scholarly journals New Design of the Reversible Jet Fan

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1671
Author(s):  
Miroslav H. Benišek ◽  
Đorđe S. Čantrak ◽  
Dejan B. Ilić ◽  
Novica Z. Janković
Keyword(s):  
Volume Flow Rate ◽  
Flow Direction ◽  
Special Focus ◽  
Outer Diameter ◽  
Ambient Conditions ◽  
Impeller Blade ◽  
Rotation Direction ◽  
Cylindrical Casing ◽  
Jet Fan ◽  
Nozzle Thrust

This paper presents two designs of the axial reversible jet fan, with the special focus on the impeller. The intention was to develop a reversible axial jet fan which operates in the same way in both rotating directions while generating thrust as high as possible. The jet fan model with the outer diameter 499.2 ± 0.1 mm and ten adjustable blades is the same, while it is in-built in two different casings. The first construction is a cylindrical casing, while the second one is profiled as a nozzle. Thrust, volume flow rate, consumed power and ambient conditions were measured after the international standard ISO 13350. Results for both constructions are presented for three impeller blade angles: 28°, 31° and 35°, and rotation speed in the interval n = 400 to 2600 rpm. The smallest differences in thrust, depending on the fan rotation direction, as well as the highest thrust are achieved for the first design with the cylindrical casing and blade angle at the outer diameter of 35°. Therefore, it was shown that fan casing significantly influences jet fan characteristics. In addition, the maximum thrust value and its independence of the flow direction is experimentally obtained for the angle of 39° in the cylindrical casing.

Low-Profile Chipset Microprocessor Heatsink Optimization for Server Form Factor

2009 ◽  
Author(s):  
Ali Akbar Merrikh ◽  
Sridhar Sundaram ◽  
David Walshak ◽  
Yizhang Yang ◽  
Tom Dolbear
Keyword(s):  
Thermal Conductivity ◽  
Boundary Condition ◽  
Form Factor ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
System Level ◽  
Ambient Conditions ◽  
Worst Case ◽  
Low Profile

We present a methodology for optimizing footprint, metal mass and thermal performance of an aluminum extruded heatsink for cooling chipset microprocessors in server form-factor. The analysis is based on predefined volume flow rate of air at a constant temperature assumed to be available upstream of the package. The front-to-back cooling assumption covers the worst case ambient conditions, typical of chipset boundary condition in servers. We present studies covering a range of heatsink footprints in order to compare and minimize the heatsink footprint, at the same time satisfying thermal specification of the chipset microprocessor. The study also focuses on the system-level assessment of the optimum 60×40 mm2 footprint and corner cases by studying the effect of motherboard thermal conductivity as well as blockages on the heatsink case-to-ambient thermal resistance.

scholarly journals Mixing Performance of a Passive Micro-Mixer with Mixing Units Stacked in Cross Flow Direction

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1530
Author(s):  
Makhsuda Juraeva ◽  
Dong-Jin Kang
Keyword(s):  
Numerical Study ◽  
Volume Flow Rate ◽  
Flow Direction ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
High Concentration ◽  
Mixing Performance ◽  
Wall Impingement ◽  
The Cross ◽  
Micro Mixer

A new passive micro-mixer with mixing units stacked in the cross flow direction was proposed, and its performance was evaluated numerically. The present micro-mixer consisted of eight mixing units. Each mixing unit had four baffles, and they were arranged alternatively in the cross flow and transverse direction. The mixing units were stacked in four different ways: one step, two step, four step, and eight step stacking. A numerical study was carried out for the Reynolds numbers from 0.5 to 50. The corresponding volume flow rate ranged from 6.33 μL/min to 633 μL/min. The mixing performance was analyzed in terms of the degree of mixing (DOM) and relative mixing energy cost (MEC). The numerical results showed a noticeable enhancement of the mixing performance compared with other micromixers. The mixing enhancement was achieved by two flow characteristics: baffle wall impingement by a stream of high concentration and swirl motion within the mixing unit. The baffle wall impingement by a stream of high concentration was observed throughout all Reynolds numbers. The swirl motion inside the mixing unit was observed in the cross flow direction, and became significant as the Reynolds number increased to larger than about five. The eight step stacking showed the best performance for Reynolds numbers larger than about two, while the two step stacking was better for Reynolds numbers less than about two.

scholarly journals Experimental studies into the performance of the lead coolant axial pump wet ends to justify main circulation pumps for the HMLC reactor plant circuits

