Parallel Fan Research Articles

Maximizing energy transfer of solar-battery charge controller using voltage balancing strategy

Off-grid and grid-connected photovoltaic (PV) systems with battery storage rely heavily on efficient energy transfer to maximize PV power utilization and battery lifespan. However, existing literature often overlooks the crucial role of energy transfer efficiency in these systems. This paper proposes a novel, fundamental-based PV power flow strategy that addresses this gap by employing a concept of source-load voltage matching. The proposed strategy ensures optimal voltage matching between the PV array and the battery bank. This is achieved by configuring the battery bank voltage range (between nominal and fully charged states) to closely align with the variation in PV voltage at its Maximum Power Point (MPP) across different operating temperatures. This systematic approach requires specifying the DC load voltage, configuring the battery bank, and selecting PV modules with compatible Vmp (voltage at maximum power) parameters. The system utilizes a high-current blocking diode and current limiter for safe connection between the PV array and battery bank. Additionally, the strategy protects against battery overcharge by controlling parallel fans used for PV panel cooling. Experimental results with a 1.62 kW PV system employing lead-acid batteries demonstrate improved efficiency compared to traditional methods. This innovative approach has the potential to significantly enhance energy transfer efficiency, contributing to improved energy sustainability in PV systems.

Study on flow characteristics of exhaust shaft with parallel fans in high-rise residential buildings

The exhaust shaft is often used to centrally extract cooking fumes captured by parallel fans on each floor of high-rise buildings. Inadequate airflow rate and excessive pressure in the exhaust shaft lead to poor ventilation and unsatisfactory air quality in kitchens. This issue is made worse by mixed installations of exhaust fans with different dynamic performances. In this study, the flow characteristics in the exhaust shaft with parallel fans are investigated by full-scale experiments and computational fluid dynamics (CFD). Based on the orthogonal experimental design, the cross-sectional area, concurrent operating rate, operating position distribution, and P-Q curves are key factors affecting the flow rate distribution significantly. Mixed installation of fans deteriorates the uniformity of the flow distribution along the shaft by even 62.6%. The competition for flow rate between different types of fans is obeying the Matthew effect. Concentration at the bottom and more simultaneous operations exacerbate this problem. An 28% enlargement in the shaft size increases the flow rate by 28.9% and improves the uniformity of the flow distribution by 50%. The stack effect is positive and unstable, with up to a 6.49% increase in system flow rate as a function of the cooking heat intensity. This work can provide guidance for the design of centralized exhaust systems in high-rise residential buildings.

Investigation of airflow characteristics under parallel fan conditions in a block cave mine

ABSTRACT Block caving is an efficient underground mining method for extracting massive and low-grade ore deposits, which are too deep for traditional open-pit mining. However, in the case of orebodies with uranium mineralization, the extraction of broken rock from drawpoints will bring harmful radon gas into working areas. Airborne diesel particulate matter and dust produced from mining activities also contribute to the emissions on the production level. Maintaining relatively negative pressure in the cave by installing exhaust fans is one of the most effective approaches to mitigate gas emission concerns. The selection of proper fan systems is highly related to airflow behavior within the cave. Due to the dynamic caving process and complex cave structure, estimation of cave airflow resistance through field studies is difficult. This study developed a 1:100 scaled experimental and numerical model to investigate the effects of cave parameters (cave porosity, particle size, and undercut structure) on airflow resistance under parallel fan conditions. Results showed that cave airflow resistance increases with decreasing cave porosity and particle size; cave airflow behavior is significantly affected by undercut drift closure and the use of additional fans. This study provides valuable information to optimize ventilation system design in block cave mines.

A Computational Fluid Dynamic Study of Developed Parallel Stations for Primary Fans

A Computational fluid dynamic (CFD) model was developed considering three geometries for primary parallel fan stations that have already been developed, implemented, and are currently in operation within Chilean mines. To standardize the comparison, the same primary fan was used in all the simulations with a unique set of settings (speed, blade angle, and density). The CFD representation was used to determine the operating point per configuration and compare the performances in terms of airflow and pressure delivered. This approach allowed ranking primary fan station geometry based on resistance curve and energy consumption of the fan. This paper presents the results obtained through the CFD simulations and the corresponding primary fans operating points of each configuration: symmetrical branches (SB), overlap branches (OB), and run around (RA) bypass. The RA configuration was identified as the best-performing station geometry on the lowest frictional and shock pressure losses, highest airflow delivery, and lowest energy cost. The results are discussed, considering pressure, velocity, and vector contours to understand the fluid dynamics phenomena occurring inside the station. The capital cost involved in the development of each primary parallel station was considered in the analysis in addition to the energy cost to determine the economic configuration over time.

