spitfire6 Posted July 3 Share Posted July 3 Hi. a picture of two fans. Blades are reversed. Electrically they can rotate opposite. I believe the top one will work better as a Pusher & the bottom as a puller. Does anybody disagree with the above? I would like to hear why not. The 80W does not mean 80Watts. @ 12VDC. Feeding the power from the alternator will get very close though. SPAL are the best but my pair are pullers. 9" 80W type were the next day and cheap. Cheers, Iain. Link to comment Share on other sites More sharing options...
egret Posted July 4 Share Posted July 4 I would expect the top fan to rotate anticlockwise and move air towards the viewer, and the bottom fan to rotate clockwise and move air away from the viewer. Axial fan blades tend to be installed so the blades are backwards curved and I'll wager that's how these are designed and will work best. I'd flip the blades to match whatever purpose you intend to use them for. As to pushers or pullers? There's a can of worms people argue about all day, but it's likely gains so marginal only an F1 team would notice! 1 Link to comment Share on other sites More sharing options...
Escadrille Ecosse Posted July 4 Share Posted July 4 ^^^^^This Link to comment Share on other sites More sharing options...
spitfire6 Posted July 4 Author Share Posted July 4 Hi, I ran some tests and came up with the below: Direction Electrical Connection Fan Blades Voltage Amperage Watts pull Correct Reversed 00.70 0.30 00.2 pull Correct Reversed 12.00 3.59 42.9 pull Correct Reversed 13.50 4.25 57.3 pull Correct Reversed 14.25 4.57 65.0 Pusher Reversed Reversed 00.70 0.33 00.2 Pusher Reversed Reversed 12.00 4.38 52.4 Pusher Reversed Reversed 13.50 5.10 69.0 Pusher Reversed Reversed 14.25 5.49 78.3 Direction Electrical Connection Fan Blades Voltage Amperage Watts Pull Correct Supplied 00.70 0.30 00.2 Pull Correct Supplied 12.00 4.13 49.0 Pull Correct Supplied 13.50 4.80 65.9 Pull Correct Supplied 14.25 5.20 74.3 Pusher Reversed Supplied 00.70 0.34 00.2 Pusher Reversed Supplied 12.00 3.50 42.0 Pusher Reversed Supplied 13.50 4.20 57.0 Pusher Reversed Supplied 14.25 4.57 65.0 To me, it's clear as said. A supplier of these fans is adamant that these fans are designed to run in the opposite direction. They will run but not as efficiently if you follow their instructions. Cheers, Iain. Link to comment Share on other sites More sharing options...
egret Posted July 4 Share Posted July 4 Drawing more power just means more load on the motor, not necessarily more air being moved. Which is what you're actually after. That extra energy could be going towards heat and turbulence. Link to comment Share on other sites More sharing options...
Nick Jones Posted July 4 Share Posted July 4 Hmm…. More current draw on fans and centrifugal pumps does tend to mean more work is being done. Though I take the point that it might not all be useful work. 1 Link to comment Share on other sites More sharing options...
