The flow surrounding the propeller of an electric fan contributes significantly to the noise emitted by low-pressure electronic fans designed to cool electronic equipment such as desktop computers. This study characterizes fan noise based on modification of geometrical features such as its hub diameter, blade length, blade thickness, blade angle of attack and number of blades. Computational Fluid Dynamics and Computational Aeroacoustics simulations were employed to analyze sound pressure level on the fan rotor. A commercially available computer cooling fan was selected as a reference fan. Two constant rotational speeds were tested, 2,400 rpm and 4,500 rpm, yielding OASPL of 31.94 dB and 48.99 dB, respectively. The sound pressure levels visualized from the reference fan were within the range of noise emission advertised by two manufacturers for the same size of fan, with number of blades and rated voltage. Velocity magnitude profiles and pressure profile distributions were also generated to visualize the flow patterns and validate aerodynamic theories citing turbulent flow in the vicinity of the rotor, characterized by a vortex field, wakes and eddies in the Trailing Edge. A reduction in hub diameter and an increase in the blade’s thickness resulted in considerable noise reduction. Consequently, an improved fan geometry was created by superimposing these design modifications yielding a 5.02 dB and 3.53 dB noise reduction for the two respective rotational speeds.

A multiblock Favre-Averaged Navier-Stokes (FANS) method has been developed in conjunction with a chimera domain decomposition technique for investigation of flat surface, discrete-hole film cooling performance. The finite-analytic method solves the FANS equations in conjunction with a near-wall second-order Reynolds stress (second-moment) closure model and a two-layer k-ε model. Comparisons of flow fields and turbulence quantities with experimental data clearly demonstrate the capability of the near-wall second-moment closure model for accurate resolution of the complex flow interaction bewteen the coolant jet and the mainstream. The near-wall second-moment anisotropic model provides better agreement in adiabatic film effectiveness prediction than the two-layer k-ε model.

A novel micro actuator for fluidic transport, mixing and particle filtering is presented. The technology uses a torsionally supported plate driven with an electrostatic signal at first-mode resonance to produce long-term reliable fluidic interactions at the chip level. Resonant frequencies from 10–20kHz have been tested with maximum fan deflections of approximately 30 microns. The resonant fans are fabricated using surface micro-machining techniques and flip-chip assembly. A simple flow visualization technique is also presented using laser illuminated smoke particles contained within the device packaging. The flow visualization setup allows for both overhead and side views as well as infinite ceiling and channel flow simulation in order to fully characterize the three dimensional flow produced by the resonant fans. Flow speeds of over 10 mm/s have been observed to exit single micro fans with large fan arrays producing over 2mL/min of volumetric flow. Fan testing in 600-micron deep channels has demonstrated the potential for suspended particle collection and filtering applications.

Cooling technology for modern servers, workstations and desktop computers has just begun a period of rapid change. As processor powers approach 100 watts, longstanding limits on air cooling are being challenged. The most recent changes are in the heatsinks themselves, as the longstanding manufacturing process of extruding is no longer capable of meeting new performance requirements. This study focuses on the history of creating an effective organization for bringing the skive heatsink to market, concentrating on development of a start-up unit within the company and a host of relationships, both technical and business, outside the company. Metals companies in Japan have long been accustomed to the necessity of constant innovation. Heatsinks fall into the vague category of a semi-custom product — each customer has almost the same requirements, with slightly different exceptions to a standard part. Additionally, a product lifetime may be measured in months rather than years. In heatsinks, the high thermal conductivity, low density and low material cost of aluminum preclued serious competition from other materials. The computer market is dominated by large players but the size distribution tails off very slowly. 51% of the market is held by 6 companies, the largest with 14%. The remaining 49% features a wide distribution of market share and technical capabilities. This results in some customers with large staffs specializing in cooling technology, others with a small number (sometimes 1) of multidisciplinary mechanical/thermal engineers, and others with no engineering staff other than system integrators. The presence of other materials is increasing, as heatsinks for the highest power processors will soon need copper bases and, ultimately, two-dimensional heatpipes known as vapor chambers. This integration of components represents a significant departure from the previous norm of attaching a one-dimensional tube heatpipe to an all-aluminum heatsink. In some cases ownership of development and production is the responsibility of the heatsink maker, in other cases the heatpipe or, in the case of an integrated cooling fan, the fan maker. In order to address this wide and rapidly moving market, we have made alliances with makers of other electronics cooling components (fans, plastic housings, thermal interface materials), jointly developed products with computer and processor makers, and co-sponsored university research. This year (2000) saw a large-scale entry into the Gigahertz processor cooling market, with a focus on high level visibility at technical conferences and trade shows. As thermal concerns move from a final step in the design cycle to a initial consideration, educating customers about the potential contributions of the skive heatsink has become a major effort in our technical marketing campaign.