2020 ◽  
Vol 6 (3) ◽  
pp. 143-147
Author(s):  
Aleksandr V. Beznosov ◽  
Pavel A. Bokov ◽  
Aleksandr V. Lvov ◽  
Tatyana A. Bokova ◽  
Nikita S. Volkov ◽  
...  
Keyword(s):  
Liquid Metal ◽  
Qualitative Difference ◽  
Experimental Studies ◽  
Heavy Liquid ◽  
Outer Diameter ◽  
Reactor Plant ◽  
Impeller Blade ◽  
08Kh18n10t Steel ◽  
Main Circulation ◽  
Design Solutions

The paper presents the results of the studies to justify the design solutions for the main circulation pumps of the heavy liquid-metal cooled reactor plant circuits. A substantial difference has been shown in the performance of pumps for the heavy liquid-metal coolant transfer. The studies have confirmed the qualitative difference in the cavitation performance of coolants, the state of the gases and vapors they contain, the influence of supply and discharge devices, and the effects of the impeller blade section performance and geometry and the hub-tip ratio on the pump performance. The studies were performed based on NNSTU’s lead-cooled test facilities with the coolant temperature in a range of 440 to 550 °C and the coolant flow rate of up to 2000 t/h. The outer diameter of the impellers and the straightening devices was about 200 mm, and the thickness of the flat 08Kh18N10T-steel blades was 4.0 mm and that of the airfoil blades was up to 6.0 mm. The pump shaft speed changed in a stepped manner from 600 rpm to 1100 rpm after each 100 rpm. The studies were conducted to justify the engineering and design solutions for pumps as applied to conditions of small and medium plants with fast neutron lead cooled reactors currently under investigation at NNSTU (BRS-GPG). The experimental results can be recommended for use to design other HLMC transfer pumps.

Feasibility Study on the Effect of Blade Inclination for Heavy Duty Centrifugal Fans – Aerodynamic Aspects

2021 ◽  
Author(s):  
Till M. Biedermann ◽  
Youssef Moutamassik ◽  
Frank Kameier
Keyword(s):  
Centrifugal Impeller ◽  
Special Focus ◽  
Original Design ◽  
Clear Trend ◽  
Impeller Blade ◽  
Characteristic Curves ◽  
Novel Approach ◽  
Two Factors ◽  
Centrifugal Fans ◽  
Blade Area

Abstract With a special focus on the industrial feasibility and the manufacturability, a recently proposed novel approach to centrifugal impeller blade inclination is adopted and investigated through extensive CFD analysis. The fan blades, originally aligned perpendicular to the impeller backplate, are inclined in either forward or backward direction. For the presented study, an industrially proven fan design is chosen for testing. Compared to the original design, the inclined fan blades possess an increased total blade area and at the same time providing variable inflow angles at the leading edges of the blades. These two factors are expected to alter the fan characteristic curves in providing an increased range of optimum performance while maintaining high aerodynamic efficiency. The results obtained show a clear trend in aerodynamic performance with the degree of inclination, where the characteristic curves rotate at about the design point, allowing local improvements either at overload conditions or part-load conditions of the fan. Moreover, the trends obtained show the tendency to agree well with the rudimentary models published in previous studies, even though it appears to be affected by the fan volute and the point of operation as well.

Unsteady Rotor-Stator Interaction of a Radial-Inflow Turbine With Variable Nozzle Vanes

2010 ◽  
Author(s):  
Tomoki Kawakubo
Keyword(s):  
Shock Wave ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Mode Analysis ◽  
Turbine Stage ◽  
Impeller Blade ◽  
Blade Loading ◽  
Clearance Flow ◽  
Rotor Stator Interaction

For radial turbines used in automotive turbochargers, the importance of variable flow capacity by means of a variable geometry system is getting higher under the growing demands for improved engine performance and reduced engine emissions. To realize a high-performance and aeromechanically-reliable turbine stage, the unsteady flow phenomena caused by the rotor-stator interaction and their impact on the mechanical integrity must be understood deeply. In the present paper, the periodic disturbance generated by the rotor-stator interaction of a research turbine stage is investigated. The research purposes are (i) to extract the flow phenomenon which is responsible for the blade excitation, (ii) to identify the operating condition at which the influence of the extracted phenomenon becomes stronger, and (iii) to clarify how and where the disturbance energy is fed into the blades. Three dimensional unsteady stage CFD simulations are conducted to investigate the unsteady stage interaction. Two parameters are mainly focused: the nozzle vane angle and the stage pressure ratio. By changing the former, the effect of different degrees of reaction can be examined, while by changing the latter, the effect of different Mach number levels can be evaluated. The unsteady blade loading is extracted from the CFD result and coupled with the blade displacement obtained from the eigen vibratory mode analysis to examine the aeromechanical influence of the unsteady loading on the impeller blade excitation at various operating conditions. The nozzle shock wave and nozzle clearance flow are identified as the principal phenomena for the impeller blade excitation. At the mean section of the impeller blade the nozzle shock wave impinges on the S/S and diffracts on the P/S periodically, these two processes constitute high unsteady blade loading at the impeller L/E. At the shroud section the nozzle clearance flow generates high fluctuation in the relative flow direction to the impeller which results in high unsteadiness in the blade loading. These two phenomena are more important at vane closed conditions due to the higher nozzle loading. The higher the pressure ratio, the higher the normalized loading, though once the nozzle shock wave is established the normalized loading does not increase appreciably. Most of the excitation energy enters the blade at the impeller L/E at the closed condition, while it enters the blade both at the L/E and T/E at the open condition.

