Ah of course…. This has a crossflow type of fan in it (also called a tangential blower). Since we virtually never see these in the industrial world, I’m not as familiar with these. A company called Ziehl-abegg out of Germany is one of the most well known companies for making this type of fan. I did a quick search and found a catalogue for their fans and if you go to say Page 30, you will find the performance curve for a fan that sort of matches the size you mentioned… https://www.ziehl-abegg.com/fileadmin/Downloadcenter_NEW/00_englisch%28EN%29_MASTER/X02_Catalogues/ZIEHL-ABEGG-Catalogue-Cross-flow-fans-english.pdf Well, at least the blower there is about your length but it doesn’t exactly say what the impeller diameter is. However, scaling off their provided diagram (bottom left of the three diagrams), it looks to be about what you have….diameter of 90.8mm (3.57”). The length of the one on page 30 is 680mm which is a bit longer than what you have 602mm (23.7”). Since the lengths are a bit different, I’d just ratio the flow capacity they show on their curve when drawing up your own curve i.e. multiply by 602/680. As for the diameter, that gets much trickier and beyond the scope of what is possible here. Hopefully you’ll find it to be close when you try to scale it.
The more difficult test parameter is the speed. You can see on performance data on page 30 that they show curves for speeds from 740 to 1,500 rpm. How are you going to get the speed of your unit? If all you want is capacity, you don’t need any of this… the curve is only useful if you are trying to plot the data to see if what you have works somewhat according to design. If you want speed, you’re going to have to get some equipment… a strobe or something that can read off a piece of reflective tape. In a pinch, I’ve also done it using vibration data (that needs some interpretation) but that is trickier.
Will the performance of your fan be the same as the Zielhl-abegg given that they are different manufacturers? Nope… but hopefully it won’t be that far off.
You are correct about measuring near elbows… it’s the same for air. This is why I would make the cardboard about 2 feet long (assuming you can at least do that long) and put holes closer to your return air inlet. You would like the flow to travel at least 1 ½ foot to give it a chance to straighten out before it gets to the point where you measure it. The holes obviously need to be big enough to allow you to insert your vane anemometer…. and make sure you put some duct tape over the holes you aren’t using so that the results won’t be distorted.
I only looked in the Z-A catalogue for a minute and if you have time to browse around it, you might find something that is closer to exactly what you and I suspect you will find this to be very useful to your testing. I have to leave you here as I’m traveling shortly and away until Monday. I will check into FR from time to time though… I am curious to hear how you made out.
Thank you!
—”How are you going to get the speed of your unit?”
I have a noncontact laser tachometer that I use for adjusting the draft inducer of my boiler and occasionally my sewing machines, and lathe...
If I can attach a bit of reflective tape or bright white paint to the blower wheel, hopefully on the periphery. With a sight path for the laser...
IIRC the CFM, the delta T will give the Btu output
and the total Watts consumed X 3.41 is the total Btu input.
I was into the pump curve as a workaround to verify the CFM and possibly correlate it to the DC current draw of the blower motor for real-time survey because the speed appears to constantly modulate.
I already have a power meter on the heat pump that logs and transmits CSV for the power consumption and also logging temperature sensors on supply and return.
The CFM is the tricky one.
Even if I manually record the CFM that will give me a good view of the lower air temperature performance.
HP manufacturers usually publish a few points on the COP curve.
I have seen test results from DOE on a few models but nothing recent.
Why go to all the trouble?
So I can determine the crossover point, where the cost of natural gas for my heated floor or the heat pump cost the least.
Also, the COP varies with load.
Thank you again!
I think I can see a light at the end of the tunnel!
Hoping it is not a TRANE. (MY old AC was from TRANE.)