Fan Model Research Articles

Aerodynamic noise analysis of a portable pneumatic extinguisher

The portable pneumatic extinguisher is one of the most important pieces of equipment for forest fire fighting in China. However, the working noise of the equipment is detrimental to the physiological and psychological health of people in terms of noise exposure. Few research studies have addressed the noise of portable pneumatic extinguishers. Changes of the geometric parameters of the fan can induce variations in the airflow field, thus modulating the resulting aerodynamic noise. This article describes how certain parameters influence the aerodynamic noise of a portable pneumatic extinguisher; the research object of this study was the 6MF-30 portable pneumatic extinguisher. Based on the literature, three parameters that influence the airflow in the fan were chosen for investigation: the stagger angle, exit installation angle and curvature ratio. Models of the portable pneumatic extinguisher fan were developed using SolidWorks, and the values of the geometric parameters were calculated using formulas incorporating trigonometric functions. The noise simulation was conducted via FLUENT based on the FW-H equation, and ten two-dimensional models with different parameters were investigated. The results show that the exit installation angle has essentially no effect on aerodynamic noise. In contrast, the stagger angle and the curvature ratio can have a large influence on aerodynamic noise. The optimal model differs for different frequency bands; for example, at frequencies below 80 Hz, a fan with a stagger angle of 30 exhibits better noise performance, and at frequencies in the range of 80 Hz to 1000 Hz, a fan with a stagger angle of 40 produces lower working noise. The results are clearly different from those of an aerodynamic performance analysis.

Fine-Grained Debris Flows In Coarse-Grained Alluvial Systems: Paleoenvironmental Implications For the Late Paleozoic Fountain and Cutler Formations, Colorado, U.S.A.

Abstract: The Fountain and Cutler formations are coarse-clastic alluvial wedges that mantled ancestral Rocky Mountain uplifts. Muddy granule sandstone (MGSF) is a volumetrically important facies to both systems. The facies is massive and unsorted with grain-size distributions that range from clay to granule. These deposits are best characterized as cohesive fine-grained debris flows. Yet, the MGSF rarely contains clasts > 10 mm, although other intercalated alluvial facies commonly contain cobbles and small boulders. Competence modeling was undertaken to assess the amount of water needed to account for the observed coarsest fraction of the MGSF. These results indicate that flows would need inflation with water by one-third to two-thirds, depending on clay mineralogy and the range of clay in the MGSF. This paper proposes that flows began as debris flows but underwent flow transformation through incorporation of water during flow in the paleohighlands. Dilation of the flow reduced competence, and each flow lost the coarser than 10 mm fraction. Flows would rheologically stiffen upon reaching the unconfined alluvial surface, ultimately behaving as cohesive fine-grained debris flows. The MGSF at both study areas does not fit into end-member facies models of alluvial fans. Depositional systems elsewhere that exhibit similar facies may want to consider flow transformation and the associated environmental implications when inferring the depositional setting.

Analysis of fluid flow and heat transfer on a solar updraft tower power plant coupled with a wind turbine using computational fluid dynamics

The objective of this study was to develop a more realistic numerical model for solar updraft tower power plants. To accomplish this, a three-dimensional (3-D) simulation for the geometric parameters of the Manzanares prototype coupled with a real turbine was carried out using computational fluid dynamics (CFD). The RNG k-ε turbulence closure, discrete ordinates (DO) non-grey radiation model and solar ray-tracing algorithm were employed. In addition, a comparatively simpler simulation using a reverse fan model to implement pressure drop across the turbine was conducted. The pressure, velocity and temperature distributions through the system were considered, and the results of the simplified model were compared to those of a system coupled with a real turbine, to assess the proper pressure jump value to be assigned in the reverse fan model. Results showed that, compared to the real turbine model pressure drop, the reverse fan model with a 43.7% lower assigned pressure jump predicted the same performance. The numerical model developed in this study provides a highly accurate and reliable approach for predicting the performance of a solar updraft tower power plant, taking into account all the main phenomena of the system.