Theoretical Interpretation of the CORDIER-Lines for Squirrel-Cage and Cross-Flow Fans

2012 ◽  
Author(s):  
Reinhard Willinger
Keyword(s):  
Flow Rate ◽  
Volume Flow Rate ◽  
Cross Flow ◽  
Pressure Rise ◽  
Low Noise ◽  
Volume Flow ◽  
Theoretical Interpretation ◽  
Outer Diameter ◽  
Flow Angle ◽  
Squirrel Cage

Squirrel-cage fans are centrifugal fans with forward-curved blades. A large number of short blades of thin circular arc sheet metal provide a low diameter drum-type rotor of high axial length. Cross-flow fans have a similar rotor design. However, the flow passes the rotor in radial direction two times. One consequence of the forward-curved blades is that there is more or less no pressure rise in the rotor and the casing has to convert the high absolute rotor exit velocity into a global pressure rise. Both types are used in applications requiring low size, relative high volume flow rates, low costs and low noise at the drawback of relative low efficiency. Volume flow rate, specific isentropic enthalpy difference, rotor outer diameter and rotational speed of a single stage fan can be transformed to speed number and diameter number. For axial, radial and mixed flow fans, a single relationship (CORDIER-diagram) exists and it is well accepted that this line represents “optimum” fan designs with high efficiency. The paper provides a theoretical interpretation of the CORDIER-lines for squirrel-cage and cross-flow fans, since they differ considerably from the classical relationship. Based on velocity triangles and energy transfer, CORDIER-line of squirrel-cage fans depends on absolute inlet flow angle, relative exit flow angle, rotor inlet to exit diameter ratio, relative axial rotor width and circumferential efficiency. Additionally, the CORDIER-line of cross-flow fans depends on the degree of admission. At a distinguished pressure coefficient, a maximum speed number is found, corresponding to maximum volume flow rate.

Rotation Effect on Jet Impingement Heat Transfer in Smooth Rectangular Channels With Four Heated Walls and Radially Outward Crossflow

1998 ◽  
Vol 120 (1) ◽  
pp. 79-85 ◽  
Author(s):  
J. A. Parsons ◽  
J. C. Han ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Temperature Difference ◽  
Flow Direction ◽  
Jet Impingement ◽  
Coolant Temperature ◽  
Test Model ◽  
Transfer Coefficients ◽  
Rotation Direction ◽  
Side Walls

The effect of channel rotation on jet impingement cooling by arrays of circular jets in two channels was studied. Jet flow direction was in the direction of rotation in one channel and opposite to the rotation direction in the other channel. The jets impinged normally on two smooth target walls. Heat transfer results are presented for these two target walls, for the jet walls containing the jet producing orifices, and for side walls, connecting the target and jet walls. The flow exited the channels in a single direction, radially outward, creating a crossflow on jets at larger radii. The mean test model radius-to-jet diameter ratio was 397. The jet rotation number was varied from 0.0 to 0.0028 and the isolated effects of jet Reynolds number (5000 and 10,000), and wall-to-coolant temperature difference ratio (0.0855 and 0.129) were measured. The results for nonrotating conditions show that the Nusselt numbers for the target and jet walls in both channels are about the same and are greater than those for the side walls of both channels. However, as rotation number increases, the heat transfer coefficients for all walls in both channels decrease up to 20 percent below those results that correspond to nonrotating conditions. As the wall-to-coolant temperature difference ratio increases, heat transfer coefficient decreases up to 10 percent with other parameters held constant.