Numerical and experimental investigation on the performance of a ventilated chamber for low-cost PM sensor calibration

Particulate matter (PM) sensors are popular for distributed monitoring due to their portability, low-cost and networking capabilities. To provide reliable data, these sensors have to be calibrated periodically in the laboratory. This is often done in chambers with several of them co-located, alongside several research grade instruments. It is important to confirm that the aerosol is well distributed to ensure reliability and accuracy of the calibration tests. This paper describes a modeling and experimental study of these chambers used for calibration of PM sensors. The experimental setup is described and calibration results for the low-cost PM sensors (MAXIMA sensor, Applied Particle Technology, Inc.) using research-grade instruments (GRIMM 11-C, GRIMM Technologies, Inc.) are presented. A computational fluid dynamics (CFD) model including effects of turbulence and Brownian motion is used to predict particle trajectories and distribution in the chamber. The simulated particle number concentration agrees well with the measured values in the chamber. Having the CFD model, the suitability of three proposed chamber designs (fan off; fan on-parallel; fan on-diagonal) are explored for a variety of conditions. Operating conditions that result in uniform concentrations are established using the model. The recommended design for the PM sensor calibration in a rectangular ventilated chamber is: parallel fan layout, fan pressure of 12 Pa, and inlet air flow rate between 10 and 15 L/min. This study shows that the numerical modeling is available to understand the performance of a calibration chamber as well as optimizing the chamber design. A broader perspective is that the results validate the use of low-cost PM sensors for checking the distribution of aerosols in chambers.

Continuous improvement of the return air-raise-silencer system at Totten Mine

ABSTRACT The Totten Mine return-air raise was designed with two parallel fans equipped with silencers to reduce the noise emitted from the outlets to the environs. As the development and production of the mine progressed, the silencer system needed to be upgraded. Additional maintenance strategies have been necessary to meet the regulatory noise limits enforced by the Province of Ontario. The current mine plan required the fans to reach the upper limit of their capacity by the first quarter 2019. To achieve this operational target, additional silencing capability was required. Within the current constraints at the mine site, Totten Mine explored alternatives to extend the noise silencing capacity, including a new silencer baffle design and a new layout that allowed doubling the length of the silencer system. Using acoustical measurement data collected on several occasions, this article presents and discusses the performance of the various silencing systems that have been installed on the return air fans at Totten Mine.

Characterization and Effects of the Shock Losses in a Parallel Fan Station in the Underground Mine

Deep underground mines are highly energy consuming due to the need to overcome the growing airflow resistance. The multi-fan station ventilation system (MFSVS), formed by several parallel fans at different locations in an underground mine generally, has greatly reduced energy costs by using high-quantity and low-pressure energy-saving fans. However, experimental data still indicates that 30–70% of the fan pressure is used to overcome the severe shock losses in a parallel fan station (PFS), in spite of more than 80% operating efficiency, and the shock losses greatly weaken the superiority and the service capacity of PFS. Based on the investigation and measured data of several PFSs in a MFSVS in an underground mine, a three-dimensional PFS model was developed by computational fluid dynamics (CFD) to demonstrate airflow performance and variation characteristics of velocity, pressure and turbulence. First, the fan characteristic in the PFS was discussed and compared with the fan operating performance under standard conditions; the shock losses were then presented from both sides of the inlet shock losses and the outlet shock losses in the PFS; meanwhile, the effects of blade angle variation and airflow mutual interference were conducted to determine whether they exert a significant influence on the shock losses. The results show that the shock losses are primarily generated in the range of 0 to 3.0 m from the fans’ exits, due to the intensely change in air velocity in the PFS. The study also provides several directions and references for recovering air pressure and reducing energy consumption in the parallel fans’ structure.