Effects of sulfurization on the optical properties of Cu2ZnxFe1-xSnS4 thin films

In order to prepare thin films of novel semiconductor materials that contain only earth abundant, low cost and nontoxic elements, Cu2ZnxFe1-xSnS4 ingots were successfully synthesized by direct fusion method. Crushed powders of these ingots were used as raw materials for the thermal evaporation. Cu2ZnxFe1-xSnS4 (with x = 0, 0.25, 0.5, 0.75 and 1) thin films were deposited on non-heated glass substrates by vacuum evaporation method. The as deposited films were sulfurized for 30 min at sulfurization temperature Ts = 400 °C. The effects of the sulfurization on the structural and optical properties of CZFTS films were realized by X-ray diffraction (XRD) and UV–Vis spectroscopy. XRD patterns show that all sulfurized CZFTS films were polycrystalline in nature with a preferential orientation along the (112) plane. CFTS films exhibit a stannite structure while CZTS films had a kesterite structure. Optical measurements showed that CZFTS films sulfurized at 400 °C exhibited an optical transmittance between 60 and 80% and all materials had relatively high absorption coefficients in the range of 104–105 cm−1. The band gap energies of sulfurized CZFTS films decreased from 1.71 to 1.50 eV with the increase of the Zn content. The dispersion of the refractive index was discussed in terms of the single oscillator model proposed by Wemple and DiDomenico and the optical parameters such as refractive index, extinction coefficient, oscillator energy and dispersion energy were calculated. The electrical free carrier susceptibility and the carrier concentration on the effective mass ratio were evaluated according to the model of Spitzer and Fan. The hot probe analysis showed that all sulfurized CZFTS films are p-type conductivity.

A new viscosity model based on Soave-Redlich-Kwong equation of state

In this study based on the Soave-Redlich-Kwong equation of state (SRK EOS), a new viscosity model for light hydrocarbons, CO2 and N2 has been proposed. The proposed model can be applied in both liquid and gas phases and in high and low ranges of pressure and temperature. The optimal values of the parameters in the proposed model are determined by using the Genetic algorithm and generalized in term of acentric factor. The performance of the proposed model has been compared with the performance of Peng-Robinson EOS-based viscosity model of Guo et al. (2001), the Peng-Robinson EOS-based viscosity model of Fan and Wang (2006) and the Lohrenz-Bray-Clark (LBC) method. In order to have a fair comparison, the binary interaction coefficients in the mixing rules are set to zero. The results of calculations for seventeen pure components (6449 data), thirty eight binary mixtures (2772 data), ten simple and twenty complex mixtures (74 data) show the superiority of the proposed model compared to the other viscosity models.

Transient three-dimensional CFD modelling of ceiling fans

Ceiling fans have been used for decades as a means of providing thermal comfort in tropical countries such as India. However, recent years have witnessed a significant increase in the use of air conditioning as a means to achieve comfort, and therefore in the total energy consumption and related CO2 emissions. Ceiling fans are still viable options to limit use of air conditioners or in combination with air conditioners without compromising on thermal comfort and still achieving energy savings. Ceiling fans generate non-uniform velocity profiles, and therefore relatively non-uniform thermal environments, whose characteristics may be tough to analyse with simple modelling methods. This issue can be investigated using CFD. However, to date, there are few works on ceiling fans, CFD and thermal comfort. More accurate models are therefore required to predict their performance. The research presented in this paper aimed to develop and validate a three-dimensional transient implicit CFD model of a typical ceiling fan available in India by comparing simulation results obtained using different URANS turbulence models with measured data collected in controlled environment. The results highlight that this ceiling fan model is able to replicate the predominant characteristics of the air flow generated by the fan such as the meandering plume and the local fine free shear layers. The best results are achieved when the SST k-ω turbulence model is used, with 83% of the simulated values being within the error bars of the respective measured value.

