Questions tagged [airflow]

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Is supersonic flow not possible in a venturi tube?

I'm trying to design a venturi tube that will have a pressure drop of 91525 Pascals where the inlet pressure is at 1 atm and the throat pressure is at 9800 Pascals. I calculated the minimum throat ...
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2 votes
2 answers
128 views

How do water tunnel experiments compare to wind tunnel experiments?

I recently stumbled across the water tunnel videos by this guy: https://youtu.be/quDLzxmJl5I?t=838 He states that for his "high flow" experiments the water speed is at 0.668 m/s. The car ...
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2 answers
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How to connect a 1/4 NPT pressure gauge to a schrader valve while being airtight

I need to attach this pressure gauge - https://www.amazon.co.uk/gp/product/B07CXM3ZGT/ref=ask_ql_qh_dp_hza - to a schrader valve with a pipe to measure the pressure. The valve has a 1/4 NPT thread. I ...
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How (mathematically) does pressure in the intake manifold vary based on size of throttle opening?

I have the intuitive picture somewhat down: the intake manifold is partially opened; during the intake stroke of a four-stroke process, the piston moves rapidly moves downwards creating a short-term ...
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Analytical / Experimental calculation of pressure loss for simple crossflow of air across a simple cylinder

I need a way to find pressure loss of air flowing across a single tube for both laminar and turbulent flows. I have referred to several sources (Y. Cengel Heat and Mass Transfer and Fluid Dynamics ...
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27 views

Gas temperature control with a mixing chamber

I am currently trying to figure out how to set up an automatic controller in order to get a precise air temperature at a specific flow rate with a hot and fresh air mix system. Picture the system like ...
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1 answer
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How to determine time taken for tyre to deflate using CFD analysis?

I am working on my final year project, and am at a point which requires us to deflate a tyre in 0.8 seconds. This needs to be simulated using CFD. We have drilled a hole into the rim and attached a ...
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0 votes
1 answer
73 views

Increasing airflow of fan

I learned at at young age from a physics kit that one can blow up a large bag with your mouth by blowing into it from a distance and letting the air pick more air with it. Later in life when Dyson ...
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is there a difference in performance between these two fan designs

These two fans are usually used in hairdryer is there a difference between them in performance if both have same rpm and same outer diameter.
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1 vote
1 answer
35 views

Can airflow through an HVAC duct be considered inviscid? Does viscid flow ever occur for HVAC?

Can airflow through an HVAC duct be considered inviscid? Does viscid flow ever occur for HVAC? If the answer to (1) is yes, how do we know airflow in an HVAC pipe is inviscid? In general, what's a ...
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1 answer
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Routing the flow from an axial "box" fan

I have a project where I need to generate a certain flow rate to levitate a ping pong ball using the Bernoulli principle. From some rough calculations, I found that it would take about 30 CFM through ...
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Calculating lift and drag coefficients

What should be the reference area when calculating the lift coefficient and drag coefficient for a 2 airfoil wing design? Should they both be the same value or different?
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2 answers
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Airflow theory in wing design

In a race car rear wing with 2 airfoils, why does the second airfoil have a greater angle of attack compared to the leading airfoil? Also, what is the best offset distance between the 2 airfoils in a ...
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0 votes
0 answers
39 views

How does temperature not affect fan airflow?

Please correct me if I am wrong : fans are devices moving a constant volume of air, given a constant rotation speed. Though, flowrate depends of the total resistance of a circuit and the ability of ...
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1 answer
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Thrust force of a fan

If I have a fan with these attributes Category Value Air flow 108.2 CFM (3.03 $m^3/min$) RPM 3100 Dimensions LxHxW (mm) 120x120x25 Is it correct to calculate the thrust force at max rpm like this:...
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1 vote
1 answer
60 views

What is the difference between a 100 USD professional pitot tube and a 5 USD hobbyist pitot tube?

