilibrium and fixed-bed exchange experiments, respectively. At solutions equilibrated with CO2 at 1.0 atm (pH = 3.9), H+ exchange capacities for the materials were similar (1.7–2.4 mmol H+/g material) and resulted in pH increases from 3.9 to greater than 8.0. Multi-component mixtures using Ca2+ and Mg2+ cations (at 10−3–10−1 M) in CO2-saturated water were used to probe competitive ion exchange. The presence of divalent cations in solution inhibited H+ exchange, reducing capacities to as low as 0.2 mmol H+/g for both resins and zeolites. Dynamic H+ exchange capacities in fixed-bed ion exchange columns were similar to equilibrium values for resins (∼1.5 mmol/g) and zeolites (∼0.8 mmol/g) using inlet solutions that were equilibrated with gaseous streams of CO2 at 1.0 atm. However, exchange kinetics were limited by intraparticle diffusion as indicated by the increased rate parameters with increasing inlet flow rates (20–160 cm3 min−1). Experimental calcite precipitation from mixing the alkaline CO32−-rich water solution obtained from the ion-exchange column with a simulated liquid waste stream solution achieved thermodynamic maximum yields. The results from these studies indicate that ion exchange processes can be used as an alternative to the addition of stoichiometric bases to induce alkalinity for the precipitation of CaCO3, thereby opening a pathway toward sustainable and economic mineralization processes.

Influence of inlet structure on thermal stratification in a heat storage tank with PCMs: CFD and experimental study

Heat storage tanks are one of the key components in solar thermal utilisation systems. In this study, the effect of the inlet stratifier on the thermal stratification in a heat storage tank with phase-change materials (PCMs) was investigated. A heat storage tank with a volume of 60 L and aspect ratio of 1.68 was developed based on the phase-change temperature of 331.15 K for sodium acetate trihydrate. The thermodynamic characteristics of the heat storage tank were measured at an initial temperature of 353.15 K and inlet water temperature of 278.15 K. Moreover, a computational fluid dynamics (CFD) model of the heat storage tank was established to simulate the discharge process. In addition, the CFD model was verified with experimental data. The impact of the PCM position on thermal stratification was thoroughly analysed for various flow rates. Furthermore, performance parameters including the Fill Efficiency (FE), Richardson number (Ri), and MIX number were considered. The results show that the equalizer enhances the thermal stratification effectively in the phase-change heat storage tank and stabilises the heat output characteristics of the water tank. Furthermore, in the water discharge process (t* = 0.1–0.7), the distances between the isothermal surfaces (279.15 K) and isothermal surfaces (352.15 K) in PCM4, PCM3, PCM2, and PCM1 increase by 6.56, 7.2, 8.98, and 12.34 cm, respectively. Thus, the mixing of hot and cold water strengthens with higher PCM position, which improves the thermal stratification in a heat storage tank. The half-life of the PCMs (melting rate reaches 50%) is prolonged with increasing inlet flow rate. For an inlet flow rate of 1 L/min, the half-life of PCM4 is t* = 0.5. For an inlet flow rate of 5 L/min, the half-life of PCM4 is t* = 0.95. Moreover, the simulated results of the FE and Ri are slightly higher than the experimental values, whereas the simulated MIX number results are below the experimental values. Finally, the simulated and experimental root mean-squared error results increase with lower PCM positions and increasing inlet flow rates.

Effects of geometric structures on flow uniformity and pressure drop in dividing manifold systems with parallel pipe arrays