Effects of film thickness on the linear and nonlinear refractive index of p-type SnO films deposited by e-beam evaporation process

Tin monoxide (SnO) films of different thickness have been deposited onto glass substrates at vacuum pressure of ∼ 8 × 10−6mbar using an e-beam evaporation system. A hot probe test revealed that the deposited films showed p-type conduction. The structure characterization and phase purity of the deposited films was confirmed using X-ray diffraction (XRD) and Raman spectroscopy. The optical transmission and reflection spectra of the deposited films recorded in the wavelength range 190–2500nm were used to calculate the optical constants employing the Murmann's exact equations. The refractive index dispersion was adequately described by the well-known effective-single-oscillator model proposed by Wemple–DiDomenico, whereby the dispersion parameters were calculated. The nonlinear refractive index and nonlinear optical susceptibility of the deposited films were successfully evaluated using the Miller empirical relations. The lattice dielectric constant and the carrier concentration to the effective mass ratio were also calculated as a function of film thickness using the Spitzer and Fan model. The variation of the optical band gap of the deposited films as a function of film thickness was also presented.

Minimization of electricity demand and cost for multi-zone buildings: Part I—Modeling and validation

Heating, ventilation, and air-conditioning systems are complex in terms of components that make them up and their different time scales. The inefficient operation of a heating, ventilation, and air-conditioning system leads to unreasonable electricity consumption during peak periods, which is accompanied by a high cost of electricity use. In a multi-zone building, multiple thermal interactions among the different thermal zones and the effects on electricity demand and cost are not well understood, due to the lack of fundamental knowledge. Meanwhile, multi-zone interactions and building dynamics play a crucial role in the overall electricity demand, cost, and load profiles due to the dependency of states of each individual zone on the thermal characteristics and states of the adjacent zones. The objective of this research is to understand multi-zone and equipment interactions in buildings energy systems, and to use that knowledge to minimize electricity demand and cost. To the best of the authors' knowledge, this is the first research to integrate building dynamics into controller formulation and design through the use of a physically representative thermal model that captures important phenomenon of building load and cooling coil operations. The current article is laid out in two parts. This first part introduces the development and validation of transient thermal models for building load and cooling coil operations in an actual air-handling unit serving a multi-zone office building. It also introduces a simplified model for supply fan power and speed. The models were developed using fundamental heat transfer equations and fan laws, with the model parameters estimated from short-period measurement data. The respective models are validated using actual data from building automation system. The results are presented, and they show high accuracy for building load, cooling coil, and the fan model, such that suitable predictive control methods could be used to minimize the overall electricity demand and cost. The minimization framework and optimization results are discussed in a subsequent article.

Computations with the multiple reference frame technique: Flow and temperature fields downstream of an axial fan

ABSTRACTIn numerical computations, axial fans are typically abstracted as two-dimensional surfaces, and this forms the basis for the “Lumped Fan” (LF) model. The LF-model relies on experimentally derived P–Q (fan) curves which should conform to the published test codes. Despite its simplicity, the LF-model’s accuracy depends on the application and acceptable error margin. Therefore, with decreasing error margins in thermal engineering, there has been an interest in accurate fan modeling techniques such as “Multiple Reference Frame” (MRF) model. The current effort provides a two-part validation of the MRF model results for an axial fan against the relevant experiments: comparison of the (i) P–Q curves, and (ii) temperature distribution in an electronic enclosure. In the former, both fan models exhibit good agreement with the experiments, however the flow structures determined by the two models exhibit substantial differences. Given these flow structures’ strong influence on the temperature field, the MRF model demonstrates good correlation and significantly better agreement with the measured temperature distribution, compared to those of the LF-model. In light of these findings, benefits, limitations, and possible applications of both models are also discussed.

