Fan Array Research Articles

Prediction of Fan Array Performance with Polynomial and Support Vector Regression Models

The increasing utilisation of demand-controlled ventilation strategies leads to the frequent operation of fans under part-load conditions. To accurately predict the energy demand of a ventilation system with a fan array in the early design stages, models that calculate reliable results across the whole operating range are required. We present the comparison of a polynomial and a machine learning approach through support vector regression (SVR) to predict the fan performance over a wide range of typical operating points. For fitting and validation, we use experimental data. We investigate the extrapolation performance of both approaches. The SVR model achieves a slightly better representation of the experimental data with a lower error, especially when only sparse data are available. Both approaches yield similar results when the evaluation is conducted within the experimentally captured domain but deviates outside the domain. At operating points that are far from the experimentally captured domain, the polynomial models yield fan efficiencies that are physically plausible, while the SVR models drastically overpredict the fan efficiency. To rate the influence of such deviations towards modelling the actual energy demand, both approaches are applied to an operation simulation of a simplified office building. Both approaches yield similar results despite differing extrapolation capabilities.

An experimental study on improving the thermal environment of data centers by optimizing fan wall arrangement

For a fan-wall data center, a large number of fans can be installed on one side of the server room to facilitate the introduction of outdoor cold air into the server room for effective heat dissipation, thereby accomplishing the objective of energy conservation. However, fewer researches are currently available on optimizing the fan array layout of fan-wall data centers to improve the thermal environment. This study aims to explore the impact of fan array layout parameters, including the area, distance, and height of the fan array, on the cooling efficiency of server rooms through both single-factor experiments and orthogonal experiments. The results indicate that: (1) In a fan-wall cooling system, racks closest to the fan wall have high temperature fluctuations and less orderly airflow organization. (2) The optimization of the fan array layout in a data center is primarily influenced by the height, area and distance of the fan array. (3) For a DC, the fan array layout, with an area of 4320 cm2, a distance of 81 cm, and a height of 18 cm, can achieve optimal conditions and effectively enhances the overall thermal performance of the rack. By optimizing the layout of the fan array, a more efficient combination of parameters for air distribution can be achieved, providing a reference for the arrangement and layout of fan arrays in actual engineering applications.

Thinking inside the box: a cost-effective approach to fan array noise reduction

Noise from fan arrays can contribute high sound pressure levels both to buildings and communities. Noise that travels from these units through ducts and into the spaces within buildings can be attenuated with silencers or duct lining. However, sound radiated from the unit through building structures or into communities can be more difficult to attenuate and often adds significant cost. While it is possible to attenuate sound from the unit using enclosures or sound walls, exploring the operation of the fan arrays themselves could be a more cost-effective noise reduction method. One particular noise reduction method for an existing fan array was proposed for a customer: review sound levels of each fan within the array to determine how they are contributing to the radiated sound power level of the unit. The assumption that sound levels between individual fans within fan arrays are consistent is not always correct. A series of acoustical tests were completed; results indicated that sound caused by turbulent airflow within the tested fan array was able to be lowered by reducing the fan speeds of individual fans. By reducing the fan speeds of problematic fans and increasing speeds for the quieter ones within the same fan array, the same level of cooling can be provided with lower overall radiated sound levels at no additional cost.

Research on active and passive schemes for safety improvement of nuclear energy hydrogen production system

Nuclear hydrogen production has the advantages of large-scale and low carbon emissions, and is expected to play an active role in the energy transition process. However, the storage and transportation of hydrogen pose potential risks of leakage and diffusion when connected to high-pressure hydrogen storage tanks and pipelines. To address this concern, this study focused on designing three distinct safety improvement schemes tailored for potential hydrogen leakage accidents. These schemes encompassed a passively distributed arrangement of obstacles (Scheme 1), a passively centralized arrangement of obstacles (Scheme 2), and an active fan array blowing (Scheme 3). Numerical simulation methods were applied on extensive spatial scales for relevant calculations. The results revealed that all three schemes effectively reduced the diffusion distance of combustible hydrogen. Specifically, at lower ambient wind speeds, Scheme 1, Scheme 2, and Scheme 3 achieved the shortest diffusion distances of 123 m, 56 m, and 46 m, respectively. Meanwhile, at higher ambient wind speeds, the corresponding distances were 282 m, 100 m, and 79 m. These results collectively offer valuable insights to mitigate the risk of leakage accidents in nuclear hydrogen production systems.