As targets for future growth of aluminum products, we sees greatest opportunity in the three areas of automotive, energy and electronics. Within electronics, uses of aluminum include capacitor materials, magnetic disk substrates, printer/copier drums, and heatsinks. Of the first three areas, other materials may soon replace aluminum. In heatsinks, the high thermal conductivity, low density and low material cost of aluminum preclued serious competition from other materials. Cooling technology for modern servers, workstations and desktop computers has just begun a period of rapid change. As processor powers approach 100 watts, longstanding limits on air cooling are being challenged. The most recent changes are in the heatsinks themselves, as the longstanding manufacturing process of extruding is no longer capable of meeting new performance requirements. Skiving and folded fins, both established manufacturing technologies which can provide much finer features than extruding, are leading candidates for mass production of the new generation of heatsinks. This study focuses on the history of evolution of an effective organization for bringing the new heatsink technologies to market, concentrating on development of a start-up unit within a large metals company and a host of relationships, both technical and business, outside the company. Metals companies have long been accustomed to the necessity of constant innovation. In Japan, which has negligible ore resources, all value added is found in processing and uniqueness of the product. As metals companies have made the transition from a supplier of various aluminum alloys in traditional form factors (rod, sheet, foil, etc.) to custom made-to-order products, the next transformation has begun. Heatsinks fall into the vague category of a semi-custom product — each customer has almost the same requirements, with slightly different exceptions to a standard part. Additionally, a product lifetime may be measured in months rather than years. The computer market is dominated by large players but the size distribution tails off very slowly. 51% of the market is held by 6 companies, the largest with 14%. The remaining 49% features a wide distribution of market share and technical capabilities. This results in some customers with large staffs specializing in cooling technology, others with a small number (sometimes 1) of multidisciplinary mechanical/thermal engineers, and others with no engineering staff other than system integrators. In order to address this wide and rapidly moving market, we have made alliances with makers of other electronics cooling components (fans, plastic housings, thermal interface materials), jointly developed products with computer and processor makers, and co-sponsored university research. This year (2000) saw a large-scale entry into the Gigahertz processor cooling market, with a focus on high level visibility at technical conferences and trade shows. As thermal concerns move from a final step in the design cycle to a initial consideration, educating customers about the potential contributions of the new heatsink technologies has become a major effort in our technical marketing campaign.

Whilst extensive work has been done on fault detection in bearings using sound, very little has been accomplished with other machine components and machinery partly due to the scarcity of datasets. The recent release of the Malfunctioning Industrial Machine Investigation and Inspection (MIMII) dataset opens the opportunity for research into malfunctioning machines like pumps, fans, slide rails, and valves. In this paper, we compare common features from audio recordings to investigate which best support the classification of malfunctioning pumps. We evaluate our results using the Area Under the Curve (AUC) as a performance metric and determine that the log mel spectrum is a very useful feature, at least for this dataset, but that other features can enhance detection performance when ambient noise is present (improving AUC from 0.88 to 0.94 in one case). Also, we find that mel Frequency Cepstral Coefficients (MFCC) perform substantially poorer as features than a sampled mel spectrogram.