Reversing of Axial Flow Fans for Ventilation

2011 ◽  
Author(s):  
Vaclav Cyrus ◽  
Jiri Pelnar ◽  
Jan Cyrus
Keyword(s):  
Volume Flow Rate ◽  
Flow Direction ◽  
Pressure Coefficient ◽  
Axial Flow ◽  
Aerodynamic Performance ◽  
Flow Reversal ◽  
Design Flow ◽  
Flow Coefficient ◽  
Final Decision ◽  
Flow Mechanism

Changing the flow direction in fans is frequently required in emergency situations in traffic tunnels, chemical plants and mines ventilation. Reverse flow in axial flow fan is often achieved using two methods: a) Changing direction of fan rotation and turning the stator vanes (Method I). b) Turning / resetting rotor blades during fan rotation (Method II). The required volume flow rate at flow reversal is usually at least 60% valid for normal fan working point. The motivation of the present paper is to compare the aerodynamic performance and 3D flow mechanism in fan stage at flow reversal carried out by the two methods above. In our paper conditions of the flow reversal are discussed. Theoretical relations are derived for both methods using fundamental equations valid for internal aerodynamics of axial flow compressors and fans. Parameters of three fan axial stages were measured on a 600 diameter test rig at standard and reverse conditions. The investigated fan ventilation stages had a design flow coefficient of 0.35 to 0.40 and pressure coefficient of 0.30. Flow field measurements were carried out with the use of 5-hole pressure probes in the stage planes. The blade rows flow mechanism at the standard and reverse conditions is described using test data obtained for both flow reversal methods. The flow simulation results were also used. It has been found in our investigations that moderate aerodynamic loading of the ventilation fans has better aerodynamic performance during flow reversal if Method II is used. Fan designers and users making the final decision relating to the selection of the flow reversal method should also include the reliability and cost of the reverse fan design with blade turning mechanism.

Flow in a dirty air fan with a semi-open centrifugal impeller and a squirrel volute

2011 ◽  
Vol 225 (4) ◽  
pp. 869-883
Author(s):  
H Li
Keyword(s):  
Flow Direction ◽  
Fluid Dynamic ◽  
Numerical Data ◽  
Centrifugal Impeller ◽  
Leakage Flow ◽  
Pressure Potential ◽  
Impeller Blade ◽  
Flow Energy ◽  
Industry Standard ◽  
Solid Objects

The flow driving performance data of a dirty air fan with a semi-open centrifugal impeller and a squirrel volute, designed for household vacuum cleaners, are experimentally obtained with the industry standard tests. The fluid flows in the fan at various conditions are numerically simulated. The agreements between the numerical data and the experimental results are reasonably good. The model-simulated flow structures show that air flow passes over the blade between the impeller blade channels. A high-velocity spot is formed at the top of each blade. The leakage flow, from the fluid-collecting squirrel back to the blade channels, represents a waste of the fluid dynamic energy and the pressure potential energy. However, such leakage flow presses the inlet air to the bottom disc of the impeller and helps in preventing the solid objects from getting to the blade top. Flow energy analysis shows that the main energy loss is in the semi-open impeller. The leakage flow and the disagreements between the flow direction and the blade angles at the leading and the trailing tips are the main causes of the low energy efficiency of the fan.

scholarly journals “Walczak’s Pipes” in the Greenhouse Heating System

2016 ◽  
Vol 64 (1) ◽  
pp. 135-140 ◽  
Author(s):  
Kazimierz Rutkowski ◽  
Jarosław Knaga ◽  
Anna Krakowiak Bal ◽  
Jan Vogelgesang ◽  
Jakub Sikora ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Flow Distribution ◽  
Heating System ◽  
Cultivated Plants ◽  
Outer Diameter ◽  
Ambient Conditions ◽  
Heat Management ◽  
Traditional System ◽  
Flow Parameters ◽  
Heating Pipes

Diversified heating circuits inertia is particularly important by high variability of external conditions were the greenhouse is often overheated or large heat losses are noted. To meet these needs a new generation of heating pipes were used. They are hexagram-shaped pipes called “Walczak’s pipe”. Tubes of such shape have several times smaller volume in comparison with traditional heating pipes of the same outer diameter and higher stiffness. The preliminary assessment of the “Walczak’s pipe” installed in the greenhouse is highly positive. Compared with the traditional system it enables better heat management. In the first research stage, the thermal efficiency was defined in different ambient conditions at selected flow parameters and various water temperatures. With regard to the accepted flow values, it is notable that “Walczak’s pipe” has greater thermal efficiency per unit of power comparing with traditional tube. During the study, there was also a thermographic analysis of pipes’ surface performed and the heat flow distribution was determined. Analyzing the temperature distribution on the “Walczak’s pipe” remarkable are the areas with higher values ​​comparing with standard tube. It can be concluded that in the heating system with “Walczak’s pipe” energy transferred by radiation increases. This is particularly advantageous solution to use in greenhouses. It allows to obtain a higher leafs temperature with respect to the ambient temperature (vegetation heating). This parameter has a beneficial effect on the vegetative growth of cultivated plants.

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