A Study on Surge and Stall under the Interaction of Parallel Axial flow fan in Tunnel

In the ventilation design for tunnels above 10km, an axial flow fan of great power needs to be set in ventilation shafts. There are few provisions on the setting modes and less discussion of parallel axial flow fan mode in the Specifications for Design of Ventilation and Lighting of Highway Tunnels. All of these bring a lot of difficulties about the axial fan selection, layout and control design. There is no specialized research on axial flow fan for tunnels and no studies on surge and stall under the interaction of parallel axial flow fan in tunnel in spite of the more and more application of parallel axial flow fan. So, this paper conducts a study on surge and stall under the interaction of parallel axial flow fan in tunnels. Through the study on the operating principle and analysis of parallel axial flow fan, we can know that the noise will increase suddenly, which will in turn result in fan vibration and running instability once the stall occurs. When a fan surges, the air volume and pressure, the motor current will fluctuate sharply, which brings significantly increased vibration and noise. At the same time, the rotary blade and the shell are subject to considerable stress effects and the fan will possibly suffer from great damage. The surge will occur in the unstable zone of axial fan performance curve. The strong pulsation and periodic oscillation of the air flow will increase the noise, which is a serious damage to the fan. So an axial fan should avoid this zone in running. With two axial flow fans of the same power parallel, the mutual influence is not very great. Therefore this research will focus on the efficiency in the case of two fans with a high and a low power parallel. Stall will occur if the outside pressure is greater than the outlet pressure. Once the stall happens, the noise will increase suddenly, which will in turn result in fan vibration and running instability. When two fans parallel, i.e. when the power ratio of the parallel fans is over 5.3, the possibility of the small fan's stall is high, otherwise it is small. With regard to the running efficiency of parallel axial flow fans and the starting safety, it is better to parallel two fans, and the fans with adjustable movable vanes or frequency control or the ordinary nonadjustable fans can be used.

An Analysis of Air Flow at Various Spacing of Fans on a Physical Model of a Road Tunnel

In this article, the influence of a jet fan spacing in a longitudinal air conditioning system in a road tunnel on a physical model of the tunnel is analyzed. The analysis of air transport on a physical model with a length of 30 metres was accomplished for various combinations of the connection of 8 jet fans (parallel connection of 8 fans, combined connection of 2 X 4 parallel fans, combined connection (of) 4 X 2 parallel fans and serial connection of 8 fans). From the analysis of measurement on the physical model follows what a big influence the fan spacing has on the speed profile, which to a great extent influences air transport in the tunnel. Our contribution deals with the interpretation of vibration data from the point of view of vibration sources identification. These sources are searched and evaluated from the measured data using a frequency and phase spectrum.

Fast reconstruction algorithm for fan‐Beam CT system

AbstractThird generation CTs which acquire projection data using wide fan‐beam X‐rays that cover the cubic surface of the test object have two widely used tomogram reconstruction algorithms: i.e., the direct method and the arrangement method. The direct method applies fan‐like back projection directly in Cartesian coordinates. The arrangement method rearranges data to transform them into parallel fan beams. This paper proposes a new fast reconstruction algorithm in which polar coordinates are established that are spatially synchronous with the measurement geometry, reconstructed images are obtained by performing back projection in the polar coordinates and coordinate transformation is achieved from the polar coordinates to Cartesian coordinates. The features of this method are (1) computation is fast because the results of the many calculations are tabulated; (2) the remaining calculations are only product sums; and (3) it is easy to implement this method in hardware. The quality of images produced by the direct method is compared with that of the arrangement method and the present method using both computer simulation data and clinical data. The comparison shows that (1) spatial resolution of images produced by this method is better than that of the arrangement method, but almost equal to that of the direct method; and (2) the number of artifacts generated by calculations is small.

A four input-and-gate with five asymmetric interferometers

The static and dynamic behavior of a four input-AND-gate for a parallel fan out of three has been simulated. Only asymmetric interferometers with two unequal Josephson junctions as input devices are used instead of interferometers with three junctions in order to save circuit area and to improve performance. The input devises have a characteristic phase λ = 2.1 and a ratio of the maximum Josephson-currents of 3:1. The AND-function of each pair of inputs is performed in a similar manner as described by Klein and Herrell. The AND-function of the two input pairs is realized with a nonlinear injection gate. The number of interferometers used in this AND-gate is reduced by two compared with known proposals. With tolerances of the maximum Josephson currents of ± 10% and additional tolerances of ± 9% of the input and supply currents the worst case and average nominal logic delays are about 170 ps and 60 ps.

The rotation of light fans by cylindrical lenses

The rotation of a parallel fan of light is accomplished when the fan is incident on a cylindrical lens with its axis rotated relative to the plane of the incident fan. A matrix representation allows the angles of rotation to be determined as a function of distance from the lens.