PPV Fans (Positive Pressure Ventilation Fans) are used in firefighting to remove smoke from a burning building, so that fire fighters can have a clear view inside the house and injured people do not have to breathe toxic smoke. This can be done by placing a PPV fan in a distance of about two meters in front of a door of the burning building. On another, carefully chosen position in the building, e. g. a window, a door or at the roof an opening has to be created, where the smoke can leave the building. The same volumetric flow rate of gas that is blown into the building by the PPV fan has to leave the building at a chosen opening. Because the gas entering the building is air and the gas leaving the building is a mixture of smoke and air, the smoke concentration in the building can be reduced. To test the performance of such PPV fans, a test building with a door in the first floor and a window in the 3rd floor has been built. To measure the volumetric flow rate of the smoke and air mixture through the window in the 3rd floor that is leaving the building, a flow meter nozzle was designed. The design process was done using the commercial Navier Stokes solver Star CCM+, where three nozzle designs, such as a nozzle with constant velocity increase, a quarter circle nozzle and a non-curved nozzle were investigated for different volumetric flow rates. Also, a rounding at the window, where the nozzle is placed, was investigated to prevent flow detachment and shock losses at the inlet of the nozzle. The volumetric flow rate through the nozzle can be calculated, by measuring the pressure at the nozzle wall (before the contraction) and applying Bernoulli’s law, the continuity equation and assuming atmospheric pressure at the free jet flow at the end of the nozzle. The so calculated volumetric flow rate was compared with the actual flow rate, given by the numerical CFD simulations. With these values, the nozzle specific coefficient of discharge for several volumetric flow rates has been calculated and a function fitting was done to get obtain analytical relation between pressure and volumetric flow rate. The detailed design process of the three nozzles, the numerical results of the CFD studies and the determination of the nozzle specific coefficients of discharge are shown and discussed in detail in this work.

The injection of choked gaseous jets into the still air is investigated experimentally motivated by many industrial applications including flares and burners. The objective is to study the effect of injection angle on the jet mixing with ambient air. The experimental methods consist of particle image velocimetry (PIV) using pulsed Nd:YAG lasers of a choked gas jet, seeded with aluminum oxide particles, injected into still air, seeded with water fog. The computational methods consisted of 7.7 million cells simulation using Star CCM+. The test conditions include injection angles of 0°, 15°, and 30°. The results including mean and fluctuating velocities and the flow vorticity are presented. The flow field is not symmetric along the injection axis due to the asymmetric triggering of expansion fans at the jet exit due to the inclined injection plane. Moreover, the numerical simulation reveals the complex interaction mechanism of the expansion fans and shockwaves within the injection port.

Piezoelectric fans have attracted attentions in the past decades because of their low energy consumption, low noise level, light weight and reliability. A novel form of piezoelectric flapping fan is characterized experimentally and numerically. An experimental setup was built to measure the pressure and flow rate of piezoelectric fans with low static pressure at various frequencies. The fan performance curve was established. A high speed camera system was used to analyze the oscillation motion of the fan wings. The displacement of the leading edge and trailing edge of the piezoelectric fan wings are used as inputs to describe the deflection of the fan in the numerical model. The flow field obtained from the model is analyzed. The vortex shedding is observed and discussed. The pressure and flow rate obtained from the 2D numerical model are compared with the experimental results. The results provide a fundamental understanding of a piezoelectric fan with opposing oscillating wings.

For fans without cooling it is possible to determine the hydraulic efficiency measuring the pressure and the temperature rise through the fan. The shaft work can be determined according applying the first law of thermodynamics for an open system. Without any losses the change of state would be isotropic and the work done equal to the specific heat at constant pressure of the fluid times the isentropic temperature rise in the impeller. Due to the losses, however, the real temperature at the exit of the impeller will be higher than the isentropic temperature since the real process is polytropic. The isentropic temperature at the exit of the impeller can be computed by the isentropic relations with the inlet temperature and the pressure rise. The hydraulic efficiency can be computed as the ratio of the isentropic temperature rise divided by the real temperature rise. In order to verify this thermodynamic approach for the determination of the hydraulic efficiency CFD simulations of a radial fan were performed. In the CFD simulation the hydraulic power, the shaft power, the pressure rise and the temperature rise can be read out and computed directly. In such a way the hydraulic efficiency computed by the ratio of the hydraulic power by the shaft power can be compared by the thermodynamically computed efficiency. In this work this comparison has been performed and the results and the precision of the thermodynamically predicted efficiency are presented and discussed in detail.