I would like to measure air flow speeds in a duct system for dust collection in a workshop. Relevant air speeds in the ducts are around 10-30 m/s. The ducts are circular tubes with a diameter of 160 ...
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1 answer
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Increasing air velocity through F1 car diffuser

I am looking into F1 car aerodynamics for a course that I am taking. I understand that because of Bernoulli's law, when the velocity increases, the pressure decreases, which is good for F1 cars if we ...
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1 answer
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Does a venturi cause strain on a pump

Excuse my terminology if it's wrong. I'd like to know if a venturi causes strain on a pump. For example, in my drawing. I have an air pump behind the house with a 50mm pipe fitting. On the other side ...
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Pressure and friction force distribution around a blunt body and a streamlined body

How to create a schematic that shows pressure and force distribution around a blunt body (for e.g. a cylinder) and an airfoil? Where can one get the data for these distributions? I looked for these ...
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1 answer
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Flow Velocity Data Automation - Platform/Controller Selection

I have been tasked with (semi) automating flow velocity data collection using a pitot tube in a minaturized wind tunnel. The pitot is mounted on a two axis stepper motor system which is controlled by ...
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-1 votes
1 answer
26 views

How can I calculate the requirements of a fan to obtain a defined airflow after a HEPA filter?

I would like to understand how can I calculate the requirements of a fan in the following scenario. I want to obtain some airflow (m^3/h or CFM)after a HEPA filter. I have found some specification ...
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Hepa 13 Filter Surface Area for Given CFM

How much (area) of HEPA 13 filter should I use for a blower with 160 CFM rating. I am planning to DIY a filter to match my blower's CFM rating. Disclaimer: I'm just a hobbyist with limited education. ...
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1 vote
1 answer
180 views

How to Convert between Air (Dry Air) Normal Liters per Minute (NLPM) and Pounds per Minute (PPM)?

I need to check the leakage of a product, the requirement is basically need to place a flow meter between dry air supply and the product, and apply a pressure of 100, 200, or 400 PSI, and ensure the ...
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1 vote
1 answer
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Influence of bigger air-pumps pulling effect over small pumps

When there are two air-circulation pumps (one powerful than the other) connected in series (as shown in the figure), how would the bigger pump affect the smaller pump? Should the smaller pump be ...
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1 vote
0 answers
30 views

Valve solution for mixing external air into a closed loop climate controlled air circulation system

I'm looking for an electronically controlled air valve solution which would provide a way to mix external air into a closed loop air circulation system used for climate control in an enclosure. The ...
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0 votes
0 answers
24 views

Using venturi effect for equilibrating pressure drop

Let me first say I am a novice in fluid dynamics, I am not sure about terminology but I will try to explain myself as clearly as possible. I need some help for understanding the following case: in a ...
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Controlling flow through an output pipe

I wish to limit my flow through the output to a certain exact value. In this case to 10 lpm, what method or valve can I use to this task? At the moment the flow keeps on fluctuating between 10.1-11.2 (...
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0 votes
1 answer
49 views

How to select a fan blade for my application (strong, focused breeze)

My question is how fan blade design relates to the focus of the air leaving the fan. I am looking to generate the most focused breeze I can with a fan blade, excluding additional ducting etc, the fan ...
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0 votes
1 answer
161 views

How to mix pure CO2 with air so that a bioreactor can be fed with air at 0.1% to 10% CO2?

The situation is we have to prepare a gas mix of air and CO2 which has to be given as input from 0.1% to 10% CO2 of air mix to the aqueous medium in a bioreactor? I'm trying to build a simple and ...
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2 votes
0 answers
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What would happen if the air conditioning failed in a skyscraper for an extended period?

I'm writing some fiction which involves the AC in a modern glass curtain skyscraper (50-80 floors?) in an American city failing for a period of weeks, maybe even for up to two months. Could anybody ...
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1 vote
2 answers
61 views

How to visualise/measure airflow in sauna?

I'd like to visualise/measure the flow of air in sauna to optimise the ventilation. Is there a way to colour the air (non-toxic!!!) so I may watch the flow? Or is there any other accessible technology ...
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0 votes
1 answer
62 views

How to transfer air heat easily?

