Effect on Inlet Vent Porosity on Fan Characteristic Performance for Electronics Cooling

2009 ◽  
Author(s):  
Takashi Fukue ◽  
Katsuhiro Koizumi ◽  
Masaru Ishizuka ◽  
Shinji Nakagawa
Keyword(s):  
Flow Rate ◽  
Perforated Plate ◽  
Electronics Cooling ◽  
Maximum Flow ◽  
Flow Area ◽  
Flow Rates ◽  
Fan Performance ◽  
Performance Metric ◽  
Cooling Fans ◽  
The Relationship

Critical fan performance metric such as characteristic output curves and maximum flow rates are affected by various environmental conditions where cooling fans are installed. This paper describes the relationship between the fan performance and configuration factors such as the flow inlet porosity of electronic enclosure, the flow obstacles which imitate high-density packages and narrow flow area configurations. We installed a test enclosure in front of a test fan and measured P-Q curves of the test fan, which were operated in the enclosure. The experiments, it was observed that the pressure difference was increased in the enclosure by the effects of a wall. We installed a perforated plate in front of the fan as an obstacle and investigated how this changed the P-Q curve. In general, addition of the perforated plate in front of the fan decreased the characteristic output of the fan. On the other hand, the flow rate by the fan supply was decreased by the existence of the narrow inlet or obstacles. When an opening area in front of a fan became smaller than double of the fan flow area, the flow rate was significantly decreased. In addition, it was observed that the maximum flow rate depended on the opening area ratio. Finally, a model for predicting flow rates decreases by the enclosure inlet and obstacles was proposed.

Study on P-Q Curves of Cooling Fans for Thermal Design of Electronic Equipment (Effects of Opening Position of Obstructions Near a Fan)

2011 ◽  
Author(s):  
Takashi Fukue ◽  
Masaru Ishizuka ◽  
Tomoyuki Hatakeyama ◽  
Shinji Nakagawa ◽  
Katsuhiro Koizumi
Keyword(s):  
Flow Rate ◽  
Perforated Plate ◽  
Pressure Rise ◽  
High Density ◽  
Thermal Design ◽  
Electronic Equipment ◽  
Flow Passage ◽  
Fan Performance ◽  
Cooling Fan ◽  
Cooling Fans

This study describes an operation pressure and supplies flow rate of an axial cooling fan installed in high-density packaging electronic equipment. Fan performance is generally defined by their P-Q curve, specifically, a relationship between fan pressure rise (ΔP) and flow rate (Q). A compact cooling fan often operates in a high-density mounting device, which may decrease the fan performance. In this study, we focus on an obstruction near a fan, which is electronic components such as PCBs, capacitors and heat sinks, as one of a factor which decreases fan performance. We installed a perforated plate which simulated the above components near a fan and measured the P-Q curve. To investigate a relationship between a fan performance decrease and an opening position near the fan, a part of the perforated plate was closed. Closed position was changed and explored an opening condition which caused the dominant fan performance decrease. From experiments, it was found that the fan performance was decreased when flow passage in front of a fan was blocked by an obstruction. Especially, when flow passage in front of a fan hub was blocked, a dominantly reduction of fan pressure was caused. An obstruction rear a fan has no effect on a fan performance curve itself. In addition, opening conditions in front of a fan tip had a little influence on a fan pressure characteristic when there was no obstruction in front of a hub.

Interaction between CO2 concentration and flow rate on peripheral airway resistance

1991 ◽  
Vol 70 (6) ◽  
pp. 2514-2521 ◽  
Author(s):  
A. Kaise ◽  
A. N. Freed ◽  
W. Mitzner
Keyword(s):  
Flow Rate ◽  
Airway Resistance ◽  
Co2 Concentration ◽  
Low Flow ◽  
Flow Rates ◽  
Peripheral Airway ◽  
Residual Capacity ◽  
Local Ventilation ◽  
End Tidal ◽  
The Relationship