Special mixing chambers are usually used to perform scientific experiments or for routine industrial production processes. This is the case, typically, of fan mixers in a baffled tank. Mixing chambers comprise, among other alternative elements, two counter-rotating fans at the bottom and top. These will eventually allow a mixing effect on the chamber with an adequate level of uniformity. Herein a computational flow simulation is performed for the mixing conditions of air and SO 2 inside the chamber used in the CLOUD experiment, by studying in detail the flow structures and uniformity inside the chamber. This Unsteady Navier-Stokes computation is performed using the kω-SST and SAS turbulence models. A first validation step is performed by using an experimental test case, comprising a T-junction geometry, that performs the mixing of air and N 2 . Following this validation step a detailed analysis of the flow structures inside the 3D chamber is conducted, and specific insights are given regarding the flow uniformity. A detailed analysis of the computed mixing flow structures for the SST and SAS turbulence models is also described. It is shown that the SAS model captures with more detail the macro and meso-mmixing process with an accuracy of, at most, 6%. This value can be further reduced to values around 2% by resorting to high density meshes, with the associated computational burden.

An analysis of the design and manufacture of a tricopter style hovercraft is realized in detail, along with the parameters for determining the geometry due to power requirements. The aircraft is constructed with three ducted fans in the vertical orientation, denoting the layout of the classic tricopter frame. The purpose of this study is to establish a design of a ground vehicle capable of multi-terrain navigation. A simplified skirt solution is presented for the aircushion. The model is robust enough for rough terrain and sufficient for maintaining the cushion pressure that enables the ground effect to work towards a higher efficiency. The design process for the model consists of the use of CAD to layout and simulate all components. The efficiency and battery life of the vehicle is compared to the tricopter and a flight test verifies its capability to follow a given path.

Radial fans for industrial applications are very commonly operated with a spiral casing, also called volute. The function of the volute is to collect the air from the impellers outlet and to transport it to the fans outlet. In the volute the tangential velocity component of the impeller is transformed in a straight velocity component at the volute’s outlet. In the volute the static pressure is increased according to the cross sectional area of the volute. When the flow exits the impeller the flow rate is given basically by the radial velocity component times the outlet area of the impeller. In the volute, however, the flow rate is basically given by the tangential velocity component at the impeller exit and in the volute considering the conservation of angular momentum. Hence, there is only one operating point, i.e. the design point of the volute, where the flow rate in the impeller matches the flow rate in the volute. In the literature the design of the volute is performed at the design point only and the cross sectional area of the volute is usually computed distributing the flow rate linearly from the tongue to the exit of the volute. In this work an extended theoretical approach was developed considering the design point flow rate and off design flow rates. At the design point, the properties of the specific impeller, i.e. it’s radial and its tangential velocity components at the impeller’s exit are considered to design the volute. Furthermore, also the off-design characteristics of the impeller, i.e. its radial and tangential velocity components are considered in the design process of the volute. The flow rates in the impeller and in the volute match only at the design point, at off-design points the flow rates in the impeller and in the volute are different. This has an important impact on the design process of impeller – volute units. Each volute has also to be matched to the specific impeller. In the numerical part a usual volute was designed considering the properties of a particular impeller. The performance of the volute and of complete fan was investigated with the commercial Navier–Stokes Solver ANSYS CFX. A detailed analysis of the results and the flow conditions in volute as well as in the impeller-volute unit and a comparison with the results predicted by the new volute theory is given.

In order to investigate the impact of the gas temperature and its relative humidity on the performance of fans, the similarity laws for fans were extended and verified and numerical computations with the commercial CFD solver ANSYS CFX were performed. First the accuracy of the original fan laws was verified for different operating conditions. In a second step the influence of the temperature on the fan characteristics was investigated. Finally, to include the effect of the relative humidity multiphase simulations with air and water vapor were performed. Therefore, the relative humidity was analyzed for different gas temperatures. In such a way the full influence of the temperature and of the relative humidity on the performance characteristics of radial fans operating in drying plants was obtained. These numerical results have been analyzed in detail and compared with the results predicted by the presented extended similarity laws for turbomachines.

