Pro/Forums - View Single Post - can we agree on the basis of "C" in C/W ?

bobo5195 · 10-24-2005, 04:18 AM

Les: hmm maybe I need to look over my notes and such. Personally i prefer the KISS approach.

After a night on it I still prefer efficiency but the fact eff and SD (aka C/W) is related is extremely useful. It means that there are two ways of getting the same result, which helps check for errors. Also generally speaking a good review already has the data in it as fan specs are known and ambient temp should really be measured. Two measured results with some accurate (differential based) errors should give you highly accurate results for less cost. It also helps eliminate mistakes as you know something’s wrong if the two do not overlap.

For a proper fan mass flow rate test you would want a long tube (10d) where d is your radiator size. This gives fully developed flow. Cutting down tube length is possible as it might not take to long for a good distribution to develop. If you have fully developed flow then you can guess mass flow rate as the velocity distribution is known. Measuring velocity at a point is tricky. Best way would be a hot wire anemometer ($$$ -$375 for one on ebay) but a pito static tube with some colour liquid is quite acceptable and DIYable in your shed.

10-24-2005, 04:18 AM	#46
bobo5195 Cooling Savant Join Date: Aug 2005 Location: uk Posts: 400	Les: hmm maybe I need to look over my notes and such. Personally i prefer the KISS approach. After a night on it I still prefer efficiency but the fact eff and SD (aka C/W) is related is extremely useful. It means that there are two ways of getting the same result, which helps check for errors. Also generally speaking a good review already has the data in it as fan specs are known and ambient temp should really be measured. Two measured results with some accurate (differential based) errors should give you highly accurate results for less cost. It also helps eliminate mistakes as you know something’s wrong if the two do not overlap. For a proper fan mass flow rate test you would want a long tube (10d) where d is your radiator size. This gives fully developed flow. Cutting down tube length is possible as it might not take to long for a good distribution to develop. If you have fully developed flow then you can guess mass flow rate as the velocity distribution is known. Measuring velocity at a point is tricky. Best way would be a hot wire anemometer ($$$ -$375 for one on ebay) but a pito static tube with some colour liquid is quite acceptable and DIYable in your shed.