spitfire6 Posted July 4 Author Share Posted July 4 Hi, Added SPAL to the bottom: Type Direction Electrical Connection Fan Blades Voltage Amperage Watts 80W Pull Correct As Sold 0.70 0.30 0.2 80W Pull Correct As Sold 12.00 4.13 49.0 80W Pull Correct As Sold 13.50 4.80 65.9 80W Pull Correct As Sold 14.25 5.20 74.3 80W Pusher Reversed As Sold 0.70 0.34 0.2 80W Pusher Reversed As Sold 12.00 3.50 42.0 80W Pusher Reversed As Sold 13.50 4.20 57.0 80W Pusher Reversed As Sold 14.25 4.57 65.0 Type Direction Electrical Connection Fan Blades Voltage Amperage Watts 80W pull Correct Reversed 0.70 0.30 0.2 80W pull Correct Reversed 12.00 3.59 42.9 80W pull Correct Reversed 13.50 4.25 57.3 80W pull Correct Reversed 14.25 4.57 65.0 80W Pusher Reversed Reversed 0.70 0.33 0.2 80W Pusher Reversed Reversed 12.00 4.38 52.4 80W Pusher Reversed Reversed 13.50 5.10 69.0 80W Pusher Reversed Reversed 14.25 5.49 78.3 Type Direction Electrical Connection Fan Blades Voltage Amperage Watts SPAL No rotate Correct As Sold 0.70 0.70 0.5 SPAL Pull Correct As Sold 12.00 5.30 64.0 SPAL Pull Correct As Sold 13.50 6.10 83.0 SPAL Pull Correct As Sold 14.25 6.50 93.0 SPAL No rotate Reversed As Sold 0.70 0.70 0.5 SPAL Pusher Reversed As Sold 12.00 4.50 54.0 SPAL Pusher Reversed As Sold 13.50 5.20 72.0 SPAL Pusher Reversed As Sold 14.25 5.80 83.0 The SPAL is made Blow or Pull. Mine has code "A" so it's a Puller. an "A" is Italian for Pull. Certainly, the current and energy drop when running in the wrong direction. All the fans consume more energy when the convex edge is leading. I was going to buy an airometer as I already have a manometer. I am saving my money. The SPAL has been in use for a couple of years. It was stalled at 700mV and started to pull more current slowly. Cheers, Iain. Link to comment Share on other sites More sharing options...
flatter4 Posted July 31 Share Posted July 31 You need an anemometer to assess air flow. This kind of thing: https://www.ebay.co.uk/itm/135118330661?itmmeta=01J44MMP2570TZZMEGHWRP9STA&itmprp=enc%3AAQAJAAAAwMxuP39BnlAOiat84KOOELACWv6WpJApkKAor6taZmMnV2DsWLapYv6akRAFc8DTFhv407kVdjD0AVXducQerE2LooUA1q5iJENTgXipQnZNci2XhwXr29d%2BM%2F0QryFW4Xiypo8luyJ%2Fn5PA2x56qwmP%2FM2pzSy%2F737GnDEUM5gYwn0FA1g0m3K4L5UPmCqQc5Q9p3EeexUZcRctwC9SnKX%2BBNrysdCo0ichfhevmIjXo4OniendE1KgiGFsENjnYw%3D%3D|tkp%3ABk9SR5bh0pShZA You would then need to measure across the grid of the radiator face and average the velocities seen. You then calculate flow from the flow area of the radiator. Expect negative (reverse) flow near the fan hub. ...ideally you should blank the area outside the fan diameter to aid the fan doing its work - but then you have lost flow area during driving when air is forced through "naturally" - so you then need blinds you can open and close!!! So...... work out which side of the radiator you can fit the fan: either in front of rad. (away from engine = pusher) or behind rad. (engine side = puller) Either fan will work so long as the leading edge remains the leading edge. Running those fans in reverse will just be inefficient / poor air flow. As stated above take the fan off and install the 'other' way round if you want to reverse flow. Loads of other influences - distance from radiator core face is a key one - but one hopes that the manufacturer has designed the fan to be 'OK' when mounted that close to the core. 1 Link to comment Share on other sites More sharing options...
flatter4 Posted July 31 Share Posted July 31 The design target is probably to move enough air when engine is idling after a hot run ...to keep coolant temp in control ...to keep air moving underbonnet for everything else (esp. fuel vapourisation) If you take readings on a warm day (20deg.C +) you will probably have the thermostat fully open. ....testing industrial machines we would prop the thermostat to a fully open position to give a good ref. point for extrapolation You can then extrapolate to the maximum ambient temp with a 1:1 ratio of coolant temp to ambient. eg. Engine reaches 92°C in a 20° ambient Maximum coolant temp permitted = 104°C (or whatever you define - 50/50 ethylene glycol mix is OK to about 132°C at 1 bar pressure - but you'll see pump cavitation way before that....) Therefore 104-92 = 12 deg.C headroom - so you should be good to an ambient of 20 + 12 = 32°C Does that make any sense! 2 Link to comment Share on other sites More sharing options...
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