In typical data centers, the servers and IT equipment are cooled by air and almost half of total IT power is dedicated to cooling. Hybrid cooling is a combined cooling technology with both air and water, where the main heat generating components are cooled by water or water-based coolants and rest of the components are cooled by air supplied by CRAC or CRAH. Retrofitting the air-cooled servers with cold plates and pumps has the advantage over thermal management of CPUs and other high heat generating components. In a typical 1U server, the CPUs were retrofitted with cold plates and the server tested with raised coolant inlet conditions. The study showed the server can operate with maximum utilization for CPUs, DIMMs, and PCH for inlet coolant temperature from 25–45 °C following the ASHRAE guidelines. The server was also tested for failure scenarios of the pumps and fans with reducing numbers of fans and pumps. To reduce cooling power consumption at the facility level and increase air-side economizer hours, the hybrid cooled server can be operated at raised inlet air temperatures. The trade-off in energy savings at the facility level due to raising the inlet air temperatures versus the possible increase in server fan power and component temperatures is investigated. A detailed CFD analysis with a minimum number of server fans can provide a way to find an operating range of inlet air temperature for a hybrid cooled server. Changes in the model are carried out in 6SigmaET for an individual server and compared to the experimental data to validate the model. The results from this study can be helpful in determining the room level operating set points for data centers housing hybrid cooled server racks.

A prototype of a hovering multi-terrain mobile robot platform that makes use of a flywheel for stabilization and heading control for rapid maneuverability was developed and presented in a prior paper. It was shown that flywheel stored energy could be transferred to the overall body to generate rapid angular motion once wheel is instantaneously stopped. Solution improved localization accuracy and reduced the overall sensitivity with respect to external disturbances such as non-flat terrain. In this paper, we present a feedback control system to measure dynamic parameters before and after the wheel is stopped. System is designed to follow a predefined path plan and instantaneous torque change causes oscillation after a waypoint is reached. To address this issue, we updated system with an inertial measurement unit (IMU) as a feedback sensor. Then, we investigate the feedback control of individual forward thrust vectors as well as wheel braking timing to minimize amplitude of transient response oscillation and to reduce the steady-state error to an acceptable level that differential drive fans could compensate this error and correct the heading after the rotation around a waypoint occurs. In addition to that, previous mechanical system could transfer all energy stored at once and was not adjustable. In this research, we also investigate varying amount of angular inertia generated by fans and wheel individually and together. To do so, system is modified with stronger forward thrusters. Prior to running the system with a full dynamic model with real mechanism, we implemented a simulation to empirically extract system parameters and adjust controller gains to follow a predefined path with open and closed loop control schemas with objective of minimizing localization error. Finally system is tested with real mechanism. Governing equations, simulation and empirical results comparison are presented and generated trajectories of various simulation and real world settings are listed. Test results verify that, with a closed loop control system, overshoot and total error about a waypoint can be minimized to an acceptable level at and after transient response phase.

An investment firm located in Peru has partnered with Western New England University to develop a novel, motorcycle mounted fast food delivery system for international markets. The project afforded students the opportunity to work on an international product development team, exposing them to the design requirements and constraints of international customers and companies. The often damp and cool climate in many countries makes food prone to becoming soggy during delivery as the moisture escaping from the hot food quickly fills the food containers and delivery box mounted to the back of the motorcycle, saturating the food. Delivery times, often in excess of 45 minutes, can also cause the food to become cold, resulting in decreased customer satisfaction, product returns and lost business. The project was conducted over a three year period using nine mechanical engineering students. The project began in 2014 when a team of two students was tasked with developing a benchtop method of keeping food hot and preventing it from becoming soggy while being delivered. They determined that the use of ceramic heaters and small fans effectively kept the food warm and dry. In 2015, two teams of two students competed to develop a box design with integrated heaters and fans which could be powered using an alternator mounted to a delivery motorcycle. While effective fans and heating elements were found, it was decided that the mounting of an additional alternator was cumbersome and motorcycle dependent, rendering the concept poorly suited for field installations. In 2016 another team of two students integrated a hand-made lithium ion Battery pack and two 300W ceramic heaters and computer fans into a production delivery box. While the system maintained food quality for up to 50 minutes, the battery pack was unable to reliably provide the required power to the system. Finally, in the fall of 2016, a student improved this design by improving the heater and fan performance while adding urethane insulation into the box. Temperature was controlled using a commercially available thermistor, and all components were integrated into a retrofit kit which could be installed by a technician in the field. The power requirement was reduced by over 50% and the system operated for 110 minutes using two, commercially available 27 Ah lithium iron phosphate batteries. Students gained global perspective of the product development process as they experienced the effects of various cultures on the requirements of customers and the international design and marketing team.