In the present study, we investigated the interaction between CO2 concentration and rate of delivered flow on peripheral airway resistance (Rp) in the intact canine lung. Dogs were anesthetized, intubated, paralyzed, and mechanically ventilated with room air to maintain end-tidal CO2 between 4.8 and 5.2%. Using a wedged bronchoscope technique, we measured Rp at functional residual capacity. The relationship between CO2 concentration and Rp was measured at flow rates of 100 and 400 ml/min with 5, 3, 2, 1, and 0% CO2 in air. Measurements were made at the end of a 3-min exposure to each gas. At low flow rates (100 ml/min) responses to hypocapnia were small, whereas at high flow rates (400 ml/min) responses were large. The PC50 (defined as the CO2 concentration required to produce a 50% increase in Rp above baseline Rp established on 5% CO2) at 400 ml/min (1.73%) was significantly larger than that at 100 ml/min (0.38%). We also directly measured the relationship between Rp and flow rate with 5% CO2 (normocapnia) or 1% CO2 (hypocapnia) delivered into the wedged segment. Increases in normocapnic flow caused small but significant decreases in Rp. In contrast, increases in hypocapnic flow from 100 to 400 ml/min caused a 108% increase in Rp. Thus the response to hypocapnia is augmented by increasing flow rate. This interaction can be explained by a simple model that considers the effect of local ventilation-perfusion ratio and gas mixing on the local CO2 concentration at the site of peripheral airway contraction.

Performance and Development of a Miniature Rotary Shaft Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 752-760 ◽  
Author(s):  
Danny Blanchard ◽  
Phil Ligrani ◽  
Bruce Gale
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Electronics Cooling ◽  
Maximum Flow ◽  
Operating Conditions ◽  
Working Fluid ◽  
Hydraulic Efficiency ◽  
Potential Applications ◽  
Total Analysis ◽  
And Performance

The development and performance of a novel miniature pump called the rotary shaft pump (RSP) is described. The impeller is made by boring a 1.168 mm hole in one end of a 2.38 mm dia shaft and cutting slots in the side of the shaft at the bottom of the bored hole such that the metal between the slots defines the impeller blades. The impeller blades and slots are 0.38 mm tall. Several impeller designs are tested over a range of operating conditions. Pump performance characteristics, including pressure rise, hydraulic efficiency, slip factor, and flow rate, are presented for several different pump configurations, with maximum flow rate and pressure rise of 64.9ml∕min and 2.1 kPa, respectively, when the working fluid is water. Potential applications include transport of biomedical fluids, drug delivery, total analysis systems, and electronics cooling.

Computer simulation of the hydraulic milking method

1992 ◽  
Vol 59 (3) ◽  
pp. 253-264
Author(s):  
M. Clare Butler ◽  
Robert J. Grindal
Keyword(s):  
Differential Equation ◽  
Flow Rate ◽  
Equations Of Motion ◽  
Flow Rates ◽  
Air Inlet ◽  
Wall Movement ◽  
Linear Differential ◽  
Milking Machine ◽  
The Relationship ◽  
Return Valve

SummaryA mathematical model of the interactions within a milking machine teatcup has been developed, which describes the relationship between liner wall movement, pressures and flow rate when milking without an air inlet. It is based on equations of motion for a column of incompressible fluid and requires a second-order, non-linear differential equation to be solved. Incorporating a non-return valve allows hydraulic milking to be modelled, and the comparison between predicted and measured pressures, flow rates and liner wall movement when milking hydraulically is shown. The model can be used to optimize milking conditions to reduce vacuum peaks, improve liner opening and thus maximize flow rate.

Experimental Study of Entrance Effects on Laminar Gas Flow Through Silicon Orifices

2005 ◽  
Author(s):  
Aaron J. Knobloch ◽  
Joell R. Hibshman ◽  
George Wu ◽  
Rich Saia
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Flow Area ◽  
Fully Developed Flow ◽  
Flow Rates ◽  
Flow Models ◽  
Entry Length ◽  
Orifice Flow ◽  
Measured Flow ◽  
Flow Through