Flow control of a vehicle using reverse flow fan

PurposeThis study aims to achieve optimum flow separation control for a road vehicle using a reverse flow fan on rear side.Design/methodology/approachA full-length reverse flow fan array (fan’s air speed is 50% of the car’s speed) is attached throughout the width of the vehicle at rear edge corner.FindingsThe reverse flow fan array positioned at rear edge of car pushes the airflow against the car’s rear window. It creates the recirculation region and alters the pressure distribution. This reduces the lift coefficient by 150%, which becomes the downforce and reduces the drag coefficient by 22%. As the car speed increases, fan speed should also be increased for effective flow control.Research limitations/implicationsThis active flow control method for 3D Ahmed car body has been studied computationally at low speed (40 m/s).Practical implicationsThis design increases the downforce, thus gives better cornering speed and stability, and decreases the drag which improves fuel efficiency. It can be used for effective flow control of cars (hatchback/sedan). The findings can be applied to the bluff bodies, road vehicles, UAV and helicopter fuselage for flow separation control.Originality/valueThe fan array is attached on car’s rear side, which blows air against the car’s rear window. It alters the pressure distribution and aerodynamics forces favorably. But the existing high-speed fan used in a sports cars sucks the air from bottom and pushes it rearward, which increases both the traction force and drag.

Research on partition control of direct air‐cooling condenser based on multivariable Hammerstein CARMA model predictive control

AbstractPartition control of the fan array within a direct air‐cooling condenser (DACC) is recognized as a highly effective energy‐saving measure and a means to mitigate the adverse effects of ambient winds. This study focuses on the development of a dynamic partition model, which establishes the relationship between mass flow rate and fan array speed under windy conditions. The model is grounded in multivariable Hammerstein controlled autoregressive moving average (H‐CARMA) systems. Additionally, an innovative extended stochastic gradient algorithm, founded on the hierarchical identification principle, is introduced to estimate the model's unknown parameters. The recursive least square is employed as a benchmark to verify the accuracy and efficiency of the approach. Subsequently, leveraging the identified model, the model predictive controller based on the differential evolution method is designed to derive the optimal control law. Finally, simulation test and analysis are carried out to testify the effectiveness of our control strategy. The experiment result shows that the dynamic characteristics of the system have been significantly improved and the fan power consumption is reduced by 3.5% compared to the PID controller.

CFD Assessment of Car Park Ventilation System in Case of Fire Event

This scientific article presents the results of computational fluid dynamics (CFD) simulations conducted using OpenFOAM to evaluate the effectiveness of a jet fan ventilation system in managing the dispersion of smoke resulting from a car fire incident within an underground car park spanning a total area of 21,670 m2, situated in Tabriz, Iran. The primary objective of the study is to determine the velocity fields and evaluate visibility conditions within a 10 m radius to gauge the efficiency and effectiveness of the system. The study employs a smoke concentration production rate of 5.49 × 10−4 kg/m3s for simulations involving fire scenarios. A total of 17 fire scenarios are examined, each extending 30 m in all directions from the initial location. The research findings demonstrate that the placement of jet fan components plays a significant role in the system’s efficiency, with fans positioned near the ceiling leading to back-layering. To mitigate this issue, the recommended design solution involves the strategic installation of multiple jet fan arrays in specific zones with the addition of 10 extra jet fans, effectively curbing lateral smoke dispersion. Furthermore, the analysis of air flow rates shows that when jet fans direct an excessive airflow towards the exhaust shafts (which have a designated flow rate of 22.5 m3/s), recirculating flows occur, leading to the dispersion of smoke throughout the car park. Consequently, the utilization of low-velocity jet fans (11.2 m/s) proves to be more effective in clearing smoke compared to high-velocity jet fans (22.3 m/s). The study also emphasizes the importance of optimal positioning of supply and exhaust shafts to achieve effective smoke control, highlighting the need for placing them on opposite walls or minimizing airflow turns. Additionally, the research underscores the significance of fire resistance in jet fan units, as their failure during fire incidents can have severe consequences.

Optimization, Control, and Design of Arbitrarily Shaped Fan Arrays

In many air conditioning applications fan arrays offer an increasingly popular alternative to single large fans due to redundancy and ease of maintainability. Additionally, there is the possibility to dynamically resize the array by selectively turning off a number of fans. In this work, a new method for the optimal control of such fan arrays is derived with the goal to minimize the overall power consumption, i.e., maximizing the system efficiency. The approach is universal in the sense that a fan array can be composed of any number, size, and type of fans or mixtures thereof. We explore the achievable power savings for a real world example by applying the method. Moreover, we give an outline of the optimal design of fan arrays and future work.

Vibration isolation of newer equipment typologies

The vibration isolation of large mechanical/electrical/pluming equipment has become an industry standard to prevent unwanted vibrations from transmitting into building structures. ASHRAE, ISO, and other organizations have published recommended guidelines for vibration isolation based on the typical operation of this MEP equipment and “best practices” over the past several decades. However, recent advancements in mechanical equipment designs have resulted in situations where the traditional approach for vibration isolation is either not feasible or ineffective, such as air handling units with extremely well balanced fan arrays or low-speed cooling towers with variable-frequency drives. Changes in power distribution system designs have also resulted in a greater need for vibration isolation of electrical equipment, particularly utility transformers. This paper reviews these recent developments in MEP systems as well as the implications to vibration isolation for this equipment.