Among different strategies available technologically to reduce energy consumption and environmental impact in buildings, there is the use of new thermal-operated air conditioning systems. An available alternative is absorption refrigeration systems, which can operate with renewable energy sources such as solar energy, and use environmentally friendly refrigerant substances. In Colombia, this type of systems has not been investigated thoroughly nor have carried out developments, because the field of solar energy is emphasized in the use of thermal energy, to be used on a refrigeration cycle that allows to condition an environment of a determined compound, and besides that, this air conditioning going to achieve through intelligent control, it has not been subject of considerable advances, neither in the part of applied research, nor its implementation. According to this, the idea is to use developments of these systems that have been simulated and implemented in other countries, including Spain, for the start in the UPB with research, development and implementation of those after making a literature review about the systems. To develop the aforementioned system, a comprehensive literature review of the technologies has been made to be implemented in terms of automation and control. A simulation in the TRNSYS software of the system to be implemented in a building on the campus of the UPB, which requires air conditioning for the comfort of the people who inhabit, is eveloped. The system will be regulated by a controle system that receives information from various parts of the plant with temperature and flow sensors. To carry out the control of this system, classical control techniques are going to be used for some water systems that constitute the demonstrative installation, but for the part of chilled water and air conditioning, intelligent control techniques will be handled, which allows to meet the needs of the air conditioning system that is intended to be implement, as this part is quite complex for the management of different variables. This system will operate automatically acting on valves, pumps, fans, fan-coil and/or mats of water (they act as radiant walls) for correct operation by previously established set points [1].

In this work the influence of different radial work distributions on the performance of low pressure axial fans for automotive cooling purposes was investigated. The general standard solution in the design of axial fans is to assume constant work distribution (free vortex design). This also leads to a constant meridional flow velocity and thus makes the calculations for the design rather simple. To fulfill the constant work assumption, however, a high swirl component of the absolute outlet flow velocity results near the hub. Assuming the incoming airflow to be swirl-free, this means that the flow near the hub must be strongly deflected, leading to a very high blade load in this area and to very long chords. Thus, the assumption of constant radial work distribution leads to a high risk of flow separation near the hub, especially for low pressure cooling fans, where a small hub to shroud diameter ratio is needed in order to achieve higher flow rates. Furthermore, in fan applications, often the total-to-static pressure and total-to-static efficiency are the relevant design parameters, and not the total-to-total pressure and the total-to-total efficiency. In order to address these issues, linear and parabolic non-constant work distributions were investigated. These distributions were parametrized and for each work distribution a series of designs was created with the airfoil theory method. These designs were computed with the commercial Navier-Stokes-Solver STAR CCM+ and the results were analyzed in detail. As an application example a series of fans for a Formula Student racing cars cooling applications was developed. With this method, it was possible to achieve smaller hub to shroud diameter ratios, higher flow rates and better total-to-static efficiencies. The result was a new series of fans with improved cooling properties for automotive applications. These new fans, the design method and the results are presented in detail in this work.

Fans in industrial plants can be exposed to a strong erosion load due to particle flows. In the present work, the erosion behavior for large radial fans with spiral casings is investigated using the Finnie erosion model, see [1] [2]. Theoretical approaches concerning particle velocity and particle impact angle are validated by numerical methods. For this purpose, a baseline impeller and a parameterized baseline spiral casing have been designed and simulated using computational fluid dynamics. Than different geometrical variations of the spiral casing shape and the blade shapes of the impellers have been designed and simulated in order to determine their respective influence on the erosion behavior as well as on the performance characteristics. Finally, recommendations for an optimal design are presented and explained in detail.