This study summarizes a fundamental investigation of flow through an array of silicon micromachined rectangular slots. The purpose of the study is to evaluate the effect of entrance pressure, flow area, orifice thickness, slot length, and slot width of the orifice on flow rate. These orifices were fabricated using a simple frontside through wafer DRIE process on a 385 μm thick wafer and wafer bonding to create thicker orifices. The dies were then packaged as part of a TO8 can and flow tested. To complement the results of this experimental work, two simple flow models were developed to predict the effect of geometrical and entrance conditions on the flow rate. These models were based on macroscale assumptions that were not necessarily true in the case of thin orifices. One relationship was based on Pouiselle flow which assumes fully developed flow conditions. Calculation of the entry length required for fully developed flow indicate that in the low Reynolds Number regime (32-550) evaluated, the entry flow development requires 2-8 times the thickness of the thickest orifices used for this study. Therefore, calculations of orifice flow based on a Pouiselle model are an overestimate of the actual measured flow rates. Another model examined typical orifice relationships using head loss at the entrance and exit of the slots did not accurately capture the particular flow rates since it overestimated the expansion or constriction losses. A series of experiments where the pressure was varied between 75 and 1000 Pa were performed. A comparison of the Pouiselle flow solution with experimental results was made which showed that the Pouiselle flow model overpredicts the flow rates and more specifically, the effect of width on the flow rates. The results of these tests were used to develop a transfer function which describes the dependence of flow rate on orifice width, thickness, length, and inlet pressure.

Assessment of the impact of water parameters on the flow rate of ceramic pot filters in a long-term experiment

2015 ◽  
Vol 15 (6) ◽  
pp. 1425-1432 ◽  
Author(s):  
C. Salvinelli ◽  
A. C. Elmore
Keyword(s):  
Flow Rate ◽  
Water Production ◽  
Premature Failure ◽  
Initial Flow ◽  
Flow Rates ◽  
Treated Water ◽  
Long Term Study ◽  
The Impact ◽  
The Relationship

Poor water quality is a major contributing factor to disease in developing countries. Silver-coated ceramic pot filters (CPFs) are a relatively common form of household water treatment system (HWTS) representing an effective and sustainable technology for poor communities. Water production seems to be the major limiting factor of the CPF's lifetime and sustainability since low flow rates do not produce an adequate daily volume of treated water. This paper describes a long-term study of CPF flow rates under controlled conditions using three different water sources. The relationship between water characteristics and flow rate was assessed with the intent of identifying the principal parameters that impact CPF water production. The study concluded that turbidity seems to be the principal indicator in determining CPF lifetime in terms of quantity of treated water. There is no evidence that biological activity also contributes to premature failure of CPFs and the data did not indicate that chemical precipitation is responsible for the filter clogging. Manufacturers commonly conduct initial flow rate tests using clear water as a measure of quality assurance. However, the relationship between initial flow rate and average flow rate during the lifetime of the CPF should be further studied.

Performance of Axial Fans in Close Proximity to the Electromagnetic Compatibility Screens

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
R. Antón ◽  
A. Bengoechea ◽  
A. Rivas ◽  
J. C. Ramos ◽  
G. S. Larraona
Keyword(s):  
Flow Rate ◽  
Electromagnetic Compatibility ◽  
Perforated Plate ◽  
The Other ◽  
Geometrical Parameters ◽  
Rate Reduction ◽  
Fan Performance ◽  
Close Proximity ◽  
Axial Fans ◽  
Good Guide

The performance of axial fans in close proximity to the electromagnetic compatibility (EMC) screens was analyzed by means of an experimental parametric study. The following geometrical parameters were studied: the hub-to-tip ratio, the ratio between fan thickness and fan diameter, the porosity and thickness of the perforated plate, and finally, the distance between the perforated plate and the inlet and the outlet of the fan. Screen porosity was found to be the most important parameter. Fan performance degradation is expressed by means of two correlations: one for the deterioration in the fan pressure at the no-flow point and the other for the flow rate reduction at the free delivery point. Both correlations were formulated as functions of screen porosity and the distance between the fan and the screen. We believe that the correlations can serve as a good guide for correct fan placement in a telecommunications cabinet.