Modeling and Control of a Multiple-Heat-Exchanger Thermal Management System for Conventional and Hybrid Electric Vehicles

The powertrain in combustion engine and electric vehicles requires a thermal management system to regulate the operating temperature of the under-hood components. The introduction of computer-controlled cooling system actuators (e.g., variable speed fans, pump, and valves) enables power savings over drive cycles. The radiator is typically sized for maximum heat rejection per environmental and vehicle thermal loading conditions. This paper explores the use of multiple radiators to adapt the cooling system operations to driving demands. A nonlinear multiple-input (i.e., fan array speed, pump, and outlet valve positions) thermal model is presented to predict system behavior. A stateflow controller has been designed and implemented to maintain the component temperature within a desired range (~80 °C). A series of experimental tests have been conducted to compare the proposed architecture’s performance against a single radiator design. A standard driving cycle featuring low (20 kW) and high (40 kW) heat loads was implemented in the laboratory for a vehicle starting from rest. The coolant temperature tracking, fan speeds, and fan power draw were studied over the representative operating cycle. The test results show a much faster warmup time (~10 min) and temperature tracking for the twin radiator experimental test as compared to the single radiator (~13 min). The net fan energy consumption was reduced by 4.6% with the twin radiator as opposed to the single-radiator configuration. Considering that engines usually operate at idle to medium loads, these findings can improve the powertrain’s overall performance.

A dimensionless framework for predicting submarine fan morphology.

Observations of active turbidity currents at field scale offers a limited scope which challenges thedevelopment of theory that links flow dynamics to the morphology of submarine fans. Here we offer a framework for predicting submarine fan morphologies by simplifying critical environmental forcings such as regional slopes and properties of sediments, through densimetric Froude (ratio of inertial to gravitational forces) and Rouse numbers (ratio of settling velocity of sediments to shear velocity) of turbidity currents. We leverage a depth-average process-based numerical model to simulate an array of submarine fans and measure rugosity as a proxy for their morphological complexity. We show a systematic increase in rugosity by either increasing the densimetric Froude number or decreasing the Rouse number of turbidity currents. These trends reflect gradients in the dynamics of channel migration on the fan surface and help discriminate submarine fans that effectively sequester organic carbon rich mud in deep ocean strata.

An Energy-saving Fuzzy Control Fan Array with Bluetooth Received Signal Strength Indicator Sensing

An Energy-saving Fuzzy Control Fan Array with Bluetooth Received Signal Strength Indicator Sensing

Multi-Model-Based Predictive Control for Divisional Regulation in the Direct Air-Cooling Condenser

Flow distortions caused by ambient wind can have complex negative effects on the performance of direct air-cooling condensers, which use air as their cooling medium. A control-oriented model of the direct air-cooling condenser model, considering fan volumetric effectiveness and plume recirculation rate, was developed, and its linearization model was derived. The influences of fan volumetric effectiveness and plume recirculation rate on backpressure were analyzed, and the optimal backpressure was calculated. To improve both the transient performance and steady-state energy saving of the condenser, a multi-model-based predictive control strategy was proposed to divisionally adjust the fan array. Four division schemes of the direct air-cooling fan array constituted the local models, and in each division scheme, axial fans were divided into three groups according to the wind direction: windward fans, leeward fans, and other fans. The simulation results showed that the turbine backpressure can be increased by 15 kPa under the influence of plume recirculation and the reduction of the fan volumetric efficiency. The fan division adjustment strategy can achieve satisfactory control performance with switching rules.

Challenges in the application of sound standards in the heating, ventilation, and air conditioning

The HVAC industry in North America self-manages sound data measurement and reporting through the Air Conditioning Heating and Refrigeration Institute (AHRI). Each product is intended to fall under a specific AHRI sound standard. But in the real world, many complications exist. Some products may be configured in ways which crossover scope boundaries for multiple standards such as fan coils due to ducting or concealing. Other products are being held to inapplicable standards by specification requirements such as air-handlers using large fan arrays. Misunderstandings around application standards such as AHRI Standard 885 also generate confusion, especially when using Appendix E as a design tool. This presentation will highlight the challenges observed when applying AHRI Standards to building design.

