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> I have done some more refinement on my earlier curves of water pump output.
> The description below and the accompaning figures provide some insite in how
> the system will work.
>
> First, some changes from my earlier curves that were posted, please throw
> away those curves. I only had one pressure guage at the outlet of the pump,
> and a considerable length of corrugated tubing to connect the pump to the
> water source. As a result, the results were interesting but not as useful as
> those attached to this email. Also, I had not calibrated the bucket used for
> the measurements.
>
> THE SETUP
> I placed a 55 gallon barrel on a workbench next to the engine on my "mock
> firewall", and filled it with water until the level was just a bit above the
> outlet of the pump. An 18 foot length of 1-1/4" sump pump hose (the cheap
> plastic corrugated kind) ran from the barrel, up over the edge, down to the
> floor, and up to the intake of the pump. A 6 foot length of the same hose
> was run from the outlet of the pump back to the barrel. A 1-1/4" plastic
> ball
> valve was installed at the outlet of the pump, before the hose. For the
> final
> test I installed two pressure guages, one on the outlet of the pump, and the
> other on the inlet of the pump. This way, I could remove the effect of
> pressure drop from sucking water through the 18' plastic hose.
>
> My 1-HP electric saw motor was mounted on the firewall such that the pump
> pulley could be driven by a long V-belt. I used 3 different pulley sizes to
> give different pump speeds. The pulley diameters were ~2-5/8, 4", and 6".
> The pump pully measured 3.7" diameter. This gave me rough pump speeds of
> 5594, 3730, and 2448 rpm.
>
> DATA COLLECTION
> I would float the bucket on the surface of the water in the barrel, turn on
> the pump, and when I diverted the water into the bucket, start a timer. The
> bucket would sink, displacing the water in the barrel and essentially
> holding
> it constant (no head change). By changing the setting of the valve, I could
> change the flow rate. The bucket (filled to overflowing) held 5.8 gallons,
> and all data points were duplicated.
>
> For each run, I would measure the pressure on the pump outlet (affected by
> the valve setting), and the pressure on the inlet to the pump, (affected by
> the flow rate). The data, plotted as pressure vs flow rate is shown on
> Figure 1, Water_pump_data.jpg. There are 5 curves, two for the 5594 rpm
> case
> (taken on two separate days), one each for 3730 and 2448 rpm, and a new one
> for the pressure at the pump inlet. Note that it starts at ~zero and goes
> negative with increasing flow rate. This 8 psi drop is due to the flow
> through the corrugated tubing at ~29 GPM. In an actual installation, one
> would not want to use 18 feet of tubing, so I wanted to adjust the data to
> allow compensating for that pressure loss.
>
> DATA ANALYSIS
> Flow through pipes causes a pressure drop, that is proportional to the
> SQUARE
> of the velocity of the flow, therefore, if I plotted the data from Figure 1
> vs the square of the flow rate, I should get a straight line. Combining the
> two 5594 rpm runs, the data as pressure drop vs the square of the flow rate
> is shown in Figure 2, Pump_fit_Data.jpg. There is some scatter, but the
> basic shape of all the curve is linear, and the equations for each of the
> lines is shown on the graph.
>
> At 5594 rpm, Pressure (psi) = 18.77 - 0.02(flow^2)
> At 3730 rpm, Pressure (psi) = 8.09 - 0.018(flow^2)
> At 2448 rpm, Pressure (psi) = 4.29 - 0.0226(flow^2)
> Pressure loss in inlet tubing = - 0.3339 - 0.0103 (flow^2)
>
> Now, for any given flow rate, I can get the performance of the pump as it
> would be installed in the airplane, (not having 18 feet of tubing to suck
> through), by just subtracting inlet pressure drop from the flow curves from
> the pump curves. However, there is one other piece of information that is
> needed to know what the flow in the system is, and that is the pressure drop
> across the heat exchanger.
>
> HEAT EXCHANGER PRESSURE DROP
> Next installment, more data to be take tonight on the heat exchangers.
> PUMP CURVES
> Using the equations above, the pressure available for the system to force
> the water through the heat exchanger cores, is shown on Figure 3
> Pump_smooth.jpg . Please note that the points beyond 29gpm are
> extrapolations based on the linear fit to the velocity squared.
>
> Bill Schertz
> KIS Cruiser #4045
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