A Novel Micropump for Electronics Cooling

2004 ◽  
Author(s):  
Vishal Singhal ◽  
Suresh V. Garimella
Keyword(s):  
Numerical Model ◽  
Charge Transport ◽  
Flow Rate ◽  
Electronics Cooling ◽  
Experimental Results ◽  
Heat Sinks ◽  
Flow Rates ◽  
Microchannel Heat Sinks ◽  
Combined Action

A novel micropump design for electronics cooling applications capable of integration into microchannel heat sinks is presented. The pumping action is due to the combined action of Coulomb forces due to induction electrohydrodynamics (EHD) and a vibrating diaphragm with nozzle-diffuser elements for flow rectification. A comprehensive numerical model of the micropump accounting for transient charge transport and vibrating diaphragm deformation is developed. Each component of the model is validated by comparing to analytical, numerical or experimental results from the literature. It is shown that the flow rate achieved by the micropump with combined action of EHD and vibrating diaphragm can be higher than the sum of flow rates achieved from the action of the EHD and the vibrating diaphragm, independent of each other.

scholarly journals The efficiency of a membrane bioreactor in drinking water denitrification

2015 ◽  
Vol 21 (2) ◽  
pp. 269-275
Author(s):  
Aleksandra Petrovic ◽  
Marjana Simonic
Keyword(s):  
Drinking Water ◽  
Flow Rate ◽  
Membrane Bioreactor ◽  
Nitrate Removal ◽  
Maximum Flow ◽  
Pilot Scale ◽  
Operational Parameters ◽  
Flow Rates ◽  
Removal Capacity ◽  
Removal Efficiencies

The membrane bioreactor (MBR) system was investigated regarding its nitrate removal capacity from drinking water. The performance of a pilot-scale MBR was tested, depending on the operational parameters, using sucrose as a carbon source. Drinking water from the source was introduced into the reactor in order to study the influence of flow-rate on the nitrate removal and denitrification efficiency of drinking water. The content of the nitrate was around 70 mg/L and the C/N ratio was 3:1. Nitrate removal efficiencies above 90% were obtained by flow-rates lower than 4.8 L/h. The specific denitrification rates varied between 0.02 and 0.16 g/L NO3/ (g/L MLSS?d). The efficiencies and nitrate removal were noticeably affected by the flow-rate and hydraulic retention times. At the maximum flow-rate of 10.2 L/h still 68% of the nitrate had been removed, whilst the highest specific denitrification rate was achieved at 0.2738 g/L NO3/ (g/L) MLSS?d). The maximum reactor removal capacity was calculated at 8.75 g NO3/m3?h.

scholarly journals At what flow rate does aortic valve gradient become severely elevated? Implications for guideline recommendations on aortic valve area cutoffs

2021 ◽  
Author(s):  
Wilbert Aronow ◽  
Ayesha Salahuddin ◽  
Daniel Spevack
Keyword(s):  
Aortic Valve ◽  
Linear Regression ◽  
Aortic Stenosis ◽  
Flow Rate ◽  
Aortic Valve Area ◽  
Flow Rates ◽  
Wide Range ◽  
The Relationship ◽  
Valve Area

IntroductionSince many patients with AVA < 1.0 cm2 do not manifest a mAVG > 40 mmHg, we sought to determine the AVA at which mAVG tends to exceed 40 mmHg in a sample of subjects with varied transvalvular flow rates.Material and methodsWe selected 200 subjects with an AVA< 1.0 cm2. The sample was selected to include subjects with a varied mean systolic flow (MSF) rates. Linear regression was performed to determine the relationship between MSF and mAVG. Since this relationship varied by AVA, the regression was stratified by AVA (critical <0.6 cm2, severe 0.6-0.79 cm2 , moderately severe 0.8-0.99 cm2)ResultsThe study sample was 79 ± 12 years-old and was 60% female. The MSF rate at which mAVG tended to exceed 40 mmHg was 120 ml/s for critical AVA, 183 ml/s for severe AVA and 257 ml/s for moderately severe AVA. Those with moderately severe AVA rarely (8%) had a mAVG > 40 mmHg at a wide range of MSF. In contrast, those with severe AVA typically (75%) had mAVG > 40 mmHg when MSF was normal (>200 ml/s). Those with critical AVA frequently (44%) had mAVG > 40 mmHg, even when MSF was reduced.ConclusionsAVA > 0.8 cm2 was rarely associated with mAVG > 40 mmHg, even when transvalvular flow rate was normal. Consideration should therefore be given to either raising the cutoff AVA or lowering the mAVG at which aortic stenosis is considered severe.

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