Energy-efficient operation of a direct air-cooled condenser based on divisional regulation

The aerodynamic behavior of the fans array of the direct air-cooled condenser is different from that of a single fan because of the interaction effect between fans and the influence of wind. In this paper, a scale-down fan array experimental platform with measurement of the airflow and ambient wind speed is established to study the fan array partition schemes and cluster effect. The divisional cluster factors are obtained by experiment and generalized by random forest regression. The dynamic models of the condenser backpressure are introduced by the moving-boundary method. To achieve transient performance, a divisional control strategy for the direct air-cooled condenser is realized by MPC-PID cascade control. The simulation result shows that the fan power consumption is reduced by 14.7% compared to the existing control strategy. Furthermore, the wind speed disturbance is quickly suppressed by cascade control.

Experimental PIV investigation of the PZT fans array coupling effect at high Reynolds numbers

Piezoelectric fan arrays are being increasingly emphasized for heat dissipation in small-sized electronic devices. In this study, PIV experiments were conducted to investigate the flow fields induced by piezoelectric fan arrays with different vibration modes and pitches at high Reynolds numbers (324< Re <509) in a stationary air environment. As a result, when the PZT fan array is vibrating in-phase, the saddle points in the time averaged flow field are formed and separated gradually as the pitch increases, the remnant vortex and the induced vortex interact to form a jet with a periodic oscillation in the direction. Jet velocity reaches a maximum at P = 3A. In counter-phase vibration, saddle points are separated from one region under large pitches, the interaction of counter-rotating induced vortices forms a vertical upward jet. The morphology of induced and remnant vortices with different vibration modes and array pitches are responsible for the jet formation and flow field pattern. The interaction of counter-rotating vortices in counter-phase vibration leads the jet intensity higher than in-phase vibration induced jet, the optimal setting of the PZT fan under this study is determined as P = 2.5A with counter-phase vibration. The experimental results provide validation for the simulation study and give guidance to the application

‘The Blackest Disney Movie of All Time!’: A Goofy Movie and the Production of ‘Film Blackness’

Disney films have a distinct way of always feeling in-time, a sensation the company understands and monetizes. A Goofy Movie (AGM) was released in 1995, and since its theatrical release, the film has continued to capture the hearts and minds of a cult audience of passionate fans. Among this array of fans is a core of Black millenials who hold the film in high regard due to its R&amp;B soundtrack and relatable narrative. However, the moments of Black representation within the film are less interesting than how a Black reading becomes possible. What are the component parts of the film’s making when arranged in such a way that invokes an essential Black lifeworld? AGM affixes Blackness to its form not through any profound representation of race. Rather, considering its animators as technical performers, the dark history behind the American cartoon, and how Black music is used to not just make Blackness known but believable instantiate what Michael Gillespie terms, ‘film Blackness’ in Film Blackness: American Cinema and the Idea of Black Film (2016).

Commercial EV Cooling

Comparing single fan versus multi-fan arrays for thermal management of commercial EVs

Mechanical noise control case studies

A few case studies of mechanical system noise are presented. These address before/after background sound levels associated with room and/or mechanical system modifications, comparison of predicted mechanical system noise to measured values, our approach to noise control recommendations, and lessons learned. Interesting cases include a college theater renovation, office noise control involving implementation of a fan array and a VFD, and a challenging hunt for the source of an exterior pharmaceutical campus noise source generating complaints in a nearby neighborhood.

Lophotrochozoa in the Cambrian evolutionary radiation and the Pelagiella problem

AbstractTiny snail‐like conchs of Pelagiella Matthew are important in discussions of lophotrochozoan and mollusc origins in the Cambrian evolutionary radiation (CER). The limited morphological features of Pelagiella conchs have led to the ‘Pelagiella problem’: (1) poorly distinguished Pelagiella species; (2) an exceptional genus range across all Cambrian palaeocontinents and climate belts; (3) an unparalleled genus‐lifespan (c. 31 myr) in the early Palaeozoic; and (4) the assumption that all Pelagiella spp. are gastropods, which compromises lophotrochozoan and mollusc phylogenies. The type species P. atlantoides is a gastropod, but we show that so‐called Pelagiella species with sub‐to‐triangular apertures and turbiniform conchs are not referable to the genus. Re‐evaluation of spectacular specimens of Pelagiella exigua Resser &amp; Howell show it to be a polychaete with two apertural paleal chaetae fan arrays. Given that some modern sedentary polychaetes have paleal fan arrays, P. exigua is regarded as a likely member of the Sabellida Levinsen and is assigned to Pseudopelagiella gen. nov. Other Pelagiella spp. and forms with similar conchs are probably polychaetes not relevant to syntheses of early mollusc diversification. Pelagiellidae fam. nov. should be restricted to the late early Cambrian (c. 508 Ma) P. atlantoides. Pseudopelagiella exigua was unattached, probably benthic and lived with the apical conch surface on the sea floor, a mode of life similar to that of another family of the Sabellida, the sessile spirorbids that are cemented to substrate. Among numerous crown groups, the late early Cambrian eve of the CER included the polychaete Pseudopelagiella exigua and gastropod P. atlantoides.