rough design

[emc]

[color=#000000]Hi all, I have been reading this forum on and off for the last while as I

[emc]

the drawing

[49-1183904562]

[color=#000000]EMC;

Welcome to the Forum as you have been reading there are a lot to people on the forum that have an exceptional grasp on the design workings and math relating to flow testing.

Your design is more of schematic than a drawing and is lacking clarity as to what the measurement device will be Averaging Pitot Tube or Orifice Plate I assume Pitot based on your schematic showing flow pickup in the test fixture area. The basic components of air source, flow control and some measuring strategy are present for what appears to be a single flow direction bench (suction only). The topic of settleling chamber has been discussed often on the forum and can be found using the search button search on the word

[Tony]

I can see three potential difficulties with your proposed design Emc.

Whatever is used for flow measurement really needs to be isolated as much as possible from what is being tested to ensure that turbulence, or highly directional flow effects, do not skew the measurement.

While a suck only bench can be useful, being able to do blow testing as well will greatly expand the usefulness of the bench.

Having the motors fully exposed will do nothing to protect the motors and high voltage wiring, or reduce the very high noise level.

I am now on my fourth home constructed flow bench. Every bench I have built so far, afterwards I could always think of many ways of how it could have been made simpler or better. Probably the very best thing you could do right now would be to get some plans from Bruce. Study these plans, and understand why it has been made the way it has. These plans are the result of a great deal of experience and would make an excellent starting point for a first home built flow bench project.

[emc]

[color=#000000]cheers for the replies
Sorry failed to mention the instrument used for flow measurement is a digital airflow meter with a remote
probe(similar to HWA2005DL )that will be located in the line of flow underneath the test piece
although with what you are saying It might be a better idea locating it in area with less turbulence alright.
Also I thought by using the digital recorder I wouldn't be required to create a pressure difference to record flow rate and so did not need to use a pitot tube or orifice plate

[racehead]

[color=#000000]I am building a pitot tube flowbench. Bruce has helped me with the dimensions of the pipe work and some other details.
The rest I am on my own, there is a lot of measure twice and cut once, there is a lot of work into it. Bruce

[bruce]

Wow did you see the price on that HWA2005DL? For that price you can buy an FP1 and a copy of FPexcel for data logging and still be under the cost.

I think one big thing most people need to think about when they first start is how much they are willing to spend to get where they want to go. Knowing that info sure helps the "forum collective" in assisting someone in getting them the most bang for the $$$'s

Being able to upgrade one's design as they gain knowledge and skills is also a plus.

[Tony]

Emc, the hot wire anemometer you refer to will measure the mass of (cooling) air passing over the actual hot wire. The wire itself is physically small, so you are only really measuring air velocity at one small point in a large air duct.

Now imagine what happens if there is something up stream that deflects a lot of air to one side, away from your velocity probe. It will read low. Or if something up stream blows a high velocity jet of air right onto your probe tip, it will read high.

Because it only measures actual air velocity in one small place right at the tip, something like a cylinder head up stream can deflect the airflow, and give false non repeatable readings. That is the purpose of a settling chamber, to allow really angry turbulent air, to even out before it gets measured.

And I agree with Bruce, your money could be much better spent.

[racehead]

[color=#000000]Bruce,like any project you think about a price for it and end up with another price most of the time, details takes care of you and there is always some improvements to be made. That

[49-1183904562]

EMC,

The first few post are always a path to enlightenment, LOL almost overwhelming. The one thing I would ask as it helps us all in our feed back, are a few simple things that always come up in a good thread on a new bench build and can give you a head start.

Where you are located US, UK, AU, DE etc. ?

How much air are you trying to measure CFM ?

What is your native Power ? 110, 240, etc ?

How much power do you have available where you want to put your bench. ?

What kind of budget are you working from, not dollars and cents but Tight (Married) Loose (Single) me I get an allowance ?

What are you planning on using for air movement?

From here you can then enjoy the rivalries between Pitot and APT and those of Digital or old school Monometer.


Enjoy the addiction there is a tremendous group of generous people her on the forum, foremost Bruce.

Rick

[emc]

i am keen to use as i already have the hot wire anemometer (don't
worry didn't buy it especially for the flow bench) mains supply over here in
Ireland is 220v. i wont be earning a crust from the work done on the flow bench,
more a hobby so high levals of accuracy and repeatability while important are not crucial
airmovement will be provided by aither a series of household vacumm motors or a single powerfull motor
the flowbench will hopefully have a range of 0-260cfm

[bruce]

Well since you already have the parts, "we're" going to help build a hot wire flowbench, I think that will be a first for the forum?

[86rocco1]

Well, I guess the way to proceed is to determine what the velocity range the hot-wire sensor works best in then calculate what size ducting is required at the flow rates you're testing that'll give air velocities in that range. Then you need to find a way of ensuring that the hot-wire gets a representative sample.