Assume two buildings, one which generates a lot of air heat inside due to electrical equipment running etc. The buildings are 20-25 meters apart. Some questions: How can one easily transfer heater ...
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1 vote
0 answers
75 views

Stokes Number (characteristic length)

I am working with a high speed flow that is non-stokesian, but that isn't the issue. There are correction factors for that. I am attempting to figure out what value to use for the "characteristic ...
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1 vote
0 answers
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Mouth-style whistles, i.e. whistles using flexible materials [closed]

I'm wondering if there is much literature around whistling, i.e. human-mouth style whistling. Either using your lips or your fingers. To make my query less vague: say I wanted to create a rubber ...
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2 votes
2 answers
263 views

How to use excel spreadsheet formulas to find optimal camshaft profile [closed]

I have a 600cc 4 cylinder Honda engine that my race car team uses. The rules of the race mandate that we install an intake that is substantially smaller than the stock factory intake size to limit ...
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3 votes
1 answer
298 views

Fan performance curve

I am being asked to compare a fan which is going obsolete with its proposed replacement. From a mechanical and electrical point of view, they are almost completely identical so I have no concerns from ...
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-1 votes
1 answer
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Momentary 250 Degree Celsius Air Heating Element

I am a complete novice and need some pointers for designing a heating element that will be installed in an air duct with 60mm diameter, to heat the air passing through it to 250deg C as fast as ...
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21 votes
10 answers
9k views

Why not put servers in a refrigerator?

Recently I was thinking about home improvement, and one idea that is haunting me is that I could use some kind of refrigerator for gaming consoles and laptops. The obvious benefit is that it maintains ...
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1 vote
1 answer
102 views

How to calculate rock permeability in m^2 from gas flux in m/s?

I am studying rock caverns lined with concrete for compressed air storage. I would like to know if it's possible to convert the permeability coefficient from m/s to m^2 or Darcy. Thank you.
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0 votes
1 answer
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How to have a watertight or airtight pipe seal that is rotating at a radius, with a stationary junction tube?

How would I have a watertight or airtight pipe that is rotating at a radius, if the main reservoir pipe is not? Since I'm pretty sure I didn't do a good job of describing what I mean, the image above ...
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0 votes
2 answers
66 views

Is controlling humidity more precise when calculating with relative or absolute humidity?

I have a tubing system where I need to precisely control relative humidity. All my sensors are giving me temperature [°C] and ...
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5 votes
1 answer
218 views

How do I choose a blower design for an induced draft brick kiln?

I am responsible for a brick kiln in the Punjab province of Pakistan. My government requires all brick kilns to be upgraded to match recent new standards, which include the addition of a blower near ...
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0 votes
2 answers
55 views

Cooling airflow calculation

I want to unplug my refrigerator in the winter, and cool it down by taking air from outside. The idea is to lead cool air from the outside through a pipe into the fridge, then let hot air out of the ...
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2 votes
2 answers
158 views

Why does accuracy of temperature PID controller drop over time and how to eliminate it?

What am I trying to control? I have a container with approximately 3*2*6 meters (width, height, length). I am controlling through PID the ...
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1 vote
1 answer
102 views

Pressure drop in a CFD simulation of an air flow too small

I am simulating a turbulent air flow through a rectangular channel with the goal to match measured velocity profiles and the static pressure at certain points. My problem is that the pressure drop in ...
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3 votes
4 answers
2k views

Benefit of removing the center "engine hub" inside a fan

Most fans (small and large) have inner hubs (see image left). Would there be a gain in efficiency by removing that center hub, thus creating more blade space? You could fix the blades to an outer ring ...
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1 vote
0 answers
15 views

Translations from "Oil" Flow Rate - Pressure drop to "Air" Flow Rate to Pressure Drop charts

I keep getting check-Valve companies that have their product data sheets registered in Pressure Drop-Flow Rate for oil(Hydraulic oil) and I need it for Air. Is there a translation between oil and air ...
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0 votes
1 answer
53 views

Extraction Fan Setup

I have recently bought myself a Flux Beamo laser cutter and am now in the process of setting up fume extraction for it to vent outside. The laser unit has a built in fan of which I haven’t been able ...
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1 answer
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Does air flow rate of an air pump imply the same rate when using it to pump water via air pressure?

I want to build a machine that pumps liquids (roughly density of water) out of an enclosed cannister. The cannister has for one inlet for air at the very top and has an outlet (near the top as well) ...
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1 vote
1 answer
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Can air flow occur in both directions in a 2 way solenoid valve?

I'm designing a system where I need to fill and exhaust air from an an air bag. The air will be supplied from a dc motor. As of right now I've been considering placing a 2 way solenoid valve for air ...
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