A new unidentified leak detection method based on the EVR ventilation condensate

The management of coolant leakage in a Nuclear Reactor Containment is important to ensure the integrity of the second barrier and the safe operation of a nuclear power plant. In the nuclear plant, several reliable leak detection systems continuously monitored coolant leak. In this paper, we introduced a new unidentified leak detection method based on monitoring the condensate in the ventilation coolers. After built a heat exchanger model of the cooler and introduced the fan model in the commercial CFD code, we validated models and got a reasonable simulation of the leak steam condensate on the cooler. Then we built the detail three-dimensional (3D) PWR containment geometry model (including internal structures and ventilation systems). Based on the detailed flow field in this containment and the moisture condensation theory, we could get the condensate character on the coolers of the EVR ventilation system after unidentified leak. Analyses were carried out to quantify the condensate after the 1.0gpm (gal/min) and 1.5gpm leak at hot leg and cold leg located at the reactor pit and steam generator room. The result indicated that the start condensation time of 1.0gpm leak was about 75min and 45min of 1.5gpm, and the leak location had slight influence on the start condensation time. This work would contribute to a reasonable design of a leakage detection method for the unidentified leak in the containment.

Influence of vane angle on the effectiveness of air conditioning of wall-mounted split-type air conditioners in residential buildings

The purpose of this study is to accurately evaluate the effect of vane angle on the effectiveness of air conditioning of wall-mounted split-type air conditioners. First, to determine the detailed characteristics of airflow from an air conditioner opening, airflow rate, turbulence characteristics, and air distribution were measured according to the vane angle. Then, the detailed characteristics were calculated using a simplified opening model with boundary conditions obtained from the calculated results of a cross-flow fan model using the overset mesh technique to validate the computational fluid dynamics simulation. Finally, to evaluate the effectiveness of air conditioning, the effectiveness of air change was calculated under isothermal conditions by varying the vane angle and the setting position of the air conditioner by using the validated computational fluid dynamics model. The measurement results showed that when the vane was set at the middle position (rather than at the left or right positions), the airflow rate increased by 19.0%–20.9% in the high airflow rate mode. The simulation results verified that the simplified opening model was consistent with actual findings, and only a slight difference was observed between actual measurements and the computational fluid dynamics simulation results. Furthermore, installing the air conditioner at the center of a wall and setting the vane at the middle position improved the effectiveness of indoor air conditioning.

Double-population differential evolution algorithm for bilinear spectral unmixing based on FAN model

Double-population differential evolution algorithm for bilinear spectral unmixing based on FAN model

Re(a)d wedding: A case study exploring everyday information behaviors of the transmedia fan

ABSTRACTAs practitioners of new forms of consumption and production, fans represent an important area for research. Specifically, fans of “transmedia systems” – media‐hopping networks of intertextualities that extend the narrative world of an original production – employ unique tactics for negotiating a complex information space. The study of such tactics provides valuable insights on the everyday information behaviors of modern post‐digital readers and media consumers that could benefit literacy and community engagement. Despite this, fans have received little attention in the information behavior literature. Therefore, this paper seeks to contribute new empirical understandings of the transmedia fan to the information behavior domain. The author undertook a pilot case study of the Game of Thrones transmedia fandom. Using a grounded theory approach, the qualitative coding of 400 online user comments revealed four types of tactics employed by fans to negotiate the transmedia system: sentimental, reasoned, relational and comic. A discussion of these tactics and the ways in which fans use them results in a preliminary definition and information behavior cycle model for the transmedia fan. The study's findings offer key observations about the everyday information behavior of fans and about reading and media consumption practices in general.

Study of Numerical Analysis on Smoke Exhaust Performance of Portable Smoke Exhaust Fan

In houses and general buildings of environment where smoke control equipment is not installed, or its operation is difficult, there is a need to develop and utilize a portable smoke exhaust fan that can perform emergency ventilation in case of fire suppression and rescue operations. As a part of the development process for portable smoke exhaust fans, a numerical analysis model of the portable smoke exhaust fan was derived from the building in which a fire occurred, and an analysis on the smoke and toxic gas exhaust effects was performed in this study. The numerical analysis results showed that under a condition where the height of an opening is less than 1.0 m after fire source disappears in a situation where the smoke exhaust fan does not operate, smoke does not come out well, and thus the density of smoke within the target area does not drop significantly. On the other hand, if the smoke exhaust fan operates after the fire source disappears, smoke is directly exhausted to the outside due to the operation of the smoke exhaust fan, and the smoke density within the space drops sharply in all opening height conditions, thereby getting close to zero.