Dividing manifold systems have been extensively used in the areas of energy transfer and conservation. The design of uniform flow distribution is a critical issue for the enhancement of performance of the manifold system. In this study, the effects of the inlet Reynolds number and structural parameters (area ratio (AR), pipe pitch (Δl), height of convex head (hhead) and number of outlets (n)) on flow uniformity and pressure drop in the DMS–PPA have been numerically investigated and validated with experiment data. The non-uniform distribution in the manifold system has been quantified using the dimensionless parameter βi (flow ratio) and Φ (non-uniformity coefficient). The results indicate that the flow rate increases along the longitudinal direction of the manifold and becomes close to the average value in the 2nd and 3rd outlets. It is found that the Ф slightly drops with the Re rising, while the ΔPj would dramatically increase owing to the increasing inlet flow rates. The AR has the greatest influence on flow uniformity, and lower AR corresponds to a more uniform distribution. The corresponding Φ values increases from 0.00351 to 0.3885 when AR varies from 0.2844 to 4. Under the same inlet flow rate, the increase of n will lead to obvious flow non-uniformity. The superiority of flow performance in the DMS–PPA can be ascribed to the anti-parallel flow direction, and the ‘plenum chamber-like’ structure of the manifold. The optimsed geometric structures with 1 < AR < 1.5, and Δl=(ϕoi+ϕo(i+1)+120) mm are recommended, considering the synergetic effect of flow uniformity and pressure drop. This study can provide a reference for engineers in designing dividing manifold systems.

Industrial-Scale Experimental Study on the Thermal Oxidation of Ventilation Air Methane and the Heat Recovery in a Multibed Thermal Flow-Reversal Reactor

In the present work, an industrial-scale experiment on ventilation air methane (VAM) utilization by a multibed thermal flow-reversal reactor (TFRR) is conducted in China. The influence of the inlet flow rate, feed methane concentration, and cycle time on the temperature distribution of the bed and heat recovery efficiency are investigated. The methane conversion in the studied cases exceeds 97%. The results show that the methane concentration during self-maintained operation of the TFRR without heat recovery should not be less than 0.22 vol % when the inlet flow rate is 103,000 Nm3/h and the cycle time is 300 s. As the inlet flow rate decreases, the lower concentration limit of automatic thermal maintenance increases. The peak temperature of the bed approaches the inlet side as the feed methane concentration increases and the cycle time decreases. The heat recovery efficiency increases linearly with increasing inlet flow rate, rises parabolically with an increasing feed methane concentration, and decreases weakly with increasing cycle time.

Visualization and quantification of separation of liquid-vapor two-phase flow in a vertical header at low inlet quality

This paper presents the experimental study of separation of two-phase flow in a vertical header of microchannel heat exchanger based on quantified visualization using fast camera. A prototype unit, representing the real condenser has an inlet in the center of the header. Downstream of the intermediate header are two branches: lower for liquid and upper vapor flow. The header for experiment provides full visual access. R-134a is used as the fluid and mass flux through the inlet microchannels is controlled at 54 kg m−2 s−1–193 kg m−2 s−1. The results indicate that within the range of lower inlet quality (5–25%), good separation in that header can happen at low mass flux up to 90 kg m−2 s−1. Results are presented in function of liquid and vapor separation efficiencies (ηl, ηv). Two-phase flow characteristics inside the header are analyzed for better understanding of separation efficiencies ηl and ηv. The efficiency deteriorates dramatically when liquid reaches the vapor exit, with increasing inlet flow rate and/or quality. Better two-phase separation can be achieved by reducing the liquid upward momentum or the vapor, and decreasing liquid and vapor interaction.

Experimental study on turbulence properties in the dual nozzle opposed impinging stream mixer

The impinging stream reactor currently under study, especially in processes of fluid mixing, is employed in a variety of applications that include pharmaceuticals, petroleum, and provisions. The distributions of three‐dimensional velocity fluctuation in the dual nozzle opposed impinging stream mixer were measured experimentally using laser Doppler velocimetry (LDV). The results showed that stagnation points were in proximity of the line of z = 0 under experimental conditions, but the exact positions of these stagnation points shifted with different nozzle diameters, nozzle spacing, and inlet flow rates. The distributions of RMS velocity and turbulent kinetic energy were similar in the same operating condition, but turbulence intensity changed obviously on the z axis ranging from −10 mm to 30 mm, in which region turbulence was intense and the large turbulence intensity was advantageous to mixing. The RMS velocity was influenced obviously by changing distance between nozzles, the turbulence intensity was affected greatly by the nozzle diameters, and the region of high turbulent kinetic energy which was beneficial to mixing was enlarged by increasing inlet flow rates.