A New Algorithm for Bilinear Spectral Unmixing of Hyperspectral Images Using Particle Swarm Optimization

Spectral unmixing is an important technique for exploiting hyperspectral data. The presence of nonlinear mixing effects poses an important problem when attempting to provide accurate estimates of the abundance fractions of pure spectral components (endmembers) in a scene. This problem complicates the development of algorithms that can address all types of nonlinear mixtures in the scene. In this paper, we develop a new strategy to simultaneously estimate both the endmember signatures and their corresponding abundances using a biswarm particle swarm optimization (BiPSO) bilinear unmixing technique based on Fan's model. Our main motivation in this paper is to explore the potential of the newly proposed bilinear mixture model based on particle swarm optimization (PSO) for nonlinear spectral unmixing purposes. By taking advantage of the learning mechanism provided by PSO, we embed a multiobjective optimization technique into the algorithm to handle the more complex constraints in simplex volume minimization algorithms for spectral unmixing, thus avoiding limitations due to penalty factors. Our experimental results, conducted using both synthetic and real hyperspectral data, demonstrate that the proposed BiPSO algorithm can outperform other traditional spectral unmixing techniques by accounting for nonlinearities in the mixtures present in the scene.

A global optimized operation strategy for energy savings in liquid desiccant air conditioning using self-adaptive differential evolutionary algorithm

This study proposes a global optimized operation strategy to reduce energy consumption of a liquid desiccant air conditioning (LDAC) driven by chiller and electric heater. Energy models of chiller, electric heater, pumps and fans are developed to predict their energy consumptions under different operating conditions with different control settings. Heat transfer models of cooling heat exchanger, heating heat exchanger and recovery heat exchanger are established to analyze the heat transfer processes in these components. An optimization problem considering system constraints and interactions between components is built to optimize the energy usage of the whole liquid desiccant air conditioning and simultaneously maintaining the required indoor air quality (IAQ) level. Nine controllable variables related to the performance and energy usage of LDAC are selected as control settings. Self-adaptive differential evolutionary (SADE) algorithm with fast convergence rate is employed to solve the optimization problem to obtain optimal control settings and to develop optimal operation strategies. Compare study is carried out on a fabricated testing facility to show the energy saving performance of the proposed global optimized operation strategy. Compared with the conventional strategy, 18.5% energy saving can be achieved by using the proposed global optimized operation strategy. The proposed global optimized operation strategy is a valid operation strategy that is suitable for application in energy reduction of the existing LDAC system in building.

Effect of the aerodynamic force modeling on the tonal noise prediction model for axial fan: Sensitivity and uncertainty analysis

The far-field acoustic pressure emitted by the unsteady rotating force acting by the fan on the fluid is computed using a tonal noise model prediction. Generally, the usefulness of any model depends in part on the accuracy and reliability of its output. Yet, because all models are imperfect abstractions of physical reality, and because precise input data are rarely if ever available, all output values are subject to imprecision. In this paper, the accuracy of the used tonal noise model prediction is easily influenced by the way in which the unsteady rotating force was modeled. To reach a good correlation between the numerical and experimental results, sensitivity and uncertainty analysis are conducted on the used model. The first one consists firstly on assigning to each model input the Sobol index. Then, according to the obtained index value, the most influential input is revealed. The second one leads to the assessment of uncertainties propagation through the model using the Monte Carlo simulation. Finally, the results from both analyses are presented and discussed.

Fan–Intake Interaction Under High Incidence

In this paper, we present an extensive numerical study on the interaction between the downstream fan and the flow separating over an intake under high incidence. The objectives of this investigation are twofold: (a) to gain qualitative insight into the mechanism of fan–intake interaction and (b) to quantitatively examine the effect of the proximity of the fan on the inlet distortion. The fan proximity is altered using the key design parameter, L/D, where D is the diameter of the intake, and L is the distance of the fan from the intake lip. Both steady and unsteady Reynolds-averaged numerical simulations (RANS) were carried out. For the steady calculations, a low-order fan model has been used, while a full 3D geometry has been used for the unsteady RANS. The numerical methodology is also thoroughly validated against the measurements for the intake-only and fan-only configurations on a high bypass ratio turbofan intake and fan, respectively. To systematically study the effect of fan on the intake separation and explore the design criteria, a simplified intake–fan configuration has been considered. In this fan–intake model, the proximity of the fan to the intake separation (L/D) can be conveniently altered without affecting other parameters. The key results indicate that, depending on L/D, the fan has either suppressed the level of the postseparation distortion or increased the separation-free operating range. At the lowest L/D (∼0.17), around a 5 deg increase in the separation-free angle of incidence was achieved. This delay in the separation-free angle of incidence decreased with increasing L/D. At the largest L/D (∼0.44), the fan was effective in suppressing the postseparation distortion rather than entirely eliminating the separation. Isentropic Mach number distribution over the intake lip for different L/D's revealed that the fan accelerates the flow near the casing upstream of the fan face, thereby decreasing the distortion level in the immediate vicinity. However, this acceleration effect decayed rapidly with increasing upstream distance from the fan-face.

A study of the matching of impellers and motors for contra-rotating fan based on electromagnetic-fluid coupling analysis

The contra-rotating fan is an electromechanical device in which electromagnetic force and aerodynamic force coordinate together. Its operation process is affected by multiple factors and is also coupled with multiple variables. In order to further reveal its working mechanism, electromagnetic-fluid coupling model for contra-rotating fan was presented and relevant numerical computations were performed by the combination of the motors’ electromagnetic-field simulation and the fan’s fluid-field simulation. Curves of electromagnetic torque and aerodynamic torque in time domain, respectively, for two motors and two impellers of the fan were obtained, and then fast Fourier transform algorithm was used to analyze their harmonic components. Meanwhile, the resonance effect induced by the same-frequency components between the harmonic electromagnetic and aerodynamic torques was investigated. Moreover, the impeller–motor interaction and matching performance were explored so as to determine the optimal combination scheme of blade number in two-stage impellers. The reasonableness of this scheme was validated experimentally. This heterogeneous physical-field simulation method targeted at electromagnetic-fluid coupling condition offers an important reference for optimizing the fan system.

Deep-lacustrine sandy debrites and turbidites in the lower Triassic Yanchang Formation, southeast Ordos Basin, central China: Facies distribution and reservoir quality

The deep lacustrine gravity-flow deposits are widely developed in the lower Triassic Yanchang Formation, southeast Ordos Basin, central China. Three lithofacies include massive fine-grained sandstone, banded sandstone, and massive oil shale and mudstone. The massive fine-grained sandstones have sharp upper contacts, mud clasts, boxed-shaped Gamma Ray (GR) log, but no grading and Bouma sequences. In contrast, the banded sandstones display different bedding characteristics, gradational upper contacts, and fine-upward. The massive, fine-grained sandstones recognized in this study are sandy debrites deposited by sandy debris flows, while the banded sandstones are turbidites deposited by turbidity currents not bottom currents. The sediment source for these deep gravity-flow sediments is a sand-rich delta system prograding at the basin margin. Fabric of the debrites in the sandy debris fields indicates initial formation from slope failure caused by the tectonic movement. As the sandy debris flows became diluted by water and clay, they became turbidity currents. The deep lacustrine depositional model is different from the traditional marine fan or turbidite fan models. There are no channels or wide lobate sand bodies. In the lower Triassic Yanchang Formation, layers within the sandy debrites have higher porosity (8–14%) and permeability (0.1–4 mD) than the turbidites with lower porosity (3–8%) and permeability (0.04–1 mD). Consequently, only the sandy debrites constitute potential petroleum reservoir intervals. Results of this study may serve as a model for hydrocarbon exploration and production for deep-lacustrine reservoirs from gravity-flow systems in similar lacustrine depositional environments.